Chandra and XMM-Newton are revolutionizing our understanding of compact binaries in external galaxies, allowing us to study sources in detail in Local Group Galaxies and study populations in more distant systems. In M31 the X-ray luminosity function depends on the local stellar population in the sense that areas with active star formation have more high luminosity sources, and a higher overall source density (Kong. Di Stefano. Garcia, & Greiner 2003). This result is also true in galaxies outside the Local Group; starburst galaxies have flatter X-ray luminosity functions than do spiral galaxies which are in turn flatter than elliptical galaxies. These observational results suggest that the high end of the luminosity function in star forming regions is dominated by short-lived high mass X-ray binaries.

In Chandra Cycle 2 we started a Large Project to survey a sample of 11 nearby (< 10Mpc) face-on spiral galaxies. We find that sources can be approximately classified on the basis of their X-ray color into low mass X-ray binaries, high mass X-ray binaries and supersoft sources. There is an especially interesting class of source that has X-ray colors softer (“redder”) than a typical low mass X-ray binary source, but not so extreme as supersoft sources. Most of these are probably X-ray bright supernova remnants, but some may be a new type of black hole accretor. Finally, when we construct a luminosity function of sources selecting only sources with low mass X-ray binary colors (removing soft sources) we find that there is a dip or break probably associated with the Eddington luminosity for a neutron star.

We have monitored the quasi-persistent neutron-star X-ray transient MXB 1659-29 in quiescence using Chandra. The purpose of our observations was to monitor the quiescent behavior of the source after its last prolonged outburst episode and to study the cooling curve of the neutron star in this system. We discuss the results obtained and how they constrain the properties of the neutron star in MXB 1659-29.

An overview is given of the type I X-ray burst properties of the transient KS 1731-260. These characteristics appear to be proto-typical for all type I X-ray bursters, and stable helium burning occuring at high mass accretion rates could explain them.

We present first results from a coordinated multiwavelength study of the neutron star low-mass X-ray binary EXO 0748 676. Fast UV, X-ray, and optical data were obtained including both spectral and timing information. We discuss how this study allows us to probe the temperature distribution within the binary and hence the geometry and efficiency of X-ray irradiation.

Gamma-ray bursts (GRBs) of long duration probably result from the core-collapse of massive stars in binary systems. After the collapse of the primary star the binary system may remain bound leaving a microquasar or ULX source as remnant. In this context, microquasars and ULXs are fossils of GRB sources and should contain physical and astrophysical clues on their GRB-source progenitors. Here I show that the identification of the birth place of microquasars can provide constrains on the progenitor stars of compact objects, and that the runaway velocity can be used to constrain the energy in the explosion of massive stars that leave neutron stars and black holes. The observations show that the neutron star binaries LS 5039, LSI +61°303 and the low-mass black hole GRO J1655-40 formed in energetic supernova explosions, whereas the black holes of larger masses (M ≥ 10 M⊙) in Cygnus X-l and GRS 1915+105 formed promptly, in the dark or in underluminous supornovao. The association with clusters of massive stars of the microquasar LSI +61°303 and the magnetars SGR 1806-20 and SGR 1900+14, suggest that very massive stars (M ≥ 50 M⊙) may -in some cases- leave neutron stars rather than black holes. The models of GRB sources of long duration have the same basic ingredients as microquasars and ULXs: compact objects with accretion disks and relativistic jets in binary systems. Therefore, the analogies between microquasars and AGN may be extended to the sources of GRBs.

The eclipsing supersoft X-ray binary CAL 87 has been observed with Chandra on August 13/14, 2001 for nearly 100 ksec, covering two full orbital cycles and three eclipses. The shape of the eclipse light curve derived from the zeroth-order photons indicates that the size of the X-ray emission region is about 1.5 R⊙. The ACIS/LETG spectrum is completely dominated by emission lines without any noticeable continuum. The brightest emission lines are significantly redshifted and double-peaked, suggestive of emanating in a 2000 km/s wind. We model the X-ray spectrum by a mixture of recombination and resonant scattering. This allows us to deduce the temperature and luminosity of the ionizing source to be kT ~ 50 — 100 eV and Lx ~ 5 x 1037 erg/s.

This paper will review a new technique of detecting companion stars in LMXBs and X-ray transients in outburst using the Bowen fluorescence NIII lines at 4634-4640. These lines are very efficiently reprocessed in the atmospheres of the companion stars and, thereby, provide estimates of the K2 velocities and mass functions. The method has been applied to Sco X-1, X1822-371 and GX339-4 which, in the latter case, provides dynamical evidence for the presence of an accreting black hole. Preliminary results from a VLT campaign on V801 Ara, V926 Sco and XTE J1814-338 are also presented.

