1. Supersoft X-ray sources in M31
Marina Orio
INAF-Padova and U Wisconsin
In collaboration with Tommy Nelson

2. Supersoft X-ray sources in M31: everywhere

3. Analysis of XMM-Newton-Chandra-LGS(WIYN)-Galex archival images
We examined 78 objects - a statistically significant sample (including SNR, excluding uncertain detections/mixed spectra states)
5 new SSS and 3 (not published) novae in XMM images
50of these SSS were observed more than once
Searched multi-wavelength counterparts and examined the long term X-ray time variability
Only 1 AGN?
Less than 10% of SSS are SNR (S And not confirmed)
Only 15% Cal 83/RXJ 0513 type sources
Are half of M31 SSS novae? (At least 17% are)
25% of SSS associated with B-stars/star formation (Nelson’s talk)

4. M31 novae seem to be X-ray sources for longer.
Selection effect? Probably not.
Different OBSERVABLE populations.
M31 MW
NOTE:
Novae also bright in UV, but only for 1 year (mostly due to shell emission)

5. Other
M31
(temptative,
partial Chandra HRC-I results)

6. Nova b: another RS Oph?
One of the brightest sources in M31, on after 34 days, peak at 2 months, ~1100s period, disappeared completely after 6 months. Effective temperature above 800,000 K!!!
It was a nova of the He/N and Fe II spectroscopic class (Shafter), typical of recurrent novae

8. Comparison: r2-12 vs.Nova 2007 12-b
r2-12 is the brightest SSS of M31 - only possible counterparts within 2” are 2-3 red stars, R~24-25
Clear periodicity 212 s - how can it be a NS?
Luminosity exceeding 1038 erg/s, variable by a factor ~few
Effective T >~ 800,000 K most of the time, fainter harder tail
Count rate, luminosity and spectral shape very similar to N b AND RS Oph at ~2 months
N b is different because of deeper and red shifted absorption feature of N VI at ~25 AA, and superimposed emission lines, like RS Oph

9. Persistent - recurrent sources:
Only 3 SSS (out of 50!!!) are always above the detection upper limits
A few other “persistent” sources are not SSS at all…
6 more SSS have “dips” or a recurrent behaviour
r1-25

10. r3-8 is NOT a foreground polar or neutron star
Luminosity “dips” by more than an order of mag (at least 2 likely) on time scale 3<=t<6 months argues against NS: variability occurs within weeks
Lack of any UV/optical counterpart with B<24, R<25 argues against foreground polar (favored by Williams et al. 2006)
One of the most interesting SSS in M31 because of similarity with LMC/SMC sources
Lack of bright red counterpart argue against symbiotic
It is probably a sister of RX J0513.

11. A distinct population of younger SSS

12. UV band of Galex are FUV=1350-1800 AA
NUV= AA
B stars are main sources
Below 200,000 K
only very extended
sources detectable in X

13. RX J040. 0 was not observed again in 2007; in SF region
RX J040.0 was not observed again in 2007; in SF region. It has colors of H-burning WD.
RX J on for at last 1 year, then off, in SF region. B-star colors.
RX J is a persistent source (Nelson’s talk).

14. Preliminary conclusions:
Only 11 out of 50 repeatedly observed sources were detected again
Three sources were “permanently detected - the best known, r2-12 is periodically and aperiodically variable, with similar spectrum to a “massive WD nova” at maximum..for ~20 years
8 repeated SSS are “wildly variable”
Up to a half (NOT MORE…) may be NOVAE
SNR can be a contaminant
A quarter of the sources (many of them transient) are… High Mass Binaries??? (Nelson)