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- Tidal dissipation in satellites prevents Hill sphere escape
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Pages: 4371 - 4377
Abstract: ABSTRACTThe transit method is a promising means of detecting exomoons, but few candidates have been identified. For planets close to their stars, the dynamical interaction between a satellite’s orbit and the star must be important in their evolution. Satellites beyond synchronous orbit spiral out due to the tide raised on their planet, and it has been assumed that they would likely escape the Hill sphere. Here we follow the evolution with a three-body code that accounts for tidal dissipation within both the planet and the satellite. We show that tidal dissipation in satellites often keeps them bound to their planet, making exomoons more observable than previously thought. The probability of escape depends on the ratio of tidal quality factors of the planet and satellite; when this ratio exceeds 0.5, escape is usually avoided. Instead, the satellite moves to an equilibrium in which the spin angular momentum of the planet is not transferred into the orbit of the satellite, but is transferred into the orbit of the planet itself. While the planet continues spinning faster than the satellite orbits, the satellite maintains a semi-major axis of approximately 0.41 Hill radii. These states are accompanied with modest satellite eccentricity near 0.1 and are found to be stable over long time-scales.
PubDate: Thu, 16 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3543
Issue No: Vol. 527, No. 3 (2023)
- Gertsenshtein–Zel’dovich effect: a plausible explanation for
fast radio bursts'-
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Pages: 4378 - 4387
Abstract: ABSTRACTWe present a novel model that may provide an interpretation for a class of non-repeating fast radio bursts (FRBs) – short ($\lt 1~\rm {s}$), bright ($0.1 - 1000~\rm {Jy}$) bursts of MHz–GHz frequency radio waves. The model has three ingredients – compact object, a progenitor with effective magnetic field strength around 1010 Gauss, and high-frequency (MHz–GHz) gravitational waves (GWs). At resonance, the energy conversion from GWs to electromagnetic waves occurs when GWs pass through the magnetosphere of such compact objects due to the Gertsenshtein–Zel’dovich effect. This conversion produces bursts of electromagnetic waves in the MHz–GHz range, leading to FRBs. Our model has three key features: (i) predict peak flux, (ii) can naturally explain the pulse width, and (iii) coherent nature of FRB. We thus conclude that the neutron star/magnetar could be the progenitor of FRBs. Further, our model offers a novel perspective on the indirection detection of GWs at high-frequency beyond detection capabilities. Thus, transient events like FRBs are a rich source for the current era of multi-messenger astronomy.
PubDate: Thu, 16 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3545
Issue No: Vol. 527, No. 3 (2023)
- A census of rotating radio transients at 150 MHz with the Irish LOFAR
station-
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Pages: 4397 - 4419
Abstract: ABSTRACTRotating radio transients (RRATs) are neutron stars that emit detectable radio bursts sporadically. They are statistically distinct in the neutron star population, in many observable properties, but by their nature are practically difficult to study in depth. In this paper, we present the results from 1408 h of observations of RRAT candidates using the Irish station of the Low Frequency Array (LOFAR) at 150 MHz. As of October 2022, this census involved observing 113 sources, leading to 29 detections which were then followed up systematically. Single-pulse emission was detected from 25 sources, and periodic emission from 14 sources. Eighteen sources were found to have emission behaviour that is not discussed in prior works using LOFAR instruments. Four novel or modified source periods have been determined, ranging from 1.5 to 3.9 s, and eight new or updated phase-coherent pulsar timing ephemerides have been produced using detected bursts. One unexpected single-pulse with a clearly-Galactic dispersion measure was detected as a part of this work but has not been re-detected in follow-up observations. Observations are ongoing to expand the number of observed sources and further characterize and improve ephemerides for the detected sources. This census has demonstrated the capability for international LOFAR stations to detect, monitor, and characterize a significant fraction of these unique sources.
PubDate: Fri, 22 Sep 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad2900
Issue No: Vol. 527, No. 3 (2023)
- Experimental atomic data of spectral lines – I. Cs, Ba, Pr, Nd, Sm,
Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Re, and Os in the 370–1000 nm
interval-
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Pages: 4440 - 4466
Abstract: ABSTRACTAtomic data are fundamental for plasma diagnostics in laboratory and astrophysics through spectroscopy. These data are extensively present in data bases for light elements, however incomplete for high-mass atoms. This paper presents the results of systematic spectroscopy of 17 elements with high Z, expected to be produced in kilonova events generated by neutron star mergers, whose spectral lines are not yet fully identified in stellar spectra and fusion devices. Experimental data are from échelle high-resolution (λ/Δλ = 60 000) spectroscopy of hollow cathode lamps obtained with the Catania Astrophysical Observatory Spectropolarimeter covering the 3700–10 000 Å range in a single exposure. A total of about 7700 spectral lines with energy level classification not previously listed in the NIST, Kurucz, and VALD data bases are here reported for neutral and singly ionized atomic transitions. For the spectral lines of any species, we report the measured wavelengths and their relative intensities. If possible, we also estimate the transition probabilities under the assumptions of optically thin emission and electric-dipole transitions. These are converted into oscillator strengths ready to be inserted in astrophysical data bases for spectral synthesis.
PubDate: Tue, 24 Oct 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3230
Issue No: Vol. 527, No. 3 (2023)
- NIGHT: A compact, near-infrared, high-resolution spectrograph to survey
helium in exoplanet systems-
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Pages: 4467 - 4482
Abstract: ABSTRACTAmong highly irradiated exoplanets, some have been found to undergo significant hydrodynamic expansion traced by atmospheric escape. To better understand these processes in the context of planetary evolution, we propose NIGHT (the Near-Infrared Gatherer of Helium Transits). NIGHT is a high-resolution spectrograph dedicated to surveying and temporally monitoring He i triplet absorption at 1083 nm in stellar and planetary atmospheres. In this paper, we outline our scientific objectives, requirements, and cost-efficient design. Our simulations, based on previous detections and modelling using the current exoplanet population, determine our requirements and survey targets. With a spectral resolution of 70 000 on a 2-m telescope, NIGHT can accurately resolve the helium triplet and detect 1 per cent peak absorption in 118 known exoplanets in a single transit. Additionally, it can search for 3σ temporal variations of 0.4 per cent in 66 exoplanets in-between two transits. These are conservative estimates considering the ongoing detections of transiting planets amenable to atmospheric characterization. We find that instrumental stability at 40 m s−1, less stringent than for radial velocity monitoring, is sufficient for transmission spectroscopy in He i. As such, NIGHT can utilize mostly off-the-shelf components, ensuring cost-efficiency. A fibre-fed system allows for flexibility as a visitor instrument on a variety of telescopes, making it ideal for follow-up observations after JWST or ground-based detections. Over a few years of surveying, NIGHT could offer detailed insights into the mechanisms shaping the hot Neptune desert and close-in planet population by significantly expanding the statistical sample of planets with known evaporating atmospheres. First light is expected in 2024.
PubDate: Thu, 26 Oct 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3285
Issue No: Vol. 527, No. 3 (2023)
- Neutron star mass in dark matter clumps
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Pages: 4483 - 4504
Abstract: ABSTRACTThis paper investigates a hypothesis proposed in previous research relating neutron star (NS) mass and its dark matter (DM) accumulation. As DM accumulates, NS mass decreases, predicting lower NS masses toward the Galactic centre. Due to limited NSs data near the Galactic centre, we examine NSs located within DM clumps. Using the CLUMPY code simulations, we determine the DM clumps distribution, with masses from 10 to 108 M⊙ and scales from 10−3 to 10 kpc. These clumps’ DM exhibit a peak at the centre, tapering toward the outskirts, resembling our Galaxy’s DM distribution. We analyse these DM clumps’ NS mass variations, considering diverse DM particle masses and galaxy types. We find relatively stable NS mass within 0.01 – 5 kpc from the clump centre. This stability supports the initial hypothesis, particularly for NSs located beyond 0.01 kpc from the clump centre, where NS mass reaches a plateau around 0.1 kpc. Nevertheless, NS mass near the clump’s periphery reveals spatial dependence: NS position within DM clumps influences its mass in Milky Way-type galaxies. Moreover, this dependence varies with the DM model considered. In summary, our study investigates the proposed link between NS mass and DM accumulation by examining NSs within DM clumps. While NS mass remains stable at certain distances from the clump centre, spatial dependencies arise near the clump’s outer regions, contingent on the specific DM model.
PubDate: Thu, 09 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3311
Issue No: Vol. 527, No. 3 (2023)
- The outer low-α disc of the Milky Way – I: evidence for the first
pericentric passage of Sagittarius'-
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Pages: 4505 - 4514
Abstract: ABSTRACTPhase-space data, chemistry, and ages together reveal a complex structure in the outer low-α disc of the Milky Way. The age-vertical velocity dispersion profiles beyond the Solar Neighbourhood show a jump at 6 Gyr for stars beyond the Galactic plane. Stars older than 6 Gyr are significantly hotter than younger stars. The chemistry and age histograms reveal a bump at [Fe/H] = −0.5, [α/Fe] = 0.1, and an age of 7.2 Gyr in the outer disc. Finally, viewing the stars beyond 13.5 kpc in the age-metallicity plane reveals a faint streak just below this bump, towards lower metallicities at the same age. Given the uncertainty in age, we believe these features are linked and suggest a pericentric passage of a massive satellite ∼6 Gyr ago that heated pre-existing stars, and led to a starburst in existing gas. New stars also formed from the metal-poorer infalling gas. The impulse approximation was used to characterize the interaction with a satellite, finding a mass of ∼1011 M⊙, and a pericentric position between 12 and 16 kpc. The evidence points to an interaction with the Sagittarius dwarf galaxy, likely its first pericentric passage.
