- ID:
- ivo://CDS.VizieR/J/A+A/624/A49
- Title:
- Spectra of Earth-like planets around M-dwarfs
- Short Name:
- J/A+A/624/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The characterisation of the atmosphere of exoplanets is one of the main goals of exoplanet science in the coming decades. We investigate the detectability of atmospheric spectral features of Earth-like planets in the habitable zone (HZ) around M dwarfs with the future James Webb Space Telescope (JWST). We used a coupled 1D climate-chemistry-model to simulate the influence of a range of observed and modelled M-dwarf spectra on Earth-like planets. The simulated atmospheres served as input for the calculation of the transmission spectra of the hypothetical planets, using a line-by-line spectral radiative transfer model. To investigate the spectroscopic detectability of absorption bands with JWST we further developed a signal- to-noise ratio (S/N) model and applied it to our transmission spectra. High abundances of methane (CH_4_) and water (H_2_O) in the atmosphere of Earth-like planets around mid to late M dwarfs increase the detectability of the corresponding spectral features compared to early M-dwarf planets. Increased temperatures in the middle atmosphere of mid- to late-type M-dwarf planets expand the atmosphere and further increase the detectability of absorption bands. To detect CH_4_, H_2_O, and carbon dioxide (CO_2_) in the atmosphere of an Earth-like planet around a mid to late M dwarf observing only one transit with JWST could be enough up to a distance of 4pc and less than ten transits up to a distance of 10pc. As a consequence of saturation limits of JWST and less pronounced absorption bands, the detection of spectral features of hypothetical Earth-like planets around most early M dwarfs would require more than ten transits. We identify 276 existing M dwarfs (including GJ 1132, TRAPPIST-1, GJ 1214, and LHS 1140) around which atmospheric absorption features of hypothetical Earth-like planets could be detected by co-adding just a few transits. The TESS satellite will likely find new transiting terrestrial planets within 15pc from the Earth. We show that using transmission spectroscopy, JWST could provide enough precision to be able to partly characterise the atmosphere of TESS findings with an Earth-like composition around mid to late M dwarfs.
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- ID:
- ivo://CDS.VizieR/J/A+A/642/A71
- Title:
- Spectra of 14 Magellanic Cloud planetary nebulae
- Short Name:
- J/A+A/642/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We obtained new spectra of fourteen Magellanic Cloud planetary nebulae with the South African Large Telescope to determine heating rates of their central stars and to verify evolutionary models of post asymptotic giant branch stars. We compared new spectra with observations made in previous years. Five planetary nebulae showed an increase of the excitation with time. Four of their central stars exhibit [WC] features in their spectra, including three new detections. This raises the total number of [WC] central stars of PNe in the Magellanic Clouds to ten. We compared determined heating rates of the four [WC] central stars with the He burning post asymptotic giant branch evolutionary tracks and the remaining star with the H-burning tracks. Determined heating rates are consistent with the evolutionary models for both H and He-burning post asymptotic giant branch stars. The central stars of the PNe which show the fastest increase of excitation are also the most luminous in the sample. This indicates that [WC] central stars in the Magellanic Clouds evolve faster than H-burning central stars and originate from more massive progenitors.
- ID:
- ivo://CDS.VizieR/J/AJ/158/147
- Title:
- Spectrophotometric parallaxes with linear models
- Short Name:
- J/AJ/158/147
- Date:
- 07 Jan 2022 11:19:14
- Publisher:
- CDS
- Description:
- With contemporary infrared spectroscopic surveys like APO Galactic Evolution Experiment (APOGEE), red-giant stars can be observed to distances and extinctions at which Gaia parallaxes are not highly informative. Yet the combination of effective temperature, surface gravity, composition, and age-all accessible through spectroscopy - determines a giant's luminosity. Therefore spectroscopy plus photometry should enable precise spectrophotometric distance estimates. Here we use the overlap of APOGEE, Gaia, the Two Micron All Sky Survey (2MASS), and the Wide-field Infrared Survey Explorer (WISE) to train a data-driven model to predict parallaxes for red-giant branch stars with 0<logg=<2.2 (more luminous than the red clump). We employ (the exponentiation of) a linear function of APOGEE spectral pixel intensities and multiband photometry to predict parallax spectrophotometrically. The model training involves no logarithms or inverses of the Gaia parallaxes, and needs no cut on the Gaia parallax signal-to-noise ratio. It includes an L1 regularization to zero out the contributions of uninformative pixels. The training is performed with leave-out subsamples such that no star's astrometry is used even indirectly in its spectrophotometric parallax estimate. The model implicitly performs a reddening and extinction correction in its parallax prediction, without any explicit dust model. We assign to each star in the sample a new spectrophotometric parallax estimate; these parallaxes have uncertainties of less than 15%, depending on data quality, which is more precise than the Gaia parallax for the vast majority of targets, and certainly any stars more than a few kiloparsec distance. We obtain 10% distance estimates out to heliocentric distances of 20 kpc, and make global maps of the Milky Way's disk.
