The T Tauri Phase Down to Nearly Planetary Masses: Echelle Spectra of 82 Very Low Mass Stars and Brown Dwarfs

Mohanty, Subhanjoy; Jayawardhana, Ray; Basri, Gibor

doi:10.1086/429794

Cited by 324 publications

(566 citation statements)

References 74 publications

(154 reference statements)

Supporting

Mentioning

499

Contrasting

Unclassified

Order By: Relevance

“…Gullbring et al (2000) derivedṀ acc = 5 × 10 −7 M yr −1 , by fitting an accretion shock model to the Balmer and UV excess continuum emission measured in 1996. Finally, the mean correlation between CaII line luminosity and accretion rate in T Tauri stars suggestsṀ acc 2 × 10 −7 M yr −1 in DG Tau in −2003(Mohanty et al 2005). …”

Section: Accretion Rate and Ejection-to-accretion Ratio In Dg Taumentioning

confidence: 87%

Sub-arcsecond [Fe ii] spectro-imaging of the DG Tauri jet

Agra-Amboage

Dougados

Cabrit

et al. 2011

A&A

111

View full text Add to dashboard Cite

Context. The origin of protostellar jets as well as their impact on the regulation of angular momentum and the inner disk physics are still crucial open questions in star formation. Aims. We aim to test the different proposed ejection processes in T Tauri stars through high-angular resolution observations of forbidden-line emission from the inner DG Tauri microjet. Methods. We present spectro-imaging observations of the DG Tauri jet obtained with SINFONI/VLT in the lines of [Fe ii]λ1.64 μm, 1.53 μm with 0. 15 angular resolution and R = 3000 spectral resolution. We analyze the morphology and kinematics, derive electronic densities and mass-flux rates and discuss the implications for proposed jet launching models. Results. (1) We observe an onion-like velocity structure in [Fe ii] in the blueshifted jet, similar to that observed in optical lines. Highvelocity (HV) gas at -200 km s −1 is collimated inside a half-opening angle of 4 • and medium-velocity (MV) gas at -100 km s −1 in a cone with an half-opening angle 14.• (2) Two new axial jet knots are detected in the blue jet, as well as a more distant bubble with corresponding counter-bubble. The periodic knot ejection timescale is revised downward to 2.5 yrs. (3) The redshifted jet is detected only beyond 0. 7 from the star, yielding revised constraints on the disk surface density. (4) From comparison to [O i] data we infer iron depletion of a factor 3 at high velocities and a factor 10 at speeds below -100 km s −1 . (5) The mass-fluxes in each of the medium and high-velocity components of the blueshifted lobe are 1.6 ± 0.8 × 10 −8 M yr −1 , representing 0.02−0.2 of the disk accretion rate. Conclusions. The medium-velocity conical [Fe ii] flow in the DG Tau jet is too fast and too narrow to trace photo-evaporated matter from the disk atmosphere. Both its kinematics and collimation cannot be reproduced by the X-wind, nor can the "conical magnetospheric wind". The level of Fe gas phase depletion in the DG Tau medium-velocity component also rules out a stellar wind and a cocoon ejected sideways from the high-velocity beam. A quasi-steady centrifugal MHD disk wind ejected over 0.25−1.5 AU and/or episodic magnetic tower cavities launched from the disk appear as the most plausible origins for the [Fe ii] medium velocity component in the DG Tau jet. The same disk wind model can also account for the properties of the high-velocity [Fe ii] flow, although alternative origins in magnetospheric and/or stellar winds cannot be excluded for this component.

show abstract

Section: Accretion Rate and Ejection-to-accretion Ratio In Dg Taumentioning

confidence: 87%

Sub-arcsecond [Fe ii] spectro-imaging of the DG Tauri jet

Agra-Amboage

Dougados

Cabrit

et al. 2011

A&A

111

View full text Add to dashboard Cite

show abstract

“…We also observed the λ Ori sources in the spectral range including the CaII infrared triplet, which can also be used to measure MARs (Mohanty et al 2005), but in the whole sample we do not find any star clearly showing CaII emission due to accretion. The discrepancy between the two clusters does not depend on the analysis method, because we compare the two clusters using homogeneous data and the same selection criteria both for membership and disk classification.…”