PubDate: Fri, 03 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3344
Issue No: Vol. 527, No. 3 (2023)
- Detection and preliminary characterization of polluted white dwarfs from
Gaia EDR3 and LAMOST-
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Pages: 4515 - 4544
Abstract: ABSTRACTWe present a catalogue of 62 polluted white dwarfs observed by the 9th Low-Resolution Data Release of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST LRS DR9v1; R≈1800) and the Early Data Release 3 (EDR3) of the Gaia Mission. Among these stellar remnants, 30 are new discoveries with previously unknown traces of calcium pollution. To generate our catalogue, we used a data base of 4324 unique Gaia EDR3 white dwarf candidates with LAMOST LRS DR9v1 observations, many of which have been spectroscopically confirmed by other telescopes. For these stars, we developed a quantitative method to detect calcium absorption in their spectra between 3900–4000 Å, which we then validated through visual inspection and multiple literature cross-checks. Our catalogue provides the astrometric and photometric properties of the white dwarf candidates, incorporates supplementary data (e.g. Montreal White Dwarf Database, MWDD; PanSTARRS; the Hubble Space Telescope), and indicates the possibility of calcium pollution in their atmospheres. For our final sample of polluted white dwarfs, we also determine the main atmospheric properties of 23 sources with effective temperatures Teff ≤ 25 000 K and no existing calcium abundances in the MWDD. Our analysis represents a first step towards measuring the full atmospheric composition of these stars and learning about the bulk properties of their accreted material. As we venture into the era of wide-field spectroscopic surveys, our work highlights the importance of combining large-scale data bases for identifying and characterizing new polluted white dwarfs.
PubDate: Tue, 03 Oct 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3362
Issue No: Vol. 527, No. 3 (2023)
- Can the low-redshift Lyman alpha forest constrain AGN feedback models'
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Pages: 4545 - 4562
Abstract: ABSTRACTWe investigate the potential of low-redshift Lyman alpha (Lyα) forest for constraining active galactic nuclei (AGNs) feedback models by analysing the Illustris and IllustrisTNG simulation at z = 0.1. These simulations are ideal for studying the impact of AGN feedback on the intergalactic medium (IGM) as they share initial conditions with significant differences in the feedback prescriptions. Both simulations reveal that the IGM is significantly impacted by AGN feedback. Specifically, feedback is stronger in Illustris and results in reducing cool baryon fraction to 23 per cent relative to 39 per cent in IllustrisTNG. However, when comparing various statistics of Lyα forest such as 2D and marginalized distributions of Doppler widths and H i column density, line density, and flux power spectrum with real data, we find that most of these statistics are largely insensitive to the differences in feedback models. This lack of sensitivity arises because of the fundamental degeneracy between the fraction of cool baryons and the H i photoionization rate (ΓHI) as their product determines the optical depth of the Lyα forest. Since the ΓHI cannot be precisely predicted from first principles, it needs to be treated as a nuisance parameter adjusted to match the observed Lyα line density. After adjusting ΓHI, the distinctions in the considered statistics essentially fade away. Only the Lyα flux power spectrum at small spatial scales exhibits potentially observable differences, although this may be specific to the relatively extreme feedback model employed in Illustris. Without independent constraints on either ΓHI or cool baryon fraction, constraining AGN feedback with low-redshift Lyα forest will be very challenging.
PubDate: Wed, 08 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3374
Issue No: Vol. 527, No. 3 (2023)
- The black widow pulsar J1641+8049 in the optical, radio, and X-rays
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Pages: 4563 - 4572
Abstract: ABSTRACTPSR J1641+8049 is a 2 ms black widow pulsar with the 2.2 h orbital period detected in the radio and γ-rays. We performed new phase-resolved multiband photometry of PSR J1641+8049 using the OSIRIS instrument at the Gran Telescopio Canarias. The obtained data were analysed together with the new radio-timing observations from the Canadian Hydrogen Intensity Mapping Experiment (CHIME), the X-ray data from the Spectrum-RG/eROSITA all-sky survey, and all available optical photometric observations. An updated timing solution based on CHIME data is presented, which accounts for secular and periodic modulations in pulse dispersion. The system parameters obtained through the light-curve analysis, including the distance to the source 4.6–4.8 kpc and the orbital inclination 56–59 deg, are found to be consistent with previous studies. However, the optical flux of the source at the maximum brightness phase faded by a factor of ∼2 as compared to previous observations. Nevertheless, the face of the J1641+8049 companion remains one of the most heated (8000–9500 K) by a pulsar among the known black widow pulsars. We also report a new estimation on the pulsar proper motion of ≈2 mas yr−1, which yields a spin-down luminosity of ≈4.87 × 1034 erg s−1 and a corresponding heating efficiency of the companion by the pulsar of 0.3–0.7. The pulsar was not detected in X-rays implying its X-ray-luminosity was $\lesssim$3 × 1031 erg s−1 at the date of observations.
PubDate: Fri, 03 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3391
Issue No: Vol. 527, No. 3 (2023)
- Strong constraints on the gravitational law from Gaia DR3 wide binaries
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Pages: 4573 - 4615
Abstract: ABSTRACTWe test Milgromian dynamics (MOND) using wide binary stars (WBs) with separations of 2–30 kAU. Locally, the WB orbital velocity in MOND should exceed the Newtonian prediction by $\approx 20~{{\ \rm per\ cent}}$ at asymptotically large separations given the Galactic external field effect (EFE). We investigate this with a detailed statistical analysis of Gaia DR3 data on 8611 WBs within 250 pc of the Sun. Orbits are integrated in a rigorously calculated gravitational field that directly includes the EFE. We also allow line-of-sight contamination and undetected close binary companions to the stars in each WB. We interpolate between the Newtonian and Milgromian predictions using the parameter αgrav, with 0 indicating Newtonian gravity and 1 indicating MOND. Directly comparing the best Newtonian and Milgromian models reveals that Newtonian dynamics is preferred at 19σ confidence. Using a complementary Markov Chain Monte Carlo analysis, we find that $\alpha _{\rm {grav}} = -0.021^{+0.065}_{-0.045}$, which is fully consistent with Newtonian gravity but excludes MOND at 16σ confidence. This is in line with the similar result of Pittordis and Sutherland using a somewhat different sample selection and less thoroughly explored population model. We show that although our best-fitting model does not fully reproduce the observations, an overwhelmingly strong preference for Newtonian gravity remains in a considerable range of variations to our analysis. Adapting the MOND interpolating function to explain this result would cause tension with rotation curve constraints. We discuss the broader implications of our results in light of other works, concluding that MOND must be substantially modified on small scales to account for local WBs.
PubDate: Fri, 03 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3393
Issue No: Vol. 527, No. 3 (2023)
- Astroclimatic parameters characterization at lenghu site with ERA5
products-
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Pages: 4616 - 4631
Abstract: ABSTRACTAtmospheric turbulence and wind speed distributions are essential in determining the quality of astronomical sites and implementing adaptive optics systems. In this study, the optical turbulence with a general turbulence model and the wind speed characteristics at Lenghu are investigated by employing the 21-yr European Centre for Medium-Range Weather Forecasts’ fifth set of reanalysis (ERA5) data. The vertical distributions and seasonal behaviours of the wind speed and atmospheric turbulence are analysed. The wind speed values at 200 hPa pressure level (V200) are low in spring and summer except for June, and high in autumn and winter. The highest and lowest values of V200 at Lenghu are 39.93 m s−1 in September and 27.48 m s−1 in April, respectively. Additionally, atmospheric conditions are relatively stable above 20 km throughout the year. The locations of the peaks in the $C_n^2$ profiles correspond to the tropopause and the jet wind stream regions at the Lenghu site. Furthermore, the median seeing value from ERA5 is 0.72 arcsec, generally consistent with the statistically measured value of 0.75 arcsec. Moreover, the astronomical parameters (r0, θAO, and τAO) were initially provided at the Lenghu site. The median values of r0, ε, θAO, and τAO are 15.17 cm, 0.72 arcsec, 1.19 arcsec, and 2.83 ms, respectively, thus providing the potential reference for astronomical applications.
PubDate: Mon, 06 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3414
Issue No: Vol. 527, No. 3 (2023)
- A new derivation of the Hubble constant from γ-ray attenuation using
improved optical depths for the Fermi and CTA era-
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Pages: 4632 - 4642
Abstract: ABSTRACTWe present γ-ray optical-depth calculations from a recently published extragalactic background light (EBL) model built from multiwavelength galaxy data from the Hubble Space Telescope Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (HST/CANDELS). CANDELS gathers one of the deepest and most complete observations of stellar and dust emissions in galaxies. This model resulted in a robust derivation of the evolving EBL spectral energy distribution up to z ∼ 6, including the far-infrared peak. Therefore, the optical depths derived from this model will be useful for determining the attenuation of γ-ray photons coming from high-redshift sources, such as those detected by the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope, and for multi-TeV photons that will be detected from nearby sources by the future Cherenkov Telescope Array. From these newly calculated optical depths, we derive the cosmic γ-ray horizon and also measure the expansion rate and matter content of the Universe including an assessment of the impact of the EBL uncertainties. We find H0 = 62.4 $^{+4.1}_{-3.9}$ km s−1 Mpc−1 when fixing Ωm = 0.32, and H0 = 65.1 $^{+6.0}_{-4.9}$ km s−1 Mpc−1 and Ωm = 0.19 ± 0.08, when exploring these two parameters simultaneously.
PubDate: Mon, 06 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3425
Issue No: Vol. 527, No. 3 (2023)
- The contribution of supermassive black holes in stripped nuclei to the
supermassive black hole population of UCDs and galaxy clusters-
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Pages: 4643 - 4656
Abstract: ABSTRACTWe use the hydrodynamic EAGLE simulation to predict the numbers and masses of supermassive black holes in remnant nuclei of disrupted galaxies (stripped nuclei) and compare these to confirmed measurements of black holes in observed ultra-compact dwarf galaxies (UCDs). We find that black holes in stripped nuclei are consistent with the numbers and masses of those in observed UCDs. Approximately 50 per cent of stripped nuclei with M > 2 × 106 M⊙ should contain supermassive black holes. We further calculate how the presence of a black hole increases the dynamical mass of a stripped nucleus via the mass elevation ratio, Ψ defined as the ratio of the kinematically derived mass to the expected mass from stellar population synthesis. We find Ψsim$= 1.51^{+0.06}_{-0.04}$ for M > 107 M⊙ stripped nuclei, consistent with that of observed UCDs, which have Ψobs = 1.7 ± 0.2 above M > 107 M⊙. We also find that the mass elevation ratios of stripped nuclei with supermassive black holes can explain the observed number of UCDs with elevated mass-to-light ratios. Finally, we predict the relative number of massive black holes in stripped nuclei and galaxy nuclei and find that stripped nuclei should increase the number of black holes in galaxy clusters by 30 − 100 per cent, depending on the black hole occupation fraction of low-mass galaxies. We conclude that the population of supermassive black holes in UCDs represents a large and unaccounted-for portion of supermassive black holes in galaxy clusters.
