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: 143) 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: 116) Journal of Geophysical Research : Space Physics       (Followers: 136) 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: 118) Space Science Reviews       (Followers: 92) Space Weather       (Followers: 27) Transport and Aerospace Engineering       (Followers: 13) Universe       (Followers: 6)
Similar Journals
 Experimental AstronomyJournal Prestige (SJR): 0.908 Citation Impact (citeScore): 2Number of Followers: 38      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1572-9508 - ISSN (Online) 0922-6435 Published by Springer-Verlag  [2469 journals]
• An autonomous lunar geophysical experiment package (ALGEP) for future
space missions

Abstract: Abstract Geophysical observations will provide key information about the inner structure of the planets and satellites and understanding the internal structure is a strong constraint on the bulk composition and thermal evolution of these bodies. Thus, geophysical observations are a key to uncovering the origin and evolution of the Moon. In this article, we propose the development of an autonomous lunar geophysical experiment package, composed of a suite of instruments and a central station with standardized interface, which can be installed on various future lunar missions. By fixing the interface between instruments and the central station, it would be possible to easily configure an appropriate experiment package for different missions. We describe here a series of geophysical instruments that may be included as part of the geophysical package: a seismometer, a magnetometer, a heat flow probe, and a laser reflector. These instruments will provide mechanical, thermal, and geodetic parameters of the Moon that are strongly related to the internal structure. We discuss the functionality required for future geophysical observations of the Moon, including the development of the central station that will be used commonly by different payloads.
PubDate: 2022-05-12

• Portraying the missing baryonic mass at the cosmic noon: the contribution
of CUBES

Abstract: Abstract The cosmological and galactic missing baryon problems are briefly reviewed with a particular focus on the contributions to the baryonic census derived from the analysis of quasar absorption spectra. The CUBES spectrograph foreseen for the ESO VLT, with its exceptional efficiency ( $$> 40$$ %), blue wavelength coverage ( $$\lambda \simeq 300-405$$ nm) and intermediate resolution ( $$R\simeq 24,000$$ ) will allow us to tackle this issue with two approaches: using H i Lyman- $$\alpha$$ lines at $$z \simeq 1.5-2.3$$ , just after the peak of star formation, and using O vi absorbers at $$z \simeq 1.9-2.9$$ , at the cosmic noon. In both cases, in order to derive the baryonic masses it will be necessary to acquire also higher-resolution spectra of the same target quasars to cover the region at longer wavelengths. We simulate the observations with the CUBES E2E simulator considering a sample of 40 bright quasars at redshifts $$z_\mathrm{em}\sim 2-3$$ observed for a total time of $$\sim 13$$ h to reach a signal-to-noise ratio of $$\sim 15$$ in the H i Lyman- $$\alpha$$ , O vi forests.
PubDate: 2022-04-30

• Mock HUBS observations of hot gas with IllustrisTNG

Abstract: Abstract The lack of adequate X-ray observing capability is seriously impeding the progress in understanding the hot phase of circumgalactic medium (CGM), which is predicted to extend to the virial radius of a galaxy or beyond, and thus in acquiring key boundary conditions for studying galaxy evolution. To this end, the Hot Universe Baryon Surveyor (HUBS) is proposed. HUBS is designed to probe hot CGM by detecting its emission or absorption lines with a non-dispersive X-ray spectrometer of high resolution and high throughput. The spectrometer consists of a 60 × 60 array of microcalorimeters, with each detector providing an energy resolution of 2 eV, and is placed in the focal plane of an X-ray telescope of 1∘ field-of-view. With such a design, the spectrometer is highly optimized for detecting X-ray-emitting hot gas in the CGM of local galaxies, as well as in intra-group medium (IGrM), intra-cluster medium (ICM), or intergalactic medium (IGM). To assess the scientific potential of HUBS, in this work, we created mock observations of galaxies, groups, and clusters at different redshifts with the IllustrisTNG simulation. Focusing exclusively on emission studies, we took into account the effects of light cone, Galactic foreground emission, and background AGN contribution in the mock observations. From the observations, we made mock X-ray images and spectra, analyzed them to derive the properties of the emitting gas in each case, and compared the results with the input parameters from the simulation. The results show that HUBS is well suited for studying hot CGM at low redshifts. The redshift range is significantly extended for measuring IGrM and ICM. The sensitivity limits are also presented for detecting extended emission of low surface brightness.
PubDate: 2022-04-29

