scholarly journals Finding orbital motion of sub-stellar companions - the case of TWA 5B

2007 ◽  
Vol 3 (S248) ◽  
pp. 126-127 ◽  
Author(s):  
T. Schmidt ◽  
R. Neuhäuser ◽  
M. Mugrauer
Keyword(s):  
Proper Motion ◽  
Main Sequence ◽  
Orbital Motion ◽  
T Tauri Stars ◽  
Brown Dwarf ◽  
T Tauri ◽  
Combining Data ◽  
Tw Hydrae Association ◽  
Astrometric Data ◽  
Triple Star

AbstractTWA 5B is a brown dwarf companion of H=12 mag, 2″ off the ~5 mag brighter triple star CoD-33° 7795 (=TWA 5), a member of the TW Hydrae association of T Tauri stars at ~55 pc. This object is the first brown dwarf around a pre-main-sequence star (confirmed by common proper motion) ever found. In the last year we have newly reduced VLT NaCo data originally taken in 2003 and combined it with all the available astrometric data of the system to investigate possibly detectable orbital motion of the system. Indeed we were able to find linear orbital motion of the system combining data from HST, VLT and Gemini-North.

Discovery of Seven T Tauri Stars and a Brown Dwarf Candidatein the Nearby TW Hydrae Association

1999 ◽  
Vol 512 (1) ◽  
pp. L63-L67 ◽  
Author(s):  
R. A. Webb ◽  
B. Zuckerman ◽  
I. Platais ◽  
J. Patience ◽  
R. J. White ◽  
...  
Keyword(s):  
T Tauri Stars ◽  
Brown Dwarf ◽  
T Tauri ◽  
Tw Hydrae Association

The Infancy of Solar-Type Stars and its Relevance for the Origin of Life

1997 ◽  
Vol 161 ◽  
pp. 267-282 ◽  
Author(s):  
Thierry Montmerle
Keyword(s):  
Main Sequence ◽  
Solar Nebula ◽  
Circumstellar Disks ◽  
T Tauri Stars ◽  
Necessary Condition ◽  
Sequence Evolution ◽  
T Tauri ◽  
Solar Type ◽  
Optical Domain ◽  
The Origin Of Life

AbstractFor life to develop, planets are a necessary condition. Likewise, for planets to form, stars must be surrounded by circumstellar disks, at least some time during their pre-main sequence evolution. Much progress has been made recently in the study of young solar-like stars. In the optical domain, these stars are known as «T Tauri stars». A significant number show IR excess, and other phenomena indirectly suggesting the presence of circumstellar disks. The current wisdom is that there is an evolutionary sequence from protostars to T Tauri stars. This sequence is characterized by the initial presence of disks, with lifetimes ~ 1-10 Myr after the intial collapse of a dense envelope having given birth to a star. While they are present, about 30% of the disks have masses larger than the minimum solar nebula. Their disappearance may correspond to the growth of dust grains, followed by planetesimal and planet formation, but this is not yet demonstrated.

scholarly journals Variability of young stellar objects in the star-forming region Pelican Nebula

2019 ◽  
Vol 627 ◽  
pp. A135 ◽  
Author(s):  
A. Bhardwaj ◽  
N. Panwar ◽  
G. J. Herczeg ◽  
W. P. Chen ◽  
H. P. Singh
Keyword(s):  
Main Sequence ◽  
T Tauri Stars ◽  
Young Stellar Objects ◽  
Spectral Energy ◽  
Physical Parameters ◽  
Main Sequence Stars ◽  
Stellar Objects ◽  
Star Forming ◽  
T Tauri ◽  
Optical Wavelengths

Context. Pre-main-sequence variability characteristics can be used to probe the physical processes leading to the formation and initial evolution of both stars and planets. Aims. The photometric variability of pre-main-sequence stars is studied at optical wavelengths to explore star–disk interactions, accretion, spots, and other physical mechanisms associated with young stellar objects. Methods. We observed a field of 16′ × 16′ in the star-forming region Pelican Nebula (IC 5070) at BVRI wavelengths for 90 nights spread over one year in 2012−2013. More than 250 epochs in the VRI bands are used to identify and classify variables up to V ∼ 21 mag. Their physical association with the cluster IC 5070 is established based on the parallaxes and proper motions from the Gaia second data release (DR2). Multiwavelength photometric data are used to estimate physical parameters based on the isochrone fitting and spectral energy distributions. Results. We present a catalog of optical time-series photometry with periods, mean magnitudes, and classifications for 95 variable stars including 67 pre-main-sequence variables towards star-forming region IC 5070. The pre-main-sequence variables are further classified as candidate classical T Tauri and weak-line T Tauri stars based on their light curve variations and the locations on the color-color and color-magnitude diagrams using optical and infrared data together with Gaia DR2 astrometry. Classical T Tauri stars display variability amplitudes up to three times the maximum fluctuation in disk-free weak-line T Tauri stars, which show strong periodic variations. Short-term variability is missed in our photometry within single nights. Several classical T Tauri stars display long-lasting (≥10 days) single or multiple fading and brightening events of up to two magnitudes at optical wavelengths. The typical mass and age of the pre-main-sequence variables from the isochrone fitting and spectral energy distributions are estimated to be ≤1 M⊙ and ∼2 Myr, respectively. We do not find any correlation between the optical amplitudes or periods with the physical parameters (mass and age) of pre-main-sequence stars. Conclusions. The low-mass pre-main-sequence stars in the Pelican Nebula region display distinct variability and color trends and nearly 30% of the variables exhibit strong periodic signatures attributed to cold spot modulations. In the case of accretion bursts and extinction events, the average amplitudes are larger than one magnitude at optical wavelengths. These optical magnitude fluctuations are stable on a timescale of one year.