PubDate: Mon, 06 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3428
Issue No: Vol. 527, No. 3 (2023)
- Evolution of helium triplet transits of close-in gas giants orbiting K
dwarfs-
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Pages: 4657 - 4676
Abstract: ABSTRACTAtmospheric escape in exoplanets has traditionally been observed using hydrogen Lyman-α and Hα transmission spectroscopy, but more recent detections have utilized the metastable helium triplet at 1083 nm. Since this feature is accessible from the ground, it offers new possibilities for studying atmospheric escape. Our goal is to understand how the observability of escaping helium evolves during the lifetime of a highly irradiated gas giant. We extend our previous work on 1D self-consistent hydrodynamic escape from hydrogen-only atmospheres as a function of planetary evolution to the first evolution-focused study of escaping hydrogen–helium atmospheres. Additionally, using these novel models we perform helium triplet transmission spectroscopy. We adapt our previous hydrodynamic escape model to now account for both hydrogen and helium heating and cooling processes and simultaneously solve for the population of helium in the triplet state. To account for the planetary evolution, we utilize evolving predictions of planetary radii for a close-in 0.3 MJup gas giant and its received stellar flux in X-ray, hard and soft extreme-ultraviolet (UV), and mid-UV wavelength bins assuming a K-dwarf stellar host. We find that the helium triplet signature diminishes with evolution. Our models suggest that young (≲ 150 Myr), close-in gas giants (∼1 to 2 RJup) should produce helium 1083 nm transit absorptions of $\sim 4~{{\ \rm per\ cent}}$ or $\sim 7~{{\ \rm per\ cent}}$, for a slow- or fast-rotating K dwarf, respectively, assuming a 2 per cent helium abundance.
PubDate: Tue, 07 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3432
Issue No: Vol. 527, No. 3 (2023)
- Machine learning-based photometric classification of galaxies, quasars,
emission-line galaxies, and stars-
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Pages: 4677 - 4689
Abstract: ABSTRACTThis paper explores the application of machine learning methods for classifying astronomical sources using photometric data, including normal and emission line galaxies (ELGs; starforming, starburst, AGN, broad-line), quasars, and stars. We utilized samples from Sloan Digital Sky Survey (SDSS) Data Release 17 (DR17) and the ALLWISE catalogue, which contain spectroscopically labelled sources from SDSS. Our methodology comprises two parts. First, we conducted experiments, including three-class, four-class, and seven-class classifications, employing the Random Forest (RF) algorithm. This phase aimed to achieve optimal performance with balanced data sets. In the second part, we trained various machine learning methods, such as k-nearest neighbours (KNN), RF, XGBoost (XGB), voting, and artificial neural network (ANN), using all available data based on promising results from the first phase. Our results highlight the effectiveness of combining optical and infrared features, yielding the best performance across all classifiers. Specifically, in the three-class experiment, RF and XGB algorithms achieved identical average F1 scores of 98.93 per cent on both balanced and unbalanced data sets. In the seven-class experiment, our average F1 score was 73.57 per cent. Using the XGB method in the four-class experiment, we achieved F1 scores of 87.9 per cent for normal galaxies (NGs), 81.5 per cent for ELGs, 99.1 per cent for stars, and 98.5 per cent for quasars (QSOs). Unlike classical methods based on time-consuming spectroscopy, our experiments demonstrate the feasibility of using automated algorithms on carefully classified photometric data. With more data and ample training samples, detailed photometric classification becomes possible, aiding in the selection of follow-up observation candidates.
PubDate: Wed, 08 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3436
Issue No: Vol. 527, No. 3 (2023)
- The eROSITA final equatorial-depth survey (eFEDS): host-galaxy
demographics of X-ray AGNs with Subaru Hyper Suprime-Cam-
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Pages: 4690 - 4704
Abstract: ABSTRACTWe investigate the physical properties, such as star-forming activity, disc versus bulge nature, galaxy size, and obscuration of 3811 SRG/eROSITA-detected AGNs at 0.2 < z < 0.8 in the eFEDS field. Using Subaru Hyper Suprime-Cam imaging data in the grizy bands, we measure the structural and stellar properties for their host galaxies by performing a 2D AGN-host image decomposition. We find that (1) AGNs can contribute significantly to the total optical light down to ${\rm log}\, L_{\rm X}\sim 42.5\ \rm erg\ s^{-1}$, thus ignoring the AGN component can significantly bias the structural measurements; (2) AGN hosts are predominately star-forming galaxies at ${\rm log}\, \mathcal {M}_\star \lesssim 11.3\, \mathrm{M}_\odot$; (3) the bulk of AGNs (64 per cent) reside in galaxies with significant stellar discs ($\rm S\acute{e}rsic$ index n < 2), while their host galaxies become increasingly bulge dominated (n ∼ 4) and quiescent at ${\rm log}\, \mathcal {M}_\star \gtrsim 11.0\, \mathrm{M}_\odot$; (4) the size–stellar mass relation of AGN hosts tends to lie between that of inactive (i.e. non-AGN) star-forming, and quiescent galaxies, suggesting that the physical mechanism responsible for building the central stellar density also efficiently fuel the black hole growth; (5) the hosts of X-ray unobscured AGNs are biased towards face-on systems, suggesting that some of the obscuration of the nuclei could come from galaxy-scale gas and dust. This will bias against the detection of unobscured AGNs in gas-rich star-forming galaxies, which may partly account for the deficiency of star-forming discs as host galaxies for the most massive AGNs (missing star-forming fraction up to $\sim 40{{\ \rm per\ cent}}$). Our results are consistent with a scenario in which the black hole and galaxy transform in structure and star-forming activity while grow in mass, as desired to establish the local $\mathcal {M}_{\rm BH}-\mathcal {M}_{\rm bulge}$ relation.
PubDate: Tue, 14 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3438
Issue No: Vol. 527, No. 3 (2023)
- Are the fates of supermassive black holes and galaxies determined by
individual mergers, or by the properties of their host haloes'-
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Pages: 4705 - 4716
Abstract: ABSTRACTThe fates of massive galaxies are tied to the evolution of their central supermassive black holes (BHs), due to the influence of AGN feedback. Correlations within simulated galaxy populations suggest that the masses of BHs are governed by properties of their host dark matter haloes, such as the binding energy and assembly time, at a given halo mass. However, the full picture must be more complex, as galaxy mergers have also been shown to influence the growth of BHs and the impact of AGN. In this study, we investigate this problem through a controlled experiment, using the genetic modification technique to adjust the assembly history of a Milky Way-like galaxy simulated with the EAGLE model. We change the halo assembly time (and hence the binding energy) in the absence of any disruptive merger events, and find little change in the integrated growth of the BH. We attribute this to the angular momentum support provided by a galaxy disc, which reduces the inflow of gas towards the BH and effectively decouples the BH’s growth from the halo’s properties. Introducing major mergers into the assembly history disrupts the disc, causing the BH to grow ≈4 × more massive and inject feedback that reduces the halo baryon fraction by a factor of ≈2 and quenches star formation. Merger events appear essential to the diversity in BH masses in EAGLE, and we also show that they increase the halo binding energy; correlations between these quantities may therefore be the result of merger events.
PubDate: Tue, 14 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3456
Issue No: Vol. 527, No. 3 (2023)
- Mitigating the effect of 1/f noise on the detection of the
H i intensity mapping power spectrum from single-dish measurements-
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Pages: 4717 - 4729
Abstract: ABSTRACTWe present and compare several methods to mitigate time-correlated (1/f) noise within the H i intensity mapping component of the MeerKAT Large Area Synoptic Survey (MeerKLASS). By simulating scan strategies, the H i signal, foreground emissions, white and correlated noise, we assess the ability of various data-processing pipelines to recover the power spectrum of H i brightness temperature fluctuations. We use MeerKAT pilot data to assess the level of 1/f noise expected for the MeerKLASS survey and use these measurements to create realistic levels of time-correlated noise for our simulations. We find the time-correlated noise component within the pilot data to be between 10 and 20 times higher than the white noise level at the scale of $k = 0.04 \, {\rm {Mpc}}^{-1}$. Having determined that the MeerKAT 1/f noise is partially correlated across all the frequency channels, we employ Singular Value Decomposition (SVD) as a technique to remove both the 1/f noise and Galactic foregrounds but find that over-cleaning results in the removal of H i power at large (angular and radial) scales; a power loss of 40 per cent is seen for a 3-mode SVD clean at the scale of $k = 0.04 \, {\rm {Mpc}}^{-1}$. We compare the impact of map-making using weighting by the full noise covariance (i.e. including a 1/f component), as opposed to just a simple unweighted binning, finding that including the time-correlated noise information reduces the excess power added by 1/f noise by up to 30 per cent.
PubDate: Wed, 08 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3457
Issue No: Vol. 527, No. 3 (2023)
- Three new identifications of extended UV emission around AGB stars
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Pages: 4730 - 4738
Abstract: ABSTRACTAsymptotic giant branch (AGB) stars experience heavy episodes of mass-loss through a slow stellar wind during the thermal pulse phase that form large, pc-scale structures around them. As the AGB stellar wind interacts with the interstellar medium (ISM), the otherwise isotropic ejecta gets distorted, resulting in asymmetric shapes, bow-shock structures and, in the case of fast motion relative to the surrounding ISM, extended wakes and tails as unexpectedly detected in GALEX ultraviolet (UV) images of o Cet, also known as Mira. Since that discovery, another fourteen AGB stars have been reported to exhibit extended UV emission around them. Here, we present the discovery of extended UV emission around another three AGB stars, namely R For, R Hor, and DM Tuc. The analysis of the overall properties of the regions of extended UV emission indicates that these are preferentially detected in closer AGB stars far away from the Galactic plane, i.e. sources less extincted. Faster AGB stars tend to have more elongated shapes, with bow-shocks and wakes or tails of material, while AGB stars farther away from the Galactic plane tend to be surrounded by larger regions of UV emission.