• Heavy elements

Abstract: Abstract How are the heavy elements formed' This has been a key open question in physics for decades. Recent direct detections of neutron star mergers and observations of evolved stars show signatures of chemical elements in the blue range of their spectra that bear witness of recent nuclear processes that led to heavy element production. The formation of heavy elements typically takes place through neutron-capture reactions creating radioactive isotopes, which following beta-decay turn into the stable isotopes we today can measure indirectly in the surfaces of cool, low-mass stars or meteoritic grains. The conditions (such as the neutron density or entropy) of these n-capture reactions remain to date poorly constrained, and only through a multidisciplinary effort can we, by combining and comparing observations, experiments, and theoretical predictions, improve on one of the top 10 most important open physics questions posed at the turn of the century. This emphasises the need for detailed observations of the near-UV to blue wavelength region. The shortage of spectrographs and hence spectra covering this range with high-resolution and high signal-to-noise has for decades played a limiting factor in our understanding of how heavy elements form in the nuclear reactions as well as how they behave in the stellar surfaces. With CUBES (Cassegrain U-Band Efficient Spectrograph) we can finally improve the observations, by covering the crucial blue range in more remote stars and also achieve a higher signal-to-noise ratio (SNR). This is much needed to detect and accurately deblend the absorption lines and in turn derive more accurate and precise abundances of the heavy elements.
PubDate: 2022-04-28

• Closing gaps to our origins

Abstract: Abstract This article reproduces the contents of the White Paper entitled by the same name submitted to the call issued by the European Space Agency soliciting ideas from the scientific community for the science themes that should be covered during the Voyage 2050 planning cycle. This contribution focus in the investigation of the emergence of life and the role that astronomy has to play in it. Three fundamental areas of activity are identified: [1] measuring the chemical enrichment of the Universe, [2] investigating planet formation and searching for exoplanets with signatures of life and, [3] determining the abundance of amino acids and the chemical routes to amino acid and protein growth in astronomical bodies. This proposal deals with the first two. The building blocks of life in the Universe began as primordial gas processed in stars and mixed at galactic scales. The mechanisms responsible for this development are not well-understood and have changed over the intervening 13 billion years. To follow the evolution of matter over cosmic time, it is necessary to study the strongest (resonance) transitions of the most abundant species in the Universe. Most of them are in the ultraviolet (UV; 950 Å - 3000 Å ) spectral range that is unobservable from the ground; the “missing” metals problem cannot be addressed without this access. Habitable planets grow in protostellar discs under ultraviolet irradiation, a by-product of the accretion process that drives the physical and chemical evolution of discs and young planetary systems. The electronic transitions of the most abundant molecules are pumped by this UV field that is the main oxidizing agent in the disc chemistry and provides unique diagnostics of the planet-forming environment that cannot be accessed from the ground. Knowledge of the variability of the UV radiation field is required for the astrochemical modelling of protoplanetary discs, to understand the formation of planetary atmospheres and the photochemistry of the precursors of life. Earth’s atmosphere is in constant interaction with the interplanetary medium and the solar UV radiation field. The exosphere of the Earth extends up to 35 planetary radii providing an amazing wealth of information on our planet’s winds and the atmospheric compounds. To access to it in other planetary systems, observation of the UV resonance transitions is required. The investigation for the emergence of life calls for the development of large astronomical facilities, including instrumentation in optical and UV wavelengths. In this contribution, the need to develop a large observatory in the optical and in the UV is revealed, in order to complete the scientific goals to investigate the origin of life, inaccessible through other frequencies in the electromagnetic spectrum.
PubDate: 2022-04-23

