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Evidence of a Black Hole in the X-Ray Transient GS 1354-64 (=BW Circini)
We present the first radial velocity curve of the companion star to BWCir that demonstrates the presence of a black hole in this X-raytransient that recorded outbursts in 1987 and 1997 (and possibly1971-1972). We identify weak absorption features corresponding to a G0-5III donor star, strongly veiled by a residual accretion disk thatcontributes 61%-65% of the total light at 6300 Å. The Dopplermotions of these features trace an orbit of P=2.54448 days (or its 1 yralias of P=2.56358 days) and a velocity semiamplitudeK2=279+/-5 km s-1 (or K2=292+/-5 kms-1). Both solutions are equally possible. The mass functionimplied by the shorter period solution is f(M)=5.75+/-0.30Msolar, which, when combined with the rotational broadeningof the tidally locked companion (Vsini=71+/-4 km s-1), yieldsa compact object mass of M1sin3i=7.34+/-0.46 Msolar.This is substantially above the mass of a neutron star under anystandard equation of state of nuclear matter. The companion star isprobably a G subgiant that has evolved off the main sequence in order tofill its Roche lobe. Remarkably, a distance of >=27 kpc is inferredby the companion's luminosity, and this is supported by the largeobserved systemic velocity (γ=103+/-4 km s-1), whichrequires such a distance in order to be consistent with the Galacticrotation curve.
| 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.
| Radial velocities of southern stars obtained with the photoelectric scanner CORAVEL. III - 790 late-type bright stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985A&AS...59...15A&db_key=AST
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Observation and Astrometry data
| Constellation: | Στέφανος Νότιος |
| Right ascension: | 18h29m12.90s |
| Declination: | -43°50'45.0" |
| Apparent magnitude: | 6.36 |
| Distance: | 156.986 parsecs |
| Proper motion RA: | 1.4 |
| Proper motion Dec: | 23.2 |
| B-T magnitude: | 7.492 |
| V-T magnitude: | 6.451 |
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