scholarly journals Classical T Tauri-like Outflow Activity in the Brown Dwarf Mass Regime

2009 ◽  
Vol 5 (H15) ◽  
pp. 754-754
Author(s):  
E. T. Whelan ◽  
T. P. Ray ◽  
F. Bacciotti ◽  
L. Podio ◽  
S. Randich
Keyword(s):  
Brown Dwarf ◽  
T Tauri ◽  
Relative Brightness ◽  
Accretion Rates ◽  
Outflow Rate ◽  
Mass Outflow ◽  
Complete Discussion ◽  
Comprehensive Comparison ◽  
Low Mass ◽  
Measured Mass

Since 2005 we have been analysing the spectra of brown dwarfs (BDs) using the technique of spectro-astrometry and to date have found 5 outflows driven by BDs. Our aim is to obtain an understanding of outflow activity in the BD mass regime and make a comprehensive comparison with low mass protostars, in particular the classical T Tauri stars (CTTSs). Table 1 summarises some results for the sources in our sample. Also see Whelan et al. (2009b) for a complete discussion and comparison with CTTSs. Some noteworthy results include the asymmetry in the ISO-217 bipolar outflow which is revealed in the relative brightness of the two lobes (red-shifted lobe is brighter) and the factor of two difference in radial velocity (the red-shifted lobe is faster). Asymmetries are common in jets from low mass protostars (0.1 Msun to 2 Msun) and the observation of a strong asymmetry at such a low mass supports the idea that BD outflow activity is scaled down from CTTSs. In addition, Whelan et al. (2009a) find a strong contribution to the Hα line emitted by LS-RCrA 1 and evidence of a dust hole in its disk. Using methods previously applied to CTTS Whelan et al. (2009b) estimate the mass outflow rate (Ṁout) for LS-RCrA 1, ISO and ISO-Oph 102 Ṁout to be in the range 10−10 to 10−9 Msun yr−1 which is comparable to measured mass accretion rates.

scholarly journals The near-infrared outflow and cavity of the proto-brown dwarf candidate ISO-Oph 200

2018 ◽  
Vol 610 ◽  
pp. L19 ◽  
Author(s):  
E. T. Whelan ◽  
B. Riaz ◽  
B. Rouzé
Keyword(s):  
Field Study ◽  
Electron Density ◽  
Near Infrared ◽  
Position Angle ◽  
Brown Dwarf ◽  
Protostellar Jets ◽  
Outflow Rate ◽  
Mass Outflow ◽  
Low Mass ◽  
Integral Field

In this Letter a near-infrared integral field study of a proto-brown dwarf candidate is presented. A ~0.′′5 blue-shifted outflow is detected in both H2 and [Fe II] lines at Vsys = (–35 ± 2) km s−1 and Vsys = (–51 ± 5) km s−1 respectively. In addition, slower (~±10 km s−1) H2 emission is detected out to <5.′′4, in the direction of both the blue and red-shifted outflow lobes but along a different position angle to the more compact faster emission. It is argued that the more compact emission is a jet and the extended H2 emission is tracing a cavity. The source extinction is estimated at Av = 18 ± 1 mag and the outflow extinction at Av = 9 ± 0.4 mag. The H2 outflow temperature is calculated to be 1422 ± 255 K and the electron density of the [Fe II] outflow is measured at ~10 000 cm−3. Furthermore, the mass outflow rate is estimated at Ṁout [H2]  = 3.8 × 10−10 M⊙ yr−1 and Ṁout[Fe II] = 1 × 10−8 M⊙ yr−1. Ṁout[Fe II] takes a Fe depletion of ~88% into account. The depletion is investigated using the ratio of the [Fe II] 1.257 μm and [P II] 1.188 μm lines. Using the Paβ and Brγ lines and a range in stellar mass and radius Ṁacc is calculated to be (3–10) × 10−8 M⊙ yr−1. Comparing these rates puts the jet efficiency in line with predictions of magneto-centrifugal models of jet launching in low mass protostars. This is a further case of a brown dwarf outflow exhibiting analogous properties to protostellar jets.

