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On the Apparent Lack of Be X-Ray Binaries with Black Holes
In our Galaxy there are 64 Be X-ray binaries known to date. Out ofthese, 42 host a neutron star (NS), and for the remainder the nature ofthe companion is unknown. None, so far, are known to host a black hole(BH). There seems to be no apparent mechanism that would preventformation or detection of Be stars with BHs. This disparity is referredto as a missing Be-BH X-ray binary problem. We point out that currentevolutionary scenarios that lead to the formation of Be X-ray binariespredict that the ratio of binaries with NSs to the ones with BHs israther high, F NStoBH ~ 10-50, with the more likely formationmodels providing the values at the high end. The ratio is a naturaloutcome of (1) the stellar initial mass function that produces more NSsthan BHs and (2) common envelope evolution (i.e., a major mechanisminvolved in the formation of interacting binaries) that naturallyselects progenitors of Be X-ray binaries with NSs (binaries withcomparable mass components have more likely survival probabilities) overones with BHs (which are much more likely to be common envelopemergers). A comparison of this ratio (i.e., F NStoBH ~ 30)with the number of confirmed Be-NS X-ray binaries (42) indicates thatthe expected number of Be-BH X-ray binaries is of the order of only~0-2. This is entirely consistent with the observed Galactic sample.
| Finding Periods in High Mass X-Ray Binaries
This is a call for amateur astronomers who have the equipment andexperience for producing high quality photometry to contribute to aprogram of finding periods in the optical light curves of high massX-ray binaries (HMXB). HMXBs are binary stars in which the lighter staris a neutron star or a black hole and the more massive star is a Type Osupergiant or a Be type main sequence star. Matter is transferred fromthe ordinary star to the compact object and X-rays are produced as thegravitational energy of the accreting gas is converted into light. HMXBsare very bright, many are brighter than 10th magnitude, and so makeperfect targets for experienced amateur astronomers with photometrycapable CCD equipment coupled with almost any size telescope.
| Unveiling the nature of INTEGRAL objects through optical spectroscopy. III. Observations of seven southern sources
Context: . The detection, thanks to the INTEGRAL satellite, of a numberof new hard X-ray sources calls for the identification of their natureby means of observations at longer wavelengths. Aims. In our continuingcampaign to identify longer-wavelength counterparts of thesenewly-discovered hard X-ray sources detected by INTEGRAL, we observedthe putative optical counterparts of seven southern sources at the SouthAfrican Astronomical Observatory and at the European SouthernObservatory. Methods. Optical spectroscopy was performed on allcandidates of these X-ray sources. For two of these objects, opticalphotometry was also acquired. Results. These observations firmlyestablished the nature of four of these sources: we found that IGRJ10404-4625 (=LEDA 93974), 4U 1344-60 and IGR J16482-3036 are ActiveGalactic Nuclei (AGNs) at redshifts z = 0.0237, 0.013 and 0.0313,respectively, and that 2RXP J130159.6-635806 is a Galactic High-MassX-ray Binary (HMXB). We also give possible optical identifications forthree further objects, namely IGR J11215-5952, IGR J11305-6256 and IGRJ16207-5129, which are consistent with being Galactic HMXBs. Physicalparameters for these objects are also evaluated by collecting anddiscussing the available multiwavelength information. Conclusions. Thedetection of four definite or likely HMXBs out of seven objects in oursample further stresses INTEGRAL's crucial contribution in hunting thisclass of object. Also, the determination of the extragalactic nature ofa substantial fraction of the INTEGRAL survey sources underlines theimportance of hard X-ray observations for the study of background AGNslocated beyond the "Zone of Avoidance" of the Galactic Plane.
| High-energy sources before INTEGRAL. INTEGRAL reference catalog
We describe the INTEGRAL reference catalog which classifies previouslyknown bright X-ray and gamma-ray sources before the launch of INTEGRAL.These sources are, or have been at least once, brighter than ~ 1 mCrababove 3 keV, and are expected to be detected by INTEGRAL. This catalogis being used in the INTEGRAL Quick Look Analysis to discover newsources or significantly variable sources. We compiled several publishedX-ray and gamma-ray catalogs, and surveyed recent publications for newsources. Consequently, there are 1122 sources in our INTEGRAL referencecatalog. In addition to the source positions, we show an approximatespectral model and expected flux for each source, based on which wederive expected INTEGRAL counting rates. Assuming the default instrumentperformances and at least ~ 105 s exposure time for anypart of the sky, we expect that INTEGRAL will detect at least ~ 700sources below 10 keV and ~ 400 sources above 20 keV over the missionlife.The Catalog is available in electronic form at the CDS via anonymous ftpto cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?/A+A/411/L59
| The Hard X-Ray Luminosity of OB Star Populations: Implications for The Contribution of Star Formation to the Cosmic X-Ray Background
We present an empirical analysis of the integrated X-ray luminosityarising from populations of OB stars. In particular, we utilize resultsfrom the All-Sky Monitor on RXTE, along with archival data from previousmissions, to assess the mean integrated output of X-rays in the 2-10 keVband from accreting early-type binaries within 3 kpc of the Sun. Using arecent OB star census of the solar neighborhood, we then calculate thespecific X-ray luminosity per O star from accretion-powered systems. Wealso assess the contribution to the total X-ray luminosity of an OBpopulation from associated T Tauri stars, stellar winds, and supernovae.We repeat this exercise for the major Local Group galaxies, concludingthat the total X-ray luminosity per O star spans a broad range from 2 to20×1034 ergs s-1. Contrary to previousresults, we do not find a consistent trend with metallicity; in fact,the specific luminosities for M31 and the SMC are equal, despite havingmetallicities that differ by an order of magnitude. In light of theseresults, we assess the fraction of the observed 2-10 keV emission fromstarburst galaxies that arises directly from their OB star populations,concluding that, while binaries can explain most of the hard X-rayemission in many local starbursts, a significant additional component orcomponents must be present in some systems. A discussion of the natureof this additional emission, along with its implications for thecontribution of starbursts to the cosmic X-ray background, concludes ourreport.
