R. Hudec, V. Šimon F. Munz, J. Š trobl , P. Kubánek , P. Sobotka, R. Urban

1. INTEGRAL cataclysmic and symbiotic stars R. Hudec, V. Šimon F. Munz, J. Štrobl, P. Kubánek, P. Sobotka, R. Urban Astronomical Institute, Academy of Sciences 251 65 Ondrejov, Czech Republic & ISDC, Versoix, Switzerland IBWS, Oct 25-28, 2006 v

2. Non-magnetic cataclysmic variable (CV) • Accretion disk – thermal • radiation (UV, optical, IR) Donor, lobe-filling star Bright spot (stream impact onto disk) • Opt. thick, geom. thin boundary • layer (therm. rad. - soft X-rays) • (high m) . Mass stream Non-mag. white dwarf • Opt. thin, geom. thick boundary • layer (bremsstrahlung – hard • X-rays) (low m) Accretion disk . Dominant source of luminosity: accretion process Intermediate polar (IP) – mildly magnetized white dwarf • Impact region near the • magnetic pole of the WD • (bremsstrahlung – hard • X-rays)

3. Magnetic CVs (polars) ST LMi – orbital modulation in hard Xrays (1.9-8.5 keV) (EXOSAT) Mason (1985) hard X-ray sources • cyclotron emission from • accretion column (mainly • optical and UV) • bremsstrahlung from • shocks above impact • region on the WD (X-rays) IBIS AM Her – orbial modulation top – soft X-rays (40-120 A) bottom- hard X-rays (1.9-8.5 keV) (EXOSAT) AM Her (kTbrem~31 keV) (Rothschild et al. 1981) Heise et al. (1985)

4. Production of gamma-rays in CVs can reach even TeV energies Acceleration of particles by the rotating magnetic field of the WD inintermediate polars in the propeller regime – AE Aqr – detected by ground-based Cherenkov telescopes in the TeV passband (e.g. Meintjes et al. 1992) _________________________________________________________ TeV emission from the polar AM Her detected byground-based Cherenkov telescopes(Bhat et al. 1991) Domain of hard X-rays/soft gamma rays was little exploited before INTEGRAL _________________________________________________________

5. Totalexposure times of IBIS INTEGRAL– suitable for: (a) detection of the populations of CVs and symbiotics with the hardest X-ray spectra (b) simultaneous observations in the optical and hard X-ray regions (c) long-term observations with OMC – including a search for rapid variations in observing series during science window (OMC observations also for systems bellow the detection limit in hard X-rays) IBIS – all obs. Known CVs: Catalog and Atlas of Cataclysmic Variables (Downes et al. 2001) Totalexposure times of IBIS IBIS – Core Program

6. The summary of CV observations/detections by INTEGRAL during the first 3 years of INTEGRAL • In total, 19 CVs detected (surprise, more than expected, almost 10% of INTEGRAL detections) • 15 seen by IBIS (Barlow et al., 2006) – correlation of IBIS data and Downes CV catalogue • 4 are CV candidates revealed by optical spectroscopy of IGR sources (Masetti et al., 2006) – new CVs, not in Downes catalogue • Mainly magnetic systems: • 11 confirmed or propably IPs, 3 polars, 1 dwarf nova, 4 probable magnetic CVs

7. Barlow et al., MNRAS 2006. The results of cross-correlation with Downes CV catalogue

8. Periods: Vast majority Porb > 3 h, ie. above the period gap (only one < 3 h) 5 long period systems with Porb > 7 h Variation: No significant modulation has been found in the 20-30 keV light curves. The majority of the CVs displays persistent soft gamma ray fluxes with exception of V1223 Sgr and SS Cyg Spectrum: Similar in most cases, power law or thermal bremsstrahlung model , Compare well with previous high energy spectral fits (de Martino et al. 2004, Suleimanov et al. 2005, Barlow et al. 2006) Mean: G~2.8, kT~20 keV

9. Some statistics Intermediate polars – only ~2% of the catalogued CVs,but dominate the group of CVs seen by IBIS More such detections and new identifications can be hence expected Many CVs covered by CP remain unobservable by IBIS, but new have been discovered IBIS tends to detect IPs and asynchronous polars: in hard X-rays, these objects seem to be more luminous (up to the factor of 10) than single synchronous polars Detection of CVs by IBIS (non-flarig state) typically requires 150-250 ksec or more, but some remained invisible even after 500 ksec

