Subjects -> ASTRONOMY (Total: 94 journals)
 Showing 1 - 46 of 46 Journals sorted alphabetically Advances in Astronomy       (Followers: 49) Annual Review of Astronomy and Astrophysics       (Followers: 50) Annual Review of Earth and Planetary Sciences       (Followers: 67) Artificial Satellites       (Followers: 21) Astrobiology       (Followers: 11) Astronomical & Astrophysical Transactions: The Journal of the Eurasian Astronomical Society       (Followers: 7) Astronomical Review       (Followers: 5) Astronomische Nachrichten       (Followers: 4) Astronomy & Geophysics       (Followers: 49) Astronomy and Astrophysics       (Followers: 67) Astronomy and Computing       (Followers: 6) Astronomy Letters       (Followers: 22) Astronomy Reports       (Followers: 22) Astronomy Studies Development       (Followers: 15) Astroparticle Physics       (Followers: 10) Astrophysical Bulletin       (Followers: 4) Astrophysics       (Followers: 35) Astrophysics and Space Science       (Followers: 49) Astrophysics and Space Sciences Transactions (ASTRA)       (Followers: 60) Astropolitics: The International Journal of Space Politics & Policy       (Followers: 13) Celestial Mechanics and Dynamical Astronomy       (Followers: 15) Chinese Astronomy and Astrophysics       (Followers: 25) Colloid Journal       (Followers: 2) Comptes Rendus : Physique       (Followers: 2) Computational Astrophysics and Cosmology       (Followers: 6) Earth and Planetary Science Letters       (Followers: 142) Earth, Moon, and Planets       (Followers: 47) Earth, Planets and Space       (Followers: 77) EAS Publications Series       (Followers: 8) EPL Europhysics Letters       (Followers: 8) Experimental Astronomy       (Followers: 38) Expert Opinion on Astronomy and Astrophysics       (Followers: 8) Extreme Life, Biospeology & Astrobiology - International Journal of the Bioflux Society       (Followers: 4) Few-Body Systems       (Followers: 1) Foundations of Physics       (Followers: 40) Frontiers in Astronomy and Space Sciences       (Followers: 15) Galaxies       (Followers: 6) Globe, The       (Followers: 3) Gravitation and Cosmology       (Followers: 6) Icarus       (Followers: 71) International Journal of Advanced Astronomy       (Followers: 21) International Journal of Astrobiology       (Followers: 4) International Journal of Astronomy       (Followers: 22) International Journal of Astronomy and Astrophysics       (Followers: 36) International Journal of Satellite Communications Policy and Management       (Followers: 15) International Letters of Chemistry, Physics and Astronomy       (Followers: 8) ISRN Astronomy and Astrophysics       (Followers: 14) Journal for the History of Astronomy       (Followers: 20) Journal of Astrobiology & Outreach       (Followers: 5) Journal of Astronomical Instrumentation       (Followers: 3) Journal of Astrophysics       (Followers: 33) Journal of Astrophysics and Astronomy       (Followers: 58) Journal of Atmospheric and Solar-Terrestrial Physics       (Followers: 133) Journal of Geophysical Research : Planets       (Followers: 115) Journal of Geophysical Research : Space Physics       (Followers: 134) Journal of High Energy Astrophysics       (Followers: 25) Kinematics and Physics of Celestial Bodies       (Followers: 11) KronoScope       (Followers: 1) Macalester Journal of Physics and Astronomy       (Followers: 5) Monthly Notices of the Royal Astronomical Society       (Followers: 13) Monthly Notices of the Royal Astronomical Society : Letters       (Followers: 2) Nature Astronomy       (Followers: 14) New Astronomy       (Followers: 26) New Astronomy Reviews       (Followers: 19) Nonlinear Dynamics       (Followers: 19) NRIAG Journal of Astronomy and Geophysics       (Followers: 4) Physics of the Dark Universe       (Followers: 4) Planetary and Space Science       (Followers: 106) Planetary Science       (Followers: 52) Proceedings of the International Astronomical Union       (Followers: 2) Publications of the Astronomical Society of Australia       (Followers: 3) Publications of the Astronomical Society of Japan       (Followers: 4) Research & Reviews : Journal of Space Science & Technology       (Followers: 20) Research in Astronomy and Astrophysics       (Followers: 38) Revista Mexicana de Astronomía y Astrofísica       (Followers: 3) Science China : Physics, Mechanics & Astronomy       (Followers: 4) Science China Physics, Mechanics & Astronomy       (Followers: 4) Solar Physics       (Followers: 29) Solar System Research       (Followers: 15) Space Science International       (Followers: 117) Space Science Reviews       (Followers: 92) Space Weather       (Followers: 27) Transport and Aerospace Engineering       (Followers: 13) Universe       (Followers: 6)
Similar Journals
 Research in Astronomy and AstrophysicsJournal Prestige (SJR): 0.681 Citation Impact (citeScore): 1Number of Followers: 38      Subscription journal ISSN (Print) 1674-4527 Published by IOP  [7 journals]
• Discovery of Extended Structure Around Open Cluster COIN-Gaia 13 Based on
Gaia EDR3

