X-ray luminosity function of faint point sources in the Milky Way

By S. Sazonov, M. Revnivtsev, M. Gilfanov, E. Churazov, R. Sunyaev. 2005

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We assessed the contribution to the X-ray (above 2 keV) luminosity of the Milky Way by different classes of low-mass binary systems and single stars. We began by using the RXTE Slew Survey of the sky at $|b|>10^\circ$ to construct an X-ray luminosity function (XLF) of nearby X-ray sources in the range $10^{30}~{\rm erg}~{\rm s}^{-1} L x is the luminosity over 2–10 keV), occupied by coronally active binaries (ABs) and cataclysmic variables (CVs). We then extended this XLF down to $L_{\rm x}\sim 10^{27.5}~{\rm erg}~{\rm s}^{-1}$ using the Rosat All-Sky Survey in soft X-rays and available information on the 0.1–10 keV spectra of typical sources. We found that the local cumulative X-ray (2–10 keV) emissivities (per unit stellar mass) of ABs and CVs are $(2.0\pm 0.8)$ $\times$ 10 27 and $(1.1\pm 0.3)$ $\times$ 10 27 erg s -1 $M_\odot^{-1}$, respectively. In addition to ABs and CVs representing old stellar populations, young stars locally emit $(1.5\pm 0.4)$ $\times$ 10 27 erg s$^{-1}~M_\odot^{-1}$. Finally to the XLF of ABs and CVs we attached a high luminosity branch (up to ~10 39 erg s -1 ) composed of neutron-star and black-hole low-mass X-ray binaries (LMXBs), derived in previous work. The combined XLF covers ~12 orders of magnitude in luminosity. The estimated combined contribution of ABs and CVs to the 2–10 keV luminosity of the Milky Way is ~2 $\times$ 10 38 erg s -1 , or ~3% of the integral luminosity of LMXBs averaged over nearby galaxies. The XLF obtained in this work is used elsewhere to assess the contribution of point sources to the Galactic ridge X-ray emission.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/01b495f320fbac6cc7488cab8cb3653888bd4005

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Citations in the corpus

REVISITING WITH CHANDRA THE SCALING RELATIONS OF THE X-RAY EMISSION COMPONENTS (BINARIES, NUCLEI, AND HOT GAS) OF EARLY-TYPE GALAXIES (2010, background): “In the solar vicinity, RXTE and ROSAT X-ray observations have resolved point sources (ABs and CVs) in the 1030–1034 erg s−1 range (Sazonov et al. 2006).”
Magnetic White Dwarfs (2015, methodology): “The hard X-ray surveys of the Galactic Ridge conducted by the INTEGRAL (Revnivtsev et al. 2009, 2011), Rossi-XTE (Sazonov et al. 2006) and Suzaku (Yuasa et al. 2012) satellites have also resolved a large fraction of the diffuse emission into discrete low luminosity hard X-ray sources largely…”
X-ray emission from star-forming galaxies - II. Hot interstellar medium (2012, background): “…same reason, although the LX−M scaling relation is well established for cataclysmic variables (CVs) and active binaries (ABs) in solar neighbourhood (Sazonov et al. 2006) and in early-type galaxies (Bogdán & Gilfanov 2011), it cannot be directly applied to the stellar environment in star-forming…”