Hipparcos observations of pre-main-sequence stars

Wichmann, R.; Bastian, U.; Krautter, J.; Jankovics, I.; Ruciński, S. M.

doi:10.1046/j.1365-8711.1998.02162.x

Cited by 174 publications

(176 citation statements)

References 14 publications

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“…Krautter 1991 andHughes et al 1993 for a discussion). The Hipparcos measurements of the T Tauri stars in Lupus confirms this result with 145 ± 50 pc mean distance (see Wichmann et al 1998 for T Tauri stars known before the ROSAT mission and Neuhäuser & Brandner 1998 for T Tauri stars newly found by the ROSAT mission). However, some members of Lupus also appeared to be as far as ∼ 190 pc (Wichmann et al 1998), while Knude & Hog (1998) Nakajima et al (2000) give ∼ 150 pc for Lupus; Franco (2002) argues for ∼ 150 pc as the most probable distance to the dark cloud known as Lupus I;and Sartori et al (2003) specify 147 pc.…”

Section: The Common Proper Motion Pairsupporting

confidence: 67%

GQLup and its common proper motion companion

Mugrauer¹,

Neuhaeuser²

2005

Astron. Nachr.

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Abstract. Recently, Neuhäuser et al. (2005a) presented evidence for a sub-stellar, common proper motion companion to GQ Lup. With two theoretical mass estimates, both below the Deuterium burning minimum mass limit, the companion is probably a planet imaged directly. We present here a more detailed astrometric analysis of the GQ Lup system, using all the (different) proper motions published for the primary. The common proper motion is significant in all cases, also when taking into account the error in parallax or distance (140 ± 50 pc). When using the weighted mean, the significance for common proper motion of GQ Lup and its companion is 7 σ + 4 σ for no change in separation plus 8 σ for no change in position angle. We also discuss the question, whether GQ Lup and its common-proper motion companion are not bound, but share the same or similar proper motion as two independent members of the Lupus T association, which is a moving group, where most members should have the same motion anyway. Given our discussion, this hypothesis can be rejected by several σ: The probability to find by chance an L-dwarf fainter than KS = 14 mag within 0. 7325 with (almost) the same proper motion of GQ Lup is only ≤ 3 · 10 −10 . The orbital motion of the system is not yet detected (1.4 ± 2.2 mas/yr), but is probably smaller than the escape velocity (5.3 ± 2.1 mas/yr), so that the system may well be gravitationally bound and stable. This is different for the 2MASSWJ 1207334-393254 system, as we also show.

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Section: The Common Proper Motion Pairsupporting

confidence: 67%

GQLup and its common proper motion companion

Mugrauer¹,

Neuhaeuser²

2005

Astron. Nachr.

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“…The Taurus star-formation region has a distance of ≈ 140 pc (Kenyon et al 1994;Wichmann et al 1998;Torres et al 2012) and extends over a region of one hundred square degrees on the sky. The age of its population is ≈ 1 − 2 Myr, but Daemgen et al (2015) found an additional co-moving sub-population of ≈ 20 Myr.…”

Section: The Stellar and Substellar Population Inmentioning

confidence: 99%

Using binary statistics in Taurus-Auriga to distinguish between brown dwarf formation processes

Marks¹,

Martín

Béjar

et al. 2017

A&A

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Context. Whether brown dwarfs (BDs) form just as stars directly from the gravitational collapse of a molecular cloud core ("star-like") or whether BDs and some very low-mass stars (VLMSs) constitute a separate population which form alongside stars comparable to the population of planets, e.g. through circumstellar disk ("peripheral") fragmentation, is one of the key questions of the star-formation problem. Aims. For young stars in Taurus-Auriga the binary fraction has been shown to be large with little dependence on primary mass above ≈ 0.2M⊙, while for BDs it is < 10%. Here we investigate a case in which BDs in Taurus formed dominantly, but not exclusively, through peripheral fragmentation, which naturally results in low binary fractions. The decline of the binary frequency in the transition region between star-like formation and peripheral formation is modelled. Methods. A dynamical population synthesis model is employed in which stellar binary formation is universal with a large binary fraction close to unity. Peripheral objects form separately in circumstellar disks with a distinctive initial mass function (IMF), own orbital parameter distributions for binaries and a low binary fraction according to observations and expectations from smoothed particle hydrodynamics (SPH) and grid-based computations. A small amount of dynamical processing of the stellar component is accounted for as appropriate for the low-density Taurus-Auriga embedded clusters. Results. The binary fraction declines strongly in the transition region between star-like and peripheral formation, exhibiting characteristic features. The location of these features and the steepness of this trend depend on the masslimits for star-like and peripheral formation. Such a trend might be unique to low density regions like Taurus which host dynamically largely unprocessed binary populations in which the binary fraction is large for stars down to M-dwarfs and low for BDs. Conclusions. The existence of a strong decline in the binary fraction -primary mass diagram will become verifiable in future surveys on BD and VLMS binarity in the Taurus-Auriga star forming region. It is a test of the (non-)continuity of star formation along the mass-scale, the separateness of the stellar and BD populations and the dominant formation channel for BDs and BD binaries in regions of low stellar density hosting dynamically unprocessed populations.

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“…For this calculation we have assumed a distance of 136 +54 −30 pc for V410 Tau (Wichmann et al 1998); errors in the distance could affect fluxes by up to a factor of almost 2. In order to convert magnitudes into absolute fluxes, we used the table provided by Rydgren et al (1984) for the Johnson filters, and by Gray (1998) for the Strömgren filters.…”

Section: Photometric Monitoringmentioning

confidence: 99%

The weak-line T Tauri star V410 Tau

Fernández¹,

Stelzer

Henden

et al. 2004

A&A

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Abstract. We show that V410 Tau, a weak-line T Tauri star, is a flaring star. This result comes from an intensive, coordinated monitoring campaign carried out in November 2001 at visible and X-ray wavelength ranges. It is confirmed by previous, isolated observations found in the literature. Flares tend to occur mainly around the star's minimum brightness, when the most active regions face us. We report on the strongest flare detected up to now on this star, for which we have obtained simultaneous visible Strömgren photometry and intermediate resolution spectroscopy. We derive decay times from 3 to 0.7 h at several wavelengths for the continuum in the 3600−5600 Å range. We estimate the energy involved in this and the other flares for which we have good time sampling, and conclude that the strongest event, at least, could have important consequences for the matter in the surroundings of the star. If similar events took place on the young Sun and lasted for several Myr, they could explain the anomalous abundances of elemental isotopes found in some meteorites. They could have also contributed to eliminate part of the primary atmospheres of the planet embryos and would have provided enough energy for the melting of solid iron-magnesium silicates, a process that may explain the presence of chondrules in chondritic meteorites. High resolution spectroscopy of the H α emission line in the quiescent states of V410 Tau enables us to study the variability of the broad component. We suggest that this component is related to microflaring activity, such as the one observed on more evolved, magnetically-active stars. The large velocities and the energy associated with this component support this hypothesis.

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Hipparcos observations of pre-main-sequence stars

Cited by 174 publications

References 14 publications

GQLup and its common proper motion companion

GQLup and its common proper motion companion

Using binary statistics in Taurus-Auriga to distinguish between brown dwarf formation processes

The weak-line T Tauri star V410 Tau

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