Near-infrared observations: Dust enshrouds Nova Sgr 2015b
ATel #7748; D. P. K. Banerjee, N. M. Ashok, M. Srivastava (Physical Research Laboratory, Ahmedabad, India)
on 2 Jul 2015; 14:31 UT
Credential Certification: Dipankar P.K. Banerjee (orion@prl.res.in)
Subjects: Infra-Red, Cataclysmic Variable, Nova
Nova Sgr 2015b, discovered on 15.634 March 2015, has been actively
monitored photo-spectroscopically since outburst from Mount Abu (ATel #7265).
It was seen to exhibit Carbon monoxide and certain diagnostic features
early in its evolution, predictive of future dust formation (ATel #7299,
#7303). After several months of oscillations in its optical light curve,
characterized by several secondary maxima, the object began a deep decline
starting from around 1 June 2015 signifying the formation of dust which was
confirmed from NIR observations (ATel #7643). The object's
brightness has plummeted by 6 magnitudes in the V band in the last 15 days.
Observations from Mt. Abu using the 1.2m telescope and the 256x256
NICMOS3 imager/spectrograph show J = 7.93 +/- 0.15, H = 4.90 +/- 0.15 and K = 2.65 +/- 0.15
on 2015 June 30.95 UT.
The contemporaneous V band magnitude is ~ 12 (from AAVSO records).
The bright NIR magnitudes especially in the K band, and the J-K color of
~ 5.3 indicates that substantial dust formation has occured in the nova.
