ULXs and Evidence for Two IMBHs in M82

Hua FengTsinghua University

Collaborators: Phil Kaaret (Iowa), Fengyun Rao (Tsinghua), Jing Jin (Tsinghua)

XMM-Newton 2010 Science Workshop, Madrid, Spain

M82 – a nearby starburst galaxy

Three ULXs in M82

X41.4+60; X-1

X42.3+59

X37.8+54

Companion’s density for Roche-lobe overflow system

= 510-5 g cm-3 a giant or supergiant star

(Kaaret et al. 2006; Kaaret & Feng 2007)

X41.4+60: 62-day X-ray periodicity

X41.4+60: Low frequency QPOs

(Strohmayer & Mushotzky 2003; Dewangan et al. 2006; Mucciarelli et al. 2006; Feng & Kaaret 2007)

Frequency varies from 50-100 mHz

Joint Chandra/XMM Observations

Off-axis & subarray configuration to minimize the pileup effect

2008 Oct 4 2009 Apr 17 2009 Apr 29

X41.4+60 was observed at the highest flux on 2008 Oct 4.

XMM-Newton observations: No QPOs, no timing noise above the Poisson level at > 1mHz

Spectral change: from power-law to disk model

Chandra spectrum on 2008 Oct 4

Multicolor accretion disk model2/dof = 67.8/70

Power-law model with pileup2/dof = 201.8/71

Power-law model without pileup2/dof = 102.1/70

Ldisk T4

X41.4+60: thermal dominant state

• No QPOs and low timing noise

• Disk model with L T4

• Emission States– hard, thermal dominant, steep power-law (Remillard &

McClintock 2006)

DiskCorona

Thermal dominant state

• L T4: constant inner radius• The accretion disk extends all the way to ISCO

• RISCO depends on MBH and Spin

(Gierlinski & Done 2004)

Fitting with a fully relativistic disk model

M = 200-800 Msun

a* > 0.93

i > 60

IMBH with nearly maximal spinning !

Hard to Thermal transition

Relatively low fluxHard power-law spectrumQPOs + flat-top PSD

Three ULXs in M82

X41.4+60; X-1

X42.3+59

X37.8+54

X42.3+59: sometimes brighter than X41.4+60

15 radius

X41.4+60X42.3+59

XMM-Newton Chandra

X42.3+59: A transient ULX

Chandra Chandra

X42.3+59: A transient ULX

Stellar mass black hole with massive donor: stable accretion diskIMBH: unstable accretion disk (Kalogera et al. 2004)

> 1000

(Feng & Kaaret 2007)

X42.3+59: discovery of QPOs• Confirmed by simultaneous Chand

ra/XMM observations

• Narrow range: 3-4 mHz

• Broad & strong

• No red noise (down to QPO / 100)

• Only appear when LX > ~1040 erg/s

(Feng, Rao, & Kaaret 2010)

Three Types of LFQPOs

(Casella et al. 2004)

GX 339-4; Type B QPOs

(Belloni et al. 2005)

XTE J1859+226

X42.3 QPOs are of Type A or B

Type A/B QPOs: narrow frequency range

X42.3 QPOs: 103 times lower than in stellar mass BHsX42.3: 104 solar masses; companion star not needed

(Casella et al. 2005)

Three ULXs in M82

X41.4+60; X-1

X42.3+59

X37.8+54

X-ray dips during one outburst

Source spectrum: soft excess + hard componentSoft excess: blackbody emission from a massive outflow (King 2004; Poutanen et al. 2007)

Summary• X41.4+60: ~102 solar masses

– hard state• Orbital period of 62 days• Low frequency QPOs and strong variability• Power-law spectrum with = 1.7

– thermal dominant state• outbursts• No QPOs, low timing noise• Thermal spectrum, L T4

• X42.3+59: ~104 solar masses– Low frequency type A/B QPOs around 3-4 mHz– 103 lower than the frequency of the same type QPOs in stellar mass bla

ck holes

• X37.8+54: tens of solar masses– A thrid, new ULX in M82– Stellar BH with massive outflow

Feng & Kaaret 2010Feng, Rao, & Kaaret 2010Jin, Feng, & Kaaret 2010