Populations of Galactic X-ray (compact) sources visible to Spectrum-RG Revnivtsev M., Space Research Institute; Moscow, Russia

Discrete X-ray emitters in the Galaxy 1.Binaries with relativistic objects – X-ray binaries. High mass and low mass companions 2.Single relativistic objects: cooling neutron stars, rotation powered pulsars.. 3.Binaries with accreting white dwarfs 4.Stars with active coronae, binary stars (the most numerous sources)

Expected spatial distribution of CVs, LMXBs… High interstellar absorption

Extragalactic sky Galactic ISM It is very hard to study Galactic sources

You should see through walls But you often find something interesting and useful

ROSAT 1-2 keV sens.limit erg/s/cm 2 Severe absorption in the G.Plane

INTEGRAL keV sens. limit ~ erg/sec/cm 2 Harder X-rays are extremely valuable for Galactic surveys – ART-XC

Why population studies? 1. Search for sources to be studied individually 2. Properties of populations can tell us about their formation … about interactions in binary systems (MSW, GW, outflows?) 3 …. about average properties of compact objects (e.g. magnetic field, rotation rates at birth etc) 4 … about long term evolution of objects (e.g. accumulation/erosion of WD masses etc)

M31 Bulge of the Milky Way Only in our Galaxy we can study companions of X-ray binaries –> clues to physical mechanisms of their evolution

Voss, Gilfanov 2006 LMXB ? What is the origin of this break? L Edd for NS binary

Revnivtsev et al MS WD LogLx~37 -- boundary between main sequence and giants companions?

Kuranov et al.. (preliminary)

LMXB age evolution? Lx L 2 dN/dL

Illarionov, Sunyaev 1975 Campana et al G Propeller effect 3535

propeller? This is the reason of absence of faint LMXBs? Task for Spectrum-XG

Simulated LMXBs in the Galactic bulge (sensitivity erg/s/cm^2, no absorption)

High mass X-ray binaries INTEGRAL view of the Gal.Plane

HMXB “hole” in the Galactic disk? Lutovinov et al. (2012, in preparation)

Galactic HMXBs Parameter space, reachable for Spectrum-XG In total sources! L x < erg/sec

Study of HMXB population is beyond reach of telescopes like CHANDRA, XMM or NuSTAR due to their limited fields of view ~2-3/sq.deg!! figure of R.Krivonos

Cataclysmic variables

All sky survey – spatial distribution of cataclysmic variables Revnivtsev et al Post bounce (older?) systems wider spreaded? Now only ~20 objects SRG expects >100000

Howell et al Numerical modeling of cataclysmic variables Old and the most numerous

Littlefair et al Low Mdot CVs accumulate mass in a long run? No WD erosion? We need bias-free surveys! Zero age WD mass

Counting CVs in the Galaxy is a complicated problem: biases One of the latest results:usage of wide uniform surveys of the sky - SDSS Szkody et al Typical CV discovery: 1)Dwarf nova outbursts, 2)classical nova 3)UV color excess …………

Optical selection of CVs Selection: WD contribution in blue part of spectrum

Even this simple attempt to have less biased search revealed a completely different CV population Gansicke et al Before SDSS sample

Colors and brightnesses of WD of different masses Bias toward lower masses WDs? T Bergeron et al. 1995

CVs in X-rays Depends on mass of WD and B-field X-ray surveys Spectrum-XG area

Van Paradijs & McClintock 1994 O’Brien et al Mescheryakov et al Problems of finding low-Lx LMXBS (even worse for qLMXB M K as faint as >4-5! Revnivtsev et al. 2011

IGR J17254 Extremely faint sources in crowded regions Hard targets -hunt for low Lx LMXBs SAX J1747

LMXBHMXB CV

eROSITA energy range ART-XC energy range Spectra of CVs and Active Binaries

For populations studies – future X-ray surveys Spectrum-XG (eROSITA+ART) Stars - millions CVs –

Summary: Studies of populations provide us handles on: 1.formation of binaries 2.mechanisms of their long term evolution 3.On averaged properties of populations (compact objects magnetic fields, spatial distribution/kinematic age etc… Vital issue: algorithms of identification of Galactic sources among huge number of sources expected in Spectrum-XG surveys