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1051. Spectra of nearby late K and M Kepler stars
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.
1052. Spectra of normal stars in the J-band
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.
1053. Spectra of normal stars in the K band
ID:
ivo://CDS.VizieR/J/ApJS/111/445
Title:
Spectra of normal stars in the K band
Short Name:
J/ApJS/111/445
Date:
21 Oct 2021
Publisher:
CDS
Description:
An Atlas of 115 medium-resolution K-band (2.0-2.4um) stellar spectra, spanning spectral types O-M and luminosity types I-V, is presented. K-band spectra are also presented for one N- and one J-type carbon star. A time series of spectra is presented for an S-type Mira variable. All the spectra are at a resolution of ~3000 (1.4cm^-1^) and have had the terrestrial absorption removed by dividing a featureless spectrum. The spectra are plotted with the major spectral features identified and are available digitally.
1054. Spectra of normal stars in the L-band
ID:
ivo://CDS.VizieR/J/AJ/124/3393
Title:
Spectra of normal stars in the L-band
Short Name:
J/AJ/124/3393
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a brief atlas of L-band (3.3-4.2um) spectra for 42 stars plus the Sun and a sunspot observed at a resolving power of R~3000. This contribution is intended to supplement our previous K-band, H-band, and J-band spectral atlases. The L-band data, which cover some or all of the 2400 to 3000cm^-1^ (3.3-4.2um) region, are mainly for luminous late-type stars. In reducing these data, special care has been taken to remove telluric features, especially water vapor. We identify temperature- and luminosity-sensitive atomic and molecular indices to aid in the classification of stellar spectra in the L band.
1055. Spectra of three nearby star-forming regions
ID:
ivo://CDS.VizieR/J/ApJ/703/1964
Title:
Spectra of three nearby star-forming regions
Short Name:
J/ApJ/703/1964
Date:
21 Oct 2021
Publisher:
CDS
Description:
We analyze samples of Spitzer Infrared Spectrograph spectra of T Tauri stars in the Ophiuchus, Taurus, and Chamaeleon I star-forming regions, whose median ages lie in the <1-2Myr range. The median mid-infrared spectra of objects in these three regions are similar in shape, suggesting, on average, similar disk structures. When normalized to the same stellar luminosity, the medians follow each other closely, implying comparable mid-infrared excess emission from the circumstellar disks. We use the spectral index between 13 and 31um and the equivalent width of the 10um silicate emission feature to identify objects whose disk configuration departs from that of a continuous, optically thick accretion disk. Based on their medians and fraction of evolved disks, T Tauri stars in Taurus and Chamaeleon I are very alike.
1056. Spectroscopic transit depths of LHS 3844b
ID:
ivo://CDS.VizieR/J/AJ/160/188
Title:
Spectroscopic transit depths of LHS 3844b
Short Name:
J/AJ/160/188
Date:
21 Oct 2021
Publisher:
CDS
Description:
Atmospheric studies of spectroscopically accessible terrestrial exoplanets lay the groundwork for comparative planetology between these worlds and the solar system terrestrial planets. LHS3844b is a highly irradiated terrestrial exoplanet (R=1.303{+/-}0.022R{Earth}) orbiting a mid-M dwarf 15parsecs away. Work based on near-infrared Spitzer phase curves ruled out atmospheres with surface pressures >~10bars on this planet. We present 13 transit observations of LHS3844b taken with the Magellan Clay telescope and the LDSS3C multi-object spectrograph covering 620-1020nm. We analyze each of the 13 data sets individually using a Gaussian process regression, and present both white and spectroscopic light curves. In the combined white light curve we achieve an rms precision of 65ppm when binning to 10minutes. The mean white light-curve value of (Rp/Rs)^2^ is 0.4170{+/-}0.0046%. To construct the transmission spectrum, we split the white light curves into 20 spectrophotometric bands, each spanning 20nm, and compute the mean values of (Rp/Rs)^2^ in each band. We compare the transmission spectrum to two sets of atmospheric models. We disfavor a clear, solar composition atmosphere ({mu}=2.34) with surface pressures >~0.1bar to 5.2{sigma} confidence. We disfavor a clear, H2O steam atmosphere ({mu}=18) with surface pressures >~0.1bar to low confidence (2.9{sigma}). Our observed transmission spectrum favors a flat line. For solar composition atmospheres with surface pressures >~1bar we rule out clouds with cloud-top pressures of 0.1bar (5.3{sigma}), but we cannot address high-altitude clouds at lower pressures. Our results add further evidence that LHS3844b is devoid of an atmosphere.