Authors: Leya Bai; Jing Zhong, Li Chen, Jing Li, Jinliang Hou
Abstract: COIN-Gaia 13 is a newly discovered open cluster revealed by Gaia DR2 data. It is a nearby open cluster with a distance of about 513 pc. Combined with the five-dimensional astrometric data of Gaia EDR3 with higher accuracy, we use the membership assignment algorithm (pyUPMASK) to determine the membership of COINGaia 13 in a large extended spatial region. The cluster has 478 identified candidate members. After obtaining reliable cluster members, we further study its basic properties and spatial distribution. Our results show that there is an obvious extended structure of the cluster in the X–Y plane. This elongated structure is distributed along the spiral arm, and the whole length is about 270 pc. The cluster age is 250 Myr, the total mass is about 439 $$M_{\odot}$$ and the tidal radius of the cluster is about 11 pc. Since more than half of member stars (352 stars) are located outside twice the tidal radius, it is suspected that this cluster is undergoing the dynamic dissolution process. Furthermore, the spatial distribution and kinematic analysis indicate that the extended structure in COIN-Gaia 13 is more likely to be caused by differential rotation of the Galaxy.
PubDate: Mon, 09 May 2022 18:47:41 +080

• Constraining Brans–Dicke Cosmology with the CSST Galaxy Clustering
Spectroscopic Survey

Authors: Anda Chen; Yan Gong, Fengquan Wu, Yougang Wang, Xuelei Chen
Abstract: The Brans–Dicke (BD) theory is the simplest Scalar-Tensor theory of gravity, which can be considered as a candidate of modified Einstein’s theory of general relativity. In this work, we forecast the constraints on BD theory in the CSST galaxy clustering spectroscopic survey with a magnitude limit ∼23 AB mag for point-source 5σ detection. We generate mock data based on the zCOSMOS catalog and consider the observational and instrumental effects of the CSST spectroscopic survey. We predict galaxy power spectra in the BD theory from z = 0 to 1.5, and the galaxy bias and other systematical parameters are also included. The Markov Chain Monte Carlo technique is employed to find the best-fits and probability distributions of the cosmological and systematical parameters. A BD parameter ζ is introduced, which satisfies $$\zeta=\ln\left(1+\frac{1}{\omega}\right)$$. We find that the CSST spectroscopic galaxy clustering survey can give ζ < 10−2 , or equivalently $$\omega > \mathcal{O}(10^2)$$ and $$\dot{G}/G <10^{-13}$$, under the assumption ζ = 0. These constraints are almost at the same order of magnitude compared to the joint constraints using the current cosmic microwave background, baryon acoustic oscillations and Type Ia supernova data, indicating that the CSST galaxy clustering spectroscopic survey would be powerful for constraining the BD theory and other modified gravity theories.
PubDate: Mon, 09 May 2022 18:47:37 +080

• The First Photometric Study of AH Mic Contact Binary System

Authors: Atila Poro; M. G. Blackford, S. Ranjbar Salehian, E. Jahangiri, M. Samiei Dastjerdi, M. Gozarandi, R. Karimi, T. Madayen, E. Bakhshi, F. Hedayati
Abstract: The first multi-color light curve analysis of the AH Mic binary system is p_{\odot}sented. This system has very few past observations from the southern hemisphere. We extracted the minima times from the light curves based on the Markov Chain Monte Carlo (MCMC) approach and obtained a new ephemeris. To provide modern photometric light curve solutions, we used the Physics of Eclipsing Binaries (PHOEBE) software package and the MCMC approach. Light curve solutions yielded a system temperature ratio of 0.950, and we assumed a cold starspot for the hotter star based on the O’Connell effect. This analysis reveals that AH Mic is a W-subtype W UMa contact system with a fill-out factor of 21.3% and a mass ratio of 2.32. The absolute physical parameters of the components are estimated by using the Gaia Early Data Release 3 (EDR3) parallax method to be (M_h(M_{\odot})\) = 0.702(26), $$M_c(M_{\odot})$$ = 1.629(104), $$R_h(R_{\odot})$$ = 0.852(21), $$R_c(R_{\odot})$$ = 1.240(28), $$L_h(L_{\odot})$$= 0.618(3) and $$L_c(L_{\odot})$$ = 1.067(7). The orbital angular momentum of the AH Mic binary system was found to be 51.866(35). The components’ positions of this system are plotted in the Hertzsprung–Russell diagram.
PubDate: Mon, 09 May 2022 18:47:33 +080