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 Sporadic and intense accretion in a 1 Myr-old brown dwarf candidate

2020 ◽  
Vol 634 ◽  
pp. A128
Author(s):  
D. Nguyen-Thanh ◽  
N. Phan-Bao ◽  
S. J. Murphy ◽  
M. S. Bessell
Keyword(s):  
Spectral Energy Distribution ◽  
Brown Dwarfs ◽  
Photometric Data ◽  
Spectral Energy ◽  
Brown Dwarf ◽  
M Dwarfs ◽  
Trigonometric Parallax ◽  
Accretion Process ◽  
Accretion Rates ◽  
Low Mass

Context. Studying the accretion process in very low-mass objects has important implications for understanding their formation mechanism. Many nearby late-M dwarfs that have previously been identified in the field are in fact young brown dwarf members of nearby young associations. Some of them are still accreting. They are therefore excellent targets for further studies of the accretion process in the very low-mass regime at different stages. Aims. We aim to search for accreting young brown dwarf candidates in a sample of 85 nearby late-M dwarfs. Methods. Using photometric data from DENIS, 2MASS, and WISE, we constructed the spectral energy distribution of the late- M dwarfs based on BT-Settl models to detect infrared excesses. We then searched for lithium and Hα emission in candidates that exhibit infrared excesses to confirm their youth and the presence of accretion. Results. Among the 85 late-M dwarfs, only DENIS-P J1538317−103850 (M5.5) shows strong infrared excesses in WISE bands. The detection of lithium absorption in the M5.5 dwarf and its Gaia trigonometric parallax indicate an age of ~1 Myr and a mass of 47 MJ. The Hα emission line in the brown dwarf shows significant variability that indicates sporadic accretion. This 1 Myr-old brown dwarf also exhibits intense accretion bursts with accretion rates of up to 10−7.9 M⊙ yr−1. Conclusions. Our detection of sporadic accretion in one of the youngest brown dwarfs might imply that sporadic accretion at early stages could play an important role in the formation of brown dwarfs. Very low-mass cores would not be able to accrete enough material to become stars, and thus they end up as brown dwarfs.

scholarly journals Brown dwarf jets: Investigating the universality of jet launching mechanisms at the lowest masses

2010 ◽  
Vol 6 (S275) ◽  
pp. 396-399
Author(s):  
Emma Teresa Whelan ◽  
Francesca Bacciotti ◽  
Tom Ray ◽  
Catherine Dougados
Keyword(s):  
Accretion Rate ◽  
T Tauri Stars ◽  
Brown Dwarf ◽  
Central Mass ◽  
Mass Accretion Rate ◽  
T Tauri ◽  
Mass Outflow ◽  
The Common ◽  
Protostellar Objects

AbstractRecently it has become apparent that proto-stellar-like outflow activity extends to the brown dwarf (BD) mass regime. While the presence of accretion appears to be the common ingredient in all objects known to drive jets fundamental questions remain unanswered. The more prominent being the exact mechanism by which jets are launched, and whether this mechanism remains universal among such a diversity of sources and scales. To address these questions we have been investigating outflow activity in a sample of protostellar objects that differ considerably in mass and mass accretion rate. Central to this is our study of brown dwarf jets. To date Classical T Tauri stars (CTTS) have offered us the best touchstone for decoding the launching mechanism. Here we shall summarise what is understood so far of BD jets and the important constraints observations can place on models. We will focus on the comparison between jets driven by objects with central mass <0.1M⊙ and those driven by CTTSs. In particular we wish to understand how the the ratio of the mass outflow to accretion rate compares to what has been measured for CTTSs.

scholarly journals Low mass T Tauri and young brown dwarf candidates in the Chamaeleon II dark cloud found by DENIS

2001 ◽  
Vol 379 (1) ◽  
pp. 208-214 ◽  
Author(s):  
M. H. Vuong ◽  
L. Cambrésy ◽  
N. Epchtein
Keyword(s):  
Brown Dwarf ◽  
Dark Cloud ◽  
T Tauri ◽  
Low Mass

scholarly journals Accretion in Very Low Mass Young Objects

2003 ◽  
Vol 211 ◽  
pp. 141-142
Author(s):  
James Muzerolle ◽  
Lynne Hillenbrand ◽  
César Briceño ◽  
Nuria Calvet ◽  
Lee Hartmann
Keyword(s):  
Emission Line ◽  
T Tauri Stars ◽  
Line Profiles ◽  
Upper Limit ◽  
T Tauri ◽  
Accretion Rates ◽  
Hα Emission ◽  
Optical Continuum ◽  
Low Mass ◽  
Gas Accretion

