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2461. Spectra of candidate standard stars in mid-IR
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.
2462. Spectra of CO and [CI] in protoplanetary disks
ID:
ivo://CDS.VizieR/J/A+A/588/A108
Title:
Spectra of CO and [CI] in protoplanetary disks
Short Name:
J/A+A/588/A108
Date:
21 Oct 2021
Publisher:
CDS
Description:
The gas-solid budget of carbon in protoplanetary disks is related to the composition of the cores and atmospheres of the planets forming in them. The principal gas-phase carbon carriers CO, C^0^, and C^+6 can now be observed regularly in disks. The gas-phase carbon abundance in disks has thus far not been well characterized observationally. We obtain new constraints on the [C]/[H] ratio in a large sample of disks, and compile an overview of the strength of [CI] and warm CO emission. We carried out a survey of the CO 6-5 line and the [CI] 1-0 and 2-1 lines towards 37 disks with the APEX telescope, and supplemented it with [CII] data from the literature. The data are interpreted using a grid of models produced with the DALI disk code. We also investigate how well the gas-phase carbon abundance can be determined in light of parameter uncertainties.
2463. Spectra of Earth-like planets around M-dwarfs
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.
2464. Spectra of 5 faint cataclysmic variables
ID:
ivo://CDS.VizieR/J/MNRAS/373/687
Title:
Spectra of 5 faint cataclysmic variables
Short Name:
J/MNRAS/373/687
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present medium-resolution VLT/FORS2 spectroscopy of six cataclysmic variables (CVs) discovered by the Sloan Digital Sky Survey (SDSS). We determine orbital periods for SDSS J023322.61+005059.5 (96.08+/-0.09min), SDSS J091127.36+084140.7 (295.74+/-0.22min), SDSS J103533.02+055158.3 (82.10+/-0.09min) and SDSS J121607.03+052013.9 (most likely 98.82+/-0.16min, but the one-day aliases at 92 and 107min are also possible) using radial velocities measured from their H{alpha} and H{beta} emission lines. Three of the four orbital periods measured here are close to the observed 75-80min minimum period for CVs, indicating that the properties of the population of these objects discovered by the SDSS are substantially different to those of the CVs found by other means. Additional photometry of SDSS J023322.61+005059.5 reveals a periodicity of approximately 60min which we interpret as the spin period of the white dwarf, suggesting that this system is an intermediate polar with a low accretion rate. SDSS J103533.02+055158.3 has a period right at the observed minimum value, a spectrum dominated by the cool white dwarf primary star and exhibits deep eclipses, so is an excellent candidate for an accurate determination of the parameters of the system. The spectroscopic orbit of SDSS J121607.03+052013.9 has a velocity amplitude of only 13.8+/-1.6km/s, implying that this system has an extreme mass ratio. From several physical constraints we find that this object must contain either a high-mass white dwarf or a brown-dwarf-mass secondary component or both.
2465. Spectra of 2 halo red horizontal branch stars
ID:
ivo://CDS.VizieR/J/A+A/559/A12
Title:
Spectra of 2 halo red horizontal branch stars
Short Name:
J/A+A/559/A12
Date:
21 Oct 2021
Publisher:
CDS
Description:
High-velocity halo stars provide important information about the properties of the extreme Galactic halo. The study of Population II unbound and bound stars enables us better estimate the mass of the halo. We carried out a detailed spectroscopic and kinematic study of two red horizontal branch stars, CD-41 5048 and HD 214362.
2466. Spectra of 7 H{alpha} emission line stars in MBM 18
ID:
ivo://CDS.VizieR/J/A+A/547/A85
Title:
Spectra of 7 H{alpha} emission line stars in MBM 18
Short Name:
J/A+A/547/A85
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate star formation in translucent, high-latitude clouds. Our aim is to understand the star-formation history and rate in the solar neighbourhood. We used spectroscopic observations of newly found candidate H{alpha} emission-line stars to establish their pre-main-sequence nature. The environment was studied through molecular line observations of the cloud (MBM 18/LDN 1569) in which the stars are presumably embedded.
2467. Spectra of HD 120678
ID:
ivo://CDS.VizieR/J/A+A/546/A92
Title:
Spectra of HD 120678
Short Name:
J/A+A/546/A92
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the detection of a shell-like event in the Oe-type star HD 120678. HD 120678 has been intensively observed as part of a high-resolution spectroscopic monitoring program of southern Galactic O stars and Wolf-Rayet stars of the nitrogen sequence. An optical spectrogram of HD 120678 obtained in June 2008 shows strong H and HeI absorption lines instead of the double-peaked emission profiles observed both previously and subsequently, as well as a variety of previously undetected absorption features, mainly of OII, SiIII and FeIII. Photometric data reveal that the development of the absorption spectrum coincided with a remarkable dip in the V-band lightcurve. The "shell phase" of HD 120678 did not persist for very long: the V magnitude recovered its previous average value in fewer than 120 days, whereas H and He emission lines became detectable one year later. Similar spectral variations have been observed in a few Be stars, and they are usually interpreted as changes in the circumstellar disk.
2468. Spectra of high-mass X-ray binaries
ID:
ivo://CDS.VizieR/J/A+A/590/A122
Title:
Spectra of high-mass X-ray binaries
Short Name:
J/A+A/590/A122
Date:
21 Oct 2021
Publisher:
CDS
Description:
High-mass X-ray binaries are bright X-ray sources. The high-energy emission is caused by the accretion of matter from the massive companion onto a neutron star. The accreting material comes from either the strong stellar wind in binaries with supergiant companions or the circumstellar disk in Be/X-ray binaries. In either case, the H{alpha} line stands out as the main source of information about the state of the accreting material. We present the results of our monitoring program to study the long-term variability of the H{alpha} line in high-mass X-ray binaries. Our aim is to characterise the optical variability timescales and study the interaction between the neutron star and the accreting material. We fitted the H{alpha} line with Gaussian profiles and obtained the line parameters and equivalent width. The peak separation in split profiles was used to determine the disk velocity law and estimate the disk radius. The relative intensity of the two peaks (V/R ratio) allowed us to investigate the distribution of gas particles in the disk. The equivalent width was used to characterise the degree of variability of the systems. We also studied the variability of the H{alpha} line in correlation with the X-ray activity.
2469. Spectra of IPHAS symbiotic stars
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.
2470. Spectra of IRAS 17449+2320
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.

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