• Detections of Gamma-Rays from Globular Clusters ESO 452-SC11, NGC 6380,
Palomar 6 and UKS 1 with Fermi-LAT

Authors: Min Yuan; Jiao Zheng, Pengfei Zhang, Li Zhang
Abstract: The events from 157 globular clusters (GCs) are analyzed by using 12 yr long-term Pass 8 data from Fermi Large Area Telescope. Besides the 34 GCs reported in previous literatures, four additional GCs (ESO 452-SC11, NGC 6380, Palomar 6 and UKS 1) in the Milky Way are detected as gamma-ray GC candidates. Especially for UKS 1, these are known as the faintest GCs in long-wavelength bands. Further data analysis has been performed for the four GCs. While no pulsars are determined in radio and/or X-ray wavelengths so far, their gamma-ray pulsation emissions are not found, and no significant gamma-ray flux variability is detected. The numbers of MSPs within the four GCs are estimated based on the assumption that the MSPs within each GC emit similar amounts of gamma-rays. The gamma-ray results reported here could help us better understand the nature of gamma-ray emission origins for GCs.
PubDate: Mon, 09 May 2022 18:47:30 +080

• Crust Cooling of Soft X-Ray Transients—the Uncertainties of Shallow
Heating

Authors: Xiang-Yang Lu; Guo-Liang Lü, He-Lei Liu, Chun-Hua Zhu, Zhao-Jun Wang
Abstract: Crust cooling of soft X-ray transients has been observed after outbursts, but an additional shallow heating during accretion in outburst is needed to explain the quiescent light curve. However, shallow heating is significantly different between sources and even within one source between different outbursts, and the source of shallow heat is as yet unknown. Using the open source code “dStar” which solves the fully general relativistic heat diffusion equation for the crust, we investigate the effect of magnitude and depth of shallow heating on crust cooling and find that some exceptional sources (Swift J174805.3-244637, MAXI J0556-332 during outburst II and GRO J1750-27) in which shallow heating may be inactive could be explained by a deeper shallow heating mechanism. We compare our results with those from previous works and find that the shallow heating is model dependent. In addition, the effects of mass and radius of a neutron star on shallow heating are studied, and it is shown that the more compact the star, the less shallow heating will be needed to fit the crust cooling light curves.
PubDate: Mon, 09 May 2022 18:47:26 +080

• Quasi-periodic Oscillation Analysis for the BL Lacertae Object 1823+568

Authors: Huai-Zhen Li; Quan-Gui Gao, Long-Hua Qin, Ting-Feng Yi, Qi-Rui Chen
Abstract: We studied the optical band periodic variability of 1823+568 using the Jurkevich method, the Lomb–Scargle periodogram and the REDFIT38 software, and found evidence of quasi-periodic oscillation. An unprecedented variability with period $$P= 283_{- 13}^{+ 17}$$ days was identified by three different analysis methods. This quasi-periodic variability most likely results from nonballistic helical jet motion driven by the orbital motion in a binary black hole system. Considering the light-travel time effect, the real physical period is $$P_d = 67.1$$ yr. Moreover, we estimated that the primary black hole mass is $$M\simeq 1.92 \times 10^9 M_{\odot}$$ to $$3.43 \times 10^9 M_{\odot}$$.
PubDate: Mon, 09 May 2022 18:47:23 +080

• Evolution Toward the Observational Features of a Stripped Envelope Type
IIb Supernova in a Binary System