We have investigated evidence for active accretion in a sample of ~ 30 young, very low mass objects, including at least 10 brown dwarfs. About 30% of the sample exhibits broad, asymmetric Hα emission line profiles, indicative of gas accretion via magnetospheric infall. There is a distinct lack of associated optical continuum veiling in these accretors, suggesting very low mass accretion rates. Our models yield an upper limit to the accretion rates that is several orders of magnitude smaller than typical of higher-mass T Tauri stars, suggesting a dependence of accretion rates with stellar mass.

scholarly journals Taking snapshots of the jet-ISM interplay with ALMA

2020 ◽  
Vol 15 (S359) ◽  
pp. 243-248
Author(s):  
Raffaella Morganti ◽  
Tom Oosterloo ◽  
Clive N. Tadhunter
Keyword(s):  
Large Scale ◽  
Radio Galaxies ◽  
Plasma Jets ◽  
Molecular Gas ◽  
Radio Jets ◽  
Evolutionary Phase ◽  
Outflow Rate ◽  
Mass Outflow ◽  
Low Mass ◽  
The Impact

AbstractWe present an update of our ongoing project to characterise the impact of radio jets on the interstellar medium (ISM). This is done by tracing the distribution, kinematics and excitation of the molecular gas at high spatial resolution using ALMA. The radio active galactic nuclei (AGN) studied are in the interesting phase of having a recently born radio jet. In this stage, the plasma jets can have the largest impact on the ISM, as also predicted by state-of-the-art simulations. The two targets we present have quite different ages, allowing us to get snapshots of the effects of radio jets as they grow and evolve. Interestingly, both also host powerful quasar emission, making them ideal for studying the full impact of AGN. The largest mass outflow rate of molecular gas is found in a radio galaxy () hosting a newly born radio jet still in the early phase of emerging from an obscuring cocoon of gas and dust. Although the molecular mass outflow rate is high (few hundred), the outflow is limited to the inner few hundred pc region. In a second object (), the jet is larger (a few kpc) and is in a more advanced evolutionary phase. In this object, the distribution of the molecular gas is reminiscent of what is seen, on larger scales, in cool-core clusters hosting radio galaxies. Interestingly, gas deviating from quiescent kinematics (possibly indicating an outflow) is not very prominent, limited only to the very inner region, and has a low mass outflow rate. Instead, on kpc scales, the radio lobes appear associated with depressions in the distribution of the molecular gas. This suggests that the lobes have broken out from the dense nuclear region. However, the AGN does not appear to be able, at present, to stop the star formation observed in this galaxy. These results support the idea that the effects of the radio source start in the very first phases by producing outflows which, however, tend to be limited to the kpc region. After that, the effects turn into producing large-scale bubbles which could, in the long term, prevent the surrounding gas from cooling. Thus, our results provide a way to characterise the effect of radio jets in different phases of their evolution and in different environments, bridging the studies done for radio galaxies in clusters.

scholarly journals Complex structure of a proto-brown dwarf

2021 ◽  
Author(s):  
B Riaz ◽  
M N Machida
Keyword(s):  
Complex Structure ◽  
Brown Dwarf ◽  
Moment Maps ◽  
Molecular Outflow ◽  
Outflow Rate ◽  
Chemical Modelling ◽  
Stage System ◽  
Low Mass ◽  
Partial View ◽  
The Moment

