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2481. Spectra of 28 nearby young late-M dwarfs
ID:
ivo://CDS.VizieR/J/A+A/600/A19
Title:
Spectra of 28 nearby young late-M dwarfs
Short Name:
J/A+A/600/A19
Date:
21 Oct 2021
Publisher:
CDS
Description:
Late M-type dwarfs in the solar neighborhood include a mixture of very low-mass stars and brown dwarfs that is difficult to disentangle due to the lack of constraints on their age, such as trigonometric parallax, lithium detection, and space velocity. We search for young brown dwarf candidates among a sample of 28 nearby late-M dwarfs with spectral types between M5.0 and M9.0, and we also search for debris disks around three of them. Based on theoretical models, we used the color I-J, the J-band absolute magnitude, and the detection of the LiI 6708{AA} doublet line as a strong constraint to estimate masses and ages of our targets. For the search of debris disks, we observed three targets at submillimeter wavelength of 850um. We report here the first clear detections of lithium absorption in four targets and a marginal detection in one target. Our mass estimates indicate that two of them are young brown dwarfs, two are young brown dwarf candidates, and one is a young very low-mass star. The closest young field brown dwarf in our sample at only ~15pc is an excellent benchmark for further studying physical properties of brown dwarfs in the range 100-150Myr. We did not detect any debris disks around three late-M dwarfs, and we estimated upper limits to the dust mass of debris disks around them.
2482. Spectra of NGC 1333 Class I-Class II stars
ID:
ivo://CDS.VizieR/J/A+A/650/A43
Title:
Spectra of NGC 1333 Class I-Class II stars
Short Name:
J/A+A/650/A43
Date:
21 Oct 2021
Publisher:
CDS
Description:
The mass accretion rate (dM/dt_acc_) is the fundamental parameter to understand the process of mass assembly that results in the formation of a low-mass star. This parameter has been largely studied in Classical T Tauri stars in star-forming regions with ages of ~1-10Myr. However, little is known about the accretion properties of young stellar objects (YSOs) in younger regions and early stages of star formation, such as in the Class 0/I phases. We present new near-infrared spectra of 17 Class I/Flat and 35 Class II sources located in the young (<1Myr) NGC 1333 cluster, acquired with the KMOS instrument at the Very Large Telescope. Our goal is to study whether the mass accretion rate evolves with age, as suggested by the widely adopted viscous evolution model, by comparing the properties of the NGC 1333 members with samples of older regions. For the Class II sources in our sample, we measured the stellar parameters (SpT, AV, and L*) through a comparison of the IR spectra with a grid of non-accreting Class III stellar templates. We then computed the accretion luminosity by using the known correlation between Lacc and the luminosity of HI lines (Pa{beta} and Br{gamma}). For the Class I sample, where the presence of a large IR excess makes it impossible to use the same spectral typing method, we applied a procedure that allowed us to measure the stellar and accretion luminosity in a self-consistent way. Mass accretion rates dM/dt_acc_ were then measured once masses and radii were estimated adopting suitable evolutionary tracks. The NGC 1333 Class II sources of our sample have L_acc_~10^-4^-1L_{sun}_ and dM/dt_acc_~10^-11^-10^-7^M_{sun}_/yr. We find a correlation between accretion and stellar luminosity in the form of log L_acc_=(1.5+/-0.2)logL*+(-1.0+/-0.1), and a correlation between the mass accretion rate and stellar mass in the form of log(dM/dt_acc_)=(2.6+/-0.9)logM*+(-7.3+/-0.7). Both correlations are compatible within the errors with the older Lupus star-forming region, while only the latter is consistent with results from Chamaeleon I. The Class I sample shows larger accretion luminosities (~10^-2^-10^2^L_{sun}_) and mass accretion rates (~10^-9^-10^-6^M_{sun}_/yr) with respect to the Class II stars of the same cloud. However, the derived mass accretion rates are not sufficiently high to build up the inferred stellar masses, assuming steady accretion during the Class I lifetime. This suggests that the sources are not in their main accretion phase and that most of their mass has already been accumulated during a previous stage and/or that the accretion is an episodic phenomenon. We show that some of the targets originally classified as Class I through Spitzer photometry are in fact evolved or low accreting objects. This evidence can have implications for the estimated protostellar phase lifetimes. The accretion rates of our sample are larger in more embedded and early stage YSOs. Further observations of larger samples in young star-forming regions are needed to determine if this is a general result. In addition, we highlight the importance of spectroscopic surveys of YSOs to confirm their classification and perform a more correct estimate of their lifetime.
2483. 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.
2484. 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.
2485. 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.
