Populations of GalacticPopulations of GalacticX-ray (compact) sources X-ray (compact) sources

visible visible to Spectrum-RGto Spectrum-RG

Revnivtsev M.,Revnivtsev M.,Space Research Institute;Space Research Institute;

Moscow, RussiaMoscow, 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 dwarfs4. 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 findsomething interesting and useful

ROSAT 1-2 keVsens.limit 10-12 erg/s/cm2

Severe absorption in the G.Plane

INTEGRAL 17-60 keVsens. limit ~10-11 erg/sec/cm2

Harder X-rays are extremely valuable for Galactic surveys – ART-XC

Why population studies?1. Search for sources to be studied

individually2. 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)

M31Bulge 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?

LEdd for NS binary

Revnivtsev et al. 2011

MS

WD

LogLx~37 -- boundary between main sequence and giants companions?

Kuranov et al..(preliminary)

LMXB age evolution?

Lx

L2 d

N/d

L

Illarionov, Sunyaev 1975

Campana et al. 1998

sec/104 3/73

28

36min ergsPBL

81061~ B G

Propeller effect

35

pro

pel

ler?

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

Simulated LMXBs in the Galactic bulge(sensitivity 10-13 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-XGIn total 100-200 sources!

Lx<1034-34.5 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. 2008

Post bounce (older?) systems wider spreaded?

Now only ~20 objectsSRG expects >100000

Howell et al. 2001

Numerical modeling of cataclysmic variables

Old and the most numerous

Littlefair et al. 2008

Low Mdot CVsaccumulate massin a long run?No WD erosion?

We need bias-freesurveys!

Zero age WD mass

Counting CVs in the Galaxy is a complicated problem: biases

One of the latest results:usage of wideuniform surveys of the sky - SDSS

Szkody et al. 2003

Typical CV discovery: 1)Dwarf nova outbursts, 2)classical nova 3)UV color excess…………

Optical selection of CVs

Selection: WD contributionin blue part of spectrum

Even this simple attempt to have less biasedsearch revealed a completely different

CV population

Gansicke et al. 2009

BeforeSDSS

SDSSsample

Colors and brightnesses of WD of different masses

Bias toward lower masses WDs?

T

Bergeron et al. 1995

CVs in X-rays

Dependson mass of WDand B-field

X-ray surveys

Spectrum-XG area

Van Paradijs & McClintock 1994O’Brien et al. 2002Mescheryakov et al. 2011

Problems of finding low-Lx

LMXBS(even worsefor qLMXB

MK 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

LMXB HMXB

CV

eROSITAenergy range

ART-XCenergy range

Spectra of CVs and Active Binaries

For populations studies –future X-ray surveys

Spectrum-XG(eROSITA+ART)

Stars - millionsCVs – 100 000 -500 000

Summary:Studies of populations provide us handles

on:1.formation of binaries2.mechanisms of their long term evolution3.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 inSpectrum-XG surveys