1057. Spectroscopy of candidate members in Taurus
ID:
ivo://CDS.VizieR/J/AJ/153/46
Title:
Spectroscopy of candidate members in Taurus
Short Name:
J/AJ/153/46
Date:
21 Oct 2021
Publisher:
CDS
Description:
Previous studies have found that ~1deg^2^ fields surrounding the stellar aggregates in the Taurus star-forming region exhibit a surplus of solar-mass stars relative to denser clusters like IC 348 and the Orion Nebula Cluster. To test whether this difference reflects mass segregation in Taurus or a variation in the initial mass function, we have performed a survey for members of Taurus across a large field (~40deg^2^) that was imaged by the Sloan Digital Sky Survey (SDSS). We obtained optical and near-infrared spectra of candidate members identified with those images and the Two Micron All Sky Survey, as well as miscellaneous candidates that were selected with several other diagnostics of membership. We have classified 22 of the candidates as new members of Taurus, which includes one of the coolest known members (M9.75). Our updated census of members within the SDSS field shows a surplus of solar-mass stars relative to clusters, although it is less pronounced than in the smaller fields toward the stellar aggregates that were surveyed for previously measured mass functions in Taurus. In addition to spectra of our new members, we include in our study near-IR spectra of roughly half of the known members of Taurus, which are used to refine their spectral types and extinctions. We also present an updated set of near-IR standard spectra for classifying young stars and brown dwarfs at M and L types.
1058. Spectroscopy of CH3OH in layered and mixed ices
ID:
ivo://CDS.VizieR/J/A+A/652/A126
Title:
Spectroscopy of CH3OH in layered and mixed ices
Short Name:
J/A+A/652/A126
Date:
22 Feb 2022
Publisher:
CDS
Description:
The molecular composition of interstellar ice mantles is defined by gas-grain processes in molecular clouds, with the main components being H_2_O, CO, and CO_2_. Methanol (CH_3_OH) ice is detected towards the denser pre-stellar cores and star-forming regions, where large amounts of CO molecules freeze out and get hydrogenated on top of the icy grains. The thermal heating from nearby protostars can further change the ice structure and composition. Despite the several observations of icy features carried out towards molecular clouds and along the line of site of protostars, it is not yet clear if interstellar ices are mixed or if they have a layered structure. We aim to examine the effect of mixed and layered ice growth in dust grain mantle analogues, with specific focus on the position and shape of methanol infrared bands, so dedicated future observations could shed light on the structure of interstellar ices in different environments. Mixed and layered ice samples were deposited on a cold substrate kept at a temperature of 10K using a closed-cycle cryostat placed in a vacuum chamber. The spectroscopic features were analysed by Fourier transform infrared spectroscopy. Different proportions of the most abundant four molecular species in ice mantles, namely H_2_O, CO, CO_2_, and CH_3_OH, were investigated, with a special attention placed on the analysis of the CH_3_OH bands. We measure changes in the position and shape of the CH and CO stretching bands of CH_3_OH depending on the mixed or layered nature of the ice sample. Spectroscopic features of methanol are also found to change due to heating. A layered ice structure best reproduces the CH_3_OH band position recently observed towards a pre-stellar core and in star-forming regions. Based on our experimental results, we conclude that observations of CH_3_OH ice features in space can provide information about the structure of interstellar ices, and we expect the James Webb Space Telescope to put stringent constraints on the layered or mixed nature of ices in different interstellar environments, from molecular clouds to pre-stellar cores to protostars and protoplanetary discs.
1059. Spectroscopy of comet C/2004 Q2 (Machholz)
ID:
ivo://CDS.VizieR/J/ApJ/703/121
Title:
Spectroscopy of comet C/2004 Q2 (Machholz)
Short Name:
J/ApJ/703/121
Date:
21 Oct 2021
Publisher:
CDS
Description:
We observed comet C/2004 Q2 (Machholz) with the Keck II telescope in late 2005 January and we obtained the spectra of C/2004 Q2 including many emission lines of volatile species such as H_2_O, HCN, C_2_H_2_, NH_3_, CH_4_, C_2_H_6_, CH_3_OH, and H_2_CO with high-signal-to-noise ratios. Based on our observations, we determined the mixing ratios of the molecules relative to H_2_O in C/2004 Q2. C/2004 Q2 might be the intermediate type between Oort Cloud and Jupiter Family comets. To investigate the formation conditions of such intermediate type comet, we focused on the (C_2_H_2_+C_2_H_6_)/H_2_O ratios and C_2_H_6_/(C_2_H_6_+C_2_H_2_) ratios in comets from the viewpoint of conversion from C_2_H_2_ to C_2_H_6_ in the precometary ices. We employed the dynamical-evolutional model and the chemical-evolutional model to determine the formation region of C/2004 Q2 more precisely. We found that comet C/2004 Q2 might have formed in relatively inner region of the solar nebula than the typical Oort Cloud comet (but slightly further than 5AU from the proto-Sun).
1060. Spectroscopy of HD 45677 = MWC 142
ID:
ivo://CDS.VizieR/J/A+AS/124/441
Title:
Spectroscopy of HD 45677 = MWC 142
Short Name:
J/A+AS/124/441
Date:
21 Oct 2021
Publisher:
CDS
Description:
On the basis of spectroscopic CCD material obtained at the Haute Provence Observatory, we provide line identifications and equivalent width measurements in the wavelength regions 3750-5112 and 7065-10212{AA} of the spectrum of HD 45677. Over 235 features are identified and a comparison of our results with those of other authors is provided. We also discuss the variability of the lines using equivalent widths and the line spectrum. We conclude that the gaseous shell surrounding the star has a temperature of the order of 7000K and that its distance to the star is less than ten stellar radii. We discuss the similarity of this star to other stars previously analyzed.