| On the origin of the difference between the runaway velocities of the OB-supergiant X-ray binaries and the Be/X-ray binaries
The recent finding by Chevalier & Ilovaisky (1998) from Hipparcosobservations that OB-supergiant X-ray binaries have relatively largerunaway velocities (mean peculiar tangential velocity avvt = 42 +/- 14\kms), whereas Be/X-ray binaries have low runaway velocities (avvt = 15+/- 6 \kms), provides confirmation of the current models for theformation of these two types of systems. These predict a difference inrunaway velocity of this order of magnitude. This difference basicallyresults from the variation of the fractional helium core mass as afunction of stellar mass, in combination with the conservation oforbital angular momentum during the mass transfer phase that precededthe formation of the compact object in the system. This combinationresults into: (i) Systematically narrower pre-supernova orbits in theOB-supergiant systems than in the Be-systems, and (ii) A largerfractional amount of mass ejected in the supernovae in high-mass systemsrelative to systems of lower mass. Regardless of possible kickvelocities imparted to neutron stars at birth, this combination leads toa considerable difference in average runaway velocity between these twogroups. If one includes the possibility for non-conservative masstransfer the predicted difference between the runaway velocity of thetwo groups becomes even more pronounced. The observed low runawayvelocities of the Be/X-ray binaries confirm that in most cases not morethan 1 to 2 \msun\ was ejected in the supernovae that produced theirneutron stars. This, in combinatioThe values given here are not identical (though similar) to those listedin Chevalier & Ilovaisky (1998). The corrections we applied areoutlined below.
| A catalogue of high-mass X-ray binaries
We present a catalogue of high-mass X-ray binaries. The catalogue is anupdated version of the catalogue of van Paradijs (1995). This newcatalogue contains 130 sources, 61 new high-mass X-ray binaries inaddition to the 69 sources listed in van Paradijs' catalogue. Most ofthe new sources are identified to be Be/X-ray binaries. Some sources,however, are only tentatively identified as high-mass X-ray binaries onthe basis of a transient character and/or a hard X-ray spectrum. Furtheridentification in other wavelength bands is needed to finally determinethe features of these sources. The aim of this catalogue is to providethe reader with some basic information on the X-ray sources and theircounterparts in other wavelength ranges (UV, optical, IR, radio). Incases where there is some doubt about the high-mass nature of the X-raybinary this is mentioned. Some doubtful cases have not been included inthe catalogue although they had been suggested by some authors to behigh-mass X-ray binaries, for example GRS 1915+105 and 1WGAJ1958.2+3232. The catalogue and references are also available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://vizier.u-strasbg.fr/cgi-bin/qcat?J/A+AS/147/25
| HIPPARCOS results on massive X-ray binaries
We present results on parallaxes, magnitudes and proper motions for 17optically identified massive X-ray binaries (MXRB) which were observedduring the Hipparcos astrometry mission. This sample includes thesources detected in the medium-energy range (2-10 keV) having opticalcounterparts brighter than V=12. We compare the Hipparcos results withground-based optical data and derive probable values for absolutemagnitudes and peculiar tangential velocities (vt). The 4 OBsupergiant systems in our sample are high-velocity objects (the averagevalue of vt is greater than 60 km/s), while the 13 Be systemshave low velocities ( = 11.3 +/- 6.7 km/s),suggesting a different formation mechanism for the two subgroups. Theunusual X-ray/radio source LSI+61(deg) 303 lies much closer thanpreviously believed and its low optical luminosity (MV =+2.2) and blue intrinsic colors now suggest it may be a peculiar type oflow-mass X-ray binary.
| Near-IR photometry of southern X-ray binary systems
We report IR measurements of 30 optical counterparts to a group ofpossible and probable High Mass X-ray Binaries (HMXRBs). In the majorityof the systems these measurements represent the first reported IR fluxvalues. In common with many other similar systems, the results show thepresence of a strong, frequently variable IR signal. The implications ofsome of the results are discussed.
| X-Ray Emission from Be Star/X-Ray Binaries
Not Available
| The HEAO A-1 X-ray source catalog
The catalog of X-ray sources detected during the NRL Large Area SkySurvey (LASS) with the HEAO 1 satellite is presented. The catalog isderived from the first six months of data from HEAO 1 and includessources detected during one full scan. Positions and intensities for atotal of 842 different sources are included, with a limiting flux of 250nJy at 5 keV. The catalog is more than 90 percent complete at a fluxlevel equivalent to 1.5 microjoules at 5 keV for a Crab-like spectrum.Cross-references with published literature are provided and coincidentalidentifications are proposed for some of the sources which have beennever studied before. A cross-sectional line drawing of the sensormodule of HEAO I is also provided.
| Discoveries on southern, red-sensitive objective-prism plates. IV Extension to higher latitudes
This fourth in a series of papers (MacConnel, (1978, 1979, 1981) listingnewly-found objects detected on Curtis Schmidt objective-prism platesextends the previous, 4500-sq deg coverage, confined to within 15 deg ofthe southern galactic plane, to higher galactic latitudes and to anadditional 3100 sq deg. The lists presented cover 107 non-banded H-alphaemission stars, 12 M-type H-alpha emission stars, five suspectedplanetary nebulae, 10 carbon stars, 121 S/MS stars, three M dwarfs, anda peculiar and previously unreported star.
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