scholarly journals Spectroscopic Binaries Among Low-Mass Pre-Main Sequence Stars

1989 ◽  
Vol 8 ◽  
pp. 111-115
Author(s):  
Robert D. Mathieu
Keyword(s):  
Radial Velocity ◽  
Main Sequence ◽  
Spectroscopic Binaries ◽  
Short Paper ◽  
Measurement Technology ◽  
Spectroscopic Binary ◽  
T Tauri ◽  
Low Mass ◽  
Pms Stars ◽  
T Tau

Although the unusual nature of T Tau was noted over four decades ago, the first orbit for a low-mass pre-main sequence (PMS) spectroscopic binary was not determined until Mundt et al. (1983) serendipitously discovered the double-lined nature of V826 Tau. To some degree the paucity of spectroscopic binary detections may be attributed to the faintness of such stars and the consequent difficulty in obtaining high resolution spectra; the first high-precision radial-velocity survey was that of Herbig (1977). Advances in radial-velocity measurement technology now permit relatively easy velocity measurements of PMS stars. However, V826 Tau was also one of the first discovered members of the naked T Tauri (NTTS) class of PMS stars (Walter 1987) and its discovery as a spectroscopic binary foreshadowed a prevalence for binary detection among this population. In this short paper we review the present observational status of PMS spectroscopic binaries and present several initial results and thoughts for consideration.

scholarly journals Chromospheric Properties of T Tauri Stars Determined from EUV Spectra

1983 ◽  
Vol 71 ◽  
pp. 509-511
Author(s):  
A. Brown ◽  
C. Jordan
Keyword(s):  
Large Scale ◽  
Main Sequence ◽  
Emission Measure ◽  
Stellar Winds ◽  
Coronal Emission ◽  
Absolute Level ◽  
T Tauri ◽  
The Mean ◽  
Pms Stars ◽  
T Tau

IUE spectra of six pre-main-sequence (PMS3 stars are analysed and the resultant emission measure distributions compared with that of T Tau for which a chromospheric model has been calculated. The general shape and absolute level of the mean emission measure distributions are remarkably similar, indicating the relevance of the T Tau chromospheric model to other PMS stars. Evidence for the influence of large scale motions and/or stellar winds on the transition region and coronal emission measures is found. The relative importance of different energy balance terms is discussed.

scholarly journals Magnetic Activity of T Tauri Stars

1992 ◽  
Vol 9 ◽  
pp. 653-654
Author(s):  
T. Montmerle
Keyword(s):  
Solar Activity ◽  
Main Sequence ◽  
Magnetic Activity ◽  
T Tauri Stars ◽  
X Rays ◽  
General Review ◽  
Near Ir ◽  
T Tauri ◽  
Low Mass ◽  
Pms Stars

T Tauri stars (TTS) are low-mass (M ≲ 1M⊙) pre-main sequence (PMS) stars (for a general review, see Bertout 1989). They have long been known to be variable from near-TIV to near-IR wavelengths, on timescales ranging from a few minutes to a few decades. They are observed to flare in many wavenlength rages, from X-rays to the radio, and all the existing evidence is consistent with a very strong magnetic activity, in many ways analogous to solar activity (for a review, see, e.g., Montmerle et al. 1991).

scholarly journals The PMS Eclipsing Binary RXJ 0529.4+0041

2001 ◽  
Vol 200 ◽  
pp. 468-471 ◽  
Author(s):  
E. Covino ◽  
S. Catalano ◽  
A. Frasca ◽  
E. Marilli ◽  
J.M. Alcalá ◽  
...  
Keyword(s):  
Main Sequence ◽  
Light Curves ◽  
Spectroscopic Binaries ◽  
Evolutionary Models ◽  
Eclipsing Binary ◽  
Star Forming ◽  
T Tauri ◽  
Low Mass ◽  
Using Data ◽  
Orbital Solution

We report the discovery of the first low–mass pre–main sequence eclipsing binary among a sample of double-lined spectroscopic binaries in the Orion star forming region found in a previous high-resolution spectroscopic investigation on ROSAT–discovered weak-T Tauri stars. Here we present the preliminary results from the combined analysis of the spectroscopic orbit and B and V light–curves, using data available till spring 2000. We then compare the fundamental stellar parameters derived from the orbital solution with those inferred from some widely used theoretical evolutionary models.

scholarly journals The Mass Distribution of Secondaries to Solar-Type Stars

2004 ◽  
Vol 191 ◽  
pp. 37-40 ◽  
Author(s):  
Helmut A. Abt ◽  
Daryl W. Willmarth
Keyword(s):  
Radial Velocity ◽  
Mass Distribution ◽  
Main Sequence ◽  
Mass Function ◽  
Spectroscopic Binaries ◽  
Orbital Elements ◽  
Main Sequence Stars ◽  
Solar Type ◽  
Low Mass ◽  
Good Agreement

AbstractTwo previous studies of the secondary mass function in spectroscopic binaries by Abt & Levy (1976) and by Duquennoy & Mayor (1991) are shown to be in good agreement if they are both plotted with the same abscissa scale. A new study of 271 main-sequence stars later than F6 V made with a radial-velocity accuracy of ±0.10 km s-1 yielded 10 new sets of orbital elements in addition to the 59 published ones. The resulting secondary mass function is nearly flat and shows that 2.2±1.5% of the primaries have low-mass (0.01–0.10 M⊙) companions. In contrast, the secondary mass function for visual binaries with separations >500 AU fits a van Rhijn function, as was shown previously by Abt and Levy.

