An XMM-Newton View An XMM-Newton View of the Luminous X-ray of the Luminous X-ray Source Population of Source Population of M101M101

Leigh JenkinsLeigh JenkinsTim Roberts, Robert Warwick, Roy Kilgard*, Martin Tim Roberts, Robert Warwick, Roy Kilgard*, Martin WardWard

University of Leicester, UKUniversity of Leicester, UK*Harvard-Smithsonian CfA, USA *Harvard-Smithsonian CfA, USA

XMM-Newton EPIC Consortium XMM-Newton EPIC Consortium Meeting, Palermo. October 14Meeting, Palermo. October 14thth-16-16thth 2003.2003.

Discrete Source Discrete Source Populations in SpiralsPopulations in Spirals

• X-ray BinariesX-ray Binaries – – Black hole/neutron star + stellar Black hole/neutron star + stellar companioncompanion– High State: High State: dominated by thermal accretion disc emissiondominated by thermal accretion disc emission– Low State: Low State: dominated by powerlaw emission dominated by powerlaw emission

(comptonization of accretion disc corona) (comptonization of accretion disc corona)

• Supernova RemnantsSupernova Remnants– Thermal emission from collisionally ionized gasThermal emission from collisionally ionized gas

• Ultraluminous X-ray Sources (ULXs)Ultraluminous X-ray Sources (ULXs) – LLXX ≥ 10 ≥ 103939 erg/s i.e. super-Eddington for a 1.4 solar mass erg/s i.e. super-Eddington for a 1.4 solar mass

neutron starneutron star True super-Eddington emissionTrue super-Eddington emission Anisotropic (beamed) emissionAnisotropic (beamed) emission Intermediate mass black holes (IMBHs) (LIntermediate mass black holes (IMBHs) (LXX ≥ 5x10 ≥ 5x103939 erg/s) erg/s)

– Link with star formation Link with star formation High Mass X-ray Binaries High Mass X-ray Binaries (HMXBs)?(HMXBs)?

M101M101

• Grand design Grand design supergiant spiralsupergiant spiral

• Nearby (D~7 Nearby (D~7 Mpc)Mpc)

• Face on Face on

• low foreground Nlow foreground NHH

Ideal Ideal laboratory for laboratory for studies of studies of galactic X-ray galactic X-ray emissionemission

EPIC 3-Colour Image

X-ray DataX-ray Data

• 43 ks 43 ks observationobservation

• Encompasses Encompasses entire Dentire D2525 ellipse ellipse (23.8 arcmin)(23.8 arcmin)

• ~100 sources ~100 sources in fieldin field

Red = 0.2-0.5 keV

Green=0.5-2.0 keV

Blue = 2.0-4.5 keV

Source Selection Source Selection

• Sufficient counts for spectral fitting (> 300 counts in the Sufficient counts for spectral fitting (> 300 counts in the PN data)PN data)

14 14 suitable sources (excluding 2 bright stars in field) suitable sources (excluding 2 bright stars in field) − Intrinsic X-ray luminosities 3x10Intrinsic X-ray luminosities 3x103838 – 3x10 – 3x103939 erg/s i.e. erg/s i.e.

≥ ≥ Eddington limit for accretion onto a 1.4 Eddington limit for accretion onto a 1.4 neutron neutron starstar

• Investigate their nature by studying their:Investigate their nature by studying their:

– LocationsLocations– Spectral shapesSpectral shapes– Timing properties Timing properties variability variability accretion accretion

• Amongst the first detailed spectroscopic studies of a large Amongst the first detailed spectroscopic studies of a large number of compact sources in a single spiral galaxy with number of compact sources in a single spiral galaxy with XMM-NewtonXMM-Newton

Source LocationsSource Locations

• Sources spread over galaxy

• Positions correlate with:

Nucleus

HII regions (star formation)

Spiral arm structure

Indicates that all sources are likely to be associated with M101

XMM EPIC DSS Optical

Spectra - QualitySpectra - Quality

XMM-1 XMM-14

Brightest – 3800 counts

Faintest – 300 counts

Spectral ModelsSpectral Models

• Absorbed single and two-component:Absorbed single and two-component:

– Powerlaw Powerlaw Non-thermal emission from accreting objectsNon-thermal emission from accreting objects

– Multicolour Disc BlackbodyMulticolour Disc Blackbody Thermal emission from accretion disc in a Thermal emission from accretion disc in a

high/soft statehigh/soft state

– BlackbodyBlackbody Outflowing material – Black hole wind modelOutflowing material – Black hole wind model

– MEKALMEKAL Thermal emission from collisionally ionized gas Thermal emission from collisionally ionized gas

(e.g. stellar winds, supernovae)(e.g. stellar winds, supernovae)

Spectral Fits – Spectral Fits – Single-componentSingle-component

• 9 sources with single-9 sources with single-component fits:component fits:

4 Disc Blackbody 4 Disc Blackbody

(T(Tinin=0.96-1.33 keV)=0.96-1.33 keV)

