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HD 137013


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Direct evidence of a sub-stellar companion around CT Chamaeleontis
Aims: In our ongoing search for close and faint companions around TTauri stars in the Chamaeleon star-forming region, we here presentobservations of a new common proper motion companion to the youngT-Tauri star and Chamaeleon member CT Cha and discuss its properties incomparison to other young, low-mass objects and to synthetic modelspectra from different origins. Methods: Common proper motion ofthe companion and CT Cha was confirmed by direct Ks-band imaging datataken with the VLT Adaptive Optics (AO) instrument NACO in February 2006and March 2007, together with a Hipparcos binary for astrometriccalibration. An additional J-band image was taken in March 2007 toobtain color information for a first classification of the companion.Moreover, AO integral field spectroscopy with SINFONI in J, and H+Kbands was obtained to deduce physical parameters of the companion, suchas temperature and extinction. Relative flux calibration of the bandswas achieved using photometry from the NACO imaging data. Results: We found a very faint (Ks = 14.9 mag, Ks0 = 14.4mag) object, just ~2.67´´ northwest of CT Cha correspondingto a projected separation of ~440 AU at 165 ± 30 pc. We show thatCT Cha A and this faint object form a common proper motion pair and thatthe companion is by ?4? significance not a stationarybackground object. The near-infrared spectroscopy yields a temperatureof 2600 ± 250 K for the companion and an optical extinction ofAV = 5.2 ± 0.8 mag, when compared to spectracalculated from Drift-Phoenix model atmospheres. We demonstrate thevalidity of the model fits by comparison to several other well-knownyoung sub-stellar objects. Conclusions: We conclude that the CTCha companion is a very low-mass member of Chamaeleon and very likely aphysical companion to CT Cha, as the probability for a by chancealignment is ?0.01. Due to a prominent Pa-? emission in theJ-band, accretion is probably still ongoing onto the CT Cha companion.From temperature and luminosity (log(L_bol/L?) = -2.68± 0.21), we derive a radius of R = 2.20_-0.60+0.81RJup. We find a consistent mass of M = 17 ± 6MJup for the CT Cha companion from both its luminosity andtemperature when placed on evolutionary tracks. Hence, the CT Chacompanion is most likely a wide brown dwarf companion or possibly even aplanetary mass object.Based on observations made with ESO telescopes at the ParanalObservatory under program IDs 076.C-0292(A), 078.C-0535(A), &279.C-5010(A).Color versions of Figs. 4, 6, 8 and 11 are only available in electronicform at http://www.aanda.org

The infrared void in the Lupus dark clouds revisited: a polarimetric approach
The results of B-band CCD imaging linear polarimetry obtained for starsfrom the Hipparcos catalogue are used to re-examine the distribution ofthe local interstellar medium towards the IRAS 100-μm emission voidin the Lupus dark clouds. The analysis of the obtainedparallax-polarization diagram assigns to the dark cloud Lupus1 adistance between 130 and 150pc and assures the existence of a low columndensity region coincident with the observed infrared void. Moreover,there are clear indications of the existence of absorbing material atdistances closer than 60-100pc, which may be associated with theinterface boundary between the Local Bubble and its neighbourhood LoopIsuperbubble.

Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.

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观测天体数据

星座:豺狼座
右阿森松:15h24m47.82s
赤纬:-32°08'29.8"
视星:8.744
距离:73.421 天文距离
右阿森松适当运动:-105.5
赤纬适当运动:-65.1
B-T magnitude:9.541
V-T magnitude:8.81

目录:
适当名称
HD 1989HD 137013
TYCHO-2 2000TYC 7317-756-1
USNO-A2.0USNO-A2 0525-19327991
HIPHIP 75445

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