scholarly journals New Results on the Binary Companion of T Tauri

1983 ◽  
Vol 71 ◽  
pp. 505-507 ◽  
Author(s):  
Theodore Simon ◽  
P.R. Schwartz ◽  
H.M. Dyck ◽  
B. Zuckerman
Keyword(s):  
Main Sequence ◽  
Position Angle ◽  
Speckle Interferometry ◽  
Main Sequence Star ◽  
Near Ir ◽  
T Tauri ◽  
Optical Star ◽  
T Tau

We have recently reported the discovery of a cool (650–800 K) low-luminosity companion to the pre-main-sequence star, T Tauri (Dyck et al. 1982). We proposed that the optical star and its infrared companion form a physical pair with a N-S separation of 100 a.u. However, there remained in our 2-5 μm speckle interferometry an ambiguity of 180° in the position angle of the secondary. In addition, Cohen et al. (1982) noted an 800 milliarcsec (mas) offset between the visual and 6 cm radio positions at T Tau. Both of these positional discrepancies have now been clarified by accurate visual and radio astrometry of T Tau, and by further near-IR speckle interferometry.

scholarly journals Testing Pre-Main Sequence Models with Young Binaries

2001 ◽  
Vol 200 ◽  
pp. 472-482
Author(s):  
Francesco Palla
Keyword(s):  
Binary System ◽  
Binary Systems ◽  
Main Sequence ◽  
Young Stars ◽  
System A ◽  
Spectroscopic Binary ◽  
Low Mass ◽  
Good Agreement

I will discuss several tests to gauge the accuracy of pre–main-sequence (PMS) models. Methods to determine the mass of young stars are overviewed, with emphasis on the information provided by double-lined, spectroscopic binary systems. A comparison of the dynamically determined masses with those estimated using the PMS models of Palla & Stahler (1999) is presented. Good agreement between empirical and theoretical masses is found. The analysis of the inferred ages from the isochrones shows a remarkable coevality within each binary system. A complete assessment of the accuracy of PMS tracks needs the identification of eclipsing systems of low-mass.

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 Masses of the components of SB2 binaries observed with Gaia – V. Accurate SB2 orbits for 10 binaries and masses of the components of 5 binaries

2020 ◽  
Vol 496 (2) ◽  
pp. 1355-1368
Author(s):  
J-L Halbwachs ◽  
F Kiefer ◽  
Y Lebreton ◽  
H M J Boffin ◽  
F Arenou ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Binary Stars ◽  
Main Sequence ◽  
Spectroscopic Binaries ◽  
Orbital Elements ◽  
Evolved Stars ◽  
The Individual ◽  
The Masses ◽  
Stellar Masses ◽  
Selection Of

ABSTRACT Double-lined spectroscopic binaries (SB2s) are one of the main sources of stellar masses, as additional observations are only needed to give the inclinations of the orbital planes in order to obtain the individual masses of the components. For this reason, we are observing a selection of SB2s using the SOPHIE spectrograph at the Haute-Provence observatory in order to precisely determine their orbital elements. Our objective is to finally obtain masses with an accuracy of the order of one per cent by combining our radial velocity (RV) measurements and the astrometric measurements that will come from the Gaia satellite. We present here the RVs and the re-determined orbits of 10 SB2s. In order to verify the masses, we will derive from Gaia, we obtained interferometric measurements of the ESO VLTI for one of these SB2s. Adding the interferometric or speckle measurements already published by us or by others for four other stars, we finally obtain the masses of the components of five binary stars, with masses ranging from 0.51 to 2.2 solar masses, including main-sequence dwarfs and some more evolved stars whose location in the HR diagram has been estimated.

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.

scholarly journals On the origin of the bimodal rotational velocity distribution in stellar clusters: rotation on the pre-main sequence

2020 ◽  
Vol 495 (2) ◽  
pp. 1978-1983
Author(s):  
Nate Bastian ◽  
Sebastian Kamann ◽  
Louis Amard ◽  
Corinne Charbonnel ◽  
Lionel Haemmerlé ◽  
...  
Keyword(s):  
Main Sequence ◽  
Rotational Velocity ◽  
Open Clusters ◽  
Observational Constraints ◽  
Stellar Clusters ◽  
Period Distribution ◽  
Low Mass ◽  
Rotational Distribution ◽  
Set Up ◽  
Pms Stars

ABSTRACT We address the origin of the observed bimodal rotational distribution of stars in massive young and intermediate age stellar clusters. This bimodality is seen as split main sequences at young ages and also has been recently directly observed in the Vsini distribution of stars within massive young and intermediate age clusters. Previous models have invoked binary interactions as the origin of this bimodality, although these models are unable to reproduce all of the observational constraints on the problem. Here, we suggest that such a bimodal rotational distribution is set-up early within a cluster’s life, i.e. within the first few Myr. Observations show that the period distribution of low-mass ($\lesssim\! 2 \, \mathrm{M}_\odot$) pre-main-sequence (PMS) stars is bimodal in many young open clusters, and we present a series of models to show that if such a bimodality exists for stars on the PMS that it is expected to manifest as a bimodal rotational velocity (at fixed mass/luminosity) on the main sequence for stars with masses in excess of ∼1.5 M⊙. Such a bimodal period distribution of PMS stars may be caused by whether stars have lost (rapid rotators) or been able to retain (slow rotators) their circumstellar discs throughout their PMS lifetimes. We conclude with a series of predictions for observables based on our model.

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