A Chandra grating observation of T Pyxidis
ATel #3762; Ben Tofflemire (University of Wisconsin), M. Orio (U Wisconsin and INAF-Padova), E. Kuulkers (ESA-ESAC), J. P. Osborne, K. L. Page, A. P. Beardmore (U. Leicester), J. J. Drake (CfA), J.-U. Ness (ESA/ESAC), S. Shore (U. Pisa), S. Starrfield (Arizona State U.)
on 14 Nov 2011; 17:58 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Marina Orio (orio@astro.wisc.edu)
T Pyx has been observed in eruption with Swift since 2011 April 14 (ATel 3285). Having become
a bright soft X-ray source (ATel 3647) it was observed with the Chandra X-ray telescope using the
LETG grating and HRC-S detector for 40,130 seconds continuously from 2011 November 3 to 4.
The spectrum is very soft with little emission above 1.5 keV, it is dominated by emission lines of
carbon, nitrogen, oxygen and iron in H- and He-like ionization states. The count rate is 0.097+-0.005 cts/s in the 0.15-1.5 keV range. The measured flux is about 3.7 x 10(-12) erg/cm 2 /s, of which at least half is in the lines. The continuum is measurable only at wavelengths greater than 25 AA and an upper limit to the contribution of a white dwarf atmosphere is a few 2x10 34 erg/s for column density N(H) not exceeding 3 x 10(-12) cm(-2) and a distance of 3.5 kpc. This is a factor of about 100 less luminous than a hot WD burning hydrogen in a shell. If the WD is responsible for the continuum emission, there must be a large level of intrinsic absorption that does not effect the lines.
The strongest lines are O VIII Ly at 18.96 AA and N VII Ly alpha at 24.78 AA. Initial measurements show blueshifted emission ~1500km/s for the O VIII Ly alpha line, and variable line broadening up to ~3000 km/s.
We find aperiodic variability in the light curve, with the count rate varying by a factor of more than 3 during more than 11 hours of exposure.
