- ID:
- ivo://CDS.VizieR/J/AJ/112/241
- Title:
- Spectral irradiance calibration. VI.
- Short Name:
- J/AJ/112/241
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present three new absolutely calibrated continuous stellar spectra from 3 to 35um, constructed as far as possible from actual observed spectral fragments taken from the Kuiper Airborne Observatory (KAO), and the IRAS Low Resolution Spectrometer (LRS). These stars - alpha1 Cen, alpha TrA, and epsilon Car - augment our previous archive of complete absolutely calibrated spectra for northern K and M giants. All these spectra have a common calibration pedigree. The wavelength coverage is ideal for calibration of many existing and proposed ground-based, airborne, and satellite sensors. KAO and IRAS data in the 15-30 um range suggest that the spectra of cool giants are close to Rayleigh-Jeans slopes. Our observations of alpha1 Cen, absolutely calibrated via our adopted Sirius model, indicate an angular diameter in very good agreement with values in the literature, demonstrating "closure" of the set of spectra within our absolute framework. We compare our observed alpha1 Cen spectrum with a published grid of theoretical models from Kurucz, and adopt a plausible theoretical shape, that fits our spectrum, as a secondary reference spectrum in the southern sky.
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- ID:
- ivo://CDS.VizieR/J/AJ/112/2274
- Title:
- Spectral irradiance calibration. VII.
- Short Name:
- J/AJ/112/2274
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present five new absolutely calibrated continuous stellar spectra constructed as far as possible from spectral fragments observed from the ground, the Kuiper Airborne Observatory (KAO), and the IRAS Low Resolution Spectrometer. These stars, alpha Boo, gamma Dra, alpha Cet, gamma Cru, and mu UMa, augment our six, published, absolutely calibrated spectra of K and early-M giants. All spectra have a common calibration pedigree. A revised composite for alpha Boo has been constructed from higher quality spectral fragments than our previously published one. The spectrum of gamma Dra was created in direct response to the needs of instruments aboard the Infrared Space Observatory (ISO); this star's location near the north ecliptic pole renders it highly visible throughout the mission. We compare all our low-resolution composite spectra with Kurucz model atmospheres and find good agreement in shape, with the obvious exception of the SiO fundamental, still lacking in current grids of model atmospheres. The CO fundamental seems slightly too deep in these models, but this could reflect our use of generic models with solar metal abundances rather than models specific to the metallicities of the individual stars. Angular diameters derived from these spectra and models are in excellent agreement with the best observed diameters. The ratio of our adopted Sirius and Vega models is vindicated by spectral observations. We compare IRAS fluxes predicted from our cool stellar spectra with those observed and conclude that, as 12 and 25um, flux densities measured by IRAS should be revised downwards by about 4.1% to 5.7%, respectively, for consistency with our absolute calibration. We have provided extrapolated continuum versions of these spectra to 300um, in direct support of ISO (PHT and LWS instruments). These spectra are consistent with IRAS flux densities at 60 and 100um.
- ID:
- ivo://CDS.VizieR/J/ApJ/888/54
- Title:
- Spectra of a rare low-mass Wolf-Rayet star in LMC
- Short Name:
- J/ApJ/888/54
- Date:
- 25 Oct 2021 10:12:43
- Publisher:
- CDS
- Description:
- We report the serendipitous discovery of an object, UVQSJ060819.93-715737.4, with a spectrum dominated by extremely intense, narrow CII emission lines. The spectrum is similar to those of the very rare, late-type [WC11] low-mass Wolf-Rayet stars. Despite the recognition of these stars as a distinct class decades ago, there remains barely a handful of Galactic members, all of which are also planetary-nebula central stars. Although no obvious surrounding nebulosity is present in J0608, [OII], [NII], and [SII] emission suggest the presence of an inconspicuous, low-excitation nebula. There is low-amplitude incoherent photometric variability on timescales of days to years, as well as numerous prominent P Cygni profiles, implying mass loss. There are indications of a binary companion. The star is located on the outskirts of the LMC, and the observed radial velocity (~+250km/s) and proper motion strongly suggest membership. If indeed an LMC member, this is the first extragalactic late [WC] star, and the first with an accurately determined luminosity, as the Galactic examples are too distant for precise parallax determinations. A high-quality, broad-coverage spectrum of the prototype of the late [WC] class, CPD -56 8032, is also presented. We discuss different excitation mechanisms capable of producing the great strength of the CII emission. Numerous autoionizing levels of C II are definitely populated by processes other than dielectronic recombination. Despite the spectacular emission spectra, observational selection makes objects such as these difficult to discover. Members of the [WC11] class may in fact be considerably more common than the handful of previously known late [WC] stars.
