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