Spectra of late-type standard stars in the region 2.0-2.5 microns

Kleinmann, S. G.; Hall, Donald N. B.

doi:10.1086/191149

Cited by 271 publications

(355 citation statements)

References 0 publications

Supporting

Mentioning

335

Contrasting

Order By: Relevance

“…The depth of these bands increases with decreasing temperatures, thus the values of their EWs, once corrected for the proper A V , can be related to the spectral subtype (see, e.g., Kleinmann & Hall 1986;Greene & Lada 1996;Luhman et al 2003;Gorlova et al 2010). Usually the 1.3−1.5 μm absorption feature is detected for A V < 20 mag, and the EW of the 1.7−2.1 μm feature decreases by about a factor of 2, as the visual extinction increases from 0 to 30 mag (A V = 25 mag is the maximum extinction value in our sample, see also Table 7, Col. 5).…”

Section: Stellar Spectral Typesmentioning

confidence: 99%

POISSON project

Garatti

Lopez

Antoniucci

et al. 2012

A&A

View full text Add to dashboard Cite

Context. Characterising stellar and circumstellar properties of embedded young stellar objects (YSOs) is mandatory for understanding the early stages of the stellar evolution. This task requires the combination of both spectroscopy and photometry, covering the widest possible wavelength range, to disentangle the various protostellar components and activities. Aims. As part of the POISSON project (Protostellar Optical-Infrared Spectral Survey On NTT), we present a multi-wavelength spectroscopic and photometric investigation of embedded YSOs in L 1641, aimed to derive the stellar parameters and evolutionary stages and to infer their accretion properties. Methods. Our multi-wavelength database includes low-resolution optical-IR spectra from the NTT and Spitzer (0.6−40 μm) and photometric data covering a spectral range from 0.4 to 1100 μm, which allow us to construct the YSOs spectral energy distributions (SEDs) and to infer the main stellar parameters (visual extinction, spectral type, accretion, stellar, bolometric luminosity, mass accretion, and ejection rates). Results. The NTT optical-NIR spectra are rich in emission lines, which are mostly associated with YSO accretion, ejection, and chromospheric activities. A few emission lines, prominent ice (H 2 O and CO 2 ), and amorphous silicate absorption features have also been detected in the Spitzer spectra. The SED analysis allows us to group our 27 YSOs into nine Class I, eleven Flat, and seven Class II objects. However, on the basis of the derived stellar properties, only six Class I YSOs have an age of ∼10 5 yr, while the others are older (5 × 10 5 −10 6 yr), and, among the Flat sources, three out of eleven are more evolved objects (5 × 10 6 −10 7 yr), indicating that geometrical effects can significantly modify the SED shapes. Inferred mass accretion rates (Ṁ acc ) show a wide range of values (3.6 × 10 −9 to 1.2 × 10 −5 M yr −1 ), which reflects the age spread observed in our sample well. Average values of mass accretion rates, extinction, and spectral indices decrease with the YSO class. The youngest YSOs have the highestṀ acc , whereas the oldest YSOs do not show any detectable jet activity in either images and spectra. Apart from the outbursting source #25 and, marginally, #20, none of the remaining YSOs is accretion-dominated (L acc > L * ). We also observe a clear correlation among the YSOṀ acc , M * , and age. For YSOs with t > 10 5 yr and 0.4 M ≤ M * ≤ 1.2 M , a relationship betweenṀ acc and t (Ṁ acc ∝ t −1.2 ) has been inferred, consistent with mass accretion evolution in viscous disc models and indicating that the mass accretion decay is slower than previously assumed. Finally, our results suggest that episodic outbursts are required for Class I YSOs to reach typical classical T Tauri stars stellar masses.

show abstract

Section: Stellar Spectral Typesmentioning

confidence: 99%

POISSON project

Garatti

Lopez

Antoniucci

et al. 2012

A&A

View full text Add to dashboard Cite

show abstract

“…The simple interpretation is that gravity is responsible for the difference between the strong 2.3 lm CO band in K-M giants and the weaker one in dwarfs (Kleinmann & Hall 1986). This argument suggests that the strength should be intermediate in young BDs.…”

Section: Comentioning

confidence: 99%

Gravity Indicators in the Near‐Infrared Spectra of Brown Dwarfs

Gorlova

Meyer

Rieke

et al. 2003

ApJ

149

183

View full text Add to dashboard Cite

We investigate the sensitivity to temperature and gravity of the strong absorption features in the J-and K-band spectra of substellar objects. We compare the spectra of giants and young M dwarfs (of low gravity) to field M and L dwarfs (of high gravity) and to model spectra from the Lyon group. We find that low-resolution spectra of M4-M9 stars and young brown dwarfs at R $ 350 and signal-to-noise ratios greater than 70 can determine the spectral type to a precision of AE1 subtype using the H 2 O and CO bands and can measure the surface gravity to AE0.5 dex using the atomic lines of K i and Na i. This result points toward the development of photometric spectral indices to separate low-mass members from foreground and background objects in young clusters and associations. We also emphasize the complexity of the interpretation of the empirical quantities (e.g., spectral types) in terms of the physical variables (e.g., temperature, opacities) in the cool atmospheres of young brown dwarfs.

show abstract

“…Furthermore, there is no evidence of additional Dv ¼ 2 band heads (3-1, 4-2, etc.) at longer wavelengths, which accompany the 2-0 band head in spectra of late-type stars (Kleinmann & Hall 1986). …”

Section: Spectramentioning

confidence: 99%

Spatially Resolved Imaging Spectroscopy of T Tauri

Kasper

Feldt

Herbst

et al. 2002

ApJ

View full text Add to dashboard Cite

The small separation of the individual stellar components in the T Tau system has prevented spectroscopy of the individual components in the near-infrared (NIR) in the past. We present NIR data (H and K band) on this object taken using the Adaptive Optics with a Laser for Astronomy (ALFA) system in combination with the 3D integral field spectrograph. Except for the Brackett series seen in emission, the NIR spectra of T Tau S appear featureless, suggesting that warm dust dominates the radiation. No rovibrational lines of molecular hydrogen were found in close vicinity to the stars. The Brackett line emission from T Tau N and S could not be resolved with the 3.5 m telescope, implying that it arises within 6 AU from the stars. The line ratios between Br (2.166 lm) and Br10 (1.736 lm) toward T Tau N and T Tau S are similar, suggesting similar selective extinctions toward the respective emitting regions. Our results are consistent with a model that describes T Tau S as a pre-main-sequence star surrounded by a small edge-on disk, leaving the polar regions relatively unobscured. We present numerical simulations which support this model.

show abstract

Spectra of late-type standard stars in the region 2.0-2.5 microns

Cited by 271 publications

References 0 publications

POISSON project

POISSON project

Gravity Indicators in the Near‐Infrared Spectra of Brown Dwarfs

Spatially Resolved Imaging Spectroscopy of T Tauri

Contact Info

Product

Resources

About