XMM monitoring of the state transition of the supersoft source CAL 83 Robert Schwarz Astrophysikalisches Institut Potsdam Jochen Greiner MPE Garching Gloria Sala Uni Barcelona Ronald Mennickent Uni 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 SSS Observations of RXJ 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 Radius/temperature changes of the WD Increased irradiation of the outer disk

Wind regulated accretion in RXJ

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 variation Free fits: kTbb varies from 25 to 33 eV fixing Nh to 8 x 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 and luminosity to the value of the high state spectrum Cold absorption fails Ionized absorber N h = cm -2

Summary New complex variability patterns 1. short repetition time 2. Long transitions to optical high state Long term variability Ambiguous X-ray spectroscopy 50% temperature change or strong ionized absorber Tight anti-correlation between optical and X-rays

Ende…

RGS Spectrum

PN spectrum