Jonathan Tedds

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The 2XMMp Catalogue and Extragalactic Variability
2XMMp all sky map
Jonathan Tedds, University of Leicester Mike
Watson, John Pye, Silvia Mateos, Anja Schroeder,
Ann-Marie Stobbart Natalie Webb, Masa Sakano,
Julie Wardlow on behalf of the XMM-Newton Survey
Science Centre Consortium
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THE 2XMMp CATALOGUE

• 2XMM new serendipitous X-ray source catalogue
  from XMM
• EPIC public observations Feb 2000 April 2006
• 2XMMp pre-release of 2XMM released July 2006
• Filtered subset by field quality
• Largest X-ray catalogue ever
• 150K detections from 2400 observations
• 117K unique point sources
• 5K unique extended sources
• 400 sq.deg. (280 sq deg overlap corrected)

• 2XMMp ACCESS ONLINE/VO
• Project Website http//xmmssc-www.star.le.ac.uk/
• XSA archive http//xmm.esac.esa.int/xsa/
• LEDAS archive http//www.ledas.ac.uk/

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THE 2XMMp CATALOGUE

• median flux (0.2 - 12 keV) of sources
  2.4  10-14 erg cm-2 s-1
• 20 have fluxes lt 1   10-14 erg cm-2 s-1

Distribution of 2-12 keV fluxes for 2XMMp
catalogue. The catalogue matches the typical
fluxes where most of the Cosmic X-ray Background
(CXRB) energy density originates.
Sky area covered by the 2XMMp catalogue as
function of exposure time.
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THE 2XMMp CATALOGUE

• KEY FEATURES
• Includes extended source search and
  parameterisation
• science grade catalogue
• high reliability
• excellent astrometry and photometry
• spectra time series for gt10 of all 2XMM
  sources (15000 sources)

Example X-ray light curve automatically
extracted as 2XMMp data product
Example X-ray spectrum automatically extracted
as 2XMMp data product
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Coming Soon (Aug07) THE 2XMM CATALOGUEsee also
talks by M.Watson, S. Mateos, A. Del Moro, G.
Stewart re 2XMM science

• 247K detections ? 192K unique sources
• 520 sq.deg. / 330 sq.degs excluding overlap
• Full catalogue product set available
• Available Aug 2007
• 2XMM is 50 larger than 2XMMp
• 3491 observations vs 2400 in 2XMMp
• Source level flagging important near e.g. bright
  sources

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2XMMp time series and spectra

• Time Series Spectra generated if
• Total EPIC gt 500 cts (PNMOS 3.51 assumed)
• Energy 0.2-12 keV
• Region
• 28 radius circle (source)
• 60-180 annulus (background)
• Exclude DET_ML gt 15 sources at 60 radius
• Short term variability - within exposures
• SAS task ekstest
• Use ?2 probability (based on null hypothesis)
  that source is constant
• Pearsons approximation to ?2 for Poissonian data
• Model is used as estimator of its own variance
• Flag as variable if ?2 probability lt 1e-5 in at
  least 1 exposure based on stellar flares

2XMMp variables 15900 sources with
lightcurves, spectra 1100 flagged as variable
using ?2 test
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2XMMp time series, spectra variability flags
0.2-12 keV Flux Distributions
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Sanity check known stellar variable published
light curve Pallavicini et al.
automatically generated time series plot from
2XMMp reprocessing pipeline
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2XMMp SDSS DR5 CROSS-CORRELATION see
M.Watson, A. Del Moro talks

• 25 overlap by sky area
• 20,000 secure matches within 2.5s or 3 (using
  likelihood ratio analysis)
• 60 of 2XMMp sources in overlap region have
  SDSS match
• 1200 matched XMM sources SDSS spectra (1 of
  2XMMp)

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Identify Extragalactic sample with 2XMMp
lightcurves

• Use SDSS DR5 confirmed spectroscopic IDs
  extragalactic
• 683 unique objects (301 gals, 370 qsos, 12
  hiz_qsos)

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Extragalactic variability in 2XMMp

• by SDSS DR5 sub-class (gals, qso, hiz_qso)

