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Near-Infrared Spectra of the Black Hole X-Ray Binary A0620-00
We present broadband near-IR (NIR) spectra of A0620-00 obtained withSpeX on the IRTF. The spectrum is characterized by a blue continuum onwhich are superimposed broad emission lines of H I and He II and a hostof narrower absorption lines of neutral metals and molecules. Spectraltype standard star spectra scaled to the dereddened spectrum of A0620-00in K exceed the A0620-00 spectrum in J and H for all stars of spectraltype K7 V or earlier, demonstrating that the donor star, unless laterthan K7 V, cannot be the sole NIR flux source in A0620-00. In addition,the atomic absorption lines in the K3 V spectrum are too weak withrespect to those of A0620-00 even at 100% donor star contribution,restricting the spectral type of the donor star in A0620-00 to laterthan K3 V. Comparison of the A0620-00 spectrum to scaled K star spectraindicates that the CO absorption features are significantly weaker inA0620-00 than in field dwarf stars. Fits of scaled model spectra of aRoche lobe-filling donor star to the spectrum of A0620-00 show that thebest match to the CO absorption lines is obtained when the C abundanceis reduced to [C/H]=-1.5. The donor star contribution in the H wave bandis determined to be (82+/-2)%. Combined with previous published resultsfrom Froning & Robinson and Marsh et al., this gives a precise massfor the black hole in A0620-00 of M1=9.7+/-0.6Msolar.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Observational Constraints on Cool Disk Material in Quiescent Black Hole Binaries
We consider current observational constraints on the presence of cool,optically thick disk material in quiescent black hole binaries,specifically focusing on a case study of the prototypical systemA0620-00. Such material might be expected to be present theoreticallybut is usually claimed to make a negligible contribution at optical andIR wavelengths. The primary argument is based on measurements of theveiling of stellar photospheric absorption lines, in which it is assumedthat the disk spectrum is featureless. We use simulated spectra toexplore the sensitivity of veiling measurements to uncertainties incompanion temperature, gravity, and metallicity. We find that thederived veiling is extremely sensitive to a mismatch between thetemperature and metallicity of the companion and template but that theeffect of a plausible gravity mismatch is much smaller. In general, theresulting uncertainty in the amount of veiling is likely to be muchlarger than the usually quoted statistical uncertainty. We also simulatespectra in which the disk has an emergent spectrum similar to the starand find that in this case, optical veiling constraints are moderatelyrobust. This is because the rotational broadening of the disk is solarge that the two line profiles effectively decouple, and themeasurement of the depth of stellar lines is largely unbiased by thedisk component. We note, however, that this is only true at intermediateresolutions or higher and that significant bias might still affectlow-resolution IR observations. Assuming that the optical veiling isreliable, we then examine the constraints on the temperature andcovering factor of any optically thick disk component. These arestringent if the disk is warm (Teff>~3500 K), but verytemperature sensitive, and cooler disks are largely unconstrained byoptical measurements. Current IR veiling estimates do not help much,representing rather high upper limits. Probably the best constraintcomes from the relative amplitudes of ellipsoidal variations indifferent bands, as these are sensitive to differences in veiling thatare expected for disks cooler than the companion star. A significantdisk contribution in the IR, up to ~25%, is not ruled out in this or anyother way considered, however.
| The Vienna-KPNO search for Doppler-imaging candidate stars. I. A catalog of stellar-activity indicators for 1058 late-type Hipparcos stars
We present the results from a spectroscopic Ca ii H&K survey of 1058late-type stars selected from a color-limited subsample of the Hipparcoscatalog. Out of these 1058 stars, 371 stars were found to showsignificant H&K emission, most of them previously unknown; 23% withstrong emission, 36% with moderate emission, and 41% with weak emission.These spectra are used to determine absolute H&K emission-linefluxes, radial velocities, and equivalent widths of theluminosity-sensitive Sr ii line at 4077 Ä. Red-wavelengthspectroscopic and Strömgren y photometric follow-up observations ofthe 371 stars with H&K emission are used to additionally determinethe absolute Hα -core flux, the lithium abundance from the Li i6708 Å equivalent width, the rotational velocity vsin i, theradial velocity, and the light variations and its periodicity. Thelatter is interpreted as the stellar rotation period due to aninhomogeneous surface brightness distribution. 156 stars were found withphotometric periods between 0.29 and 64 days, 11 additional systemsshowed quasi-periodic variations possibly in excess of ~50 days. Further54 stars had variations but no unique period was found, and four starswere essentially constant. Altogether, 170 new variable stars werediscovered. Additionally, we found 17 new SB1 (plus 16 new candidates)and 19 new SB2 systems, as well as one definite and two possible new SB3systems. Finally, we present a list of 21 stars that we think are mostsuitable candidates for a detailed study with the Doppler-imagingtechnique. Tables A1--A3 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Infrared spectroscopy of V616 Monocerotis (=A0620-00): the accretion disc contamination
We have obtained for the first time K-band infrared spectra of the softX-ray transient V616 Mon (=A0620-00). We determine the 2-sigma upperlimit to the fraction of light arising from the accretion disc to be 27percent. The effect this has on the binary inclination, determined frommodelling the infrared ellipsoidal variations is to increase it by lessthan 7 degrees and decrease the mass of the black hole by less than 3.6Msun.
| Dwarf K and M stars in the southern hemisphere.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972AJ.....77..486U&db_key=AST
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| קבוצת-כוכבים: | ארנבת |
| התרוממות ימנית: | 06h11m03.13s |
| סירוב: | -13°48'02.9" |
| גודל גלוי: | 8.778 |
| מרחק: | 42.409 פארסק |
| תנועה נכונה: | -11.5 |
| תנועה נכונה: | -61.3 |
| B-T magnitude: | 10.119 |
| V-T magnitude: | 8.889 |
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