No Evidence for Extended X-ray Emission around Recurrent Nova T Pyx
ATel #4097; R. Montez Jr. (Rochester Institute of Technology), J. L. Sokoloski (Columbia University), T. Nelson (University of Minnesota)
on 5 May 2012; 18:10 UT
Credential Certification: Rodolfo Montez Jr. (rxmpcia@cis.rit.edu)
Subjects: X-ray, A Comment, Nova
Contrary to the analysis reported in ATel #3915, we do not find any evidence for extended X-ray structure in three quiescent-state observations of recurrent nova T Pyx taken in early 2011 by the Chandra X-ray Observatory (CXO). A comparison among sub-pixel images and simulated point spread functions (PSFs) for the CXO observations reveals that, given the large uncertainties on the centroids due to the low count rate, the apparent extended structure reported in ATel #3915 was likely due to the relative offset of the three separate pointings and an artifact of the High Resolution Mirror Assembly (HRMA).
Prior to the latest outburst of the recurrent nova T Pyx on 14 April 2011, CXO observed T Pyx for approximately 100 ks (PI: Balman). The total observing time was split into three parts: 34.6 ks on 31 January 2011 (ObsID: 12399), 33.4 ks on 02 February 2011 (ObsID: 13223), and 30.9 ks on 05 February 2011 (ObsID: 13224)). On 7 February 2012, ATel#3915 reported the detection of an X-ray nebulosity around T Pyx based on these CXO observations. The telegram described a purportedly resolved nebula with an elliptical shape and a conical elongation in the southern direction.
We acquired all three observations (which are publicly available in the Chandra Data Archive), extracted individual and combined source spectra, and merged the event lists to a generate sub-pixel images of the event distributions. We used the source spectra to generate event lists for a simulated PSF using a combination of the Chandra Ray Trace (ChaRT) program and the MIT Model of AXAF Response to X-rays (MARX). After merging the event lists for the simulated PSFs, we compared the merged event distributions for the simulated PSFs and the observations.
We did not find any compelling evidence for the reported X-ray nebulosity. Instead, we found that the spatial distribution of the X-ray emission is consistent with that expected from the PSF, given the low count rate and the offsets between the three individual pointings. Furthermore, we believe the conical elongation in the southern direction was due to the HRMA artifact described on the Chandra X-ray Center artifact website. Images and radial profiles of the observed X-ray emission and simulated PSFs are included here.
No Evidence for Extended X-ray Emission around Recurrent Nova T Pyx