- ID:
- ivo://CDS.VizieR/J/A+A/392/1
- Title:
- Spectrophotometry of simulated Stellar Populations
- Short Name:
- J/A+A/392/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new set of evolutionary synthesis spectra are presented for Simple Stellar Populations (SSPs) covering ranges in metallicity from 0.02<=Z/Z_{sun}_<=2.5 and ages from 4*10^6^yr<=t<=16Gyr. They are based on the most recent isochrones from the Padova group that extend earlier models by the inclusion of the thermal pulsing AGB phase for stars in the mass range 2M_{sun}_<=m<=7M_{sun}_ in accordance with the fuel consumption theorem. We show that with respect to earlier models, inclusion of the TP-AGB phase leads to significant changes in the (V-I) and (V-K) colors of SSPs in the age range from 10^8^ to >~10^9^yr. Using model atmosphere spectra from Lejeune et al. (1997, Cat. <J/A+AS/125/229>, 1998, Cat. <J/A+AS/130/65>), we calculate the spectral evolution of single burst populations of various metallicities covering the wavelength range from 90{AA} through 160{mu}m. Isochrone spectra are convolved with filter response functions to describe the time evolution of luminosities and colors in Johnson, Thuan & Gunn, Koo, HST, Washington and Stroemgren filters. The models and their results are not only intended for use in the interpretation of star clusters but also for combination with any kind of dynamical galaxy formation and/or evolution model that contains a star formation criterion. Moreover, the evolution of these single burst single metallicity stellar populations is readily folded with any kind of star formation -- and eventually chemical enrichment -- history to describe the evolutionary spectral synthesis of composite stellar populations like galaxies of any type with continuous or discontinuous star formation. For these latter purposes we also present the time evolution of ejection rates for gas and metals for two different Initial Mass Functions (IMFs) as well as cosmological and evolutionary corrections for all the filters as a function of redshift for 0<=z<=5 and two different cosmologies.
- ID:
- ivo://CDS.VizieR/J/A+A/482/989
- Title:
- Spectropolarimetric model for Earth-like planets
- Short Name:
- J/A+A/482/989
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of numerical simulations of flux F and degree of polarization P of light that is reflected by Earth-like extrasolar planets orbiting solar type stars. Our results are presented as functions of the wavelength (from 0.3 to 1.0{mu}m, with 0.001{mu}m spectral resolution) and as functions of the planetary phase angle. We use different surface coverages for our model planets, including vegetation and a Fresnel reflecting ocean, and clear and cloudy atmospheres.
- ID:
- ivo://CDS.VizieR/J/A+A/425/263
- Title:
- Spectroscopic atlas of HD175640
- Short Name:
- J/A+A/425/263
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a high resolution spectral atlas of the HgMn star HD 175640 covering the 3040-10000{AA} region. UVES spectra observed with 90000-110000 resolving power and signal to noise ratio ranging from 200 to 400 are compared with a synthetic spectrum computed with the SYNTHE code (Kurucz, 1993, CD-ROM, No. 18). The model atmosphere is an ATLAS12 model (Kurucz, 1997, in The 3rd Conf. on Faint Blue Stars, ed. Philip, Liebert & Saffer (Schenectady: L. Davis Press), 33) with parameters Teff=12000K,logg=3.95, vturb=0km/s. The stellar individual abundances in ATLAS12 were derived from an iterative procedure. The starting atomic line lists downloaded from the Kurucz website have been improved and extended by examining different sources in the literature and by comparing the computed profiles with the observed spectrum. The high quality of the data allowed us to study the isotopic and hyperfine structure for several lines of Mn II, Ga II, Ba II, Pt II, Hg I, and Hg II. Numerous weak emission lines from Cr II and Ti II have been identified in the red part of the spectrum, starting at about 5847{AA}. Two emission lines of C I (mult. 10, mult. 9) have been observed for the first time. All Cr II and Ti II emission lines originate from the high excitation states (Elow>89000cm^-1^ for Cr II and Elow>62000cm^-1^ for Ti II) with large transition probabilities (loggf>-1.00). The synthetic spectrum superimposed on the observed spectrum are available at http://wwwuser.oat.ts.astro.it/castelli/stars.html . An extended discussion on each identified ion and related atomic data is available both in the quoted website and in an electronic Appendix to the paper.