PubDate: Wed, 15 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3458
Issue No: Vol. 527, No. 3 (2023)
- First detection of soft-lag in GRS 1915 + 105 at HFQPO using
AstroSat observations-
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Pages: 4739 - 4750
Abstract: ABSTRACTThe Galactic black hole GRS 1915 + 105 exhibits generic high-frequency quasi-periodic oscillations (HFQPOs) at ∼ 67 Hz only during the radio-quiet ‘softer’ variability classes. We present the time-lag properties associated with HFQPOs in the wide energy band (3–60 keV) using all AstroSat observations. For the first time, we detect soft-lag of 6–25 keV band w.r.t. 3–6 keV band for all ‘softer’ variability classes (δ, ω, κ, and γ). Moreover, our findings reveal that soft-lag increases gradually with the energy of the photons. These features are entirely opposite to the previous report of hard-lag obtained with the RXTE observations. The energy-dependent time-lag study exhibits a maximum soft-lag of ∼ 3 and ∼ 2.5 ms for the δ and ω classes, respectively, whereas the κ and γ classes both exhibit a maximum soft-lag of ∼2.1 ms. We find a coherent lag-energy correlation for all four variability classes, where the amplitude of soft-lag increases with energy and becomes maximum at ∼18 keV. We interpret this observed soft-lag as the reflection of hard photons in the ‘cooler’ accretion disc. A generic lag-rms correlation implies that the soft-lag increases with the rms amplitude of the HFQPO. The wideband (0.7–50 keV) spectral study suggests a high value of the optical depth (τ ∼ 6.90–12.55) of the Comptonized medium and the magnitude of the soft-lag increases linearly with the increase in optical depth (τ). We explain the observed time-lag features at the HFQPOs in the context of a possible accretion disc scenario.
PubDate: Thu, 09 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3465
Issue No: Vol. 527, No. 3 (2023)
- Correction to: Star formation in CALIFA survey perturbed galaxies – III.
Stellar and ionized-gas kinematic distributions-
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Pages: 4751 - 4751
Abstract: This is a correction to: A. Morales-Vargas, J. P. Torres-Papaqui, F. F. Rosales-Ortega, M. Chow-Martínez, R. A. Ortega-Minakata, A. C. Robleto-Orús, (the CALIFA Survey Collaboration), Star formation in CALIFA survey perturbed galaxies – III. Stellar and ionized-gas kinematic distributions, Monthly Notices of the Royal Astronomical Society, Volume 526, Issue 2, December 2023, Pages 2863–2879, https://doi.org/10.1093/mnras/stad2865.
PubDate: Tue, 28 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3479
Issue No: Vol. 527, No. 3 (2023)
- Effects of general relativity on habitable zone particles under the
presence of an inner perturber around solar-mass stars-
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Pages: 4752 - 4762
Abstract: ABSTRACTWe analyse the role of the general relativity (GR) on the nodal librations of test particles located at the Habitable Zone (HZ) around a solar-mass star, which evolve under the influence of an eccentric planetary-mass perturber with a semimajor axis of 0.1 au. Based on a secular Hamiltonian up to quadrupole level, we derive analytical criteria that define the nodal libration region of an HZ particle as a function of its eccentricity e2 and inclination i2, and the mass m1 and the eccentricity e1 of the perturber. We show that an HZ particle can experience nodal librations with orbital flips or purely retrograde orbits for any m1 and e1 by adopting a suitable combination of e2 and i2. For m1 < 0.84 MJup, the greater the m1 value, the smaller the e2 value above which nodal librations are possible for a given e1. For m1 > 0.84 MJup, an HZ test particle can undergo nodal librations for any e2 and appropriate values of e1 and i2. The same correlation between m1 and e2 is obtained for nodal librations with orbital flips, but a mass limit for m1 of 1.68 MJup is required in this case. Moreover, the more massive the inner perturber, the greater the nodal libration region associated with orbital flips in the (e1, i2) plane for a given value of e2. Finally, we find good agreements between the analytical criteria and results from N-body simulations for values of m1 ranging from Saturn-like planets to super-Jupiters.
PubDate: Mon, 13 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3491
Issue No: Vol. 527, No. 3 (2023)
- Constraints on redshifts of blazars from extragalactic background light
attenuation using Fermi-LAT data-
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Pages: 4763 - 4776
Abstract: ABSTRACTThe extragalactic high-energy γ-ray sky is dominated by blazars, which are active galactic nuclei with their jets pointing towards us. Distance measurements are of fundamental importance yet for some of these sources are challenging because any spectral signature from the host galaxy may be outshone by the non-thermal emission from the jet. In this paper, we present a method to constrain redshifts for these sources that relies only on data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. This method takes advantage of the signatures that the pair-production interaction between photons with energies larger than approximately 10 GeV and the extragalactic background light leaves on γ-ray spectra. We find upper limits for the distances of 303 γ-ray blazars, classified as 157 BL Lacertae objects, 145 of uncertain class, and 1 flat-spectrum-radio quasar, whose redshifts are otherwise unknown. These derivations can be useful for planning observations with imaging atmospheric Cherenkov telescopes and also for testing theories of supermassive black hole evolution. Our results are applied to estimate the detectability of these blazars with the future Cherenkov Telescope Array, finding that at least 21 of them could be studied in a reasonable exposure of 20 h.
PubDate: Mon, 13 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3492
Issue No: Vol. 527, No. 3 (2023)
- WInDI: a Warp-Induced Dust Instability in protoplanetary discs
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Pages: 4777 - 4789
Abstract: ABSTRACTWe identify a new dust instability that occurs in warped discs. The instability is caused by the oscillatory gas motions induced by the warp in the bending wave regime. We first demonstrate the instability using a local 1D (vertical) toy model based on the warped shearing box coordinates and investigate the effects of the warp magnitude and dust Stokes number on the growth of the instability. We then run 3D smoothed particle hydrodynamics (SPH) simulations and show that the instability is manifested globally by producing unique dust structures that do not correspond to gas pressure maxima. The 1D and SPH analysis suggest that the instability grows on dynamical time-scales and hence is potentially significant for planet formation.
PubDate: Mon, 13 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3494
Issue No: Vol. 527, No. 3 (2023)
- On the core-collapse supernova explanation for LAMOST
J1010 + 2358-
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Pages: 4790 - 4796
Abstract: ABSTRACTLow-metallicity very massive stars with an initial mass of ∼140–$260\, \mathrm{M}_\odot$ are expected to end their lives as pair-instability supernovae (PISNe). The abundance pattern resulting from a PISN differs drastically from regular core-collapse supernova (CCSN) models and is expected to be seen in very metal-poor (VMP) stars of [Fe/H] ≲ −2. Despite the routine discovery of many VMP stars, the unique abundance pattern expected from PISNe has not been unambiguously detected. The recently discovered VMP star LAMOST J1010 + 2358, however, shows a peculiar abundance pattern that is remarkably well fit by a PISN, indicating the potential first discovery of a bonafide star born from gas polluted by a PISN. In this paper, we study the detailed nucleosynthesis in a large set of models of CCSN of Pop III and Pop II star of metallicity [Fe/H] = −3 with masses ranging from 12 to $30\, \mathrm{M}_\odot$. We find that the observed abundance pattern in LAMOST J1010 + 2358 can be fit at least equally well by CCSN models of ∼12–$14\, \mathrm{M}_\odot$ that undergo negligible fallback following the explosion. The best-fitting CCSN models provide a fit that is even marginally better than the best-fitting PISN model. We conclude the measured abundance pattern in LAMOST J1010 + 2358 could have originated from a CCSN and therefore cannot be unambiguously identified with a PISN given the set of elements measured in it to date. We identify key elements that need to be measured in future detections in stars like LAMOST J1010 + 2358 that can differentiate between CCSN and PISN origin.
PubDate: Wed, 15 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3498
Issue No: Vol. 527, No. 3 (2023)
- The origin of the metallicity distributions of the NE and W stellar
shelves in the Andromeda Galaxy-
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Pages: 4797 - 4805
Abstract: ABSTRACTTidal streams and stellar shells are naturally formed in galaxy interactions and mergers. The Giant Stellar Stream (GSS), the North-East (NE), and Western (W) stellar shelves observed in Andromeda Galaxy (M31) are examples of these structures and were formed through the merger of M31 and a satellite galaxy. Recent observational papers have provided strong evidence that the shells and GSS originate from a single progenitor. In this paper, we investigate the formation of these two stellar shelves and the detailed nature of their relationship to the GSS. We present numerical simulations of tidal disruption of a satellite galaxy assuming that it is a progenitor of the GSS and the shell system. We represent the progenitor as a dwarf spheroidal galaxy with the stellar mass of 109 M⊙ and evolve its merger with M31 for 3 Gyr to reproduce the chemodynamical properties of the NE and W shelves. We find that an initial metallicity of the progenitor with a negative radial gradient of ΔFeH = −0.3 ± 0.2 successfully reproduces observed metallicities of the NE, W shelves, and the GSS, showing that all these structures can originate from the same merger event.
PubDate: Thu, 16 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3503
Issue No: Vol. 527, No. 3 (2023)
- Eruptive novae in symbiotic systems
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Pages: 4806 - 4820
Abstract: ABSTRACTWe conduct numerical simulations of multiple nova eruptions in detached, widely separated symbiotic systems that include an asymptotic giant branch (AGB) companion to investigate the impact of white dwarf (WD) mass and binary separation on the evolution of the system. The accretion rate is determined using the Bondi–Hoyle–Lyttleton method, incorporating orbital momentum loss caused by factors such as gravitational radiation, magnetic braking, and drag. The WD in such a system accretes matter coming from the strong wind of an AGB companion until it finishes shedding its envelope. This occurs on an evolutionary time-scale of ≈3 × 105 yr. Throughout all simulations, we use a consistent AGB model with an initial mass of 1.0 M⊙ while varying the WD mass and binary separation, as they are the critical factors influencing nova eruption behaviour. We find that the accretion rate fluctuates between high and low rates during the evolutionary period, significantly impacted by the AGB’s mass loss rate. We show that unlike novae in cataclysmic variables, the orbital period may either increase or decrease during evolution, depending on the model, while the separation consistently decreases. Furthermore, we have identified cases in which the WDs produce weak, non-ejective novae and experience mass gain. This suggests that provided the accretion efficiency can be achieved by a more massive WD and maintained for long enough, they could potentially serve as progenitors for type Ia supernovae.