10. V1223 Sgr Intermediate polar Most significantly detected CV in the IBIS survey, with a significance of 38 sigma in the 20-40 keV final mosaic Accretion via disk Bright X-ray source (4U 1849–31) Orbital period: Porb = 3.37 h (Osborne et al. 1985, Jablonski and Steiner 1987) Rotational period of the white dwarf: Prot = 746 sec (Osborne et al. 1985) Beat period (combined effect of Porb and Prot): Pbeat = 794.3 sec (Steiner et al. 1981) Prominent long-term brightness variations: - outburst with a duration of ~6 hr and amplitude >1 mag (van Amerongen & van Paradijs 1989) - episodes of deep low state (decrease by several mgnitudes) (Garnavich and Szkody 1988)

11. Indications for flaring activity: • Seen by IBIS (flare lasting for ~ 3.5 hrs • during revolution 61 (MJD 52743), peak flux • ~ 3 times of average (Barlow et al., 2006) • Seen by INTEGRAL OMC in optical one year later (MJD=53110, 53116) lasting for ~ 15 min and ~ 2.5 hrs (Simon et al., 2005) • Seen in optical by groud-based instrument (duration 6-24 hrs), Amerrongen & van Paradijs (1989) • Confirms the importance of OMC instrument onboard INTEGRAL: even with V lim mag 15, it can provide valuable optical simultaneous data to gamma-ray observations

12. Similar flares known also for another IPs in optical, but not in soft gamma: • Example TV Col (Hudec et al., 2005), where 12 optical flares have been observed so far, five of them on archival plates from the Bamberg Observatory. TV Col is an intermediate polar (IP) and the optical counterpart of the X-ray source 2A0526-328 (Cooke et al. 1978, Charles et al. 1979). This is the first cataclysmic variable (CV) discovered through its X-ray emission. • Physics of the outbursts in IPs: • Disk instability or • An increase in mass transfer from the secondary :

13. 15 – 25 keV 25 – 40 keV V1223 Sgr Field of the intermediate polarV1223 Sgr. Co-addedframes from IBIS. Start exp. JD 2452730.17 Integration time: 66 700 sec Size of the field: 9.1ox7.1o. North is up, East to the left. 40 – 60 keV

14. Relation between far X-ray flux and optical magnitude Relating processes in different regions: Disk (optical) Impact region near magnetic pole of white dwarf (X-ray) V1223 Sgr Time evolution of the V band magnitude and X-ray flux in the 15 – 60 keV passband IBIS spectrum in the 15 – 60 keV region Spectral profile remains largely unchanged during shallow low state (~ 400 days) Relation between the V band magnitude and X-ray flux in the 15 – 60 keV passband

15. Fluctuations of brightness for JD < 2 452 250 Short low state (LS) in JD 2 451 650 Long LS after JD 2 452 250 V1223 Sgr INTEGRAL observations in lower than average level of brightness – long-lasting and rather shallow low state Peak of high state Shallow low state Means for each science window Relation between mass transfer rate and V band magnitude, assuming the system parameters according to Model A of Beuermann et al. (2004) Disk may become thermally unstable in shallow low state – this is not observed (irradiation of the disk by the X-rays can occur) Statistical distribution of the optical brightness

16. Search for rotational and beat modulation in OMC data during shallow low state V1223 Sgr All OMC data Smoothed beat modulation in folded OMC data (100 sec exp. only) (ephemeris ofJablonski and Steiner (1987): Pbeat = 794.3 sec) Prot Pbeat Beat modulation still dominates over the rotational modulation (stream–disk overflow still operates in the shallow low state) Stream–disk overflow persists when mass transfer rate decreases ~3 times OMC data between JD 2 453 000 and JD 2 453 100 Prot Pbeat Time (days)

17. V1223 Sgr Orbital modulation V & gamma OMC data (100 sec exp. only) Ephemeris ofJablonski and Steiner (1987):Porb = 3.37 hr The profile and phasing of the optical modulation appears to be quite similar to that observed by Jablonski and Steiner (1987) in the high state Smooth curve: moving averages Observations of all three time intervals follow the modulation and possess the same mean level of brightness Scatter – rotational modulation of the WD contributes Optical 15-40 keV NH=0 atoms/cm2 Flat modulation in hard X-rays Possible dip at phase ~0.9 may be caused by a very dense material pushed away from the orbital plane by the stream impact Observable emission region does not vary through the orbital cycle NH=5x1023 atoms/cm2 NH=1024 atoms/cm2

18. Desynchronized polar (e.g. Patterson et al. 1995). Orbital period (3.37 hr) and the rotational period of the WD differ by ~0.3 percent V 1432 Aql Flux(15 – 40keV)= (8.8 +/- 0.9) x 10-4 photon/cm2/s L (15 – 40 keV) = 1.4 x 1032 erg/s Averaged OMC light curve Field of V1432 Aql. Co-added fully coded images from IBIS: JD 2 452 756. Integration time: 37 160 sec. Size of the field:9ox7o. North is up, East to the left. 15 – 40 keV 40 – 80 keV