Authors: Gang Long; Han-Feng Song, Rui-Yu Zhang, Ying Qin, Liu-Yan Zhao, Shi-Tao Qi, Fang-Wen Wu
Abstract: Type IIb supernovae (SNe IIb) that have a thin layer of hydrogen left in their outer envelope have been believed to belong to core collapse supernovae. Mass transfer via Roche lobe overflow can significantly change the nucleosynthesis and surface chemical elements of the progenitors of SNe IIb. We aim to explore what conditions a close binary can meet with the observational features of SNe IIb. We find that an observed low mass SN IIb cannot be produced by a low mass isolated star with $$M < 20 M_{\odot}$$ due to the existence of a thick hydrogen envelope regardless of rotation. Binaries dominate as progenitors in the mass interval (i.e., $$M < 20 M_{\odot}$$) considered in this paper. The $$16 M_{\odot}$$ primary with a $$14 M_{\odot}$$ companion in a binary system with ∼10 days < Porb < 720 days can reproduce observational features of SNe IIb (i.e., $$T_{\rm eff}$$, log$$L/L_{\odot}$$, $$M_{\rm He}, M_{\rm H}$$, etc.). With the decrease of the hydrogen-rich envelope mass, the radius of the progenitor shrinks. The associated types of SN IIb progenitors from RSGs and YSGs to BSGs are closely related to the amount of hydrogen left in the envelopes. Rotation can bring the production of the CNO reaction to the stellar surface at an early phase, which would explain the nitrogen-rich circumstellar material of SN 1993J and can also explain the large He/H ratio of supernova ejecta. Rotation can increase the corresponding region of the orbital period which can produce an SN IIb.
PubDate: Mon, 09 May 2022 18:47:19 +080

• The Evolution of the Nucleus Surface in the Context of the Change in the
Brightness of a Comet

Authors: Marcin Wesołowski
Abstract: The paper presents a model of the thermodynamic evolution of the comet nucleus surface. In the proposed approach, we focus on the analysis of the formation of pits visible on the surface of the cometary nucleus. These pits are a consequence of the thermodynamic evolution of both the surface layers and the inner layers of the cometary nucleus. As a result of complex thermodynamic processes, the surface layer is destroyed. A measure of this destruction is the amount of comet material that is thrown into a coma as a result of sublimation. The effect of this process is an increase in the area on which the incident light scatters. Then we can notice a sudden increase in the brightness of the comet, i.e., its outburst. A measure of the amplitude of a given outburst is the diameter and thickness of the surface layer that has been destroyed. The mechanism of the evolution of the pits was proposed based on the analysis of many photos taken by the Rosetta probe. The obtained numerical values correspond to the actual brightness changes of the Jupiter family comets during their outburst.
PubDate: Mon, 09 May 2022 18:47:16 +080

• Testing the Empirical Relationship between Forbush Decreases and Cosmic
Ray Diurnal Anisotropy

Authors: Jibrin Adejoh Alhassan; Ogbonnaya Okike, Augustine Ejikeme Chukwude
Abstract: The abrupt aperiodic modulation of cosmic ray (CR) flux intensity, often referred to as Forbush decrease (FD), plays a significant role in our understanding of the Sun–Earth electrodynamics. Accurate and precise determinations of FD magnitude and timing are among the intractable problems in FD-based analysis. FD identification is complicated by CR diurnal anisotropy. CR anisotropy can increase or reduce the number and amplitude of FDs. It is therefore important to remove its contributions from CR raw data before FD identification. Recently, an attempt was made, using a combination of the Fourier transform technique and FD-location machine, to address this. Thus, two FD catalogs and amplitude diurnal variation (ADV) were calculated from filtered (FD1 and ADV) and raw (FD2) CR data. In the current work, we test the empirical relationship between FD1, FD2, ADV and solar-geophysical characteristics. Our analysis shows that two types of magnetic fields - interplanetary and geomagnetic (Dst) - govern the evolution of CR flux intensity reductions.
PubDate: Mon, 09 May 2022 18:47:13 +080

• Photometric Investigation of Contact Binary DY Cet Based on TESS Data

Authors: M. F. Yıldırım
Abstract: We present a photometric analysis of the Transiting Exoplanet Survey Satellite (TESS) light curve of contact binary system DY Cet and the behavior of its orbital period variation. The light curve and published radial velocity data analysis was performed using the Wilson–Devinney code. As a result of simultaneous analysis of the light curve with radial velocity data, the masses and radii of the system’s components were determined as $$M_1 = 1.55 \pm 0.02 M_{\odot}$$, $$M_2 = 0.55 \pm 0.01 M_{\odot}$$ and $$R_1 = 1.51 \pm 0.02 R_{\odot}$$, $$R_2 = 0.95 \pm 0.02 R_{\odot}$$, respectively. The degree of contact ( f ) and mass ratio (q) of the system were determined as 23% and 0.355 ± 0.012, respectively. Orbital period analysis of DY Cet was conducted for the first time in this study. It was observed that the orbital period has a sinusoidal change with decreasing parabola. To explain the orbital period change, mass transfer between components is proposed with the assumption of conservative mass, and the transfer rate was calculated to be $$dM/dt = 1.1 \times 10^{-7} M_{\odot}\rm yr^{-1}$$ . A possible third component is suggested for explaining the sinusoidal change, and the mass of the unseen component was determined as 0.13 Me. The age of the DY Cet system was estimated as 3.77 Gyr.
PubDate: Mon, 09 May 2022 18:47:10 +080