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Extragalactic variability in 2XMMp

• Histogram by SDSS DR5 sub-class (Gals, QSOs)

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0.2-12keV Flux potential variability?
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Extragalactic variability in 2XMMp-DR5

• QSOs - PN ?2 probability lt 0.05

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Extragalactic variability in 2XMMp-DR5

• Gals- PN ?2 probability lt 0.05

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Lone Extragalactic short-term variable example

• PN ?2 probability 10-18
• Fx 3 x 10-13 cgs (0.2-12keV)

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Lone Extragalactic short-term variable example

• NELG, z0.03

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Multi-epoch Stellar Tidal Disruptions and
Accretion-Disk Instabilities
Disruption and Accretion Ejection of Debris
Accretion Disk Instabilities in Active Galaxies
e.g., Siemiginowska et al. (1996)
e.g., Rees (1988)
Stellar tidal disruptions (transient fueling)
inevitable in crowded galactic centers? Should
lead to X-ray / UV flares of AGN-level
luminosities over month-to-year timescales.
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IC 3599 Example X-ray Outburst from the ROSAT
All-Sky Survey
1990-1992 ROSAT Light Curve
1991 May spectrum 1992 Feb spectrum

• X-ray variability by factor of 60. Peak LX
  5 x 1043 erg s-1
• X-ray outburst induced optical variability
• Outburst only fully recognized after it was
  largely over
• IC 3599 has a weak AGN. Other outbursts seen
  from non-AGN

Brandt et al. (1995) Grupe et al. (1995)
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Early X-ray Outburst Rate Constraints

• Donley et al. (2002) set systematic outburst-rate
  constraints
• RASS vs. pointed ROSAT PSPC survey
• soft X-ray outbursts
• 5 galaxies satisfied survey criteria - 3 non-AGN
  and 2 AGN
• Rate for normal galaxies was 1 x 10-5 galaxy-1
  yr-1 (for z lt 0.1)
• but with substantial uncertainties
• Updated Rate Predictions for Tidal Disruptions
  Wang Merritt (2004)
• Predicted rate has risen by a factor 10
• lower SMBH masses than previously used
• Predicted rate now uncomfortably high compared to
  Donley02 results and this work
• Obscuration?
• Short duration?
• Different spectral signature than expected?

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Extragalactic long-term variable example
SDSS DR5

• Known QSO in LH
• Clear long term decline over XMM lifetime
• No obvious short term variability

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Extragalactic long-term variable example
SDSS DR5

• Known QSO z0.78 in LH
• Clear long term decline over XMM lifetime
• No obvious short term variability

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Extragalactic long-term variability

• Known QSO z0.78 in Lockman Hole
• Clear long term decline over XMM lifetime
• No obvious short term variability
• See Mateos 07 for study of deep LH field
  variability
• 80 objects vary on timescales of months ?
  years!
• but very rare to find short term extragalactic
  variables
• Only handfuls of long term variables found with
  multi-epoch data in 2XMMp
• Need wide area repeat coverage ? XMM slew survey
• See talks by R.Saxton and A.Read

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Summary

• 2XMMp a unique resource to study X-ray
  variability 15,000 lightcurves!
• Extragalactic variable candidates are rare and as
  likely to be QSOs as galaxies?
• 683 unique 2XMMp sources in SDSS DR5
• XMM lightcurves, spectra
• optical spectroscopic IDs, spectral-z, linewidths
  
• 10 show ?2 probability lt 0.05
• No clear correlation of potential variability
  with Fx or z for gals or QSOs
• Serendipitous discovery potential of rare
  extragalactic variability in 2XMMp
• Short-term - e.g use ?2 probability lt 0.05 for
  gals and QSOs
• Long-term - compare multi-epoch XMM and Chandra,
  ROSAT
• Outstanding issues of constraints on expected
  X-UV outbursts
• No closer to resolution based on this study
  butXMM slew survey
• need larger identified samples to pick up rare
  short term extragalactic variables
• Extend to include XWAS XMM-2dF wide angle survey
  (Tedds 07) , AXIS (Barcons 07)
• Use much bigger statistically IDd samples next?