19. V2400 Oph Diskless intermediate polar Orbital period: Porb = 3.4 hr Rotational period of the WD: Prot = 927 sec Beat period: Pbeat = 1003 sec (Buckley et al. 1997) 15 – 40 keV IBIS image of the field of the intermediate polarV2400Ophand the symbiotic (neutron star) system V2116 Oph. Co-added fully coded images from IBIS: JD 2452733 + JD 2452920 + JD 2453054. Integration time: 53 760 sec. Size of field: 9.1ox7.1o. North is up, East to the left. Averaged OMC light curve Flux(15–40keV)= (9.37 +/- 1.14) x 10-4 photon/cm2/s

20. outburst GK Per IBIS range quiescence (Ishida et al. 1992) Intermediate polar, very long Porb=1.99 days (Crampton et al. 1986) Spin period of the white dwarf Pspin=351 sec(Watson et al. 1985) Exploded as a classical nova in 1901 Fluctuations by ~1 mag after return to quiescence, later they developed into infrequent dwarf nova-type outbursts(Sabbadin & Bianchini 1983, Hudec 1981) X-ray (2.5 – 11 keV) spin modulation – 351 s (EXOSAT) during optical outburst (Watson et al. 1985) X-ray start can precede the optical start by up to 40 days (Binachini & Sabbadin 1985) Models: up to 80 – 120 days (Kim et al. 1992) Relation between profile of optical and X-ray outburst (Simon 2004)

21. GK Per INTEGRAL Interval between outbursts:D t = 973days IBIS obs.: start at ~42percent of this interval (measured since the previous outburst). Ishida’s et al. reference spectrum:Dt = 983days (start at ~29percent of this interval). Amount of matter arriving to the WD and the parameters of the X-ray emitting region on the WD remained almost the same during these phases of the quiescent intervals. Flux(15–40keV)= (2.7 +/- 1.2) x 10-4 photon/cm2/s L (15 – 40 keV) = 4.6 x 1032 erg/s IBIS Quiescent X-ray spectrum Parameters from Ishida et al. (1992) (kT = 32 keV, NH = 1022 cm-2, norm. factor: 0.0039+/-0.0002photon/cm2/s1/keV) IBIS (25–40 keV) image of GK Per(Integr. time: 79 980 sec Co-added images: 19 March 2003, 27 – 29 July 2003. Size of field:4.1ox3.0o. North is up, East to the left.

22. Nova-like CV INTEGRAL OMC – two intervals covered Rapid variations (flickering) superimposed on the long-term changes (a) Outburst (duration <14 days) (b) Short episode of a low state Examples of OMC light curves IX Vel Superposition of both events: the time scales of the decaying and rising branches of both events appear to be comparable

23. RSOphExamples of OMC light curves • relatively bright symbiotic system • orbital period Porb=460days • inclination angle 30o – 40o • giant component underfilling its lobe (Dobrzycka & Kenyon 1994) • white dwarf (WD) – recurrent nova(five observed explosions)(e.g. Warner 1995) • Quiescent brightness – fluctuations(months and years) 11 – 12 mag(V), sometimes • 10mag(V)(e.g. Dobrzycka & Kenyon 1994, Oppenheimer and Mattei 1996) • Rapid optical variations– time scale of tens of minutes, similar to those often seen in • short-period CVs(e.g. Walker 1977, Dobrzycka et al. 1996)

24. Mag.scale Intens. scale 1 7 1 7 3 9 3 9 5 10 5 10 Weighted wavelet Z-transform WWZ indicateswhether ornot there is a periodic fluctuation at a giventime at a givenfrequency (method ofFoster 1996). RS Oph 6 6 V band OMC light curves Strong flickering

25. Symbiotic stars as Hard-X-ray emitters: RT Cru and CD -57 3057 identified with IGR sources (Masetti et al., 2005) Novae, some of which occur in symbiotic stars, play an important role in the chemical evolution of the Galaxy and the symbiotic stars themselves. A common feature of symbiotic recurrent novae (RNe) is rapid optical flickering. At least one symbiotic RN (T CrB) has also produced very hard X-ray emission. RT Cru produces optical flickering, has an optical spectrum like that of T CrB, and has recently been discovered by Integral to produce X-ray emission out to ~60 keV. X-ray observations of RT Cru from the Chandra and Swift satellitesclearly shows both thermal and non-thermal X-ray emission. Absorption of soft X-rays that is variable on a time scale of months suggests occultation by the red giant. There are two possible models for RT Cru: a jet-producing system viewed nearly edge on, or a magnetic white dwarf viewed pole on.

26. RT Cru optical monitoring More detailed and more precise observations by southern FRAM and WATCHER robotic telescopes (Kubanek et al.) is in progress This one and the newly detected symbiotics with INTEGRAL - CD-57 3057 (Masetti et al., 2005) – are optically very bright stars

27. The End