• Venus sample return mission revisited

Abstract: Abstract A Venus sample return mission is very interesting from a scientific point of view, for example, analysing the composition of the soil will help us to understand the differences between Venus and Earth. However, such a mission is extremely challenging. On Venus the ground conditions are very harsh (460 °C, 9.6 MPa), the Delta V requirement from surface to orbit is close to the Earth case, and atmospheric drag means that a rocket launch must occur above 55 km and so an Unmanned Aerial Vehicle is required to lift the samples to rocket altitude. Sample return missions have been studied in depth by NASA/JPL and ESA, and in the former case the proposed profile involves several critical points, each with a significant probability of failure: Thermal exposure during sample drilling and ascent to launch altitude. Fast balloon inflation, at 55 km altitude. Difficulties to perform a rendezvous with an orbital vehicle if the upper stage is not manoeuvrable. The purpose of this paper is to propose new methods for meeting the challenge at each critical step and reducing the risks to such a mission. In particular, we propose two innovative methods for thermal control on the lander: advanced thermal insulation and phase change materials.
PubDate: 2022-04-22

• Qualification of the thermal stabilization, polishing and coating
procedures for the aluminum telescope mirrors of the ARIEL mission

Abstract: Abstract ARIEL, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, was selected as the fourth medium-class mission in ESA’s Cosmic Vision program. ARIEL is based on a 1 m class telescope optimized for spectroscopy in the waveband between 1.95 and 7.8 micron and operating in cryogenic conditions. Fabrication of the 1.1 m aluminum primary mirror for the ARIEL telescope requires technological advances in the three areas of substrate thermal stabilization, optical surface polishing and coating. This article describes the qualification of the three procedures that have been set up and tested to demonstrate the readiness level of the technological processes employed. Substrate thermal stabilization is required to avoid deformations of the optical surface during cool down of the telescope to the operating temperature below 50 K. Purpose of the process is to release internal stress in the substrate that can cause such shape deformations. Polishing of large aluminum surfaces to optical quality is notoriously difficult due to softness of the material, and required setup and test of a specific polishing recipe capable of reducing residual surface shape errors while maintaining surface roughness below 10 nm RMS. Finally, optical coating with protected silver must be qualified for environmental stability, particularly at cryogenic temperatures, and uniformity. All processes described in this article have been applied to aluminum samples of up to 150 mm of diameter, leading the way to the planned final test on a full size demonstrator of the ARIEL primary mirror.
PubDate: 2022-04-19

• Study of water Cherenkov detector to improve the angular resolution of an
air-shower array for ultra-high-energy gamma-ray observation

Abstract: Abstract For research on cosmic gamma rays with energies in the range of several tens of teraelectronvolts or more, we investigated a method to improve the angular resolution of an air shower. In an air shower, the density of secondary gamma rays is several times higher than that of electrons and those measurement is important for determining the shower direction. It was found that the angular resolution in the shower front-fit method decreases in inverse proportion to the square root of the number of measured particles. Even if the total number of measured particles is the same, secondary gamma rays contribute more to the improvement of angular resolution than electrons. If secondary gamma rays could be measured at an altitude of 4,740 m with a sensitivity of 100 %, an improvement of approximately 40 % was determined for a 500 TeV shower. A water Cherenkov detector with high gamma-ray sensitivity was investigated through Monte Carlo simulation. Detection efficiencies of approximately 0.38 and 0.76 were obtained for vertically incident gamma rays and electrons, respectively, using 19 8-inch diameter PMTs inside a detector installed in a water tank of radius 4.5 m and water depth 1.6 m. The detection time error for secondary gamma rays is approximately 2.18 ns at an incident angle of 0∘ and the standard error in the detection time for shower front particles was found to be approximately 10 times lower than that obtained by using a plastic scintillation detector with an area of 1 m2.
PubDate: 2022-04-14

