Dust formation in V1831 Aql (Nova Aquila 2015)
ATel #8332; Mudit K Srivastava, D. P.K. Banerjee and N. M.Ashok, Physical Research Laboratory, Ahmedabad, India
on 24 Nov 2015; 20:11 UT
Credential Certification: Dipankar P.K. Banerjee (orion@prl.res.in)
Subjects: Infra-Red, Nova
Nova Aquila 2015 (PNV J19215012+15092480), discovered in outburst on 2015-10-01.29 (ATel #8126 for further details), is being regularly monitored in the near-infrared from the Mount Abu Observatory, India. The nova lies in a direction of high galactic extinction and is hence more amenable for observations in the IR vis-a-vis the optical. Our earlier spectra had shown it to be a nova of the FeII class (ATel #8142 ).
Several epochs of observation in October-November 2015 show the formation of dust in the nova around
5 November 2015. The (J-K) color on this date increased to 3.83 (viz. J= 9.40, H= 7.33, K= 5.57) from its post-outburst (J-K) = 1.23 value
on 8 October 2015 when J was = 8.32, H=7.75, K=7.09 indicating the build-up of an IR excess. The typical photometric error is +- 0.04 magnitude. The latest observation on 20 November 2015 shows that significant emission from dust is present; the (J-K) color on this date is = 4.22 and the NIR magnitudes are J=10.36, H= 8.08, K= 6.14. Spectra in the 0.85-2.4 mcron region at R ~1000 with the near-IR camera/spectrograph (NICS) shows a rising red continuum in the H and K bands due to the dust, which partially blankets the Brackett H lines
of this region which were earlier seen prominently in emission (ATel #8142 ).
The J band, less influenced by dust, shows specially strong emission in the HeI 1.0831 micron line and prominent emission in the
Lyman-beta fluoresced OI 1.1287 micron and HI lines with the Paschen beta 1.2818 micron line having an FWHM of 1600 km/s. Further observations are ongoing.