- ID:
- ivo://CDS.VizieR/J/AJ/117/2308
- Title:
- Spectroscopy of hot stars in the halo
- Short Name:
- J/AJ/117/2308
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss a spectroscopic and photometric technique that enables the identification and classification of field horizontal-branch (FHB) and other A-type stars, even from relatively low signal-to-noise ratio medium-resolution spectra. This technique makes use of broadband UBV colors predicted from model atmosphere calculations and Balmer line profiles and Ca II K equivalent widths determined from synthetic spectra to estimate the physical parameters T_eff_, log(g), and [Fe/H] for stars in the effective temperature range 6000 - 10,000 K.
- ID:
- ivo://CDS.VizieR/J/MNRAS/361/1102
- Title:
- Spectrum of {epsilon} Eri
- Short Name:
- J/MNRAS/361/1102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Measurements of ultraviolet line fluxes from Space Telescope Imaging Spectrograph and Far-Ultraviolet Spectroscopic Explorer spectra of the K2-dwarf eps Eri are reported. These are used to develop new emission measure distributions and semi-empirical atmospheric models for the chromosphere and lower transition region of the star. These models are the most detailed constructed to date for a main-sequence star other than the Sun. New ionization balance calculations, which account for the effect of finite density on dielectronic recombination rates, are presented for carbon, nitrogen, oxygen and silicon. The results of these calculations are significantly different from the standard Arnaud & Rothenflug ion balance, particularly for alkali-like ions. The new atmospheric models are used to place constraints on possible first ionization potential (FIP)-related abundance variations in the lower atmosphere and to discuss limitations of single-component models for the interpretation of certain optically thick line fluxes.
- ID:
- ivo://CDS.VizieR/J/A+A/569/A125
- Title:
- Spiral structure of the Milky Way
- Short Name:
- J/A+A/569/A125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have updated the catalogs of Galactic HII regions, giant molecular clouds (GMCs), and 6.7-GHz methanol masers to outline the spiral structure of our Galaxy. The related parameters have been collected and (re)calculated based on the data in the literature. In particular, for each spiral tracer, we list the photometric or trigonometric distance, and/or the solutions of the kinematic distance ambiguity (KDA) when available. The kinematic distances when adopted are calculated using a flat rotation curve with two sets of R_0_, {Theta}_0_, and solar motions, where one set is the IAU standard and the other is from the new observational results. The rotation curve of Brand & Blitz (1993, Cat. J/A+A/275/67) is also used to derive the kinematic distances.
- ID:
- ivo://CDS.VizieR/J/ApJ/803/109
- Title:
- Spitzer/IRS spectral decompositon of AGN
- Short Name:
- J/ApJ/803/109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results on the spectral decomposition of 118 Spitzer Infrared Spectrograph (IRS) spectra from local active galactic nuclei (AGNs) using a large set of Spitzer/IRS spectra as templates. The templates are themselves IRS spectra from extreme cases where a single physical component (stellar, interstellar, or AGN) completely dominates the integrated mid-infrared emission. We show that a linear combination of one template for each physical component reproduces the observed IRS spectra of AGN hosts with unprecedented fidelity for a template fitting method with no need to model extinction separately. We use full probability distribution functions to estimate expectation values and uncertainties for observables, and find that the decomposition results are robust against degeneracies. Furthermore, we compare the AGN spectra derived from the spectral decomposition with sub-arcsecond resolution nuclear photometry and spectroscopy from ground-based observations. We find that the AGN component derived from the decomposition closely matches the nuclear spectrum with a 1{sigma} dispersion of 0.12dex in luminosity and typical uncertainties of ~0.19 in the spectral index and ~0.1 in the silicate strength. We conclude that the emission from the host galaxy can be reliably removed from the IRS spectra of AGNs. This allows for unbiased studies of the AGN emission in intermediate- and high-redshift galaxies--currently inaccesible to ground-based observations--with archival Spitzer/IRS data and in the future with the Mid-InfraRed Instrument of the James Webb Space Telescope.