• Cometary science with CUBES

Abstract: Abstract The proposed CUBES spectrograph for ESO’s Very Large Telescope will be an exceptionally powerful instrument for the study of comets. The gas coma of a comet contains a large number of emission features in the near-UV range covered by CUBES (305-400 nm), which are diagnostic of the composition of the ices in its nucleus and the chemistry in the coma. Production rates and relative ratios between different species reveal how much ice is present and inform models of the conditions in the early solar system. In particular, CUBES will lead to advances in detection of water from very faint comets, revealing how much ice may be hidden in the main asteroid belt, and in measuring isotopic and molecular composition ratios in a much wider range of comets than currently possible, provide constraints on their formation temperatures. CUBES will also be sensitive to emissions from gaseous metals (e.g., FeI and NiI), which have recently been identified in comets and offer an entirely new area of investigation to understand these enigmatic objects.
PubDate: 2022-04-13

• The thermal architecture of the ESA ARIEL payload at the end of phase B1

Abstract: Abstract The Atmospheric Remote-sensing Infrared Exoplanets Large-survey (ARIEL) is the fourth medium (M4) mission selected in the context of the ESA Cosmic Vision 2015–2025 programme, with a launch planned in 2028. During 4 years of flight operations, ARIEL will probe the chemical and physical properties of approximately 1000 known exoplanets by observing their atmosphere, to study how planetary systems form and evolve [1, 2]. The mission is designed as a transit and eclipse spectroscopy survey, operated by a 1-m class telescope feeding two instruments, the Fine Guidance system (FGS) and the ARIEL InfraRed Spectrometer (AIRS), that accommodate photometric and spectroscopic channels covering the band from 0.5 to 7.8 μm in the visible to near-IR range [3, 4]. The mission high sensitivity requirements ask for an extremely stable thermo-mechanical platform. The payload thermal control is based on a passive and active cooling approach. Passive cooling is achieved by a V-Groove shields system that exploits the L2 orbit favourable thermal conditions to cool the telescope and the optical bench to stable temperatures <60 K. The FGS focal planes operate at the optical bench temperature while the AIRS channel detectors require a colder reference, lower than 42 K. This is provided by an active cooling system based on a Neon Joule-Thomson cold end, fed by a mechanical compressor. In this paper we report the thermal architecture of the payload at the end of Phase B1 and present the requirements that drive the design together with the analyses results and the expected performances.
PubDate: 2022-03-31

• A compact instrument for gamma-ray burst detection on a CubeSat platform
II

Abstract: Abstract The Gamma-ray Module, GMOD, is a miniaturised novel gamma-ray detector which will be the primary scientific payload on the Educational Irish Research Satellite (EIRSAT-1) 2U CubeSat mission. GMOD comprises a compact (25 mm $$\times$$ 25 mm $$\times$$ 40 mm) cerium bromide scintillator coupled to a tiled array of 4 $$\times$$ 4 silicon photomultipliers, with front-end readout provided by the IDE3380 SIPHRA. This paper presents the detailed GMOD design and the accommodation of the instrument within the restrictive CubeSat form factor. The electronic and mechanical interfaces are compatible with many off-the-shelf CubeSat systems and structures. The energy response of the GMOD engineering qualification model has been determined using radioactive sources, and an energy resolution of 5.4% at 662 keV has been measured. EIRSAT-1 will perform on-board processing of GMOD data. Trigger results, including light-curves and spectra, will be incorporated into the spacecraft beacon and transmitted continuously. Inexpensive hardware can be used to decode the beacon signal, making the data accessible to a wide community. GMOD will have scientific capability for the detection of gamma-ray bursts, in addition to the educational and technology demonstration goals of the EIRSAT-1 mission. The detailed design and measurements to date demonstrate the capability of GMOD in low Earth orbit, the scalability of the design for larger CubeSats and as an element of future large gamma-ray missions.
PubDate: 2022-03-29

