Search

Start Over Subject spectroscopy Content Level Research
711. Evolu. star mass-metallicity relation. II.
ID:
ivo://CDS.VizieR/J/ApJ/885/100
Title:
Evolu. star mass-metallicity relation. II.
Short Name:
J/ApJ/885/100
Date:
16 Mar 2022 11:50:55
Publisher:
CDS
Description:
We present the stellar mass-[Fe/H] and mass-[Mg/H] relation of quiescent galaxies in two galaxy clusters at z~0.39 and z~0.54. We derive the age, [Fe/H], and [Mg/Fe] for each individual galaxy using a full-spectrum fitting technique. By comparing with the relations for z~0 Sloan Digital Sky Survey galaxies, we confirm our previous finding that the mass-[Fe/H] relation evolves with redshift. The mass-[Fe/H] relation at higher redshift has lower normalization and possibly steeper slope. However, based on our sample, the mass-[Mg/H] relation does not evolve over the observed redshift range. We use a simple analytic chemical evolution model to constrain the average outflow that these galaxies experience over their lifetime, via the calculation of mass-loading factor. We find that the average mass-loading factor {eta} is a power-law function of galaxy stellar mass, {eta}{prop}M*^-0.21{+/-}0.09^. The measured mass-loading factors are consistent with the results of other observational methods for outflow measurements and with the predictions where outflow is caused by star formation feedback in turbulent disks.
712. Evolution of spectral early-type galaxies
ID:
ivo://CDS.VizieR/J/A+A/524/A6
Title:
Evolution of spectral early-type galaxies
Short Name:
J/A+A/524/A6
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study the evolution of spectral early-type galaxies in clusters, groups, and the field up to redshift 0.9 using the ESO Distant Cluster Survey (EDisCS) dataset. We measure structural parameters (circularized half-luminosity radii Re, surface brightness Ie, and velocity dispersions sigma) for 154 cluster and 68 field galaxies. On average, we achieve precisions of 10% in Re, 0.1dex in logIe, and 10% in sigma. We sample ~20% of cluster and ~10% of field spectral early-type galaxies to an I band magnitude in a 1arcsec radius aperture as faint as I1=22. We study the evolution of the zero point of the fundamental plane (FP) and confirm results in the literature, but now also for the low cluster velocity dispersion regime.
713. Evolution state of red giants from seismology
ID:
ivo://CDS.VizieR/J/A+A/572/L5
Title:
Evolution state of red giants from seismology
Short Name:
J/A+A/572/L5
Date:
21 Oct 2021
Publisher:
CDS
Description:
The detection of oscillations with a mixed character in subgiants and red giants allows us to probe the physical conditions in their cores. With these mixed modes, we aim at determining seismic markers of stellar evolution. Kepler asteroseismic data were selected to map various evolutionary stages and stellar masses. Seismic evolutionary tracks were then drawn with the combination of the frequency and period spacings.
714. EW-Teff calibration for solar-type stars
ID:
ivo://CDS.VizieR/J/A+A/512/A13
Title:
EW-Teff calibration for solar-type stars
Short Name:
J/A+A/512/A13
Date:
21 Oct 2021
Publisher:
CDS
Description:
The precise determination of the stellar effective temperature of solar type stars is of extreme importance for Astrophysics. We present an effective temperature calibration for FGK dwarf stars using line equivalent width ratios of spectral absorption lines. The ratios of spectral line equivalent width can be very sensitive to effective temperature variations for a well chosen combination of lines. We use the automatic code ARES to measure the equivalent width of several spectral lines, and use these to calibrate with the precise effective temperature derived from spectroscopy presented in a previous work.
715. EX Lup SPHERE and SINFONI images
ID:
ivo://CDS.VizieR/J/A+A/641/A33
Title:
EX Lup SPHERE and SINFONI images
Short Name:
J/A+A/641/A33
Date:
21 Oct 2021
Publisher:
CDS
Description:
EX Lup is a well-studied T Tauri star that represents the prototype of young eruptive stars EXors. These are characterized by repetitive outbursts due to enhanced accretion from the circumstellar disk onto the star. In this paper we analyze new adaptive optics imaging and spectroscopic observations to study EX Lup and its circumstellar environment in near-infrared in its quiescent phase. We aim at providing a comprehensive understanding of the circumstellar environment around EX Lup in quiescence that builds upon the vast literature data. We observed EX Lup in quiescence with the high contrast imager SPHERE/IRDIS in the dual-beam polarimetric imaging mode to resolve the circumstellar environment in near-infrared scattered light. We complemented these data with earlier SINFONI spectroscopy, also taken in quiescence. Results.We resolve for the first time in scattered light a compact feature around EX Lup azimuthally extending from ~280{deg} to ~360{deg}, and radially extending from 0.3" to 0.55" in the plane of the disk. We explore two different scenarios for the detected emission. The first one accounts for the emission as coming from the brightened walls of the cavity excavated by the outflow whose presence was suggested by ALMA observations in the J=3-2 line of ^12^CO. The second one accounts for the emission as coming from an inclined disk. In this latter case we detect for the first time a more extended circumstellar disk in scattered light, which shows that a region between 10 and 30au is depleted of um-size grains. We compare the J-, H- and K- band spectra obtained with SINFONI in quiescence with the spectra taken during the outburst, showing that all the emission lines were due to the episodic accretion event. Based on the morphology analysis we favour the scenario in which the scattered light is coming from a circumstellar disk rather than the outflow around EX Lup. We analyze the origin of the observed feature either as coming from a continuous circumstellar disk with a cavity, or from the illuminated wall of the outer disk or from a shadowed disk. Moreover, we discuss what is the origin of the m-size grains depleted region, exploring the possibility that a sub-stellar companion may be the cause of it.
716. Exocomets. A Spectroscopic Survey
ID:
ivo://CDS.VizieR/J/A+A/639/A11
Title:
Exocomets. A Spectroscopic Survey
Short Name:
J/A+A/639/A11
Date:
21 Oct 2021
Publisher:
CDS
Description:
While exoplanets are now routinely detected, the detection of small bodies in extrasolar systems remains challenging. Since the discovery of sporadic events, which are interpreted to be exocomets (falling evaporating bodies) around beta Pic in the early 1980s, Monly 20 stars have been reported to host exocomet-like events. We aim to expand the sample of known exocomet-host stars, as well as to monitor the hot-gas environment around stars with previously known exocometary activity. We have obtained high-resolution optical spectra of a heterogeneous sample of 117 main-sequence stars in the spectral type range from B8 to G8. The data were collected in 14 observing campaigns over the course of two years from both hemispheres. We analysed the CaII K&H and NaI D lines in order to search for non-photospheric absorptions that originated in the circumstellar environment and for variable events that could be caused by the outgassing of exocomet-like bodies. We detected non-photospheric absorptions towards 50% of the sample, thus attributing a circumstellar origin to half of the detections (i.e. 26% of the sample). Hot circumstellar gas was detected in the metallic lines inspected via narrow stable absorptions and/or variable blue- and red-shifted absorption events. Such variable events were found in 18 stars in the CaII and/or NaI lines; six of them are reported in the context of this work for the first time. In some cases, the variations we report in the CaII K line are similar to those observed in beta^L Pic. While we do not find a significant trend in the age or location of the stars, we do find that the probability of finding CS gas in stars with larger vsini is higher. We also find a weak trend with the presence of near-infrared excess and with anomalous (lambda Boo-like) abundances, but this would require confirmation by expanding the sample.
717. ExoMol line lists for BeH, MgH and CaH
ID:
ivo://CDS.VizieR/J/MNRAS/425/34
Title:
ExoMol line lists for BeH, MgH and CaH
Short Name:
J/MNRAS/425/34
Date:
21 Oct 2021
Publisher:
CDS
Description:
Accurate line lists for three molecules, BeH, MgH and CaH, in their ground electronic states are presented. These line lists are suitable for temperatures relevant to exoplanetary atmospheres and cool stars (up to 2000K). A combination of empirical and ab initio methods is used. The rovibrational energy levels of BeH, MgH and CaH are computed using the programs Level and DPotFit in conjunction with 'spectroscopic' potential energy curves (PECs). The PEC of BeH is taken from the literature, while the PECs of CaH and MgH are generated by fitting to the experimental transition energy levels. Both spin-rotation interactions (except for BeH, for which it is negligible) and non-adiabatic corrections are explicitly taken into account. Accurate line intensities are generated using newly computed ab initio dipole moment curves for each molecule using high levels of theory. Full line lists of rotation-vibration transitions for ^9^BeH, ^24^MgH, ^25^MgH, ^26^MgH and ^40CaH are made available in an electronic form as supplementary data to this article and at www.exomol.com .