PubDate: Wed, 15 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3507
Issue No: Vol. 527, No. 3 (2023)
- Compact groups from semi-analytical models of galaxy formation – V.
Their assembly channels as a function of the environment-
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Pages: 4821 - 4833
Abstract: ABSTRACTWe delved into the assembly pathways and environments of compact groups (CGs) of galaxies using mock catalogues generated from semi-analytical models (SAMs) on the Millennium simulation. We investigate the ability of SAMs to replicate the observed CG environments and whether CGs with different assembly histories tend to inhabit specific cosmic environments. We also analyse whether the environment or the assembly history is more important in tailoring CG properties. We find that about half of the CGs in SAMs are non-embedded systems, 40 per cent are inhabiting loose groups or nodes of filaments, while the rest distribute evenly in filaments and voids, in agreement with observations. We observe that early-assembled CGs preferentially inhabit large galaxy systems ($\sim 60~{{\ \rm per\ cent}}$), while around 30 per cent remain non-embedded. Conversely, lately formed CGs exhibit the opposite trend. We also obtain that lately formed CGs have lower velocity dispersions and larger crossing times than early-formed CGs, but mainly because they are preferentially non-embedded. Those lately formed CGs that inhabit large systems do not show the same features. Therefore, the environment plays a strong role in these properties for lately formed CGs. Early-formed CGs are more evolved, displaying larger velocity dispersions, shorter crossing times, and more dominant first-ranked galaxies, regardless of the environment. Finally, the difference in brightness between the two brightest members of CGs is dependent only on the assembly history and not on the environment. CGs residing in diverse environments have undergone varied assembly processes, making them suitable for studying their evolution and the interplay of nature and nurture on their traits.
PubDate: Wed, 15 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3512
Issue No: Vol. 527, No. 3 (2023)
- The taurid resonant swarm at mercury
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Pages: 4834 - 4846
Abstract: ABSTRACTIt has previously been suggested that ejection and vaporization of Hermean surface material by meteoroids from comet 2P/Encke causes a seasonal enhancement in Mercury’s Ca exosphere observed by the NASA MESSENGER spacecraft in 2011-2015. The ESA/JAXA BepiColoen mission, now routeute to Mercury, will likely provide the next set of observational tests of this hypothesis after it enters orbit in late 2025. Here we study the Taurid Swarm Complex (IAU Code: STS), a population of cm-sized or larger meteoroids from Encke’s comet that encounters the Earth every 3–7 yr. Through analysis of previous observations of the STS and many-particle numerical simulations, we study the circumstances of encounters between the STS and Mercury and find that, unlike the Earth where STS encounters is observed in some years but not others, each time the STS is at perihelion it encounters Mercury on three consecutive planetary orbits. We further predict that the STS will encounter this planet during the early stages of BepiColombo’s orbital mission. The temporal flux profile during each encounter will be broad and possibly double-peaked with total number fluence 0.4×–1.7× that of the sporadic fluence for >1 kg meteoroids on the sub-radiant hemisphere of the planet. The meteoroid arrival direction and sub-radiant point strongly depend on True Anomaly Angle, switching from mainly nightside to mainly dayside impacts as Mercury travels from orbital perihelion to aphelion. Our predictions may be used to create detailed models of exosphere generation by Encke stream meteoroids.
PubDate: Wed, 15 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3516
Issue No: Vol. 527, No. 3 (2023)
- 3D hydrodynamics simulations of a 3 M⊙ core helium burning
star-
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Pages: 4847 - 4862
Abstract: ABSTRACTThe inner structure of core helium burning (CHeB) stars remains uncertain due to the yet unknown nature of mixing at the boundary of their cores. Large convective cores beyond a bare Schwarzschild model are favoured both from theoretical arguments and from asteroseismological constraints. However, the exact nature of this extra mixing, and in particular the possible presence of semiconvective layers, is still debated. In this work, we approach this problem through a new avenue by performing the first full-sphere 3D hydrodynamics simulations of the interiors of CHeB stars. We use the ppmstar explicit gas dynamics code to simulate the inner 0.45$\, {\rm M}_{\odot }$ of a 3 M⊙ CHeB star. Simulations are performed using different Cartesian grid resolutions (7683, 11523, and 17283) and heating rates. We use two different initial states, one based on mesas's predictive mixing scheme (which significantly extends the core beyond the Schwarzschild boundary) and one based on the convective premixing approach (which exhibits a semiconvective interface). The general behaviour of the flow in the convective core and in the stable envelope (where internal gravity waves are observed) is consistent with our recent simulations of core convection in massive main-sequence stars, and so are the various luminosity scaling relations. The semiconvective layers are dominated by strong internal gravity waves that do not produce measurable species mixing, but overshooting motions from the convective core gradually homogenize the semiconvective interface. This process can possibly completely erase the semiconvective layers, which would imply that CHeB stars do not harbour a semiconvection zone.
PubDate: Wed, 15 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3518
Issue No: Vol. 527, No. 3 (2023)
- Warp and flare of the old Galactic disc as traced by the red clump stars
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Pages: 4863 - 4873
Abstract: ABSTRACTOur study aims to investigate the outer disc structure of the Milky Way Galaxy using the red clump (RC) stars. We analysed the distribution of the largest sample of RC stars to date, homogeneously covering the entire Galactic plane in the range of 40° ≤ ℓ ≤ 340° and −10° ≤ b ≤ +10°. This sample allows us to model the RC star distribution in the Galactic disc to better constrain the properties of the flare and warp of the Galaxy. Our results show that the scale length of the old stellar disc weakly depends on azimuth, with an average value of 1.95 ± 0.26 kpc. On the other hand, a significant disc flaring is detected, where the scale height of the disc increases from 0.38 kpc in the solar neighbourhood to ∼2.2 kpc at R ≈15 kpc. The flare exhibits a slight asymmetry, with ∼1 kpc more scale height below the Galactic plane as compared to the Northern flare. We also confirm the warping of the outer disc, which can be modelled with Zw = (0.0057 ± 0.0050) [R − (7358 ± 368)(pc)]1.40 ± 0.09sin (ϕ − (− 2${_{.}^{\circ}}$03 ± 0${_{.}^{\circ}}$18)). Our analysis reveals a noticeable north–south asymmetry in the warp, with a greater amplitude observed in the southern direction compared to the northern. Comparing our findings with younger tracers from the literature, we observe an age dependency of both the flare and warp. An increase in flare strength with age suggests the secular evolution of the disc as the preferred mechanism for forming the flare. The increase of the maximum warp amplitude with age indicates that the warp dynamics could be the possible cause of the variation in the warp properties with age.
PubDate: Wed, 15 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3525
Issue No: Vol. 527, No. 3 (2023)
- An analytical late–Universe approach to the weaving of modern
cosmology-
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Pages: 4874 - 4888
Abstract: ABSTRACTCombining cosmological probes has consolidated the standard cosmological model with per cent precision, but some tensions have recently emerged when certain parameters are estimated from the local or primordial Universe. The origin of this behaviour is still under debate; however, it is crucial to study as many probes as possible to cross-check the results with independent methods and provide additional pieces of information to the cosmological puzzle. In this work, by combining several late-Universe probes (0 < z < 10), namely, Type Ia supernovae, baryon acoustic oscillations, cosmic chronometers, and gamma-ray bursts, we aim to derive cosmological constraints independently of local or early-Universe anchors. To test the standard cosmological model and its various extensions, considering an evolving dark energy equation of state and the curvature as a free parameter, we analyse each probe individually and all their possible permutations. Assuming a flat Lambda cold dark matter (ΛCDM) model, the full combination of probes provides $H_0=67.2^{+3.4}_{-3.2}$ km s−1 Mpc−1 and Ωm = 0.325 ± 0.015 [68 per cent confidence level (C.L.)]. Considering a flat wCDM model, we measure $w_0=-0.91^{+0.07}_{-0.08}$ (68 per cent C.L.), while by relaxing the flatness assumption (ΛCDM model, 95 per cent C.L.) we obtain $\Omega _k=0.125^{+0.167}_{-0.165}$. Finally, we analytically characterize the degeneracy directions and the relative orientation of the probes’ contours. By calculating the figure-of-merit, we quantify the synergies among independent methods, estimate the constraining power of each probe, and identify which provides the best contribution to the inference process. Pending the new cosmological surveys, this study confirms the exigency for new emerging probes in the landscape of modern cosmology.
PubDate: Thu, 16 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3546
Issue No: Vol. 527, No. 3 (2023)
- Orbit injection of planet-crossing asteroids
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Pages: 4889 - 4898
Abstract: ABSTRACTSolar system Centaurs originate in trans-Neptunian space from where planet orbit crossing events inject their orbits inside the giant planets’ domain. Here, we examine this injection process in the three-body problem by studying the orbital evolution of trans-Neptunian asteroids located at Neptune’s collision singularity as a function of the Tisserand invariant, T. Two injection modes are found, one for T > 0.1, or equivalently prograde inclinations far from the planet, where unstable motion dominates injection, and another for T ≤ 0.1, or equivalently polar and retrograde inclinations far from the planet, where stable motion dominates injection. The injection modes are independent of the initial semimajor axis and the dynamical time at the collision singularity. The simulations uncovered a region in the polar corridor where the dynamical time exceeds the Solar system’s age suggesting the possibility of long-lived primordial polar trans-Neptunian reservoirs that supply Centaurs to the giant planets’ domain.