• Plasma-neutral gas interactions in various space environments: Assessment
beyond simplified approximations as a Voyage 2050 theme

Abstract: Abstract In the White Paper, submitted in response to the European Space Agency (ESA) Voyage 2050 Call, we present the importance of advancing our knowledge of plasma-neutral gas interactions, and of deepening our understanding of the partially ionized environments that are ubiquitous in the upper atmospheres of planets and moons, and elsewhere in space. In future space missions, the above task requires addressing the following fundamental questions: (A) How and by how much do plasma-neutral gas interactions influence the re-distribution of externally provided energy to the composing species' (B) How and by how much do plasma-neutral gas interactions contribute toward the growth of heavy complex molecules and biomolecules' Answering these questions is an absolute prerequisite for addressing the long-standing questions of atmospheric escape, the origin of biomolecules, and their role in the evolution of planets, moons, or comets, under the influence of energy sources in the form of electromagnetic and corpuscular radiation, because low-energy ion-neutral cross-sections in space cannot be reproduced quantitatively in laboratories for conditions of satisfying, particularly, (1) low-temperatures, (2) tenuous or strong gradients or layered media, and (3) in low-gravity plasma. Measurements with a minimum core instrument package (< 15 kg) can be used to perform such investigations in many different conditions and should be included in all deep-space missions. These investigations, if specific ranges of background parameters are considered, can also be pursued for Earth, Mars, and Venus.
PubDate: 2022-03-26

• Molecular hydrogen in absorption at high redshifts

Abstract: Abstract Absorption lines from molecular hydrogen ( $$\mathrm H_2$$ ) in the spectra of background sources are a powerful probe of the physical conditions in intervening cold neutral medium. At high redshift, $$z>2$$ , $$\mathrm H_2$$ lines are conveniently shifted in the optical domain, allowing the use of ground-based telescopes to perform high-resolution spectroscopy, which is essential for a proper analysis of the cold gas. We describe recent observational progress, based on the development of efficient pre-selection techniques in low-resolution spectroscopic surveys such as the Sloan Digital Sky Survey (SDSS). The next generation of spectrographs with high blue-throughput, such as CUBES, will certainly significantly boost the efficiency and outcome of follow-up observations. In this paper, we discuss high priority science cases for CUBES, building on recent $$\mathrm H_2$$ observations at high-z: probing the physical conditions in the cold phase of regular galaxies and outflowing gas from active galactic nucleus.
PubDate: 2022-03-25

• Monitoring fast solar chromospheric activity: the MeteoSpace project

Abstract: Abstract We present in this reference paper an instrumental project dedicated to the monitoring of solar activity during solar cycle 25. It concerns the survey of fast evolving chromospheric events implied in Space Weather, such as flares, coronal mass ejections, filament instabilities and Moreton waves. Coronal waves are produced by large flares around the solar maximum and propagate with chromospheric counterparts; they are rare, faint, difficult to observe, and for that reason, challenging. They require systematic observations with automatic, fast and multi-channel optical instruments. MeteoSpace is a high cadence telescope assembly specially designed for that purpose. The large amount of data will be freely available to the solar community. We describe in details the optical design, the qualification tests and capabilities of the telescopes, and show how waves can be detected. MeteoSpace will be installed at Calern observatory (Côte d’Azur, 1270 m) and will be in full operation in 2023.
PubDate: 2022-03-24

• CASPER: A mission to study the time-dependent evolution of the magnetic
solar chromosphere and transition regions

