Observations of Nova Mon 2012 after it emerged from the conjunction with the Sun
ATel #5500; U. Munari (INAF Padova), A. Siviero (Univ. Padova), M. Zerjal (Univ. Ljubljana), S. Dallaporta (ANS Collaboration)
on 22 Oct 2013; 17:30 UT
Credential Certification: U. Munari (ulisse.munari@oapd.inaf.it)
We resumed the photometric and spectroscopic monitoring of Nova Mon 2012
(V959 Mon) as soon as it emerged from the conjunction with the Sun in early
September, using the same instrumentation adopted by Munari et al.
(2013, MNRAS, 435, 771) to investigate the earlier evolution.
The photometric decline is monitored with ANS Collaboration telescope 030
and it is proceeding very smoothly. The nova is still considerably bright.
Our observations for Sept 03.113, 13.126, 24.116 and Oct 18.086 UT give
for B band 14.557, 14.668, 14.767, 14.919, for V 13.803, 13.814, 13.884, 14.067,
for Rc 14.049, 14.111, 14.164, 14.322, and for Ic 14.032, 14.080, 14.110 and
14.259 mag, respectively.
The nova was already well into its nebular stage before entering the
conjunction with the Sun, but a number of changes occurred during the
period of invisibility. We have obtained with the Asiago 1.22m telescope +
B&C spectrograph a low resolution spectrum (3320-7920 Ang range, 2.3 Ang/pix
dispersion) on Oct 17.008 UT, and with the Asiago 1.82m + Echelle
spectrograph a high resolution spectrum (resolving power 20,000) on Oct
19.197 UT, close in time with the lower resolution observation for Oct 21.451
UT recently reported by Woodward et al. (ATel #5499).
Comparing the Asiago 1.22m spectrum for Oct 17.008 with an identical one
we obtained on 2013 March 21.833 we find that the ratio [OIII] 4959+5007 / [NeV]
3345+3436 has increased from 1.4 to 8.7, [OIII] 4959+5007 / Hbeta from 18
to 29, and [NeIII] 3869+3968 / [NeV] 3345+3426 from 0.60 to 1.22, while
[NeV] 3345+3426 / Hbeta declined from 15.7 from 3.3, HeI 5876 / HeII 5412
from 6.3 to 3.4, and [FeVII] 6087 / Hbeta from 0.29 to 0.13. The ratio
between HeI lines and Hbeta, and [OI] 6300+6364 and Hbeta remained constant.
The 6300/6364 ratio for [OI] has increased from 1.1 to 1.4, still very far
from the 3.1 value of optically thin conditions.
Significant changes affected the emission line profiles too, which have
been 3D modelled by Ribeiro et al. (2013, ApJ 768, 49) for the early nova
evolution. Comparing the Echelle spectrum for Oct 19.197 UT with an
identical one for 2013 April 25.838 UT, the [OIII] double peaked profile of April
(characterized by a width at half maximum of 2220 km/s, and a velocity
separation of 1200 km/s for the two peaks) has now turned into a trapezoidal
profile with a much flatter top and a width at half maximum of 2080 km/s,
while the blend with the strong [NII] 6548, 6584 doublet now complicates a lot
the profile of Halpha that shows a width at half maximum of 2710 km/s.
