A Chandra Low Energy Transmission Grating Spectrometer Observation of V4743 Sagittarii: A Supersoft X-Ray Source and a Violently Variable Light Curve

Abstract

V4743 Sgr (Nova Sgr 2002 No. 3) was discovered on 20 September 2002. We obtained a 5 ks ACIS-S spectrum in November 2002 and found that the nova was faint in X-rays. We then obtained a 25 ks CHANDRA LETGS observation on 19 March 2003. By this time, it had evolved into the Super Soft X-ray phase exhibiting a continuous spectrum with deep absorption features. The light curve from the observation showed large amplitude oscillations with a period of 1325 s (22 min) followed by a decline in total count rate after ∼ 13 ks of observations. The count rate dropped from ∼ 40 cts s −1 to practically zero within ∼ 6 ks and stayed low for the rest of the observation (∼ 6 ks. The spectral hardness ratio changed from maxima to minima in correlation with the oscillations, and then became significantly softer during the decay. Strong H-like and He-like lines of oxygen, nitrogen, and carbon were found in absorption during the bright phase, indicating temperatures between 1-2 MK, but they were shifted in wavelength corresponding to a Doppler velocity of -2400 km s −1 . The spectrum obtained after the decline in count rate showed emission lines of C vi, N vi, and N vii suggesting that we were seeing expanding gas ejected during the outburst, probably originating from CNO-cycled material. An XMM-Newton ToO observation, obtained on 4 April 2003 and a later LETGS observation from 18 July 2003 also showed oscillations, but with smaller amplitudes.

Nova V4743 Sagittarii 2002: An Intermediate Polar Candidate

“…Within the errors, P 2 is the beat period between the orbital period and the spin period, which we take as the mean of the two values given for the X-ray period ( Ness et al 2003;Orio & Tepedelenlioglu 2004): 1344 AE 21 s (%22 minutes). Ness et al (2003) argued that the 22 minute period could be either a pulsation or a spin period.…”

“…Ness et al (2003) argued that the 22 minute period could be either a pulsation or a spin period. However, if this periodicity represents the pulsation of the hot white dwarf, it should change as the temperature of the white dwarf cools down (e.g., Somer & Naylor 1999).…”

“…They detected a sinusoidal modulation with a period of 0:281 AE 0:003 days (6.7 hr) in the data and interpreted it as the orbital period of the binary system. Ness et al (2003) presented the results of two nights, 2003 April 4 and July 18, of Chandra X-ray observations of V4743 Sgr. They found a period of 1324 s and suggested that it might represent either a pulsation or a spin period.…”

Novae as a Class of Transient X‐Ray Sources

“…Within 1Y2 yr the nebula may have a rich line spectrum, emitting mostly below 1 keV (e.g., Ness et al 2003Ness et al , 2005. Of the novae discussed above, the time for the hard component of the X-ray emission to cool was about 6 months for the two fast novae ( Balman et al 1998;Mukai & Ishida 2001), but was longer (over 18 months) for slow novae with massive ejecta (Orio et al 1996;Greiner et al 2003), potentially exceeding the duration of the supersoft phase.…”

High Resolution XMM-Newton Data of Nova Outbursts using Warm & Hot Absorber Models

“…Optical spectroscopy reveals large expansion velocities (∼4,000-6,000 km s −1 ; Lynch et al 2008) . Both of the novae we study show a hard X-ray and a soft X-ray component during the outburst stage (V4743 Sgr: Ness et al 2003, Rauch et al 2010V2491 Cyg: Page et al 2010.…”