Abstract: Abstract Our knowledge about the solar chromosphere and transition region (TR) has increased in the last decade thanks to the huge scientific return of space-borne observatories like SDO, IRIS, and Hinode, and suborbital rocket experiments like CLASP1, CLASP2, and Hi-C. However, the magnetic nature of those solar regions remain barely explored. The chromosphere and TR of the Sun harbor weak fields and are in a low ionization stage both having critical effects on their thermodynamic behavior. Relatively cold gas structures, such as spicules and prominences, are located in these two regions and display a dynamic evolution in high-resolution observations that static and instantaneous 3D-magnetohydrodynamic (MHD) models are not able to reproduce. The role of the chromosphere and TR as the necessary path to a (largely unexplained) very hot corona calls for the generation of observationally based, time-dependent models of these two layers that include essential, up to now disregarded, ingredients in the modeling such as the vector magnetic field. We believe that the community is convinced that the origin of both the heat and kinetic energy observed in the upper layers of the solar atmosphere is of magnetic origin, but reliable magnetic field measurements are missing. The access to sensitive polarimetric measurements in the ultraviolet wavelengths has been elusive until recently due to limitations in the available technology. We propose a low-risk and high-Technology Readiness Level (TRL) mission to explore the magnetism and dynamics of the solar chromosphere and TR. The mission baseline is a low-Earth, Sun-synchronous orbit at an altitude between 600 and 800 km. The proposed scientific payload consists of a 30 cm aperture telescope with a spectropolarimeter covering the hydrogen Ly-alpha and the Mg II h&k ultraviolet lines. The instrument shall record high-cadence, full spectropolarimetric observations of the solar upper atmosphere. Besides the answers to a fundamental solar problem the mission has a broader scientific return. For example, the time-dependent modeling of the chromospheres of stars harboring exoplanets is fundamental for estimating the planetary radiation environment. The mission is based on technologies that are mature enough for space and will provide scientific measurements that are not available by other means.
PubDate: 2022-03-24

• Unveiling UV-bright stellar populations in red and dead galaxies with
CUBES

Abstract: Abstract Early-type galaxies (ETGs) exhibit a rise in their UV flux shortward of 3000Å, a phenomenon dubbed the UV upturn. It is believed that this UV flux in such old systems is driven by highly evolved hot horizontal branch (HB) stars, which are not expected to exist given standard cosmological timescales. However, observations of the evolution of the upturn with redshift suggests that the HB stars could potentially become UV-bright through a process of Helium enhancement, similar to what is observed in the multiple stellar populations of local globular clusters (GC). A highly sensitive UV detector such as CUBES can allow for the analysis of the CN and CH lines between $$3000-4000$$ Å in local ETGs, as He-rich populations are also found to be heavily enhanced in Nitrogen and have a radial gradient in [N/Fe] (i.e. the Nitrogen is centrally concentrated) in GCs. If the same correlations are recovered in ETGs, it would suggest that the He-enhancement in both systems arose through a universal mechanism and thus have similar formation channels. Furthermore, at slightly higher redshifts ( $$0.2<z<0.6$$ ), CUBES will allow us to probe directly the rest-frame near-UV indices of ETGs, particularly between $$2200-3200$$ Å, which consist of the majority of spectral lines driven by the hot HB population and hence can be used to study its intrinsic properties (e.g. temperature, strength, etc). Current detectors require in excess of 20 hours of integration time to observe the brightest ETGs to a sufficient depth in this wavelength range, necessitating a highly efficient multiplexed UV sensitive spectrograph such as CUBES to make further progress, with the potential of improving exposure times by at least a factor of 2 and allowing for nearly all galaxies at or above $$L^*$$ in a given cluster to be simultaneously observed with multi-object spectroscopy.
PubDate: 2022-03-24

