1 / 15

R. Gális 1 , L. Hric , E. Kundra 2 , & F . Münz 3

Hard X-ray and Optical Activity of Intermediate Polars. R. Gális 1 , L. Hric , E. Kundra 2 , & F . Münz 3. 1 Faculty of Sciences, University of P. J. Šafárik , Moyzesova 16, 041 54 Košice , Slovak Republic ( e-mail: rudolf . galis @ upjs . sk )

bayle
Download Presentation

R. Gális 1 , L. Hric , E. Kundra 2 , & F . Münz 3

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Hard X-ray and Optical Activity of Intermediate Polars R. Gális1, L. Hric, E. Kundra2, & F. Münz3 1Faculty of Sciences, University of P. J. Šafárik, Moyzesova 16, 041 54 Košice, Slovak Republic(e-mail: rudolf.galis@upjs.sk) 2Astronomical Institute SAS, 059 60 Tatranská Lomnica, Slovak Republic 3Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic KOLOS2012, December 6 – 8, 2012, AO Kolonica

  2. Outline • Activity of magnetic cataclysmic variables. • Hard X-ray emission of intermediate polars • INTEGRAL detections • Long-term variability

  3. Cataclysmic variables • Cataclysmic variables (CVs) manifest strong activity in the whole spectrum from radio up to gamma rays. • CVs are close binary systems of a hot white dwarf (WD) and red MS star of spectral type M or K, which fills the volume of its inner Roche lobe and transfers matter to the vicinity of the WD. • Mass transfer between the components of the CVs causes observed activity, which varied from relatively small (flickering) to enormous light variations (outbursts of novae) on time scales cover the wide range from very fast variability of fractions of seconds (flickering) to long-term variations of several years or decades (activity cycles).

  4. Cataclysmic variables • According to strength of WD magnetic field this matter is creating a accretion disk or follows magnetic lines and falls to surface of the WD. • Magnetic CVs are a small sub-set of all catalogued CVsystems and fall into two categories: polars intermediate polars (IPs). • In IPs, the WD magnetic field (106 – 107 G) is not strong enough to disrupt disc entirely and simply truncates the inner part of disc. An accretion flow is channelled down towards the magnetic poles and onto the WD surface.

  5. HardX-ray emission of IPs • Increased interest in CVs arouses after discovery of the very hard X-ray emission (up to 80 keV) of many IPs. • When this material impacts the atmosphere of the WD, a shock will form and hard X-ray / soft gamma-ray emission will result from thermal bremsstrahlung cooling by free electrons in the hot post-shock region (PSR) with kT 10s of keV. • As we showed in our previous analysis,the broad-band spectra (3 -100 keV) of studied IPs can be well fitted by a thermal bremsstrahlung model with the temperature of post-shock region kT 20 - 25 keV. • Reflection of the bremsstrahlung photons at the WD surface also contributes to the hard X-ray spectrum.

  6. Broad-band (3–100)keVspectrum of V2400 Oph • The fit of composite spectrum (3-100 keV) by only a thermal bremsstrahlung model with temperature kT = (24.6 ± 1.6) keV) is not sufficient to completely describe the data (2/d.o.f = 24.4/9). • Significant excess around  26 keV (4.3 s) can be connected with reflection from the surface of the WD. When we fit this excess by Gaussian profile the spectrum is well described with (2/d.o.f = 4.5/6).

  7. INTEGRAL detections • In total, 32 CVs (and 2 symbiotic systems) were detected (more than expected, 5% of all INTEGRAL detections) (Bird et al., 2007, Kniazev et al. 2008, Masetti et al. 2008, our previous work). • The sample of IPs detected in (20-40) keV energy band has 23 members, which represents more than 70% of all CVs detected by INTEGRAL. • In hard X-rays, IPs are more luminous (up to the factor of 10) than polars. It is assumed that, in the strongly magnetized (B ≥ 107 G) polar systems, cyclotron cooling becomesan important mechanism to suppress the bremsstrahlung high temperature emission.

  8. INTEGRAL detections • Nevertheless, this sample represent only 25% of all known IPs. • Some IPs are not detectable even we have significant exposure time (more than 4Msec) for these sources. • This fact can be related to activity state of these close interacting binaries. • To understand this relation is necessary to study the correlation between the activity state and X-ray emission of the IPs.

  9. HardX-rayvariability • No significant long-term variability has been found so far in the 20-30 keV light curves (Barlow et al. 2006). • The majority of the CVs seems to have persistent hard X-ray fluxes. • We used all available observational data from INTEGRAL/IBIS and INTEGRAL/OMC detectors to study possible variability of selected IPs in X-ray and optical, respectively.

  10. Intermediate polar V1223 Sgr • V1223 Sgr is the brightest CV detected by INTEGRAL/IBIS. • Possible X-ray flare activity(Barlow et al. 2006) and short-term bursts have also been detected from this system in the optical by van Amerongen & van Paradijs (1989). • These outbursts can be a result of disk instabilities but there wasno correlation between optical and X-rays burst activity. • Moreover the episodes of deep low state (decrease by several magnitudes) of V 1223 Sgr were also detected in optical (Garnavich and Szkody 1988).

  11. Intermediate polar V1223 Sgr • The fluxes especially in (15 - 25) keV and (25 - 40) keV bands are long-term variable with significant drop (low state) around MJD ∼ 53 650. • Optical variations are correlated with the changes in (15 – 25) keV, (25 – 40) keV and (40 – 60) keV spectral bands with correlation coefficient 0.81, 0.82 and 0.89, respectively. • Strong correlation suggests, that variations in optical and X- ray related to the same physical process – the decrease in mass transfer between components.

  12. Intermediate polars:SS Cyg, V709 Cas • Variability in X-ŕay (up to 60 KeV) is common among IPs and is related to the mass transfer between components of these systems. • Simultaneous observationsfrom optical up to X-ray allow to track the transferred matter from donor, through accretion disk, to the surface of WD.

  13. Long-term observational campaign • Photometrical campaign to obtain long-term homogenous observations (to cover whole activity cycles) as well as sets of observation with high time resolution (to detail cover of orbital cycles) of selected CVs.

  14. Conclusions and plans • The fluxes of most of IPs are long-term variable in X-ray (up to 60 – 80 KeV). Moreover these X-ray variability is correlated with the changes in optical spectral band (V 1223 Sgr). • Simultaneous analysis of multi-frequency observation (from optical to X-ray) allows to study physical mechanism related to themass transfer. • Plan to detail analyse all CVs and symbiotic systems detected by INTEGRAL. Work in progress.

  15. Thank you for your attention

More Related