We present here the results of a search for new microquasars at low galactic latitudes, based on a cross-identification between the ROSAT all sky Bright Source Catalog (RBSC) and the NRAO VLA Sky Survey (NVSS) and follow-up observations. The results obtained up to now suggest that persistent/silent microquasars such as LS 5039 are rare objects in our Galaxy, and indicate that future deeper surveys, and harder than the RBSC in X-rays, will play a fundamental role in order to discover them.

The optical counterpart of the binary millisecond X-ray pulsar SAX J 1808.4-3658 during quiescence was detected at V = 21.5 mag, inconsistent with intrinsic emission from the fain companion star. We propose that the optical emission from this system during quiescence is due to the irradiation of the companion star and a remnant accretion disk by the rotational energy released by the fast spinning neutron star, switched on, as magneto-dipole rotator (radio pulsar). In this scenario the companion behaves as a bolometer, reprocessing in optical part of the power emitted by the pulsar. The reprocessed fraction depends only on known binary parameters. Thus the blackbody temperature of the companion can be predicted and compared with the observations. Our computations indicate that the observed optical magnitudes are fully consistent with this hypothesis. In this case the observed optical luminosity may be the first evidence that a radio pulsar is active in this system in quiescence.

We present the international collaboration MINE (Multi-λ INTEGRAL NEtwork) aimed at conducting multi wavelength observations of microquasars simultaneously with the INTEGRAL satellite. The first results of GRS 1915+105 are encouraging and those to come should help us to understand the physics of the accretion and ejection phenomena around a compact object.

I consider three processes which enhance mass loss rate from a common envelope of a giant star with a main sequence or a white dwarf companion spiraling-in inside its envelope. I consider deposition of orbital energy and orbital angular momentum to the giant's envelope, and the formation of jets by an accreting companion and their propagation in the envelope. I find that in many cases the deposition of orbital angular momentum to the envelope may be more important to the mass loss process than the deposition of orbital energy. Jets blown by an accreting companion, in particular a white dwarf, orbiting inside the outer regions of the giant's envelope may also dominate over orbital energy deposition at early stage of the common envelope evolution. These imply that, studies which ignore the deposition of angular momentum to the envelope and the effects of the accreting companion may reach wrong conclusions.

Orbital periods and other parameters of symbiotic binary systems in the LMC and SMC are presented and discussed. In particular, the symbiotic stars in the MCs are compared with those in the Milky Way.

Collimated outflows from accreting white dwarfs have a vital role to play in the study of astrophysical jets.

Chandra Low Energy Transmission Grating Spectrograph observations of the pre-cataclysmic binary V471 Tau have been used to estimate the C/N abundance ratio of the K dwarf component for the first time. While the white dwarf component dominates the spectrum longward of 50 Å, at shorter wavelengths the observed X-ray emission is entirely due to coronal emission from the K dwarf. The H-like 2p 2Р3/2, 1/2 → 1s 2S1/2 resonance lines of С and N yield an estimate of their logarithmic abundance ratio relative to the Sun of [C/N]= –0.38 ± 0.15—half of the currently accepted solar value. We interpret this result as the first clear observational evidence for the presumed common envelope phase of this system, during which the surface of the K dwarf was contaminated by CN-cycle processed material dredged up into the red giant envelope

We determine the possible masses and radii of the progenitors of white dwarfs in binaries from fits to detailed stellar evolution models and use these to reconstruct the mass-transfer phase in which the white dwarf was formed. We confirm the earlier finding that in the first phase of mass transfer in the binary evolution leading to a close pair of white dwarfs, the standard common-envelope formalism based on energy balance in the system, does not work. A formalism based on angular momentum balance can explain the observations. We extend our analysis to all close binaries with at least one white dwarf component. Comparing the two, we show that the formalism based on angular momentum balance can explain all observations at least as well as the energy formalism.

The central star of the PN LMC-N66 showed an impressive outburst in 1993 - 1994, returning to its initial conditions about 8 years later. Its spectrum resembles that of a WN4.5 star, being the only confirmed central star of planetary nebulae showing such a spectral type. Recent analysis for the central star parameters, performed by Hamann et al. (2003) is presented. They have found that the bolometric luminosity increased by a factor larger than 6, during the outburst. We discuss the possible scenarios which have been proposed to explain the exceptional stellar parameters and the outburst mechanism. The stellar characteristics and the morphology and kinematics of the planetary nebula suggest the presence of binary system (massive star with a less massive companion or, a white dwarf accreting matter in a close-binary system). These cases pose the least severe contradictions with observational constraints.

We report results of Echelle and B&Ch spectroscopic observations of the emission-line object FBS 0022-021 that were obtained at SPM Observatory, Mexico. We analyze the emission-line spectra along with available optical and IR data. The Fell-rich spectrum of the object closely resembles that of the peculiar binary system η car. The discussion of the physical conditions leading to such spectrum and the nature of this peculiar object are presented.