Supersoft Xray sources in M31

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Supersoft X-ray sources in M31

• Marina Orio
• INAF-Padova and U Wisconsin
• In collaboration with Tommy Nelson

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Supersoft X-ray sources in M31 everywhere
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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 (Nelsons talk)

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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)
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Other M31 (temptative, partial Chandra HRC-I
results)
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Nova 2007 12-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
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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, R24-25
• Clear periodicity 212 s - how can it be a NS?
• Luminosity exceeding 1038 erg/s, variable by a
  factor few
• Effective T gt 800,000 K most of the time,
  fainter harder tail
• Count rate, luminosity and spectral shape very
  similar to N 2007 12-b AND RS Oph at 2 months
• N 2007 12-b is different because of deeper and
  red shifted absorption feature of N VI at 25 AA,
  and superimposed emission lines, like RS Oph

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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
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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 3lttlt6 months
  argues against NS variability occurs within
  weeks
• Lack of any UV/optical counterpart with Blt24,
  Rlt25 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.

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A distinct population of younger SSS
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UV band of Galex are FUV1350-1800
AA NUV1800-2800 AA B stars are main sources
Below 200,000 K only very extended sources
detectable in X
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RX J040.0 was not observed again in 2007 in SF
region. It has colors of H-burning WD. RX J0045.4
on for at last 1 year, then off, in SF region.
B-star colors. RX J0042.2 is a persistent source
(Nelsons talk).
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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)