Near‐Infrared Spectropolarimetry of Three Prototype Low‐Mass Young Stellar Objects in the Taurus Dark Cloud

1999 ◽  
Vol 517 (1) ◽  
pp. 256-263 ◽  
Author(s):  
Naoto Kobayashi ◽  
Tetsuya Nagata ◽  
Motohide Tamura ◽  
Taku Takeuchi ◽  
Hideki Takami ◽  
...  
Keyword(s):  
Near Infrared ◽  
Young Stellar Objects ◽  
Dark Cloud ◽  
Stellar Objects ◽  
Low Mass

The IGRINS YSO Survey II: Veiling Spectra of Pre-main-sequence Stars in Taurus-Auriga

2021 ◽  
Vol 922 (1) ◽  
pp. 27
Author(s):  
Benjamin Kidder ◽  
Gregory Mace ◽  
Ricardo López-Valdivia ◽  
Kimberly Sokal ◽  
Victoria E. Catlett ◽  
...  
Keyword(s):  
Near Infrared ◽  
Thermal Emission ◽  
Young Stellar Objects ◽  
Continuum Emission ◽  
Class Iii ◽  
Infrared Excess ◽  
Stellar Objects ◽  
Star Forming ◽  
Infrared Spectrometer ◽  
Low Mass

Abstract We present measurements of the H- and K-band veiling for 141 young stellar objects (YSOs) in the Taurus-Auriga star-forming region using high-resolution spectra from the Immersion Grating Near-Infrared Spectrometer. In addition to providing measurements of r H and r K , we produce low-resolution spectra of the excess emission across the H and K bands. We fit temperatures to the excess spectra of 46 members of our sample and measure near-infrared excess temperatures ranging from 1200–2200 K, with an average of 1575 ± 225 K. We compare the luminosity of the excess continuum emission in Class II and Class III YSOs and find that a number of Class III sources display a significant amount of excess flux in the near-infrared. We conclude that the mid-infrared SED slope, and therefore young stellar object classification, is a poor predictor of the amount of near-infrared veiling. If the veiling arises in thermal emission from dust, its presence implies a significant amount of remaining inner-disk (<1 au) material in these Class III sources. We also discuss the possibility that the veiling effects could result from massive photospheric spots, unresolved binary companions, or accretion emission. Six low-mass members of our sample contain a prominent feature in their H-band excess spectra that is consistent with veiling from cool photospheric spots.

scholarly journals Early phases in the stellar and substellar formation and evolution

2018 ◽  
Vol 612 ◽  
pp. A79 ◽  
Author(s):  
D. Barrado ◽  
I. de Gregorio Monsalvo ◽  
N. Huélamo ◽  
M. Morales-Calderón ◽  
A. Bayo ◽  
...  
Keyword(s):  
Formation Mechanism ◽  
Complete Characterization ◽  
Young Stellar Objects ◽  
Spectral Energy ◽  
Evolutionary Stage ◽  
Dark Cloud ◽  
Stellar Objects ◽  
Multiple Systems ◽  
Multi Wavelength ◽  
Low Mass

Aims. The early evolutionary stage of brown dwarfs (BDs) is not very well characterized, especially during the embedded phase. Our goal is to gain insight into the dominant formation mechanism of very low-mass objects and BDs. Methods. We have conducted deep observations at 870 μm obtained with the LABOCA bolometer at the APEX telescope in order to identify young submillimeter (submm) sources in the Barnard 30 dark cloud. We have complemented these data with multi-wavelength observations from the optical to the far-IR and compiled complete spectral energy distributions in order to identify the counterparts, characterize the sources and to assess their membership to the association and stellar or substellar status based on the available photometric information. Results. We have identified 34 submm sources and a substantial number of possible and probable Barnard 30 members within each individual APEX/LABOCA beam. They can be classified into three distinct groups. First, 15 of these 34 have a clear optical or IR counterpart to the submm peak and nine of them are potential proto-BD candidates. Moreover, a substantial number of them could be multiple systems. A second group of 13 sources comprises candidate members with significant infrared excesses located away from the central submm emission. All of them include BD candidates, some displaying IR excess, but their association with submm emission is unclear. In addition, we have found six starless cores and, based on the total dust mass estimate, three might be pre-substellar (or pre-BDs) cores. Finally, the complete characterization of our APEX/LABOCA sources, focusing on those detected at 24 and/or 70 μm, indicates that in our sample of 34 submm sources there are, at least: two WTTs, four CTTs, five young stellar objects, eight proto-BD candidates (with another three dubious cases), and one very low luminosity objects. Conclusions. Our findings provide additional evidence concerning the BD formation mechanism, which seems to be a downsized version of the stellar formation.

