ARAS Optical Spectroscopy of Classical Nova ASASSN-16ig (Nova Sgr 2016 no. 2)
ATel #9377; Olivier Garde, Stephane Charbonnel, Pascal Le Du (ARAS Group)
on 16 Aug 2016; 02:58 UT
Distributed as an Instant Email Notice Novae
Credential Certification: S. N. Shore (shore@df.unipi.it)
We obtained a series of optical of the classical nova ASASSN-16ig in Sagittarius (N Sgr 2016 no. 2) (see ATels #9375, #9343, #9352, #9359, CBET 4295, 4299) with a LISA spectrograph plus ATIK414EX CCD using a C14 at Obs. Hautes Provence on Aug. 13.83 UT and 14.49 UT with total exposures of about 6000 sec each at a resolution of around 700 covering the interval 4000 - 7550 A with sufficient S/N ratio (> 10). The spectra on both days are show the early optically thick "Fe curtain" stage of the ejecta expansion with the usual low ionization spectrum. The nova has displayed significant changes in only 24 hours. Relatively weak (at this resolution) Halpha absorption on Aug. 13 appeared broad, extending to about -2000 km/s. The second spectrum displayed weak blueshifted absorption with v_rad(abs) = -1500+/-50 km/s; Hbeta was asymmetric but showed no absorption at this resolution. The Halpha absorption on Aug. 13 was not associated with blueshifted emission, the profile on Aug. 14 had become narrower within a broader emission wing that indicated a continuing decrease in the ejecta density and line optical depth. There was no change in the red wing (vrad(max) = +2500 km/s for Halpha). No He I emission was present. The Fe II 5169 A developed absorption at vrad = -1300 km/s; Fe II 4924, 5018 A were asymmetric with no obvious absorption. None displayed such profiles one day before. In the red, C I blend at 7113 A (noted in V339 Del 2013) was present on both days, as was Fe II 7462 A (with a similar profile to Fe II 5169 A). The equivalent width ratios of the Balmer emission lines (in A) were Halpha:Hbeta:Hgamma = 103:41:14 on Aug. 13 and 140:39:(<20, wk) on Aug. 14; Hgamma was clearly detected in the first spectrum. No strong P Cyg was seen on Hbeta but its asymmetric profile on both days (with vrad(max,red) = +2200 km/s and vrad(max,blue)=-1500 km/s) suggests absorption. As noted in the cited ATels, the extinction is quite high (perhaps E(B-V) >= 1). Observations will continue and the spectra will be publicly available through the Astronomical Ring for Access to Spectroscopy (ARAS) Database.
A.R.A.S Spectral Data Base NSgr 2016
