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A SSS spectrum of V574 Pup

ATEL # 1327; J.-U. Ness, S. Starrfield (Arizona State), G. Schwarz (West Chester), J.P. Osborne and K.L. Page (University of Leicester)
on 14 Dec 2007; 16:52 UT
Password Certification: Kim Page (

Subjects: Ultra-Violet, X-ray, Cataclysmic Variables, Nova, Transients

Two Swift XRT observations of V574 Pup were carried out on 2007 December 7 and 13 with exposure times of 6410 and 5450 seconds, respectively. The average count rate is 0.0140.001 counts per second. All source photons were registered with energies below 1 keV and the spectrum is consistent with that of a supersoft X-ray source (SSS). The count rate and the spectrum are similar to the last X-ray observation taken on 2005 August 17 (Ness et al. 2007, astro-ph/0703286), The combined two spectra taken in 2007 can be fitted with a blackbody yielding kT=3210 eV and NH=(4.2+1.9-1.1)1021 cm-2, leading to an observed X-ray flux (0.3-1keV) of 3.7 10-13 erg cm-2 s-1 which, at 6.5kpc distance, corresponds to a bolometric luminosity of 8 1037 erg s-1. Weak emission features may be present at energies corresponding to emission lines from NeIX, OVII, and NVII. The X-ray spectrum may be composed of continuum plus emission lines. We obtained UV magnitudes from UVOT for the December 13 observation and found 16.4880.017 at 212nm (UVW2), 16.8720.026 at 231nm (UVM2), and 16.2890.015 at 291nm (UVW1), which corresponds to fluxes of (1.370.02)10-15, (8.100.02)10-17, and (1.210.02)10-17 erg s-1cm-2-1, respectively.

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