scholarly journals Photometric and spectroscopic studies of very low mass YSOs and young Brown Dwarfs in S106

2006 ◽  
Vol 2 (S237) ◽  
pp. 457-457
Author(s):  
Yumiko Oasa
Keyword(s):  
Massive Star ◽  
Near Infrared ◽  
Brown Dwarfs ◽  
Spectroscopic Studies ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Hii Region ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass

Young brown dwarfs have been identified in a significant population in various star forming regions. Some deep surveys have yielded less massive objects with planetary-mass (e.g., Oasa et al. 1999; Lucas & Roche 2000). Nevertheless, it is not yet clear how abundant these very low-mass objects are formed. S106 is one of the nearest massive star-forming regions associated with prominent bipolar nebulae and an HII region. We have conducted near-infrared photometric and spectroscopic observations of very low-mass young stellar objects (YSOs) in the S106 region.

scholarly journals Investigating episodic accretion in a very low-mass young stellar object

2020 ◽  
Vol 643 ◽  
pp. A181
Author(s):  
C. Stock ◽  
A. Caratti o Garatti ◽  
P. McGinnis ◽  
R. Garcia Lopez ◽  
S. Antoniucci ◽  
...  
Keyword(s):  
Near Infrared ◽  
Accretion Rate ◽  
Photometric Data ◽  
Class I ◽  
Young Stellar Objects ◽  
Line Of Sight ◽  
Stellar Objects ◽  
Steep Decrease ◽  
Order Of Magnitude ◽  
Low Mass

Context. Very low-mass Class I protostars have been investigated very little thus far. Variability of these young stellar objects (YSOs) and whether or not they are capable of strong episodic accretion is also left relatively unstudied. Aims. We investigate accretion variability in IRS 54 (YLW52), a Class I very low-mass protostar with a mass of M⋆ ∼ 0.1 − 0.2 M⊙. Methods. We obtained spectroscopic and photometric data with VLT/ISAAC and VLT/SINFONI in the near-infrared (J, H, and K bands) across four epochs (2005, 2010, 2013, and 2014). We used accretion-tracing lines (Paβ and Brγ) and outflow-tracing lines (H2 and [Fe II]) to examine physical properties and kinematics of the object. Results. A large increase in luminosity was found between the 2005 and 2013 epochs of more than 1 magnitude in the K band, followed in 2014 by a steep decrease. Consistently, the mass accretion rate (Ṁacc) rose by an order of magnitude from ∼10−8 M⊙ yr−1 to ∼10−7 M⊙ yr−1 between the two early epochs. The visual extinction (AV) has also increased from ∼15 mag in 2005 to ∼24 mag in 2013. This rise in AV in tandem with the increase in Ṁacc is explained by the lifting up of a large amount of dust from the disc of IRS 54, following the augmented accretion and ejection activity in the YSO, which intersects our line of sight due to the almost edge-on geometry of the disc. Because of the strength and timescales involved in this dramatic increase, this event is believed to have been an accretion burst possibly similar to bursts of EXor-type objects. IRS 54 is the lowest mass Class I source observed to have an accretion burst of this type, and therefore potentially one of the lowest mass EXor-type objects known so far.