• Herschel Investigation of Cores and Filamentary Structures in the Perseus
Molecular Cloud

Authors: Chang Zhang; Guo-Yin Zhang, Jin-Zeng Li, Xue-Mei Li
Abstract: Cores and filamentary structures are the prime birthplaces of stars, and play key roles in the process of star formation. Latest advances in the methods of multi-scale source and filament extraction, and in making highresolution column density map from Herschel multi-wavelength observations enable us to detect the filamentary network structures in highly complex molecular cloud environments. The statistics for physical parameters shows that core mass strongly correlates with core dust temperature, and M/L strongly correlates with M/T, which is in line with the prediction of the blackbody radiation, and can be used to trace evolutionary sequence from unbound starless cores to robust prestellar cores. Crest column densities of the filamentary structures are clearly related with mass per unit length (Mline), but are uncorrelated by three orders ranging from ∼1020 to ∼1022 cm−2 with widths. Full width at half maximum has a median value of 0.15 pc, which is consistent with the 0.1 pc typical inner width of the filamentary structures reported by previous research. We find 70% of robust prestellar cores (135/199) embedded in supercritical filaments with $$M_{\rm line} > 16 M_{\odot}\rm pc^{-1}$$ , which implies that the gravitationally bound cores come from fragmentation of supercritical filaments. On the basis of observational evidence that the probability distribution function with power-law distribution in the Perseus south is flatter than in the north, the number of young stellar objects in the south is significantly less than that in the north, and dust temperature is different. We infer that the south region is more gravitationally bound than the north region.
PubDate: Mon, 09 May 2022 18:47:06 +080

• Accurate Data Match and Call Method for the Thermal Compensation Database
of the Reflector Antenna

Authors: Yuefei Yan; Song Xue, Xinlan Hu, Peiyuan Lian, Yan Wang, Lin Li, Qian Xu, Na Wang, Wulin Zhao, Yuanpeng Zheng, Congsi Wang
Abstract: The influence of thermal deformation on the performance of reflector antennas has become increasingly significant with the increasing aperture and working frequency. The use of a thermal compensation database is an efficient method to compensate for the deformation caused by the non-uniform temperature distribution. However, how to efficiently and accurately match and call the database remains as one of the tough challenges for the antenna thermal compensation system to achieve real time compensation. Therefore, this study proposes a data match and call method for the thermal compensation database of the reflector antenna, matching the database from three aspects: the overall rms match of temperature data, the similarity area match of each data sample, and the key area match of key structural positions. The validation of this method is demonstrated in an example. The difference between the pointing adjustment amount calculated by the matched data and the collected data was found to be less than 1″, which satisfied the requirements of practical engineering, thus achieving real-time thermal compensation of the antenna.
PubDate: Mon, 09 May 2022 18:47:02 +080

• A Common Envelope Jets Supernova (CEJSN) Impostor Scenario for Fast Blue
Optical Transients

Authors: Noam Soker
Abstract: I propose a new scenario, the polar common envelope jets supernova (CEJSN) impostor scenario, to account for AT2018cow-like fast blue optical transients (FBOTs). The polar CEJSN impostor scenario evolves through four main phases. (1) A red supergiant (RSG) star expands to tidally interact with a neutron star (NS) companion (or a black hole). The interaction increases the RSG mass loss rate to form a circumstellar matter (CSM) halo to $$r\simeq0.1$$ pc. (2) Shortly before the onset of a common envelope evolution (CEE) and about a year before explosion the NS accretes mass from the RSG envelope and launches jets that inflate two opposite lobes in the CSM within ≈100 au. (3) The NS-RSG system enters a CEE phase during which the system ejects most of the envelope mass in a dense equatorial outflow. (4) At the termination of the CEE the leftover envelope forms a circumbinary disk around the NS-core system. The NS accretes mass from the circumbinary disk and launches energetic jets that, when colliding with the fronts of the CSM lobes, power an FBOT event. The low mass of the jets-lobes interaction zones and their large distance, of about 100 au, from the center account for the fast transient. In the future the core collapses to form a second NS. In the far future the two NSs might merge. I suggest that FBOTs and similar fast transients are CEJSN impostors which compose a large fraction of the progenitors of NS-NS merger binaries.
PubDate: Mon, 09 May 2022 18:46:58 +080

