Bibcode
Henze, M.; Pietsch, W.; Haberl, F.; Hernanz, M.; Sala, G.; Della Valle, M.; Hatzidimitriou, D.; Rau, A.; Hartmann, D. H.; Greiner, J.; Burwitz, V.; Fliri, J.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 523, id.A89
Fecha de publicación:
11
2010
Revista
Número de citas
47
Número de citas referidas
41
Descripción
Context. Classical novae (CNe) have recently been reported to represent
the major class of supersoft X-ray sources (SSSs) in the central region
of our neighbour galaxy M 31. Aims: We carried out a dedicated
monitoring of the M 31 central region with XMM-Newton and Chandra in
order to find SSS counterparts of CNe, determine the duration of their
SSS phase and derive physical outburst parameters. Methods: We
systematically searched our data for X-ray counterparts of CNe and
determined their X-ray light curves and spectral properties.
Additionally, we determined luminosity upper limits for all novae from
previous studies which are not detected anymore and for all CNe in our
field of view with optical outbursts between May 2005 and March 2007.
Results: We detected eight X-ray counterparts of CNe in M 31,
four of which were not previously known. Seven sources can be classified
as SSSs, one is a candidate SSS. Two SSSs are still visible more than
nine years after the nova outburst, whereas two other nova counterparts
show a short SSS phase of less than 150 days. Of the latter sources,
M31N 2006-04a exhibits a short-time variable X-ray light curve with an
apparent period of (1.6±0.3) h. This periodicity could indicate
the binary period of the system. There is no X-ray detection for 23 out
of 25 CNe which were within the field of view of our observations and
had their outburst from about one year before the start of the
monitoring until its end. From the 14 SSS nova counterparts known from
previous studies, ten are not detected anymore. Additionally, we found
four SSSs in our XMM-Newton data without a nova counterpart, one of
which is a new source. Conclusions: Out of eleven SSSs detected
in our monitoring, seven are counterparts of CNe. We therefore confirm
the earlier finding that CNe are the major class of SSSs in the central
region of M 31. We use the measured SSS turn-on and turn-off times to
estimate the mass ejected in the nova outburst and the mass burned on
the white dwarf. Classical novae with short SSS phases seem to be an
important contributor to the overall population.
Partly based on observations with XMM-Newton, an ESA Science Mission
with instruments and contributions directly funded by ESA Member States
and NASA.