• Detecting weak beryllium lines with CUBES

Abstract: Abstract Beryllium is a light element with one single stable isotope, $$^9$$ Be, which is a pure product of cosmic-ray spallation in the interstellar medium. Beryllium abundances in late-type stars can be used in studies about evolutionary mixing, Galactic chemical evolution, planet engulfment, and the formation of globular clusters. Some of these uses of Be abundances figure among the science cases of the Cassegrain U-Band Efficient Spectrograph (CUBES), a new near-UV low- and medium-resolution spectrograph under development for the Very Large Telescope. Here, we report on a study about beryllium abundances in extremely metal-poor stars in the context of the phase A of CUBES. Our motivation is to understand the limits for the detection of weak lines in extremely metal-poor stars of low Be abundances. We analyze simulated CUBES observations, performed in medium-resolution mode, based on synthetic spectra for four mock stars with [Fe/H] $$\le$$ −3.0. We find that detecting the Be lines is possible in certain cases, but is very challenging and requires high signal-to-noise ratio. Depending on the atmospheric parameters of the target stars, and if signal-to-noise per pixel of about 400 can be achieved, it should be possible to detect Be abundances between $$\log$$ (Be/H) −13.1 and −13.6, with a typical uncertainty of ± 0.15 dex. Using CUBES, the required data for such studies can be obtained for stars that are fainter by two magnitudes with respect to what is possible with current instrumentation.
PubDate: 2022-03-23

• Beryllium abundances in turn-off stars of globular clusters with the CUBES
spectrograph

Abstract: Abstract Globular clusters host multiple stellar populations that display star-to-star variation of light elements that are affected by hot hydrogen burning (e.g., He, C, N, O). Several scenarios have been suggested to explain these variations. Most involve multiple star formation episodes, where later generations are born from material contaminated by the nucleosynthetic products of the previous stellar generation(s). One difficulty in the modelling of such scenarios is knowing the extent to which processed and pristine material are mixed. In this context, beryllium abundances measured in turn-off stars of different generations can provide new information. Beryllium originates from cosmic-ray spallation and can only be destroyed inside stars. Beryllium abundances can thus directly measure the degree of pollution of the material that formed stars in globular clusters. Turn-off stars in globular clusters are however faint and such studies are beyond the capabilities of current instrumentation. In this work, we show the progress that the CUBES spectrograph will bring to this area. Our simulations indicate that CUBES will enable the detection of variations of about 0.6 dex in the Be abundances between stars from different generations, in several nearby globular clusters with turn-off magnitude down to V = 18 mag.
PubDate: 2022-03-23

• The CUBES instrument model and simulation tools

Abstract: Abstract We present the simulation tools developed to aid the design phase of the Cassegrain U-Band Efficient Spectrograph (CUBES) for the Very Large Telescope (VLT), exploring aspects of the system design and evaluating the performance for different design configurations. CUBES aims to be the ‘ultimate’ ultraviolet (UV) instrument at the European Southern Observatory (ESO) in terms of throughput, with the goal to cover the bluest part of the spectrum accessible from the ground (300 nm to 400 nm) with the highest possible efficiency. Here we introduce the End-to-End (E2E) and the Exposure Time Calculator (ETC) tools. The E2E simulator has been developed with different versions to meet the needs of different users, including a version that can be accessed for use by the broader scientific community using a Jupyter notebook. The E2E tool was used by the system team to help define the Phase A baseline design of the instrument, as well as in scientific evaluation of a possible low-resolution mode. The ETC is a web-based tool through which the science community are able to test a range of science cases for CUBES, demonstrating its potential to push the limiting magnitude for the detection of specific UV-features, such as abundance estimates of beryllium in main-sequence stars.
PubDate: 2022-03-23

• The removal method and generation mechanism of spikes in Insight-HXMT/HE
telescope

Abstract: Abstract Spikes are some obvious sharp increases that appear on the raw light curves of Insight-HXMT’s High Energy X-ray telescope(HE), which could have influences on data products like energy and power spectra. They are considered to be fake triggers generated by large signals. In this paper, we study the spikes’ characteristic and propose two methods to remove spikes from the raw data. According to the different influences on energy and power spectra, the best parameters for removing the spikes is selected and used in the Insight-HXMT data analysis software. The generation mechanism of spikes is also studied using the backup HE detectors on ground and the spikes can be reduced by the electronic design.
PubDate: 2022-03-18

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