- ID:
- ivo://CDS.VizieR/J/AJ/149/11
- Title:
- Spectra of candidate standard stars in mid-IR
- Short Name:
- J/AJ/149/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spectra obtained with the Infrared Spectrograph (IRS) on the Spitzer Space Telescope of 33 K giants and 20 A dwarfs to assess their suitability as spectrophotometric standard stars. The K giants confirm previous findings that the strength of the SiO absorption band at 8{mu}m increases for both later optical spectral classes and redder (B-V)_0_ colors, but with considerable scatter. For K giants, the synthetic spectra underpredict the strengths of the molecular bands from SiO and OH. For these reasons, the assumed true spectra for K giants should be based on neither the assumption that molecular band strengths in the infrared can be predicted accurately from optical spectral class or color nor synthetric spectra. The OH bands in K giants grow stronger with cooler stellar temperatures, and they are stronger than predicted by synthetic spectra. As a group, A dwarfs are better behaved and more predictable than the K giants, but they are more likely to show red excesses from debris disks. No suitable A dwarfs were located in parts of the sky continuously observable from Spitzer, and with previous means of estimating the true spectra of K giants ruled out, it was necessary to use models of A dwarfs to calibrate spectra of K giants from observed spectral ratios of the two groups and then use the calibrated K giants as standards for the full database of infrared spectra from Spitzer. We also describe a lingering artifact that affects the spectra of faint blue sources at 24{mu}m.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/567/A49
- Title:
- Spectra of IPHAS symbiotic stars
- Short Name:
- J/A+A/567/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The IPHAS H{alpha} survey provides a rich database to search for emission-line sources in the northern Galactic plane. We are systematically searching for symbiotic stars in the Milky Way using IPHAS. Our final goal, a complete census of this class of objects in the Galaxy, is a fundamental figure for discussing their overall properties and relevance to other classes of stars. Candidate symbiotic stars were selected using a refined combination of IPHAS and 2MASS photometric colours. Optical spectroscopy, together with the analysis of their spectral energy distribution in the IR, were obtained to confirm their nature and determine their main properties.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A35
- Title:
- Spectra of IRAS 17449+2320
- Short Name:
- J/A+A/659/A35
- Date:
- 04 Mar 2022 00:58:00
- Publisher:
- CDS
- Description:
- We report the first detection of the magnetic field in a star of FS CMa type, a subgroup of objects characterized by the B[e] phenomenon. The split of magnetically sensitive lines in IRAS 17449+2320 determines the magnetic field modulus of 6.2+/-0.2kG. Spectral lines and their variability reveal the presence of a B-type spectrum and a hot continuum source in the visible. The hot source confirms GALEX UV photometry. Because there is a lack of spectral lines for the hot source in the visible, the spectral fitting gives only the lower temperature limit of the hot source, which is 50000K, and the upper limit for the B-type star of 11100K. The V/R ratio of the Halpha line shows quasiperiodic behavior on timescale of 800 days. We detected a strong red-shifted absorption in the wings of Balmer and OI lines in some of the spectra. The absorption lines of helium and other metals show no, or very small, variations, indicating unusually stable photospheric regions for FS CMa stars. We detected two events of material infall, which were revealed to be discrete absorption components of resonance lines. The discovery of the strong magnetic field together with the Gaia measurements of the proper motion show that the most probable nature of this star is that of a post-merger object created after the leaving the binary of the birth cluster. Another possible scenario is a magnetic Ap star around Terminal-Age Main Sequence (TAMS). On the other hand, the strong magnetic field defies the hypothesis that IRAS 17449+2320 is an extreme classical Be star. Thus, IRAS 17449+2320 provides a pretext for exploring a new explanation of the nature of FS CMa stars or, at least, a group of stars with very similar spectral properties.
- ID:
- ivo://CDS.VizieR/III/114
- Title:
- Spectra of Late-Type Standards, 2.0-2.5 Microns
- Short Name:
- III/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog contains a collection of K-band spectra for 26 stars with near-solar abundances, ranging in spectral class from F8 to M7 and in luminosity from dwarfs to supergiants. The spectra cover the wavelength region from 4150 to 4950 /cm and generally exhibit a signal to noise ratio above 400. Five stars here are supergiants, 15 are giants, and six are dwarfs. Data included: observation date, starting wavenumber, wavenumber increment, scale factor of relative intensity, and offset of relative intensity.
- ID:
- ivo://CDS.VizieR/J/ApJ/779/188
- Title:
- Spectra of nearby late K and M Kepler stars
- Short Name:
- J/ApJ/779/188
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use moderate-resolution spectra of nearby late K and M dwarf stars with parallaxes and interferometrically determined radii to refine their effective temperatures, luminosities, and metallicities. We use these revised values to calibrate spectroscopic techniques to infer the fundamental parameters of more distant late-type dwarf stars. We demonstrate that, after masking out poorly modeled regions, the newest version of the PHOENIX atmosphere models accurately reproduce temperatures derived bolometrically. We apply methods to late-type hosts of transiting planet candidates in the Kepler field, and calculate effective temperature, radius, mass, and luminosity with typical errors of 57K, 7%, 11%, and 13%, respectively. We find systematic offsets between our values and those from previous analyses of the same stars, which we attribute to differences in atmospheric models utilized for each study. We investigate which of the planets in this sample are likely to orbit in the circumstellar habitable zone. We determine that four candidate planets (KOI 854.01, 1298.02, 1686.01, and 2992.01) are inside of or within 1{sigma} of a conservative definition of the habitable zone, but that several planets identified by previous analyses are not (e.g., KOI 1422.02 and KOI 2626.01). Only one of the four habitable-zone planets is Earth sized, suggesting a downward revision in the occurrence of such planets around M dwarfs. These findings highlight the importance of measuring accurate stellar parameters when deriving parameters of their orbiting planets.
- ID:
- ivo://CDS.VizieR/J/ApJ/535/325
- Title:
- Spectra of normal stars in the J-band
- Short Name:
- J/ApJ/535/325
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of J-band spectra for 88 fundamental MK standard stars observed at a resolving power of R~3000. This contribution serves as a companion atlas to the K-band spectra recently published by Wallace & Hinkle (1997, Cat. <J/ApJS/111/445>) and the H-band atlas by Meyer and coworkers. We report data from 7400 to 9550cm^-1^ (1.05-1.34um) for stars of spectral types O7-M6 and luminosity classes I-V as defined in the MK system. In reducing these data, special care has been taken to remove time-variable telluric features of water vapor. We identify atomic and molecular indexes that are both temperature and luminosity sensitive that aid in the classification of stellar spectra in the J band. In addition to being useful in the classification of late-type stars, the J band contains several features of interest in the study of early-type stellar photospheres.
