IC 10 X-1: A Long Look with XMM-Newton

with Dheeraj Pasham (UMD), Richard Mushotzky (UMD)

Tod Strohmayer: NASA’s Goddard Space Flight Center (and JSI)

IC 10 X-1: Summary• Dynamically confirmed black hole binary with Wolf-Rayet

companion ([MAC92] 17A, WNE spectral type).

• X-ray light curve shows eclipse-like intensity drops with Porb = 34.9 hr (Prestwich et al. 2007; Silverman & Filippenko 2008).

• Mass function from optical radial velocity curve: f(M) = 7.64 ± 1.26 M (Silverman & Filippenko 2008) Mbh > 23 – 34 M-- MOST MASSIVE KNOWN Stellar BH!

• Lx ~ 2 – 5 x 1038 ergs/s (d=740 kpc), X-ray spectrum consistent with a comptonized “thermal” StBH disk (~1 keV). Similar to “super-soft” behavior in Cyg X-3, but also 4-5 keV roll-over (like some ULXs)?

• Study temporal - spectral properties to compare this massive StBH with Galactic BHs and ULXs and do “eclipse mapping.” Cycle 11 observations of a complete orbit (~35 hr).

One Complete Orbit With XMM-Newton

•Very little flaring during observation! Eclipse feature clearly evident and resolved.

•Eclipse is asymmetric (steeper ingress), not total (8-9% of off eclipse), but has a “flat” minimum of duration of 5 hr.

•Significant variability evident.

New Timing Results: 7 mHz QPO

• 2003 data showed marginal feature at 7 mHz

• New Cycle 11 data clearly confirm the QPO! With amplitude (rms) of 5.6%, centroid frequency of 6.75 mHz, and coherence Q~10.

• Power-law + Lorentzian (QPO) fits the spectrum.

Wang et al. (2004)

IC 10 X-1: New QPO Detection•Feature evident in a dynamic spectrum. No obvious frequency drift, but low signal to noise.

•Power-law continuum of slope ~1.5, no break detected, but orbital modulations make it tough.

Time

Fre

qu

ency

• 7 mHz is a low frequency for a StBH! Particularly for a Type – C classification.

• Spectral state not obviously like other Type – C QPOs.

• GRS 1915+105 may have frequencies this low.

IC 10 X-1: Eclipse Timing and Mass Constraint

• Eclipse duration constrains size of WR companion (as seen from BH) and inclination.

• “flat” bottom to the eclipse feature evident in soft and hard energy bands. Duration of 5 hr.

• Wolf-Rayet winds are optically thick! Need to account (or at least approximate) this effect.

• Such winds are a strong function of Luminosity and thus stellar mass.

• Use known mass function, eclipse geometry constraint, and Reff (M) to constrain component masses and i

IC 10 X-1: Eclipse Timing and Mass Constraints

• Derive Reff using mass loss rates from Nugis & Lamers (2000), and simple approximations from Langer (1989).

• The eclipse is “direct” evidence for an optically thick WR wind!

• Solutions exist for range of companion masses. Suggest Mbh > 27 M

IC 10 X-1: X-ray Spectrum

• Spectrum is relatively “soft,” continuum can be modeled with thermal comptonization (comptb in XSPEC).

• Analogy with Cyg X-3 in its “ultra-soft” state.

• Evidence for “discrete” features near 1 keV.

• Orbit phase related variations in the spectral hardess.

• “shallow” egress appears hardest.

• Should be able to map column through the WR wind..

IC 10 X-1: Eclipse Spectrum

There is significant emission during eclipse. Likely at least partly due to scattering and an emission line spectrum from the photo-ionized wind!

Bonus Slide: RGS Line Emission!

2nd order

1st order

Several emission line features clearly detected: 12 Å, consistent with Ne X (2-1) ; at 15 Å, maybe Fe XVII; near 17 Å, perhaps OVII; at 26 Å plausibly C. Carbon, Oxygen Neon are products of He burning, so not unexpected.

Summary• Massive StBH with a low frequency QPO (7 mHz). Frequency

lower than in some claimed IMBH candidates. Mass estimates from frequency scalings are possible, but must compare “apples with apples.”

SEE POSTER 126.43 for related work in M82 X-1 • Complete eclipse observed (resolved) for the first time. Eclipse

duration constrains size of the WR companion. Direct evidence for optically thick WR wind. Mass and inclination constraints follow.

• Spectrum consistent with comptonized BH disk emission. Variations evident with orbital phase, more detailed modeling in progress.

• Rich line spectrum in RGS, probes the composition and properties of photoionized wind. Again, more details to come.