• The Simultaneous Three-channel Multicolor CCD Photometric System of the
1.2 m Telescope at Jilin Astronomical Observatory

Authors: Bing-Li Niu; Cheng-Zhi Liu, Zhen-Wei Li, Zhe Kang, You Lv
Abstract: We will introduce the construction and design of a new simultaneous three-channel multicolor CCD photometer. This photometer has been mounted on the 1.2 m telescope at Jilin Astronomical Observatory, and is applied to study space debris, gamma-ray burst afterglows, asteroids and other rapidly variable objects. As one of the ground follow-up telescopes of the Chinese-French Space-based multi-band astronomical Variable Objects Monitor (SVOM) mission, it appears very essential to evaluate the performance of the photometry system of this photometer, which can achieve simultaneous imaging within a field of view of 21’.5 × 21’.5, 21’.5 × 21’.5 and 21’.3 × 21’.3 in the Sloan Digital Sky Survey (SDSS) g′, r′, i′ bands, respectively. Photometric calibrations were carried out by using plenty of SDSS standard stars, and the relationship between the photometric system and the Johnson-Bessel filter system was also studied. The results of the performance evaluation from observing open cluster M67 are presented.
PubDate: Mon, 09 May 2022 18:46:55 +080

• The Preliminary Statistical Analysis of LAMOST DR8 Low Resolution AFGK
Stars

Authors: Y. H. Chen; G. W. Li, H. Shu
Abstract: We download the Large sky Area Multi-Object fiber Spectroscopic Telescope Data Release 8 (LAMOST DR8) low resolution catalog for 6,478,063 AFGK type stars and plot the figures of effective temperature, gravitational acceleration and metal abundance. Some small and medium mass stars are evolved from pre-main sequence or main sequence stage to planetary nebula stage or white dwarf stage by the stellar evolution code MESA. We analyze the observed statistical data and model calculation results, and then obtain some basic conclusions preliminarily. Most red giant and asymptotic giant branch stars with log g less than 0.85 have poor metal abundance. Most hot A type main-sequence stars are metal-rich stars with log g from 3.5 to 4.5. The conclusions are reasonable within a certain error range. The theory of a gap area in the Hertzsprung–Russell diagram for stellar evolutions of medium mass stars is reflected in the statistical plots. The central core hydrogen burning stage and the central core helium burning stage correspond to the peak structures in the statistical plots for gravitational acceleration. The metal abundances among A, F, G and K type stars have a wide distribution. We cannot simply replace the metal abundances of these stars with the metal abundance of the Sun when doing fine research work.
PubDate: Mon, 09 May 2022 18:46:51 +080

• The Astrometric Performance Test of 80 cm Telescope at Yaoan Station and
Precise CCD Positions of Apophis

Authors: Bifeng Guo; Qingyu Peng, Ying Chen, Zhongjie Zheng, Yijia Shang, Dan Li, Xiao Chen
Abstract: The 80 cm azimuthal telescope has newly been mounted at Yaoan Station, Purple Mountain Observatory since 2018. The astrometric performance of the telescope is tested in the following three aspects. (a) The geometric distortion of its CCD attached. It is stable in both a single epoch and multi epochs. Eight distortion solutions are derived over about one year. The maximum values range from 0.75 to 0.79 pixel and the median values range from 0.14 to 0.16 pixel. (b) The limit magnitude of stars. About 20.5 mag (Gaia-G) stars can be detected with Johnson-V filter exposured in 300 s. The astrometric error of about 20.5 mag stars is estimated at 0 14 using the fitted sigmoidal function. (c) The astrometric accuracy and the precision of stacked fast-moving faint object. 24 stacked frames of the potentially hazardous asteroid (99942) Apophis were derived on 2021 April 14 and 15 (fainter than 18 mag) based on the ephemeris shifts. During data reduction, the newest Gaia EDR3 Catalog and Jet Propulsion Laboratory Horizons ephemeris are referenced as theoretical positions of stars and Apophis, respectively. Our results show that the mean (O − C)s (observed minus computed) of Apophis are −0.”018 and 0.”020 in R.A. and decl., and the dispersions are estimated at 0.”094 and 0.”085, respectively, which show the consistency of the stacked results by Astrometrica.
PubDate: Mon, 09 May 2022 18:46:46 +080

