ASASSN-15fd = Nova LMC 2015
ATel #7350; Frederick Walter (Stony Brook University)
on 7 Apr 2015; 00:33 UT
Credential Certification: Fred Walter (frederick.walter@stonybrook.edu)
Novae in the LMC are astrophysically-useful because they form a subset
of galactic novae at a common distance and low extinction.
K.Z. Stanek et al (ATel #7313) suggested, based on its light curve and
spatial location, that ASASSN-15fd might be a nova in the LMC. They were
correct.
We obtained an R=28,000 spectrum using the SMARTS Chiron Spectrograph on the
SMARTS/CTIO 1.5m on UT 2015 April 3.0.
The Balmer lines and a number of Fe II lines were in emission at that time.
The radial velocities of the emission lines, excepting H-alpha, were consistent
with the +278 km/s radial velocity of the LMC. The spectrum is consistent
with a classical Fe II nova near maximum light. A phenomenological description of the
spectra follow.
H-alpha has a FWHM about 850 km/s; strong P Cyg absorption superposed on
the blue emission wing has a mean velocity of -750 km/s in the rest frame of the
LMC. H-beta is asymmetric, with a steeper blue side, but showed no discrete
absorption components.
No emission is seen at He I, but broad absorption lines are seen blueward of
the 588 and 668 nm He I lines. No such absorption is seen to the blue of the
707 nm line.
The Fe II lines have a sharp (70 km/s FWHM) absorption component blueshifted
by 750 km/s (rest velocities). The strong multiplet 42 lines also exhibit a
broad blueshifted absorption feature extending to about -1650 km/s. About ten
Fe II lines between 450 and 470 nm are seen only in this narrow absorption
component, and lack evidence of any emission. The Na D lines show similar
sharp absorption features superposed on a broad emission pedestal. O I 774 nm
is in emission, and shows an absorption trough extending outwards to about
1150 km/s.
Continuing observations of novae at Stony Brook are made possible by
generous support from the Provost of Stony Brook University, Dennis Assanis.
