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X-ray and optical observations of four polars | | H. Worpel
; A. D. Schwope
; T. Granzer
; K. Reinsch
; R. Schwarz
; I. Traulsen
; | | Date: |
3 May 2016 | | Abstract: | We aim to study the temporal and spectral behaviour of four polar CVs from
the infrared to X-ray regimes, refine our knowledge of the physical parameters
of these systems at different accretion rates, and to search for a possible
excess of soft X-ray photons.
We analysed four XMM X-ray observations of three of the sources, two of them
discovered in SDSS, one in RASS. The X-ray data were complemented by optical
photometry and spectroscopy and, for two sources, archival Swift observations.
SDSSJ0328 was X-ray bright in two XMM and two Swift observations, and shows
transitions from high and low accretion states over a few months. It has no
strong soft excess. We measured the magnetic field strength at the main pole to
be 39 MG, the inclination to be 45<i<77 deg, and we have refined the long-term
ephemeris. SDSSJ1333 was X-ray faint. We measured a faint phase X-ray flux and
plasma temperature for this source, which spends almost all of its time
accreting at a low level. Its inclination is less than about 76 degrees.
1RXSJ1730 was X-ray bright in the XMM data. Its spectrum contained a modest
soft blackbody component, not luminous enough to be considered a strong soft
excess. We inferred a magnetic field strength at the main pole of 20 to 25 MG,
and that the inclination is less than 77 and probably less than 63 deg. V808
Aur was faint in the Swift observation but there is still strong evidence for
bright and faint phases in X-rays and perhaps in UV. Residual X-ray flux from
the faint phase is hard to explain by thermal emission from the WD surface, or
by accretion onto the other pole. We give a revised distance estimate of 250pc.
The three systems we could study in detail appear to be normal polars, with
luminosity and magnetic field strength typical for this class of CV. None of
these systems shows the strong soft excess thought commonplace in polars prior
to the XMM era. | | Source: | arXiv, 1605.0927 | | Services: | Forum | Review | PDF | Favorites | |
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