X-ray emission lines in Nova LMC 2012 with Chandra
ATel #4116; Dai Takei, Jeremy J. Drake (CfA), Jan-Uwe Ness (ESAC), Sumner Starrfield (ASU), Greg Schwarz (AAS), Kim L. Page, Julian P. Osborne (University of Leicester), Daniel R. van Rossum (University of Chicago), and Frederick M. Walter (Stony Brook University)
on 18 May 2012; 17:14 UT
Credential Certification: Dai Takei (dtakei@head.cfa.harvard.edu)
We conducted a 20 ksec target-of-opportunity observation of Nova LMC
2012 (ATel #4002, #4043, #4092, and #4106) with the Chandra X-ray
satellite on April 26 2012, 32 days after its discovery and about
14 days after the emergence of the supersoft source (ATel #4043).
A high-resolution X-ray spectrum was obtained with the Low Energy
Transmission Grating and the High Resolution Camera (see also ATel
#4092). The spectrum is characterized by emission and absorption
lines, and the continuum is remarkably similar to those of the
bright supersoft X-ray emission of the novae RS Ophiuchi 2006 and
V2491 Cygni, except that absorption features appear considerably
weaker in Nova LMC 2012. Since the Wien tails of the spectra indicate
the source temperatures are similar, the weaker absorption is likely
due to a lower metallicity, as might be expected for an LMC nova
progenitor. We also checked a power spectrum of a light curve using
the Chandra data, but it shows no sign of any obvious periodicity.
The strongest lines are due to N VII and O VIII, with no prominent
features due to C. N VII and O VIII exhibit significant emission
components with evidence for associated P Cygni absorption
blueshifted by approximately 4000-5000 km/s. This velocity is greater
than the values 3300 km/s and 1200 km/s observed in V2491 Cygni and
RS Ophiuchi, respectively. A quasi-neutral absorption line of O,
likely of interstellar origin, is also seen near 23.5 A.
We thank the Chandra X-ray Center and Director for allocating and
scheduling discretionary time for this target-of-opportunity program.
