Presentation is loading. Please wait.

Presentation is loading. Please wait.

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,

Similar presentations


Presentation on theme: "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,"— Presentation transcript:

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

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

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

4 Production of gamma-rays in CVs can reach even TeV energies Production of gamma-rays in CVs can reach even TeV energies Acceleration of particles by the rotating magnetic field of the WD in intermediate 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 by ground-based Cherenkov telescopes (Bhat et al. 1991) Domain of hard X-rays/soft gamma rays was little exploited before INTEGRAL _________________________________________________________

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

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 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 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 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, 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 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:  ~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 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 keV final mosaic Accretion via disk Bright X-ray source (4U 1849–31) Orbital period: P orb = 3.37 h (Osborne et al. 1985, Jablonski and Steiner 1987) Rotational period of the white dwarf: P rot = 746 sec (Osborne et al. 1985) Beat period (combined effect of P orb and P rot ): P beat = 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 Seen by IBIS (flare lasting for ~ 3.5 hrs during revolution 61 (MJD 52743), peak flux ~ 3 times of average (Barlow et al., 2006) ~ 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 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) 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. 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 2A (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 Disk instability or An increase in mass transfer from the secondary An increase in mass transfer from the secondary :

13 Field of the intermediate polar V1223 Sgr. Co-added frames from IBIS. Start exp. JD Integration time: sec Size of the field: 9.1 o x7.1 o. North is up, East to the left. 15 – 25 keV 25 – 40 keV 40 – 60 keV V1223 Sgr

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) Time evolution of the V band magnitude and X-ray flux in the 15 – 60 keV passband Relation between 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)

15 V1223 Sgr Means for each science window INTEGRAL observations in lower than average level of brightness – long-lasting and rather shallow low state Fluctuations of brightness for JD < Short low state (LS) in JD Long LS after JD Long LS after JD Statisticaldistribution of the optical brightness Shallow low state Peak of high state 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)

16 Smoothed beat modulation in folded OMC data (100 sec exp. only) (ephemeris of Jablonski and Steiner (1987): P beat = sec) V1223 Sgr Search for rotational and beat modulation in OMC data during shallow low state 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 P rot P beat All OMC data OMC data between JD and JD Time (days)

17 OMC data (100 sec exp. only) Ephemeris of Jablonski and Steiner (1987): P orb = 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 V1223 Sgr Orbital modulation V & gamma Optical keV 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 N H =0 atoms/cm 2 N H =10 24 atoms/cm 2 N H =5x10 23 atoms/cm 2

18 V 1432 Aql 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 Field of V1432 Aql. Co-added fully coded images from IBIS: JD Integration time: sec. Size of the field: 9 o x7 o. North is up, East to the left. 15 – 40 keV 40 – 80 keV Averaged OMC light curve light curve Flux (15 – 40 keV) = (8.8 +/- 0.9) x photon/cm 2 /s L (15 – 40 keV) = 1.4 x erg/s

19 IBIS image of the field of the intermediate polar V2400 Oph and the symbiotic (neutron star) system V2116 Oph. Co-added fully coded images from IBIS: JD JD JD Integration time: sec. Size of field: 9.1 o x7.1 o. North is up, East to the left. V2400 Oph Averaged OMC light curve Diskless intermediate polar Orbital period: P orb = 3.4 hr Rotational period of the WD: P rot = 927 sec Beat period: P beat = 1003 sec (Buckley et al. 1997) 15 – 40 keV Flux (15 – 40 keV) = (9.37 +/- 1.14) x photon/cm 2 /s

20 (Ishida et al. 1992) quiescence outburst Relation between profile of optical and X-ray outburst 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) (Simon 2004) GK Per Intermediate polar, very long P orb =1.99 days (Crampton et al. 1986) Spin period of the white dwarf P spin =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) IBISrange

21 IBIS (25–40 keV) image of GK Per (Integr. time: sec Co-added images: 19 March 2003, 27 – 29 July Size of field: 4.1 o x3.0 o. North is up, East to the left. GK Per INTEGRAL Quiescent X-ray spectrum Parameters from Ishida et al. (1992) ( kT = 32 keV, N H = cm -2, norm. factor: / photon/cm 2 /s 1 /keV) IBIS Interval between outbursts:  t = 973 days IBIS obs.: start at ~42 percent of this interval (measured since the previous outburst). Ishida’s et al. reference spectrum:  t = 983 days (start at ~29 percent 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 – 40 keV) = (2.7 +/- 1.2) x photon/cm 2 /s L (15 – 40 keV) = 4.6 x erg/s

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

23 RS Oph Examples of OMC light curves RS Oph Examples of OMC light curves relatively bright symbiotic system relatively bright symbiotic system orbital period P orb =460 days orbital period P orb =460 days inclination angle 30 o – 40 o inclination angle 30 o – 40 o giant component underfilling its lobe (Dobrzycka & Kenyon 1994) giant component underfilling its lobe (Dobrzycka & Kenyon 1994) white dwarf (WD) – recurrent nova (five observed explosions) (e.g. Warner 1995) white dwarf (WD) – recurrent nova (five observed explosions) (e.g. Warner 1995) Quiescent brightness – fluctuations (months and years) 11 – 12 mag( V ), sometimes Quiescent brightness – fluctuations (months and years) 11 – 12 mag( V ), sometimes 10 mag( V ) (e.g. Dobrzycka & Kenyon 1994, Oppenheimer and Mattei 1996) 10 mag( 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 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) short-period CVs (e.g. Walker 1977, Dobrzycka et al. 1996)

24 Mag. scale Intens. scale RS Oph V band OMC light curves Strong flickering Strong flickering Weighted wavelet Z-transform WWZ indicates whether or not there is a periodic fluctuation at a given time at a given frequency (method of Foster 1996).

25 Symbiotic stars as Hard-X-ray emitters: RT Cru and CD 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 satellites clearly 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 (Masetti et al., 2005) – are optically very bright stars

27 The End


Download ppt "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,"

Similar presentations


Ads by Google