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Swift detects the recurrent nova T Pyx during the rise to outburst

ATel #3285; E. Kuulkers (ESA/ESAC), K. L. Page (U. Leicester), J.-U. Ness (ESA/ESAC), J. P. Osborne (U. Leicester), S. Balman (METU), S. Starrfield (Arizona State U.), A. P. Beardmore (U. Leicester), M. F. Bode (LJMU), Darnley, M. J. (LJMU), J. J. Drake (CfA), P. A. Evans (U. Leicester), S. P.S. Eyres (U. Central Lancashire), T. J. O'Brien (U. Manchester), M. Orio (INAF & U. Wisconsin), B. E. Schaefer (Louisiana State U.), G. J. Schwarz (AAS), D. Takei (CfA) & F. M. Walter (Stony Brook U.)
on 15 Apr 2011; 14:49 UT
Credential Certification: Erik Kuulkers (ekuulker@rssd.esa.int)

Subjects: Request for Observations, Binary, Cataclysmic Variable, Nova, Transient, Variables

Referred to by ATel #: 3549, 3647, 4452

After nearly 45 years of being dormant, the recurrent nova T Pyx (see, e.g., Schaefer et al. 2010, ApJ 708, 381) has been found to be in outburst again on 2011 April 14 (CBET 2700). Previous outbursts occurred in 1890, 1902, 1920, 1944 and 1966.

Following a prompt Target of Opportunity request, Swift began observing the object 7.5 hours after the discovery of the outburst (UT 2011 April 14 14:07-14:52). A source is clearly detected by the XRT, at a count rate of 0.011+/-0.002 (PC mode). All the source counts can be found below 2 keV, indicating a soft spectrum. Preliminary fits to the observed X-ray spectrum using a black-body or MEKAL model are (errors and upper limits are at 90% confidence):

Model kT
(keV)
N_H
(/cm^2)
0.3-10 keV flux
absorbed
(erg/cm^2/s)
0.3-10 keV flux
unabsorbed
(erg/cm^2/s)
C-stat/dof
Black body 0.110 (+0.018/-0.041) <3.6e21 3.0e-13 4.0e-13 19.1/21
MEKAL <0.221 <7.2e21 2.6e-13 2.2e-11 24.1/21

There is no evidence yet for hard (>1 keV) X-ray emission via shock interactions of the new ejecta with any ambient circumbinary material or ejecta from previous outbursts.

We note that Chandra has recently observed T Pyx, prior to its current outburst, in 2011 February (PI: Balman). A rough conversion using WebPIMMS from the observed Chandra/ACIS-S count rate of 0.0052 c/s to a Swift/XRT count rate, assuming a black body with kT=0.11 keV with negligible interstellar absorption, leads to an estimate of 0.0014 c/s (PC mode). The above reported observed Swift/XRT rate during rise to outburst is about a factor 10 higher than this quiescent estimate.

The Swift Nova CV group has initiated a Swift monitoring campaign, i.e., T Pyx will be observed for about 1 ksec every day for the next 3 weeks. We encourage follow-up at all wavelengths.

We thank the Swift operations team and PI for their prompt scheduling of the observations.