Flare stars in the TW Hydrae association: the HIP 57269 system

König, B.; Neuhäuser, R.; Guenther, E. W.; Hambaryan, V.

doi:10.1002/asna.200310166

Cited by 4 publications

(12 citation statements)

References 26 publications

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“…Since the binary does not show WISE IR-excess, disk accretion is unlikely to occur and we do not expect veiling (Lynden-Bell & Pringle 1974;Kenyon & Hartmann 1987;Bertout et al 1988). The resulting Li I EW is 200 ± 4 mÅ which agrees well with the previously measured values for HD 102077 (Song et al 2002) and its probable third, wider component discovered by König et al (2003).…”

Section: Using the Lithium I λ6708 å Equivalent Widthsupporting

confidence: 89%

“…However, objections have been raised based on the space motion and weaker-thanexpected lithium absorption (Song et al 2002;König et al 2003). We now revisit both points.…”

Section: Moving Group Membershipmentioning

confidence: 83%

“…Anders et al (1991) measured the radial velocity of HD 102077 in July 1987 and König et al (2003) in January 2002; we measured the radial velocity in July 2013. The results are 15.9 km s −1 , 19±3 km s −1 , and 19.8±0.1 km s −1 respectively.…”

Section: Moving Group Membershipmentioning

confidence: 99%

“…The integrated spectral type of HD 102077 of K0/1V p was first determined by Anders et al (1991) by high-dispersion observations of the Li 6707 Å doublet and König et al (2003) find K1/2 using DFOSC at the 1.54 m Danish telescope. The spectral type of the primary components is, however, less clear.…”

Section: Introductionmentioning

confidence: 99%

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The young binary HD 102077: Orbit, spectral type, kinematics, and moving group membership

Wöllert

Brandner

Reffert³

et al. 2014

A&A

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The K-type binary star HD 102077 was proposed as a candidate member of the TW Hydrae association (TWA) which is a young (5−15 Myr) moving group in close proximity (∼50 pc) to the solar system. The aim of this work is to verify this hypothesis by different means. We first combine diffraction-limited observations from the ESO NTT 3.5 m telescope in SDSS-i and SDSS-z passbands (three epochs) and ESO 3.6 m telescope in H-band (one epoch) with literature data to obtain a new, amended orbit fit of the visual binary. We then estimate the spectral types of both components from the i − z colours and reanalyse the H parallax and proper motion taking the orbital motion into account. Moreover, we use two high-resolution spectra of HD 102077 obtained with the fibre-fed optical echelle spectrograph FEROS at the MPG/ESO 2.2 m telescope to determine the radial velocity and the lithium equivalent width (EW) of the system. Finally, we use all the information to discuss the kinematic properties of HD 102077 and to estimate the age of the system. The orbital elements of the HD 102077 trajectory are well constrained and we derive a total system mass of 2.6 ± 0.8 M and a semi-major axis of 14.9 ± 1.6 AU. From the i − z colours we infer an integrated spectral type of K2V, and individual spectral types of K0 ± 1 and K5 ± 1 for primary and secondary, respectively. The radial velocity corrected for the orbital motion of the system is 17.6 ± 2 km s −1 . Even though the parallax determination from the H data is not influenced by the orbital motion, the proper motion changes to µ α * cos δ = −137.84 ± 1.26 mas yr −1 and µ δ = −33.53 ± 1.45 mas yr −1 . With the resultant space motion, the probability of HD 102077 being a member of TWA is less than 1%. Furthermore, the lithium equivalent width of 200 ± 4 mÅ is consistent with an age between 30 Myr and 120 Myr and thus older than the predicted age of TWA. The comparison of HD 102077's temperature and luminosity to isochrones supports this result. In conclusion, HD 102077's age, galactic space motion, and position do not fit TWA or any other young moving group.