scholarly journals Spectral energy distributions and structures of debris discs

2004 ◽  
Vol 202 ◽  
pp. 328-330
Author(s):  
W.R.F. Dent ◽  
M. C. Wyatt ◽  
W. S. Holland ◽  
J. S. Greaves ◽  
I. M. Coulson ◽  
...  
Keyword(s):  
Main Sequence ◽  
T Tauri Stars ◽  
Spectral Energy ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
Long Wavelength ◽  
T Tauri

New photometry of main-sequence debris discs has been carried out at 850 and 450/μm; the derived SEDs indicate that the dust can lie in either thin rings or radially-extended discs, as seen directly in the few nearby objects which are resolvable. All such objects are consistent with a long wavelength opacity index β of 1.0±0.2 - similar to T Tauri stars, but significantly lower than embedded objects.

scholarly journals Magnetic fields of intermediate-mass T Tauri stars

2019 ◽  
Vol 622 ◽  
pp. A72 ◽  
Author(s):  
F. Villebrun ◽  
E. Alecian ◽  
G. Hussain ◽  
J. Bouvier ◽  
C. P. Folsom ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Main Sequence ◽  
Large Population ◽  
T Tauri Stars ◽  
Magnetic Characteristics ◽  
Intermediate Mass ◽  
Surface Magnetic Field ◽  
T Tauri ◽  
Magnetic Stars ◽  
Pms Stars

Context. The origin of the fossil magnetic fields detected in 5 to 10% of intermediate-mass main sequence stars is still highly debated.Aims. We want to bring observational constraints to a large population of intermediate-mass pre-main sequence (PMS) stars in order to test the theory that convective-dynamo fields generated during the PMS phases of stellar evolution can occasionally relax into fossil fields on the main sequence.Methods. Using distance estimations, photometric measurements, and spectropolarimetric data from HARPSpol and ESPaDOnS of 38 intermediate-mass PMS stars, we determined fundamental stellar parameters (Teff,Landvsini) and measured surface magnetic field characteristics (including detection limits for non-detections, and longitudinal fields and basic topologies for positive detections). Using PMS evolutionary models, we determined the mass, radius, and internal structure of these stars. We compared different PMS models to check that our determinations were not model-dependant. We then compared the magnetic characteristics of our sample accounting for their stellar parameters and internal structures.Results. We detect magnetic fields in about half of our sample. About 90% of the magnetic stars have outer convective envelopes larger than ∼25% of the stellar radii, and heavier than ∼2% of the stellar mass. Going to higher mass, we find that the magnetic incidence in intermediate-mass stars drops very quickly, within a timescale on the order of few times 0.1 Myr. Finally, we propose that intermediate-mass T Tauri stars with large convective envelopes, close to the fully convective limit, have complex fields and that their dipole component strengths may decrease as the sizes of their convective envelopes decrease, similar to lower-mass T Tauri stars.

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.

IUE observations of pre-main-sequence stars. I - MG II and CA II resonance line fluxes for T Tauri stars

1981 ◽  
Vol 251 ◽  
pp. 113 ◽  
Author(s):  
M. S. Giampapa ◽  
N. Calvet ◽  
C. L. Imhoff ◽  
L. V. Kuhi
Keyword(s):  
Resonance Line ◽  
Main Sequence ◽  
T Tauri Stars ◽  
Main Sequence Stars ◽  
T Tauri

Sodium lines in T Tauri stars - Diagnostics of pre-main-sequence winds

1990 ◽  
Vol 356 ◽  
pp. 646 ◽  
Author(s):  
A. Natta ◽  
C. Giovanardi
Keyword(s):  
Main Sequence ◽  
T Tauri Stars ◽  
T Tauri

scholarly journals X-ray Flare Rate of T Tauri Stars in Taurus

1995 ◽  
Vol 151 ◽  
pp. 216-217
Author(s):  
R. Neuhäuser ◽  
Th. Preibisch
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
T Tauri Stars ◽  
Medium Size ◽  
Late Type ◽  
Large Sample ◽  
X Ray ◽  
T Tauri ◽  
Sky Survey ◽  
Low Mass

AbstractWe study the X-ray emission of several hundred (young, low-mass, late-type, pre-main sequence) T Tauri stars (TTS) in the Taurus T association, a nearby well-studied region of ongoing star formation. We report on X-ray emission variability of TTS as observed with the flux-limited ROSAT All-Sky Survey (RASS). Since RASS observations are spatially unbiased, we can investigate the X-ray flare rate of TTS on a large sample. We find that large flares are very rare (once per year), while medium-size flares can occur once in ∼ 40 days.

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