PubDate: Mon, 20 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3570
Issue No: Vol. 527, No. 3 (2023)
- ExoMol line lists – LIII: empirical rovibronic spectra of yttrium
oxide-
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Pages: 4899 - 4912
Abstract: ABSTRACTEmpirical line lists BRYTS for the open shell molecule 89Y16O (yttrium oxide) and its isotopologues are presented. The line lists cover the six lowest electronic states: $X\, {}^{2}\Sigma ^{+}$, $A\, {}^{2}\Pi$, $A^{\prime }\, {}^{2}\Delta$, $B\, {}^{2}\Sigma ^{+}$, $C\, {}^{2}\Pi$, and $D\, {}^{2}\Sigma ^{+}$ up to 60 000 cm−1 (<0.167 $\mu$m) for rotational excitation up to J = 400.5. An ab initio spectroscopic model consisting of potential energy curves (PECs), spin–orbit, and electronic angular momentum couplings is refined by fitting to experimentally determined energies of YO, derived from published YO experimental transition frequency data. The model is complemented by empirical spin-rotation and Λ-doubling curves and ab initio dipole moment and transition dipole moment curves computed using multireference configuration interaction (MRCI). The ab initio PECs computed using the complete basis set limit extrapolation and the coupled-cluster CCSD(T) method with its higher quality provide an excellent initial approximation for the refinement. Non-adiabatic coupling curves for two pairs of states of the same symmetry A/C and B/D are computed using a state-averaged complete active space self-consistant field theory (CASSCF) and used to build diabatic representations for the $A\, {}^{2}\Pi$, $C\, {}^{2}\Pi$, $B\, {}^{2}\Sigma ^{+}$, and $D\, {}^{2}\Sigma ^{+}$ curves. The experimentally derived energies of 89Y16O utilized in the fit are used to replace the corresponding calculated energy values in the BRYTS line list. Simulated spectra of YO show excellent agreement with the experiment, where it is available. Calculated lifetimes of YO are tuned to agree well with the experiment, where available. The BRYTS YO line lists are available from the ExoMol database (www.exomol.com).
PubDate: Sat, 21 Oct 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3225
Issue No: Vol. 527, No. 3 (2023)
- Time variation of fine-structure constant constrained by [O iii]
emission-lines at 1.1 < z < 3.7-
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Pages: 4913 - 4935
Abstract: ABSTRACT[O iii] λλ4960,5008 doublet are often the strongest narrow emission lines in starburst galaxies and quasi-stellar objects (QSOs), and thus are a promising probe to possible variation of the fine-structure constant α over cosmic time. Previous such studies using QSOs optical spectra were limited to z < 1. In this work, we constructed a sample of 40 spectra of Ly α emitting galaxies (LAEs) and a sample of 46 spectra of QSOs at 1.09 < z < 3.73 using the VLT/X-Shooter near-infrared spectra publicly available. We measured the wavelength ratios of the two components of the spin-orbit doublet and accordingly calculated α(z) using two methods. Analysis on all of the 86 spectra yielded Δα/α = (− 3 ± 6) × 10−5 with respect to the laboratory α measurements, consistent with no variation over the explored time interval. If assuming a uniform variation rate, we obtained α−1dα/dt = (− 3 ± 6) × 10−15 yr−1 within the last 12 Gyr. Extensive tests indicate that α variation could be better constrained using starburst galaxies’ spectra than using QSO spectra in future studies.
PubDate: Mon, 23 Oct 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3240
Issue No: Vol. 527, No. 3 (2023)
- TransitFit: combined multi-instrument exoplanet transit fitting for JWST,
HST, and ground-based transmission spectroscopy studies-
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Pages: 4936 - 4954
Abstract: ABSTRACTWe present transitfit11, a package designed to fit exoplanetary transit light curves. transitfit offers multi-epoch, multi-wavelength fitting of multi-telescope transit data. transitfit allows per-telescope detrending to be performed simultaneously with transit parameter fitting, including custom detrending. Host limb darkening can be fitted using prior conditioning from stellar atmosphere models. We demonstrate transitfit in a number of contexts. We model multi-telescope broad-band optical data from the ground-based SPEARNET survey of the low-density hot-Neptune WASP-127b and compare results to a previously published higher spectral resolution GTC/OSIRIS transmission spectrum. Using transitfit, we fit 26 transit epochs by TESS to recover improved ephemeris of the hot-Jupiter WASP-91b and a transit depth determined to a precision of 111 ppm. We use transitfit to conduct an investigation into the contested presence of TTV signatures in WASP-126b using 180 transits observed by TESS, concluding that there is no statistically significant evidence for such signatures from observations spanning 27 TESS sectors. We fit HST observations of WASP-43 b, demonstrating how transitfit can use custom detrending algorithms to remove complex baseline systematics. Lastly, we present a transmission spectrum of the atmosphere of WASP-96b constructed from simultaneous fitting of JWST NIRISS Early Release Observations and archive HST WFC3 transit data. The transmission spectrum shows generally good correspondence between spectral features present in both data sets, despite very different detrending requirements.
PubDate: Fri, 03 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3353
Issue No: Vol. 527, No. 3 (2023)
- Modelling reflected polarized light from close-in giant exoplanet WASP-96b
using PolHEx (Polarization of hot exoplanets)-
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Pages: 4955 - 4982
Abstract: ABSTRACTWe present the Polarization of Hot Exoplanets (PolHEx) code for modelling the total flux (F) and degree of linear Polarization (P) of light spectra reflected by close-in, tidally locked exoplanets. We use the output from a global climate model (GCM) combined with a kinetic cloud model of hot Jupiter WASP-96b as a base to investigate effects of atmospheric longitudinal-latitudinal inhomogeneities on these spectra. We model F and P-spectra as functions of wavelength and planet orbital phase for various model atmospheres. We find different materials and sizes of cloud particles to impact the reflected flux F, and particularly the linear Polarization state P. A range of materials are used to form inhomogeneous mixed-material cloud particles (Al2O3, Fe2O3, Fe2SiO4, FeO, Fe, Mg2SiO4, MgO, MgSiO3, SiO2, SiO, TiO2), with Fe2O3, Fe, and FeO the most strongly absorbing species. The cloud particles near the relatively cool morning terminator are expected to have smaller average sizes and a narrower size distribution than those near the warmer evening terminator, which leads to different reflected spectra at the respective orbital phases. We also find differences in the spectra of F and P as functions of orbital phase for irregularly or spherically shaped cloud particles. This work highlights the importance of including Polarization in models and future observations of the reflection spectra of exoplanets.
PubDate: Fri, 03 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3413
Issue No: Vol. 527, No. 3 (2023)
- The tidal excitation of r modes in a solar-type star orbited by a giant
planet companion and the effect on orbital evolution – II. The effect of
tides in the misaligned case-
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Pages: 4983 - 5003
Abstract: ABSTRACTWe extend the study of Papaloizou and Savonije of the tidal interactions of close orbiting giant planets with a central solar-type star to the situation where the spin axis of the central star and the orbital angular momentum are misaligned. We determine the tidal response taking into account the possibility of the excitation of r modes and the effect of tidal forcing due to potential perturbations that have zero frequency in a non-rotating frame. Although there is near resonance with r modes with degree l′ = 1 and orders m = ±1, half widths turn out to be sufficiently narrow so that in practice dissipation rates are found to be similar to those produced by non-resonant potential perturbations. We use our results to determine the evolution of the misalignment for the full range of initial inclination angles taking account of the spin-down of the central star due to magnetic braking. Overall we find the rate of tidal evolution to be unimportant for a one Jupiter mass planet with orbital period ∼3.7 d over a main-sequence lifetime. However, it becomes significant for higher mass planets and shorter orbital periods, approximately scaling as the square of the planet mass and the inverse fourth power of the orbital period.
PubDate: Wed, 08 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3460
Issue No: Vol. 527, No. 3 (2023)
- The galaxy UV luminosity function at z ≃ 11 from a suite of public JWST
ERS, ERO, and Cycle-1 programs-
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Pages: 5004 - 5022
Abstract: ABSTRACTWe present a new determination of the evolving galaxy ultraviolet (UV) luminosity function (LF) over the redshift range 9.5 < z < 12.5 based on a wide-area (>250 arcmin2) data set of JWST NIRCam near-infrared imaging assembled from 13 public JWST surveys. Our relatively large-area search allows us to uncover a sample of 61 robust z > 9.5 candidates detected at ≥8σ, and hence place new constraints on the intermediate-to-bright end of the UV LF. When combined with our previous JWST + UltraVISTA results, this allows us to measure the form of the LF over a luminosity range corresponding to four magnitudes (M1500). At these early times we find that the galaxy UV LF is best described by a double power-law function, consistent with results obtained from recent ground-based and early JWST studies at similar redshifts. Our measurements provide further evidence for a relative lack of evolution at the bright-end of the UV LF at z = 9–11, but do favour a steep faint-end slope (α ≤ −2). The luminosity-weighted integral of our evolving UV LF provides further evidence for a gradual smooth (exponential) decline in co-moving star-formation rate density (ρSFR) at least out to z ≃ 12, with our determination of ρSFR(z = 11) lying significantly above the predictions of many theoretical models of galaxy evolution.
PubDate: Fri, 10 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3471
Issue No: Vol. 527, No. 3 (2023)
- Population synthesis of Be X-ray binaries: metallicity dependence of total
X-ray outputs-
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Pages: 5023 - 5048
Abstract: ABSTRACTX-ray binaries (XRBs) are thought to regulate cosmic thermal and ionization histories during the Epoch of Reionization and Cosmic Dawn (z ∼ 5–30). Theoretical predictions of the X-ray emission from XRBs are important for modelling such early cosmic evolution. Nevertheless, the contribution from Be-XRBs, powered by accretion of compact objects from decretion discs around rapidly rotating O/B stars, has not been investigated systematically. Be-XRBs are the largest class of high-mass XRBs (HMXBs) identified in local observations and are expected to play even more important roles in metal-poor environments at high redshifts. In light of this, we build a physically motivated model for Be-XRBs based on recent hydrodynamic simulations and observations of decretion discs. Our model is able to reproduce the observed population of Be-XRBs in the Small Magellanic Cloud with appropriate initial conditions and binary stellar evolution parameters. We derive the X-ray output from Be-XRBs as a function of metallicity in the (absolute) metallicity range Z ∈ [10−4, 0.03] with a large suite of binary population synthesis (BPS) simulations. The simulated Be-XRBs can explain a non-negligible fraction ($\gtrsim 30{{\ \rm per\ cent}}$) of the total X-ray output from HMXBs observed in nearby galaxies for Z ∼ 0.0003–0.02. The X-ray luminosity per unit star formation rate from Be-XRBs in our fiducial model increases by a factor of ∼8 from Z = 0.02 to Z = 0.0003, which is similar to the trend seen in observations of all types of HMXBs. We conclude that Be-XRBs are potentially important X-ray sources that deserve greater attention in BPS of XRBs.