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Section: Using the Lithium I λ6708 å Equivalent Widthsupporting

confidence: 89%

“…However, objections have been raised based on the space motion and weaker-thanexpected lithium absorption (Song et al 2002;König et al 2003). We now revisit both points.…”

Section: Moving Group Membershipmentioning

confidence: 83%

Section: Moving Group Membershipmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The young binary HD 102077: Orbit, spectral type, kinematics, and moving group membership

Wöllert

Brandner

Reffert³

et al. 2014

A&A

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“…Several projects are under way to search for T Tauri stars within 100 pc Webb et al 1999;Hearty et al 2000;Torres et al 2000;Zuckerman & Webb 2000;Zuckerman et al 2001;König et al 2003). Hoff et al (1997) already presented four new T Tauri stars in the TWA based on spectroscopic follow-up of ROSAT sources, whose higher-resolution spectra were later published by Sterzik et al (1999); one of those four stars (PPM 288568) however, may be either a PMS or a ZAMS star, namely with relatively weak Li equivalent width (0.19Å) at relatively early spectral type (G3), hence still relatively high Li abundance (ÐÓ AE´Ä µ ¿ ¾, i.e.…”

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confidence: 99%

Proper motion and X‐ray selected search for new members of the young TW Hya association

et al. 2003

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Abstract.We have searched for new members of the TW Hya association (TWA) among unidentified ROSAT X-ray sources by identifying them in proper motion catalogues and selecting those that would be consistent with kinematical membership to the TWA. Spectroscopic follow-up observations of 19 member candidates revealed the detection of moderate lithium absorption lines for the following three stars: GSC 7206 845, TYC 7216-55, and TYC 7247-12. The isochronal ages of the latter TYC stars are estimated to be ¾¼ Myr while the other one has ½¼¼ Myr age based on a kinematic distance estimate that assumes TWA membership. However, the moderately Li-rich stars are not likely to be new pre-main sequence members of TWA partly because of the discrepant radial velocities. Infrared follow-up imaging in the À-band for the 3 stars shows companion candidates near two of them. While one system (TYC 7216-55) is probably a near-equal-magnitude stellar binary, our follow-up À-band spectrum of the faint companion candidate near GSC 7206 845 shows that it is instead a background K-type star rather than a companion.

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Expansion of the TW Hydrae association and the encounter with Vega

Макаров

Gaume

Andrievsky

2005

Monthly Notices of the Royal Astronomical Society

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We investigate the paths of several probable members of the young association around the star TW Hydrae (TWA) with accurate distances, proper motions and radial velocities. We find that three of the previously identified members, TWA 1, TWA 4 and TWA 11, together with two other young nearby stars, HD 139084 and HD 220476, form a rapidly expanding association with an expansion age of 4.7 ± 0.6 Myr. Initial velocities of member stars with respect to the common centre of mass range from 4 to 10 km s−1. A characteristic size of the association in the initial configuration is 21 pc, which may be somewhat biased upwards due to the uncertainties in the observational data. The Lower Centaurus Crux (LCC) OB association passed near TWA, at a distance of 36 ± 6 pc, 11 Myr ago. A plausible scenario, which accounts for the difference between the isochrone age (≃10 Myr) and expansion age (5 Myr), is that star formation was stimulated in the TWA progenitor cloud by the near passage of the LCC, but that the newly formed stars were not released from the cloud until a subsequent collision with one of the other molecular clouds in the North Ophiuchus region. Vega was inside the TWA association, and close to its centre of gravity, at the time of maximum compression 4.7 Myr ago. If this alignment is a chance encounter, the powerful particular disc around Vega could have been enhanced by the passage through the TWA progenitor cloud at 8 km s−1.

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Flare stars in the TW Hydrae association: the HIP 57269 system

Cited by 4 publications

References 26 publications

The young binary HD 102077: Orbit, spectral type, kinematics, and moving group membership

The young binary HD 102077: Orbit, spectral type, kinematics, and moving group membership

Proper motion and X‐ray selected search for new members of the young TW Hya association

Expansion of the TW Hydrae association and the encounter with Vega

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