2486. Spectra of Nova Scuti 2005 N.2 (V477 Sct)
ID:
ivo://CDS.VizieR/J/A+A/452/567
Title:
Spectra of Nova Scuti 2005 N.2 (V477 Sct)
Short Name:
J/A+A/452/567
Date:
21 Oct 2021
Publisher:
CDS
Description:
Our CCD photometry of Nova Scuti 2005 N.2 (=V477 Sct) shows it to be a very fast nova, which is characterized by t_2_=3 and t3_=_6 days, affected by a E(B-V)>=1.3mag reddening, and which peaked at V~9.8mag on ~Oct. 12.0 UT. The nova was probably entering a dust condensation episode or brightness oscillations during the transition phase when it became unobservable for the seasonal conjunction with the Sun. Absolute spectrophotometry shows it to belong to the He/N class. The emission line width at half intensity is 2600km/s. At least five ripples are identified in the high resolution emission lines profiles at radial velocities ranging from -980 to +700km/s. The nova erupted at a large distance from the Sun and at an appreciable height above the Galactic plane, suggesting an association with the Galactic bulge (unusual for a He/N nova). The progenitor was too faint to be recorded on DSS1/2 survey plates, when setting the outburst amplitude to DeltaV>=11mag.
2487. Spectra of 12 ON stars
ID:
ivo://CDS.VizieR/J/A+A/578/A109
Title:
Spectra of 12 ON stars
Short Name:
J/A+A/578/A109
Date:
21 Oct 2021
Publisher:
CDS
Description:
Massive stars burn hydrogen through the CNO cycle during most of their evolution. When mixing is efficient or when mass transfer in binary systems occurs, chemically processed material is observed at the surface of O and B stars. ON stars show stronger lines of nitrogen than morphologically normal counterparts. Whether this corresponds to the presence of material processed through the CNO cycle is not known. Our goal is to answer this question. We performed a spectroscopic analysis of a sample of ON stars with atmosphere models. We determined the fundamental parameters as well as the He, C, N, and O surface abundances. We also measured the projected rotational velocities. We compared the properties of the ON stars to those of normal O stars.
2488. Spectra of planets
ID:
ivo://padc.obspm.planeto/spectro_planets/q/epn_core
Title:
Spectra of planets
Short Name:
Spectro Planets
Date:
18 Sep 2024 13:52:13
Publisher:
Paris Astronomical Data Centre
Description:
This service provides a compilation of global spectra of planets and satellites in the visible and NIR range, for quick reference purpose. It is made from various libraries, including the Tohoku-Hiroshima-Nagoya Planet Spectra Library (Lundock et al 2009) and spectra from a USGS web site (R. Clark). Reformatted VOtable versions are provided together with links to the original data.
2489. Spectra of quasar narrow-line regions
ID:
ivo://CDS.VizieR/J/MNRAS/448/3354
Title:
Spectra of quasar narrow-line regions
Short Name:
J/MNRAS/448/3354
Date:
21 Oct 2021
Publisher:
CDS
Description:
In a single optical spectrum, the quasar narrow-line region (NLR) reveals low density, photoionized gas in the host galaxy interstellar medium, while the immediate vicinity of the central engine generates the accretion disk continuum and broad emission lines. To isolate these two components, we construct a library of high S/N optical composite spectra created from the Sloan Digital Sky Survey (SDSS-DR7). We divide the sample into bins of continuum luminosity and H{beta} FWHM that are used to construct median composites at different redshift steps up to 0.75. We measure the luminosities of the narrow-emission lines [NeV]{lambda}3427, [NeIII]{lambda}3870, [OIII]{lambda}5007, and [OII]{lambda}3728 with ionization potentials (IPs) of 97, 40, 35, and 13.6eV respectively. The high IP lines' luminosities show no evidence of increase with redshift consistent with no evolution in the AGN SED or the host galaxy ISM illuminated by the continuum. In contrast, we find that the [OII] line becomes stronger at higher redshifts, and we interpret this as a consequence of enhanced star formation contributing to the [OII] emission in host galaxies at higher redshifts. The SFRs estimated from the [OII] luminosities show a flatter increase with z than non-AGN galaxies given our assumed AGN contribution to the [OII] luminosity. Finally, we confirm an inverse correlation between the strength of the FeII{lambda}4570 complex and both the [OIII] EW (though not the luminosity) and the width of the H{beta} line as known from the eigenvector 1 correlations.
2490. Spectra of 6 SBS stars
ID:
ivo://CDS.VizieR/J/A+A/532/A69
Title:
Spectra of 6 SBS stars
Short Name:
J/A+A/532/A69
Date:
21 Oct 2021
Publisher:
CDS
Description:
Faint high latitude carbon stars are rare objects commonly thought to be distant, luminous giants. For this reason they are often used to probe the structure of the Galactic halo; however more accurate investigation of photometric and spectroscopic surveys has revealed an increasing percentage of nearby objects with luminosities of main sequence stars. We analyzed new optical spectra and photometry and used astronomical databases available on the web, aiming at clarifying the nature of the ten carbon star candidates present in the General Catalogue of the Second Byurakan Survey. We verified that two stars are N-type giants already confirmed by other surveys. We found that four candidates are M-type stars and confirmed the carbon nature of the remaining four stars; the characteristics of three of them are consistent with an early CH giant type. The fourth candidate, SBS 1310+561 identified with a high proper motion star, is a rare type of dwarf carbon showing emission lines in its optical spectrum. We estimated absolute magnitudes and distances to the dwarf carbon and the CH stars. Our limited sample confirmed the increasing evidence that spectroscopy or colour alone are not conclusive luminosity discriminants for CH-type carbon stars.

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