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