XMM monitoring of the state transition of the supersoft source CAL 83
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Transcript of XMM monitoring of the state transition of the supersoft source CAL 83
XMM monitoring of the state transition of the supersoft source CAL 83
Robert SchwarzAstrophysikalisches Institut Potsdam
Jochen Greiner MPE Garching Gloria Sala Uni Barcelona
Ronald MennickentUni Concepcion
Super Soft X-ray Sources – New developments ESAC, May 18, 2009
Introducing CAL 83
• Canonical SSS source in the LMC• 1-day orbital period• Low amplitude orbital modulation in
optical and X-rays • Inclination < 30• Tentative X-ray pulsations at 38 min
High-resolution X-ray spectrum• Good fit to the data with a NLTE
model (Lanz et al. 2004)
• log g = 8.5, Teff = 500 kK
• Suggests a massive WD of 1.3 Msun
X-ray off-states in CAL 83
MACHO light curve (Greiner & di Stefano 2002)
Anti-correlated brightness changes in SSSObservations of RXJ 0513-69• Short transition times• only high or low states • X-ray on state shorter than off
state
Anti-correlated brightness changes in SSS
Models• Expansion and cooling of the envelope• Limit cycle regulated by changing mass accretion rate
Hachisu & Kato 2003• Stripping of the companions
surface by a strong wind
• X-ray off: wind absorption optical high: expanded disk
Reinsch et al. 2000• Radius/temperature changes
of the WD
• Increased irradiation of the outer disk
Wind regulated accretion in RXJ 0513-69
Smarts/XMM monitoring of CAL 83
Comparison with MACHO observations
Similar pattern
Different timescale
Long term behaviour from OGLE
Recurrence time: 430 days Duty cycle: 50%
X-ray/optical lightcurves
• Sharp drop (t < 1 d) to intermediate brightness level
• Immediate recovery (t ~ 20 d) • X-ray detection during optical
high state• Anti-correlation of optical and X-ray over a wide range
Low resolution X-ray spectroscopy Blackbody fits
Correlation between Nh and kTbb
High state RGS spectrum
Black: April 2000 (Lanz et al. 2004) Red: August 2008
Spectral variationFree fits: kTbb varies from 25 to 33 eV
fixing Nh to 8 x 1020 cm-2
kTbb varies from 23 to 37 eV
Luminosity increases and radius shrinks changes by factor of 2
Broadband spectral energy distribution
Changes of the X-ray spectra can not explain the UV variation..
X-ray variation by strong absorption only?Fix temperature andluminosity to the value of the high state spectrum
Cold absorption fails
Ionized absorber Nh = 4 1022 cm-2
Summary New complex variability patterns 1. short repetition time 2. Long transitions to optical high state Long term variability
Ambiguous X-ray spectroscopy50% temperature changeor strong ionized absorber
Tight anti-correlation between optical and X-rays
Ende…
RGS Spectrum
PN spectrum