PubDate: Mon, 13 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3475
Issue No: Vol. 527, No. 3 (2023)
- Spatial distribution of NH2D in massive star-forming regions
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Pages: 5049 - 5074
Abstract: ABSTRACTTo understand the relation between NH2D and its physical environment, we mapped ortho-NH2D $1_{11}^s-1_{01}^a$ at 85.9 GHz toward 24 Galactic late-stage massive star-forming regions with Institut de Radioastronomie Millim${\rm \acute{e}}$trique (IRAM) 30-m telescope. Ortho-NH2D $1_{11}^s-1_{01}^a$ was detected in 18 of 24 sources. Comparing with the distribution of H13CN 1-0 as a dense gas tracer and radio recombination line H42α, ortho-NH2D $1_{11}^s-1_{01}^a$ present complex and diverse spatial distribution in these targets. 11 of the 18 targets, present a different distribution between ortho-NH2D $1_{11}^s-1_{01}^a$ and H13CN 1-0, while no significant difference between these two lines can be found in other 7 sources, mainly due to limited spatial resolution and sensitivity. Moreover, with H42α tracing massive young stellar objects, ortho-NH2D $1_{11}^s-1_{01}^a$ seems to show a relatively weak emission near the massive young stellar objects.
PubDate: Mon, 13 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3480
Issue No: Vol. 527, No. 3 (2023)
- Host galaxies of ultra-strong Mg ii absorbers at z ∼ 0.7
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Pages: 5075 - 5092
Abstract: ABSTRACTWe report spectroscopic identification of the host galaxies of 18 ultra-strong Mg ii systems (USMg ii) at 0.6 ≤ z ≤ 0.8. We created the largest sample by merging these with 20 host galaxies from our previous survey within 0.4 ≤ z ≤ 0.6. Using this sample, we confirm that the measured impact parameters ($\rm 6.3\leqslant D[kpc] \leqslant 120$ with a median of 19 kpc) are much larger than expected, and the USMg ii host galaxies do not follow the canonical $\rm {\it W}_{2796}-{\it D}$ anticorrelation. We show that the presence and significance of this anticorrelation may depend on the sample selection. The $\rm {\it W}_{2796}-{\it D}$ anticorrelation seen for the general Mg ii absorbers show a mild evolution at low $\rm W_{2796}$ end over the redshift range 0.4 ≤ z ≤ 1.5 with an increase of the impact parameters. Compared to the host galaxies of normal Mg ii absorbers, USMg ii host galaxies are brighter and more massive for a given impact parameter. While the USMg ii systems preferentially pick star-forming galaxies, they exhibit slightly lower ongoing star-forming rates compared to main sequence galaxies with the same stellar mass, suggesting a transition from star-forming to quiescent states. For a limiting magnitude of mr < 23.6, at least 29 per cent of the USMg ii host galaxies are isolated, and the width of the Mg ii absorption in these cases may originate from gas flows (infall/outflow) in isolated haloes of massive star forming but not starbursting galaxies. We associate more than one galaxy with the absorber in $\ge 21~{{\ \rm per\ cent}}$ cases, where interactions may cause wide velocity spread.
PubDate: Mon, 13 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3489
Issue No: Vol. 527, No. 3 (2023)
- Supervirial hot phase in Milky Way circumgalactic medium: further
evidences-
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Pages: 5093 - 5101
Abstract: ABSTRACTRecent discoveries of a supervirial hot phase of the Milky Way circumgalactic medium (CGM) have launched new questions regarding the multiphase structure of the CGM around the Galaxy. We use 1.05 Ms of archival Chandra/high-energy transmission grating observations to characterize highly ionized metal absorption at z = 0 along the line of sight of the quasar NGC 3783. We detect two distinct temperature phases with T$_1 = 5.83^{+0.15}_{-0.07}$ K, warm–hot virial temperature, and T$_2=6.61^{+0.12}_{-0.06}$ K, hot supervirial temperature. The supervirial hot phase coexisting with the warm–hot virial phase has been detected in absorption along only two other sightlines and in one stacking analysis. There is scatter in temperature of the hot as well as warm–hot gas. Similar to previous observations, we detect supersolar abundance ratios of metals in the hot phase, with a Ne/O ratio 2σ above solar mixtures. These new detections continue the mystery of the mechanism behind the supervirial hot phase, but provide evidence that this is a true property of the CGM rather than an isolated observation. The supervirial CGM could hold the key to understanding the physical and chemical history of the Milky Way.
PubDate: Thu, 16 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3497
Issue No: Vol. 527, No. 3 (2023)
- The first fireworks: A roadmap to Population III stars during the epoch of
reionization through pair-instability supernovae-
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Pages: 5102 - 5116
Abstract: ABSTRACTWith the launch of JWST and other scheduled missions aimed at probing the distant universe, we are entering a new promising era for high-z astronomy. One of our main goals is the detection of the first population of stars (Population III or Pop III stars), and models suggest that Pop III star formation is allowed well into the Epoch of Reionization (EoR), rendering this an attainable achievement. In this paper, we focus on our chance of detecting massive Pop IIIs at the moment of their death as Pair-Instability Supernovae (PISNe). We estimate the probability of discovering PISNe during the EoR in galaxies with different stellar masses (7.5 ≤ Log(M⋆/M⊙) ≤ 10.5) from six dustyGadget simulations of 50 h−1 cMpc per side. We further assess the expected number of PISNe in surveys with JWST/NIRCam and Roman/WFI. On average, less than one PISN is expected in all examined JWST fields at z ≃ 8 with Δz = 1, and O(1) PISN may be found in a ∼1 deg2 Roman field in the best-case scenario, although different assumptions on the Pop III IMF and/or Pop III star formation efficiency can decrease this number substantially. Including the contribution from unresolved low-mass haloes holds the potential for increased discoveries. JWST/NIRCam and Roman/WFI allow the detection of massive-progenitor (∼250 M⊙) PISNe throughout all the optimal F200W-F356W, F277W-F444W, and F158-F213 colours. PISNe are also pre-dominantly located at the outskirts of their hosting haloes, facilitating the disentangling of underlying stellar emission thanks to the spatial-resolution capabilities of the instruments.
PubDate: Wed, 15 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3513
Issue No: Vol. 527, No. 3 (2023)
- Using helium 10 830 Å transits to constrain planetary magnetic
fields-
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Pages: 5117 - 5130
Abstract: ABSTRACTPlanetary magnetic fields can affect the predicted mass-loss rate for close-in planets that experience large amounts of ultraviolet irradiation. In this work, we present a method to detect the magnetic fields of close-in exoplanets undergoing atmospheric escape using transit spectroscopy at the 10 830 Å line of helium. Motivated by previous work on hydrodynamic and magnetohydrodynamic photoevaporation, we suggest that planets with magnetic fields that are too weak to control the outflow’s topology lead to blueshifted transits due to dayside-to-nightside flows. In contrast, strong magnetic fields prevent this day-to-night flow, as the gas is forced to follow the magnetic field’s roughly dipolar topology. We post-process existing 2D photoevaporation simulations, computing synthetic transit profiles in helium to test this concept. As expected, we find that hydrodynamically dominated outflows lead to blueshifted transits of the order of the sound speed of the gas. Strong surface magnetic fields lead to unshifted or slightly redshifted transit profiles. High-resolution observations can distinguish between these profiles; however, eccentricity uncertainties generally mean that we cannot conclusively say that velocity shifts are due to the outflow for individual planets. The majority of helium observations are blueshifted, which could be a tentative indication that close-in planets generally have surface dipole magnetic field strengths $\lesssim \!\! 0.3$ G. More 3D hydrodynamic and magnetohydrodynamic simulations are needed to confirm this conclusion robustly.
PubDate: Wed, 15 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3528
Issue No: Vol. 527, No. 3 (2023)
- On the orbital decay of the gas giant Kepler-1658b
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Pages: 5131 - 5139
Abstract: ABSTRACTThe gas giant Kepler-1658b has been inferred to be spiralling into its sub-giant F-type host star Kepler-1658a (KOI-4). The measured rate of change of its orbital period is $\stackrel{\bf \centerdot }{\textstyle {P}}_{\rm orb}\, =\, -\, 131^{+20}_{-22}\,\rm {ms\,yr^{ -1}}$, which can be explained by tidal dissipation in the star if its modified tidal quality factor is as low as $Q^{\, \prime }\approx 2.50\times {10}^{4}$. We explore whether this could plausibly be consistent with theoretical predictions based on applying up-to-date tidal theory in stellar models (varying stellar mass, age, and metallicity) consistent with our newly derived observational constraints. In most of our models matching the combined constraints on the stellar effective temperature and radius, the dissipation in the star is far too weak, capable of providing $Q^{\, \prime }\gtrsim 10^9$, hence contributing negligibly to orbital evolution. Using only constraints on the stellar radius, efficient tidal dissipation sufficient to explain observations is possible due to inertial waves in the convective envelope during the sub-giant phase, providing $Q^{\, \prime }\sim 10^4$, but this period in the evolution is very short-lived (shorter than 102 yr in our models). We show that dissipation in the planet is capable of explaining the observed $\dot{P}_\mathrm{orb}$ only if the planet rotates non-synchronously. Tidally induced pericentre precession is a viable explanation if the periastron argument is near 3π/2 and the planet's quadrupolar Love number is above 0.26. Further observations constraining the stellar and planetary properties in this system have the exciting potential to test tidal theories in stars and planets.