Section: Accretion Propertiesmentioning

confidence: 93%

FLAMES spectroscopy of low-mass stars in the young clusters σ Ori and λ Ori

Sacco

Franciosini²,

Randich

et al. 2008

A&A

181

View full text Add to dashboard Cite

Aims. We performed a detailed membership selection and studied the accretion properties of low-mass stars in the two apparently very similar young (1-10 Myr) clusters σ Ori and λ Ori. Methods. We observed 98 and 49 low-mass (0.2-1.0 M ) stars in σ Ori and λ Ori respectively, using the multi-object optical spectrograph FLAMES at the VLT, with the high-resolution (R ∼ 17 000) HR15N grating (6470-6790 Å). We used radial velocities, Li and Hα to establish cluster membership and Hα and other optical emission lines to analyze the accretion properties of members. Results. We identified 65 and 45 members of the σ Ori and λ Ori clusters, respectively, and discovered 16 new candidate binary systems. We also measured rotational broadening for 20 stars and estimated the mass accretion rates in 25 stars of the σ Ori cluster, finding values between 10 −11 and 10 −7.7 M yr −1 and in 4 stars of the λ Ori cluster, finding values between 10 −11 and 10 −10.1 M yr −1 . Comparing our results with the infrared photometry obtained by the Spitzer satellite, we find that the fraction of stars with disks and the fraction of active disks is larger in the σ Ori cluster (52 ± 9% and 78 ± 16%) than in λ Ori (28 ± 8% and 40 ± 20%). Conclusions. The different disk and accretion properties of the two clusters could be due either to the effect of the high-mass stars and the supernova explosion in the λ Ori cluster or to different ages of the cluster populations. Further observations are required to draw a definitive conclusion.

show abstract

“…To estimateṀ acc for FU Tau A, we used the published relations presented by Herczeg & Hillenbrand (2008), Mohanty et al (2005), Rigliaco et al (2012, hereafter RNT12) and new calibrations by Alcalá et al (in prep.). The last are based on an X-shooter sample of 36 accreting YSOs from the Lupus star forming region, and they represent the largest homogeneous analysis of this kind performed so far.…”

Section: Emission Line Diagnosticsmentioning

confidence: 99%

X-shooter spectroscopy of FU Tauri A

Stelzer

Alcalá

Scholz

et al. 2013

A&A

View full text Add to dashboard Cite

We have analyzed a broad-band optical and near-infrared spectrum of FU Tau A, which is a presumed young brown dwarf in the Taurus star forming region that has intrigued both theorists and observers by its overluminosity in the Hertzsprung-Russell (HR) diagram with respect to standard pre-main sequence evolutionary models. FU Tau A is brighter than any other Taurus member of the same or similar spectral type, and various phenomena (accretion, activity, binarity) have been put forth as possible explanations. The new data, obtained with the X-shooter spectrograph at the Very Large Telescope, include an unprecedented wealth of information on stellar parameters and simultaneously observed accretion and outflow indicators for FU Tau A. We present the first measurements of gravity (log g = 3.5 ± 0.5), radial velocity (RV = 22.5 ± 2.9 km s −1 ), rotational velocity (v sin i = 20 ± 5 km s −1 ), and lithium equivalent width (EW Li = 430 ± 20 mÅ) for FU Tau A. From the rotational velocity and the published period we infer a disk inclination of i 50 • . The lithium content is much lower than theoretically expected for such a young very low-mass object, adding another puzzling feature to this object's properties. We determine the mass accretion rate of FU Tau A from comparison of the luminosities of 20 emission lines to empirical calibrations from the literature and find a mean of logṀ acc [M /yr] = −9.9 with standard deviation σ = 0.2. The accretion rate determined independently from modeling of the excess emission in the Balmer and Paschen continua is consistent with this value. The corresponding accretion luminosity is too low to make a significant contribution to the bolometric luminosity. Strong magnetic activity affecting the stellar parameters or binarity of FU Tau A, both combined with extreme youth, may be responsible for its position in the HR diagram. The existence of an outflow in FU Tau A is demonstrated through the first detection of forbidden emission lines from which we obtain an estimate for the mass loss rate, logṀ out [M /yr] < −10.4. The mass outflow and inflow rates can be combined to yieldṀ out /Ṁ acc ∼ 0.3, a value that is in agreement with jet-launching models.

show abstract

The T Tauri Phase Down to Nearly Planetary Masses: Echelle Spectra of 82 Very Low Mass Stars and Brown Dwarfs

Cited by 324 publications

References 74 publications

Sub-arcsecond [Fe ii] spectro-imaging of the DG Tauri jet

Sub-arcsecond [Fe ii] spectro-imaging of the DG Tauri jet

FLAMES spectroscopy of low-mass stars in the young clusters σ Ori and λ Ori

X-shooter spectroscopy of FU Tauri A

Contact Info

Product

Resources

About