• X-Ray Fine Structure of a Limb Solar Flare Revealed by Insight-HXMT,
RHESSI and Fermi

Authors: Ping Zhang; Wei Wang, Yang Su, Shuangnan Zhang, Liming Song, Fangjun Lu, Shu Zhang
Abstract: We conduct a detailed analysis of an M1.3 limb flare occurring on 2017 July 3, which have the X-ray observations recorded by multiple hard X-ray telescopes, including Hard X-ray Modulation Telescope (Insight-HXMT), Ramaty High Energy Solar Spectroscopic Imager (RHESSI), and the Fermi Gamma-ray Space Telescope (Fermi). Joint analysis has also used the extreme ultraviolet (EUV) imaging data from the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamic Observatory. The hard X-ray spectral and imaging evolution suggest a lower corona source, and the non-thermal broken power law distribution has a rather low break energy ∼15 keV. The EUV imaging shows a rather stable plasma configuration before the hard X-ray peak phase, and accompanied by a filament eruption during the hard X-ray flare peak phase. Hard X-ray image reconstruction from RHESSI data only shows one foot point source. We also determined the DEM for the peak phase by SDO/AIA data. The integrated EM beyond 10 MK at foot point onset after the peak phase, while the >10 MK source around reconnection site began to fade. The evolution of EM and hard X-ray source supports lower corona plasma heating after non-thermal energy dissipation. The combination of hard X-ray spectra and images during the limb flare provides the understanding on the interchange of non-thermal and thermal energies, and relation between lower corona heating and the upper corona instability.
PubDate: Mon, 09 May 2022 18:46:41 +080

• Detecting and Monitoring Tidal Dissipation of Hot Jupiters in the Era of
SiTian

Authors: Fan Yang; Wei Wang, Xing Wei, Hui Zhang, Ji-Lin Zhou, Su-Su Shan, Jie Zheng, Wei-Kai Zong, Ming Yang, Yu Bai, Song Wang, Jia-Chen Zheng, Yu-Ru Xu, Yu-Feng Li, You-Jun Lu, Ji-Feng Liu
Abstract: Transit Timing Variation (TTV) of hot Jupiters provides direct observational evidence of planet tidal dissipation. Detecting tidal dissipation through TTV needs high precision transit timings and long timing baselines. In this work, we predict and discuss the potential scientific contribution of the SiTian Survey in detecting and analyzing exoplanet TTV. We develop a tidal dissipation detection pipeline for the SiTian Survey that aims at time-domain astronomy with 72 1 m optical telescopes. The pipeline includes the modules of light curve deblending, transit timing acquisition and TTV modeling. SiTian is capable of detecting more than 25,000 exoplanets among which we expect ∼50 sources to show evidence of tidal dissipation. We present detection and analysis of tidal dissipating targets, based on simulated SiTian light curves of XO-3b and WASP-161b. The transit light curve modeling gives consistent results within 1σ to input values of simulated light curves. Also, the parameter uncertainties predicted by Markov Chain Monte Carlo are consistent with the distribution obtained from simulating and modeling the light curve 1000 times. The timing precision of SiTian observations is ∼0.5 minutes with one transit visit. We show that differences between TTV origins, e.g., tidal dissipation, apsidal precession and multiple planets, would be significant, considering the timing precision and baseline. The detection rate of tidal dissipating hot Jupiters would answer a crucial question of whether the planet migrates at an early formation stage or random stages due to perturbations, e.g., planet scattering or secular interaction. SiTian identified targets would be constructive given that the sample would extend tenfold.
PubDate: Mon, 09 May 2022 18:46:34 +080

