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