718. ExoMol line lists for CH4
ID:
ivo://CDS.VizieR/J/MNRAS/440/1649
Title:
ExoMol line lists for CH4
Short Name:
J/MNRAS/440/1649
Date:
21 Oct 2021
Publisher:
CDS
Description:
A new hot line list is calculated for ^12^CH_4_ in its ground electronic state. This line list, called 10to10, contains 9.8 billion transitions and should be complete for temperatures up to 1500K. It covers the wavelengths longer than 1{mu}m and includes all transitions to upper states with energies below hc 18000cm^-1^ and rotational excitation up to J=39. The line list is computed using the eigenvalues and eigenfunctions of CH_4_ obtained by variational solution of the SCHR equation for the rotation-vibration motion of nuclei employing program TROVE and a new 'spectroscopic' potential energy surface (PES) obtained by refining an ab initio PES (CCSD(T)-F12c/aug-cc-pVQZ) in a least-squares fitting to the experimentally derived energies with J=0, 1, 2, 3, 4 as extracted from the HITRAN database. The dipole transition probabilities are represented by the Einstein-A coefficients obtained using a previously reported ab initio dipole moment surface (CCSD(T)-F12c/aug-cc-pVTZ). Detailed comparisons with other available sources of methane transitions including HITRAN, experimental compilations and other theoretical line lists show that these sources lack transitions both higher temperatures and near infrared wavelengths. The 10to10 line list is suitable for modelling atmospheres of cool stars and exoplanets.
719. ExoMol line lists for formaldehyde H_2_CO
ID:
ivo://CDS.VizieR/J/MNRAS/448/1704
Title:
ExoMol line lists for formaldehyde H_2_CO
Short Name:
J/MNRAS/448/1704
Date:
21 Oct 2021
Publisher:
CDS
Description:
A computed line list for formaldehyde, H_2_^12^C^16^O, applicable to temperatures up to T=1500K is presented. An empirical potential energy and ab initio dipole moment surfaces are used as the input to nuclear motion program TROVE. The resulting line list, referred to as AYTY, contains 10.3 million rotational-vibrational states and around 10 billion transition frequencies. Each transition includes associated Einstein- A coefficients and absolute transition intensities, for wavenumbers below 10000cm^-1^ and rotational excitations up to J=70. Room-temperature spectra are compared with laboratory measurements and data currently available in the HITRAN database. These spectra show excellent agreement with experimental spectra and highlight the gaps and limitations of the HITRAN data. The full line list is available from the CDS database as well as at www.exomol.com.
720. ExoMol line lists for phosphine (PH_3_)
ID:
ivo://CDS.VizieR/J/MNRAS/446/2337
Title:
ExoMol line lists for phosphine (PH_3_)
Short Name:
J/MNRAS/446/2337
Date:
21 Oct 2021
Publisher:
CDS
Description:
A comprehensive hot line list is calculated for ^31^PH_3_ in its ground electronic state. This line list, called SAlTY, contains almost 16.8 billion transitions between 7.5 million energy levels and it is suitable for simulating spectra up to temperatures of 1500K. It covers wavelengths longer than 1um and includes all transitions to upper states with energies below hc.18000cm^-1^ and rotational excitation up to J=46. The line list is computed by variational solution of the Schrodinger equation for the rotation-vibration motion employing the nuclear-motion program TROVE. A previously reported ab initio dipole moment surface is used as well as an updated 'spectroscopic' potential energy surface (PES), obtained by refining an existing ab initio surface through least-squares fitting to the experimentally derived energies. Detailed comparisons with other available sources of phosphine transitions confirms SAlTY's accuracy and illustrates the incompleteness of previous experimental and theoretical compilations for temperatures above 300K. Atmospheric models are expected to severely underestimate the abundance of phosphine in disequilibrium environments, and it is predicted that phosphine will be detectable in the upper troposphere of many substellar objects. This list is suitable for modelling atmospheres of many astrophysical environments, namely carbon stars, Y dwarfs, T dwarfs, hot Jupiters and solar system gas giant planets. It is available in full as supplementary data to the article and at www.exomol.com.

Limit your search

more »

more »

more »

more »