1 Supersoft (1 Supersoft (TTinin=0.16 keV)=0.16 keV)

3 Disc Blackbody 3 Disc Blackbody oror PowerlawPowerlaw

1 Powerlaw (nucleus) 1 Powerlaw (nucleus) ГГ = 2.2 = 2.2

Consistent with all sources Consistent with all sources except nucleus being X-ray except nucleus being X-ray binaries in the binaries in the high-softhigh-soft state state

NucleusГ ~ 2.2

XMM-1Tin= 1.3 keV

Spectral Fits – Spectral Fits – Two-componentTwo-component

• 5 sources 5 sources requirerequire two-component two-component fits:fits:– Hard powerlaw (Hard powerlaw (ΓΓ = 1.5 – 2 ) + = 1.5 – 2 ) +

soft excesssoft excess Cool Disc Blackbody Cool Disc Blackbody (~0.1-0.3 keV)(~0.1-0.3 keV)

IMBH IMBH (T(Tininαα MM-1/4-1/4))

Cool Blackbody Cool Blackbody (~0.1-0.2 keV)(~0.1-0.2 keV)Ouflowing materialOuflowing material

(black hole wind)(black hole wind)

MEKAL thermal plasmaMEKAL thermal plasmaHot (~1 keV) photoionized plasma Hot (~1 keV) photoionized plasma

surrounding high-mass starsurrounding high-mass starCool (~0.2 keV) thermal emission Cool (~0.2 keV) thermal emission

related to star formation activityrelated to star formation activity

• Underlying continuum of 3 sources Underlying continuum of 3 sources can also be modelled by a 1-1.5 keV can also be modelled by a 1-1.5 keV disc blackbodydisc blackbody

XMM-2PL + DISKBB

XMM-5PL + MEKAL

Source Hardness vs. Source Hardness vs. LuminosityLuminosity

• No distinction No distinction between sources between sources above and below above and below ULX thresholdULX threshold

Implies same Implies same source populationsource population

Power law

● DISKBB Supersoft PL+MEKAL PL+DISKBB/BBODY

Source Variability - Source Variability - MethodsMethods• Short-term variabilityShort-term variability

– Chi-squared test Chi-squared test Large-amplitude Large-amplitude variabilityvariability

– K-S test K-S test Gradual small-amplitude variations Gradual small-amplitude variations

• Long-term variabilityLong-term variability– Archival data spanning ~11-23 yearsArchival data spanning ~11-23 years

Einstein, ROSAT, Chandra, XMM Einstein, ROSAT, Chandra, XMM – Observed fluxes normalized to the 0.5-2 keV bandObserved fluxes normalized to the 0.5-2 keV band

Lightcurves Lightcurves – Example (XMM-2)– Example (XMM-2)

• Short-termShort-term– PPvarvar > 99.9% over > 99.9% over

duration of XMM duration of XMM observationobservation

• Long-termLong-term– Increase by Increase by

factor of ~30 in factor of ~30 in XMM XMM observationobservation

Variability - ResultsVariability - Results

• Short-termShort-term– 11 of 14 sources show some short-term 11 of 14 sources show some short-term

variability ( > 95% level)variability ( > 95% level)

• Long-termLong-term – Majority vary Majority vary

between factor of 2-between factor of 2-4 4

– Transient varies by Transient varies by factor of ~30factor of ~30

– No grouping of No grouping of sources with certain sources with certain spectral typesspectral types

Power law

● DISKBB Supersoft PL+MEKAL PL+DISKBB/BBODY

Spectral ChangesSpectral Changes

• Compare source Compare source hardness in XMM hardness in XMM observation to observation to Chandra data for Chandra data for 9 sources (~2 9 sources (~2 years earlier)years earlier)

• General trend is General trend is softening with softening with increasing increasing luminosity – luminosity – same as same as behaviour of behaviour of many Galactic many Galactic XRBs e.g. Cyg X-XRBs e.g. Cyg X-11

What does this mean?What does this mean?

• Spectral shapes/variability/locations/spectral Spectral shapes/variability/locations/spectral behaviour consistent with all sources (except behaviour consistent with all sources (except nucleus) being accreting BH X-ray binary systemsnucleus) being accreting BH X-ray binary systems

• Intrinsic X-ray luminosities imply black hole Intrinsic X-ray luminosities imply black hole

masses of ~2-23 Mmasses of ~2-23 M (i.e. stellar-mass) if (i.e. stellar-mass) if

Eddington limitedEddington limited

• Likely to be looking at the high-luminosity end of Likely to be looking at the high-luminosity end of X-ray binary source population – no requirement X-ray binary source population – no requirement for IMBHsfor IMBHs− Supported by fact that cumulative X-ray luminosity functions Supported by fact that cumulative X-ray luminosity functions

of compact sources in star-forming galaxies extend to ULX of compact sources in star-forming galaxies extend to ULX

luminosities – no break at 10luminosities – no break at 103939 erg/s erg/s