• A New X-Ray Tidal Disruption Event Candidate with Fast Variability

Authors: J. Hampel; S. Komossa, J. Greiner, T. H. Reiprich, M. Freyberg, T. Erben
Abstract: During a close encounter between a star and a supermassive black hole, the star can get disrupted by the black hole’s tidal forces, resulting in a tidal disruption event (TDE). The accretion of the star’s material onto the black hole produces strong emission in different wavelength regimes. Here we report the discovery with the Roentgen Satellite (ROSAT) of an X-ray-selected transient source in an optically non-active galaxy. At the location R.A.: 13h 31m57s.66 and decl.: −32°43′19’’.7 a sudden rise in X-ray luminosity by a factor of 8 within 8 days has been observed. Additionally, a very soft X-ray spectrum with a blackbody temperature kT = 0.1 keV and a peak luminosity of at least 1 × 1043 erg s−1 suggests a TDE interpretation, and the observed properties are very similar to previously identified soft X-ray (ROSAT) TDEs. An optical spectrum taken of the galaxy at the position of RXJ133157.6324319.7 six years after the X-ray outburst does not show any emission lines as would be expected from a persistent active galactic nucleus. The redshift of the galaxy is determined to be 0.051 based on absorption lines. It is therefore likely a member of the galaxy cluster A3560. The rise in X-ray luminosity happens within 8 days and thus appears to be fast for such an event. No X-ray emission was detected 170 days before and 165 days after the event, and none was detected 25 yr later with the Neil Gehrels Swift Observatory. The change in X-ray luminosity is at least a factor of 40.
PubDate: Mon, 09 May 2022 18:46:30 +080

• Possibility of Searching for Accreting White Dwarfs with the Chinese Space
Station Telescope

Authors: Wei Xie; Hai-Liang Chen
Abstract: Accreting WDs are very important for the studies of binary evolution, binary population synthesis and accretion physics. So far, there are a lot of accreting WD binaries with low accretion rates, such as cataclysmic variables, detected by different surveys. However, few accreting WD binaries with high accretion rates have been detected. In this paper, we studied the spectrum properties of accreting WD binaries and investigated whether accreting WD binaries with high accretion rates can be detected by the Chinese Space Station Telescope (CSST). We found that some accreting WD binaries with high accretion rates can be distinguishable from other types of stars with (NUV − y, u − y), (NUV − r, u − g), (NUV − i, u − g), (NUV − z, u − g) and (NUV − y, u − g) color–color diagrams. Therefore, some accreting WD binaries with high accretion rates can be detected by the CSST
PubDate: Mon, 09 May 2022 18:46:27 +080

• Classifying Galaxy Morphologies with Few-shot Learning

Authors: Zhirui Zhang; Zhiqiang Zou, Nan Li, Yanli Chen
Abstract: The taxonomy of galaxy morphology is critical in astrophysics as the morphological properties are powerful tracers of galaxy evolution. With the upcoming Large-scale Imaging Surveys, billions of galaxy images challenge astronomers to accomplish the classification task by applying traditional methods or human inspection. Consequently, machine learning, in particular supervised deep learning, has been widely employed to classify galaxy morphologies recently due to its exceptional automation, efficiency, and accuracy. However, supervised deep learning requires extensive training sets, which causes considerable workloads; also, the results are strongly dependent on the characteristics of training sets, which leads to biased outcomes potentially. In this study, we attempt Few-shot Learning to bypass the two issues. Our research adopts the data set from the Galaxy Zoo Challenge Project on Kaggle, and we divide it into five categories according to the corresponding truth table. By classifying the above data set utilizing few-shot learning based on Siamese Networks and supervised deep learning based on AlexNet, VGG_16, and ResNet_50 trained with different volumes of training sets separately, we find that few-shot learning achieves the highest accuracy in most cases, and the most significant improvement is 21% compared to AlexNet when the training sets contain 1000 images. In addition, to guarantee the accuracy is no less than 90%, few-shot learning needs ∼6300 images for training, while ResNet_50 requires ∼13,000 images. Considering the advantages stated above, foreseeably, few-shot learning is suitable for the taxonomy of galaxy morphology and even for identifying rare astrophysical objects, despite limited training sets consisting of observational data only.
PubDate: Mon, 09 May 2022 18:46:23 +080

• Constraining the Parameterized Neutron Star Equation of State with
Astronomical Observations

Authors: Jaikhomba Singha; S. Mullai Vaneshwar, Ankit Kumar
Abstract: We utilize the phenomenologically parameterized piecewise polytropic equations of state to study various neutron star properties. We investigate the compliance of these equations of state with several astronomical observations. We also demonstrate that the theoretical estimates of the fractional moment of inertia cannot explain all the pulsar glitches observed. We model the crust as a solid spheroidal shell to calculate the fractional moment of inertia of fast-spinning neutron stars. We also show that the braking index obtained in a simple magnetic dipole radiation model with a varying moment of inertia deviates significantly from the observed data. Future developments in both theory and observations may allow us to use the fractional moment of inertia and braking index as observational constraints for neutron star equation of state.
PubDate: Mon, 09 May 2022 18:46:20 +080

JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762