X-ray binaries

Even stronger constraints are potentially available from the high-mass X-ray binary Vela X-l. This source contains a 20 M0 star, and radial velocity variations from the star have been measured as well as periodic timing variations from X-ray pulses. The orbital period is 8.96 days and the eccentricity of... 

Other constraints come from recent observations from X-ray satellites. Most robust seem the data from the low mass X-ray binary EXO 0478-676 obtained by Cottam et al. [37], From the redshifted absorption lines from ionized Fe and O a gravitational redshift z = 0.23 was deduced this gives rise to a mass-to-radius relation... 

Next we consider the compact star in the low mass X-ray binary 4U 1728-34. In a very recent paper Shaposhnikov et al. (2003) (hereafter STH) have analyzed a set of 26 Type-I X-ray bursts for this source. The data were collected by the Proportional Counter Array on board of the Rossi X-ray Timing Explorer (RXTE) satellite. For the interpretation of these observational data Shaposhnikov et al. 2003 used a model of the X-ray burst spectral formation developed by Titarchuk (1994) and Shaposhnikov Titarchuk (2002). Within this model, STH were able to extract very stringent constrain on the radius and the mass of the compact star in this bursting source. The radius and mass for 4U 1728-34, extracted by STH for different best-fits of the burst data, are depicted in Fig. 6 by the filled squares. Each of the four MR points is relative to a different value of the distance to the source (d = 4.0, 4.25, 4.50, 4.75 kpc, for the fit which produces the smallest values of the mass, up to the one which gives the largest mass). The error bars on each point represent the error contour for 90% confidence level. It has been pointed out (Bombaci 2003) that the semi-empirical MR relation for the compact star in 4U 1728-34 obtained by STH is not compatible with models pure hadronic stars, while it is consistent with strange stars or hybrid stars. 

Decisive informations on the mass-to-radius ratio can be provided by measuring the gravitational redshift of lines in the spectrum emitted from the compact star atmosphere. Very recently, redshifted spectral lines features have been reported for two different X-ray sources (Cottam et al. 2002 Sanwal et al. 2002). The first of these sources is the compact star in the low mass X-ray binary EXO 0748-676. Studying the spectra of 28 type-I X-ray bursts in... 

The brightest X-ray nebulas are the remnants of supernova explosions. The ejecta are thrown out so forcefully that the collision with neighbouring interstellar gases produces temperatures of several million degrees. This is sufficient to emit photons in the keV range. It is no surprise that most X-ray binaries and supernova remnants should be located in the galactic disk. 

II) Mass Flow Binaries that are the products of internal evolutionary processes also include Novae and X-ray binaries that are thought to contain compact objects. Also, there is strong evidence that many, if not all, symbiotic stars are binaries. 

Spectroscopy allows one to see not only the elements in the gas phase, but also those in the dust grains. Using bright X-ray binaries as background sources, Ueda et al. (2005) were able to determine the total abundances of the elements in the diffuse ISM and found that most of them are approximately solar, with the exception of oxygen. From the details of the X-ray absorption spectra it could be determined to some extent what fraction of the elements were in the solid phase and also to a lesser extent the lattice structure could be determined. From this, they found the silicates to be predominantly rich in magnesium and poor in iron, in agreement with the infrared absorption spectroscopic study of the diffuse ISM by Min et al. (2007). 

In this study we compare distribution of GRB galactocentric offsets with radial distributions of supernovae of types la and Ib/c, low mass and high mass X-ray binaries, and with models of dark matter (DM) halo density profile. We compare first and second moments of distributions and also their median values, moreover we apply visual technique for comparing a pair of empirical distributions — quantile-quantile plot. 

We consider the following data sets GRB, SN la, SN Ib/c, X-ray binaries, models of DM distribution in galaxies. Each data set of galactocentric offsets is normalized by typical galaxy radius (r = R/Rgaiaxy X which is usually equal to optical radius (Rgaiaxy — Rapt)- Data on GRB offset errors also avaible. 

H.-J. Grimm, M. Gilfanov, and R. Sunyaev (2001). The Milky Way in X-rays for an outside observer Log(N)-Log(S) and Luminosity Function of X-ray binaries from RXTE/ASM data Astronomy and Astrophysics , astro-ph/0109239. 

Microquasars. Microquasars are a selected class of X-ray binaries that produces relativistic radio-jets [6], The origin of the jets is related to the matter accreted by the compact object, a neutron star or a black hole, from the companion star. 

Space does not permit a more detailed discussion of the expected LEGRI scientific scope but the wide range of astronomical objects that can be studied includes pulsars, black hole candidates. X-ray, binaries, supernovae and AGN. 

---