A Near-Infrared Search for Companions around Very Low Luminosity Young Stellar Objects in Taurus

1999 ◽  
Vol 117 (3) ◽  
pp. 1471-1484 ◽  
Author(s):  
Yoichi Itoh ◽  
Motohide Tamura ◽  
Tadashi Nakajima
Keyword(s):  
Near Infrared ◽  
Young Stellar Objects ◽  
Stellar Objects

scholarly journals The Observational Evidence for Accretion

1997 ◽  
Vol 182 ◽  
pp. 391-405 ◽  
Author(s):  
Lee Hartmann
Keyword(s):  
Large Range ◽  
Observational Evidence ◽  
Young Stars ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
T Tauri ◽  
Accretion Rates ◽  
Low Mass ◽  
Stellar Magnetospheres ◽  
Mass Ejection

Outflows from low-mass young stellar objects are thought to draw upon the energy released by accretion onto T Tauri stars. I briefly summarize the evidence for this accretion and outline present estimates of mass accretion rates. Young stars show a very large range of accretion rates, and this has important implications for both mass ejection and for the structure of stellar magnetospheres which may truncate T Tauri disks.

scholarly journals Principal component analysis tomography in near-infrared integral field spectroscopy of young stellar objects – I. Revisiting the high-mass protostar W33A

2021 ◽  
Vol 503 (1) ◽  
pp. 270-291
Author(s):  
F Navarete ◽  
A Damineli ◽  
J E Steiner ◽  
R D Blum
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Rotation Axis ◽  
Principal Component ◽  
Young Stellar Objects ◽  
High Mass ◽  
Continuum Emission ◽  
Rotating Disc ◽  
Stellar Objects ◽  
K Band

ABSTRACT W33A is a well-known example of a high-mass young stellar object showing evidence of a circumstellar disc. We revisited the K-band NIFS/Gemini North observations of the W33A protostar using principal components analysis tomography and additional post-processing routines. Our results indicate the presence of a compact rotating disc based on the kinematics of the CO absorption features. The position–velocity diagram shows that the disc exhibits a rotation curve with velocities that rapidly decrease for radii larger than 0.1 arcsec (∼250 au) from the central source, suggesting a structure about four times more compact than previously reported. We derived a dynamical mass of 10.0$^{+4.1}_{-2.2}$ $\rm {M}_\odot$ for the ‘disc + protostar’ system, about ∼33 per cent smaller than previously reported, but still compatible with high-mass protostar status. A relatively compact H2 wind was identified at the base of the large-scale outflow of W33A, with a mean visual extinction of ∼63 mag. By taking advantage of supplementary near-infrared maps, we identified at least two other point-like objects driving extended structures in the vicinity of W33A, suggesting that multiple active protostars are located within the cloud. The closest object (Source B) was also identified in the NIFS field of view as a faint point-like object at a projected distance of ∼7000 au from W33A, powering extended K-band continuum emission detected in the same field. Another source (Source C) is driving a bipolar $\rm {H}_2$ jet aligned perpendicular to the rotation axis of W33A.

SiO as a chemical signature of outflows from bright, compact sources in MSX IR-dark clouds

2004 ◽  
Vol 82 (6) ◽  
pp. 740-743 ◽  
Author(s):  
P A Feldman ◽  
R O Redman ◽  
L W Avery ◽  
J Di Francesco ◽  
J D Fiege ◽  
...  
Keyword(s):  
Star Formation ◽  
Young Stellar Objects ◽  
Line Profiles ◽  
Bipolar Outflows ◽  
Dark Cloud ◽  
Stellar Objects ◽  
Dark Clouds ◽  
Dense Cores ◽  
Infrared Dark Clouds ◽  
Compact Sources

The line profiles of dense cores in infrared-dark clouds indicate the presence of young stellar objects (YSOs), but the youth of the YSOs and the large distances to the clouds make it difficult to distinguish the outflows that normally accompany star formation from turbulence within the cloud. We report here the first unambiguous identification of a bipolar outflow from a young stellar object (YSO) in an infrared-dark cloud, using observations of SiO to distinguish the relatively small amounts of gas in the outflow from the rest of the ambient cloud. Key words: infrared-dark clouds, star formation, bipolar outflows, SiO, G81.56+0.10.

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