Abstract We present ALMA 12CO (2-1), 13CO (2-1), C18O (2-1) molecular line observations of a very young proto-brown dwarf system, ISO-OPH 200. We have conducted physical+chemical modelling of the complex internal structure for this system using the core collapse simulations for brown dwarf formation. The model at an age of ∼6000 yr can provide a good fit to the observed kinematics, spectra, and reproduce the complex structures seen in the moment maps. Results from modelling indicate that 12CO emission is tracing an extended (∼1000 au) molecular outflow and a bright shock knot, 13CO is tracing the outer (∼1000 au) envelope/pseudo-disc, and C18O is tracing the inner (∼500 au) pseudo-disc. The source size of ∼8.6 au measured in the 873μm image is comparable to the inner Keplerian disc size predicted by the model. A 3D model structure of ISO-OPH 200 suggests that this system is viewed partially through a wide outflow cavity resulting in a direct view of the outflow and a partial view of the envelope/pseudo-disc. We have argued that ISO-OPH 200 has been mis-classified as a Class Flat object due to the unusual orientation. The various signatures of this system, notably, the young ∼616 yr outflow dynamical age and high outflow rate (∼1 × 10−7 M⊙ yr−1), silicate absorption in the 10$\rm{\mu m}$ mid-infrared spectrum, pristine ISM-like dust in the envelope/disc, comparable sizes of the extended envelope and outflow, indicate that ISO-OPH 200 is an early Class 0 stage system formed in a star-like mechanism via gravitational collapse of a very low-mass core.

scholarly journals CO Outflows in Low-Mass Protostar Candidates in Taurus

1994 ◽  
Vol 140 ◽  
pp. 268-269 ◽  
Author(s):  
M. Tamura ◽  
N. Ohashi ◽  
G. Moriarty-Schieven ◽  
M. Hayashi ◽  
N. Hirano
Keyword(s):  
Active Sites ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Far Infrared ◽  
Close Relation ◽  
Mass Star ◽  
Dark Cloud ◽  
T Tauri ◽  
Mass Outflow ◽  
Low Mass

The Taurus dark cloud is one of the nearest active sites of low-mass star formation. The IRAS satellite has discovered numerous low-luminosity far-infrared sources in this cloud, some of which are completely invisible at optical wavelengths. There are several arguments suggesting that the invisible sources are low-mass protostars which are younger than T Tauri stars and powered by the accretion of infalling gas and dust (Adams, Lada, & Shu 1987; Beichman et al. 1986; Myers et al. 1987; Kenyon et al. 1990)Tamura et al. (1991) made a near-infrared imaging survey of a complete, flux-limited sample of cold IRAS sources in the Taurus dark cloud, of which 8 are optical T Tauri-like objects and 16 are optically invisible sources. They identified all 24 sources with near-infrared counterparts; one is entirely nebulous without a point-like source, and the others generally have an unresolved peak with or without an extended component at 2.2 µm 75 % of the 24 sample sources are associated with infrared/optical nebulosity about 1000 AU to 10000 AU in size. A number of the sources show a clear bipolar or monopolar morphology, suggestive of a close relation of the nebulosity with a bipolar mass outflow; the nebulosity is due to scattering of light from the central source by the dust associated with the mass outflow extending to the poles of a circumstellar dust disk.

scholarly journals Very Low-Luminosity Objects in Star-Forming Regions

1998 ◽  
Vol 11 (1) ◽  
pp. 423-424
Author(s):  
Motohide Tamura ◽  
Yoichi Itoh ◽  
Yumiko Oasa ◽  
Alan Tokunaga ◽  
Koji Sugitani
Keyword(s):  
Brown Dwarfs ◽  
Mass Function ◽  
T Tauri Stars ◽  
Initial Mass Function ◽  
Formation Mechanisms ◽  
Star Forming ◽  
Star Forming Regions ◽  
T Tauri ◽  
Low Mass ◽  
Stellar Sources

Abstract In order to tackle the problems of low-mass end of the initial mass function (IMF) in star-forming regions and the formation mechanisms of brown dwarfs, we have conducted deep infrared surveys of nearby molecular clouds. We have found a significant population of very low-luminosity sources with IR excesses in the Taurus cloud and the Chamaeleon cloud core regions whose extinction corrected J magnitudes are 3 to 8 mag fainter than those of typical T Tauri stars in the same cloud. Some of them are associated with even fainter companions. Follow-up IR spectroscopy has confirmed for the selected sources that their photospheric temperature is around 2000 to 3000 K. Thus, these very low-luminosity young stellar sources are most likely very low-mass T Tauri stars, and some of them might even be young brown dwarfs.

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