PubDate: Wed, 15 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3530
Issue No: Vol. 527, No. 3 (2023)
- Multiwavelength variability and broad-band SED modelling of BL Lac during
a bright flaring period MJD 59000–59943-
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Pages: 5140 - 5154
Abstract: ABSTRACTWe carried out a detailed temporal and spectral study of the BL Lacertae (BL Lac) by using the long-term Fermi-Large Area Telescope (LAT) and Swift-X-ray Telescope (XRT)/Ultraviolet Optical Telescope (UVOT) observations, during the period MJD 59000–59943. The daily-binned γ-ray light curve displays a maximum flux of $1.74\pm 0.09\times 10^{-5} \,\rm photons\, cm^{-2}\, s^{-1}$ on MJD 59868, which is the highest daily γ-ray flux observed from BL Lac. The γ-ray variability is characterized by power spectral density (PSD), rms–flux relation, and flux distribution study. We find that the power-law model fits the PSD with index ∼1, which suggests a long-memory process at work. The observed rms–flux relation exhibits a linear trend, which indicates that the γ-ray flux distribution follows a lognormal distribution. The skewness/Anderson–Darling test and histogram fit reject the normality of flux distribution, and instead suggest that the flux distribution is a lognormal distribution. The fractional variability amplitude shows that the source is more variable in the X-ray band than in optical/ultraviolet/γ-ray bands. In order to obtain an insight into the underlying physical process, we extracted broad-band spectra from different time periods of the light curve. The broad-band spectra are statistically fitted with the convolved one-zone leptonic model with different forms of the particle energy distribution. We found that spectral energy distribution during different flux states can be reproduced well with the synchrotron, synchrotron self-Compton, and external Compton emissions from a broken power-law electron distribution, ensuring equipartition condition. A comparison between the best-fitting physical parameters shows that the variation in different flux states is mostly related to an increase in the bulk Lorentz factor and spectral hardening of the particle distribution.
PubDate: Wed, 14 Jun 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3534
Issue No: Vol. 527, No. 3 (2023)
- Nitrogen abundances of the Be-type stars in 30 Doradus
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Pages: 5155 - 5165
Abstract: ABSTRACTA sub-set of the 67 Be-type stars observed in 30 Doradus during the VLT-FLAMES Tarantula Survey (VFTS) campaign have been analysed to estimate atmospheric parameters and chemical compositions, in particular their nitrogen abundance. Reliable results were found for 23 targets comprising the largest Large Magellanic Cloud sample currently available. The nitrogen abundance estimates have been compared with predictions from evolutionary models for rapidly rotating single stars (or non-interacting multiple systems) and for interacting binaries. The observations appear to be incompatible with all the targets having a single star evolutionary history. The results agree better with a binary evolutionary history with at least 30 per cent of the VFTS sample having apparently evolved by this pathway. These conclusions are consistent with a previous analysis of the ve sin i-estimates for this Be-type sample.
PubDate: Thu, 16 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3537
Issue No: Vol. 527, No. 3 (2023)
- Constraining the long-lived supramassive neutron stars by magnetar boosted
kilonovae-
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Pages: 5166 - 5182
Abstract: ABSTRACTKilonovae are optical transients following the merger of neutron star binaries, which are powered by the r-process heating of merger ejecta. However, if a merger remnant is a long-lived supramassive neutron star supported by its uniform rotation, it will inject energy into the ejecta through spin-down power. The energy injection can boost the peak luminosity of a kilonova by many orders of magnitudes, thus significantly increasing the detectable volume. Therefore, even if such events are only a small fraction of the kilonova population, they could dominate the detection rates. However, after many years of optical sky surveys, no such event has been confirmed. In this work, we build a boosted kilonova model with rich physical details, including the description of the evolution and stability of a proto neutron star, and the energy absorption through X-ray photoionization. We simulate the observation prospects and find the only way to match the absence of detection is to limit the energy injection by the newly born magnetar to only a small fraction of the neutron star rotational energy, thus they should collapse soon after the merger. Our result indicates that most supramassive neutron stars resulting from binary neutron star mergers are short lived and they are likely to be rare in the Universe.
PubDate: Mon, 20 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3560
Issue No: Vol. 527, No. 3 (2023)
- The Galactic distribution of pulsar scattering and the τ–DM
relation-
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Pages: 5183 - 5191
Abstract: ABSTRACTInterstellar radio wave scattering leads to flux density fluctuations and pulse broadening of pulsar signals. However, Galactic distribution and the structure of the scattering medium are still poorly understood. Pulsar pulse broadening data available for a relatively large number of pulsars is well suited for such investigations. We collected an up-to-date sample of publicly available pulsar scattering data and introduced a new quantity – the reduced scattering strength $\tilde{\tau }$ to study the Galactic distribution of pulsar scattering in the Milky Way. We show that the current observations are dominated by two distinct pulsar populations: a local and an inner-Galactic one separated by $\tilde{\tau }=10^{-5.1}$ s cm6 pc−1. The stronger electron density fluctuations associated with the inner-Galactic population naturally explain the observed steepening of pulsar scattering time τ–dispersion measure relation. We measure an inner disc region with $3\, {\rm kpc}\ \lt\ \rm r\ \lt\ 5.5\, {\rm kpc}$ from the Galactic centre to have a scattering scale height of about 0.28 kpc, supporting a correlation between interstellar radio scattering and structures associating with the ionized gas and stellar activities.
PubDate: Mon, 20 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3561
Issue No: Vol. 527, No. 3 (2023)
- Compact stars with dark matter induced anisotropy in complexity-free
background and effect of dark matter on GW echoes-
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Pages: 5192 - 5205
Abstract: ABSTRACTIn this work, we consider the vanishing complexity factor scenario which has opened up a whole new way of generating solutions to the Einstein field equations for the spherically symmetric structure of celestial bodies. By using this very rare condition on the system of two metric potentials, viz. gtt and grr, we make reduce it to a uni-metric potential system satisfying all physical conditions. Along with this, we further have considered that the space–time is deformed by dark matter (DM) content in DM haloes resulting into perturbations in the gtt and grr metric potentials. This DM deformation is mathematically done by the complete geometric decoupling method where the decoupling parameter β decides the amount of DM content. In connection to the claimed post-merger object in the GW170817 event we have argued that if these compact stars were in galactic DM haloes with the assumption that the radius remains the same, the compactness factor can grow within the range 1/3 to 4/9 and therefore can generate gravitational waves (GW) echoes. Additionally, we have presented effect of β on the generation of GW echoes in accordance with the observational constraints related to the compact stars GW190814, PSR J0740+6620, PSR J1614−2230, Cen X-3, and LMC X-4.
PubDate: Fri, 17 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3562
Issue No: Vol. 527, No. 3 (2023)
- CSST WL preparation I: forecast the impact from non-Gaussian covariances
and requirements on systematics control-
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Pages: 5206 - 5218
Abstract: ABSTRACTThe precise estimation of the statistical errors and accurate removal of the systematical errors are the two major challenges for the stage IV cosmic shear surveys. We explore their impact for the China Space Station Telescope (CSST) with survey area ${\sim} 17\,500\deg ^2$ up to redshift ∼4. We consider statistical error contributed from Gaussian covariance, connected non-Gaussian covariance, and super-sample covariance. We find the non-Gaussian covariances, which is dominated by the super-sample covariance, can largely reduce the signal-to-noise ratio of the two-point statistics for CSST, leading to an ∼1/3 loss in the figure of merit for the matter clustering properties (σ8–Ωm plane) and 1/6 in the dark energy equation of state (w0–wa plane). We further put requirements of systematics mitigation on intrinsic alignment of galaxies, baryonic feedback, shear multiplicative bias, and bias in the redshift distribution, for an unbiased cosmology. The 10−2–10−3 level requirements emphasize strong needs in related studies, to support future model selections and the associated priors for the nuisance parameters.
PubDate: Mon, 20 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3563
Issue No: Vol. 527, No. 3 (2023)
- Correction to: Investigation on the orbital period variations of NN Ser:
implications for the hypothetical planets, the Applegate mechanism, and
the orbital stability-
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Pages: 5219 - 5219
Abstract: errata, addendabinaries: closebinaries: eclipsingstars: individual (NN Ser)subdwarfsplanetary systems
PubDate: Wed, 29 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3567
Issue No: Vol. 527, No. 3 (2023)
- Optical intraday variability of the blazar S5 0716+714
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Pages: 5220 - 5237
Abstract: ABSTRACTWe present an extensive recent multiband optical photometric observations of the blazar S5 0716+714 carried out over 53 nights with two telescopes in India, two in Bulgaria, one in Serbia, and one in Egypt during 2019 November – 2022 December. We collected 1401, 689, 14726, and 165 photometric image frames in B, V, R, and I bands, respectively. We monitored the blazar quasi-simultaneously during three nights in B, V, R, and I bands; four nights in B, V, and R; two nights in V, R, and I; five nights in B and R; and two nights in V and R bands. We also took 37 nights of data only in R band. Single band data are used to study intraday flux variability and two or more bands quasi-simultaneous observations allow us to search for colour variation in the source. We employ the power-enhanced F-test and the nested ANOVA test to search for genuine flux and colour variations in the light curves of the blazar on intraday time-scales. Out of 12, 11, 53, and 5 nights observations, intraday variations with amplitudes between ∼3 and ∼20 per cent are detected in 9, 8, 31 and 3 nights in B, V, R, and I bands, respectively, corresponding to duty cycles of 75, 73, 58, and 60 per cent. These duty cycles are lower than those typically measured at earlier times. On these time-scales colour variations with both bluer-when-brighter and redder-when-brighter are seen, though nights with no measurable colour variation are also present. We briefly discuss possible explanations for this observed intraday variability.
PubDate: Mon, 20 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3574
Issue No: Vol. 527, No. 3 (2023)
- Kinetic rate coefficients for electron-driven collisions with CH+:
dissociative recombination and rovibronic excitation-
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Pages: 5238 - 5243
Abstract: ABSTRACTCross-sections and rate coefficients for rovibronic excitation of the CH+ ion by electron impact and dissociative recombination of CH+ with electrons are evaluated using a theoretical approach combining an R-matrix method and molecular quantum defect theory. The method has been developed and tested, comparing the theoretical results with the data from the recent Cryogenic Storage Ring experiment. The obtained cross-sections and rate coefficients evaluated for temperatures from 1 to 10 000 K could be used for plasma modelling in the interpretation of astrophysical observations and also in the technological applications where the molecular hydrocarbon plasma is present.
PubDate: Mon, 20 Nov 2023 00:00:00 GMT
DOI: 10.1093/mnras/stad3577
Issue No: Vol. 527, No. 3 (2023)
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