Spectroscopy and photometry of Nova Oph 2018 N.3 (=PNV J17422408-2053088), still on the rise toward maximum
ATel #11940; U. Munari (INAF Padova), P. Valisa, F.-J. Hambsch, A. Frigo (ANS Collaboration
on 11 Aug 2018; 20:13 UT
Credential Certification: U. Munari (ulisse.munari@oapd.inaf.it)
Discovered on Aug 9.112 UT by C. Jacques, J. Barros, E. Pimentel, and P. Holvorcem (Brazilian Transient Search), PNV J17422408-2053088 has been classified as a FeII-type Galactic nova by Williams et al. (ATel #11928) from 2-m Liverpool Telescope spectra obtained on Aug 9.93 UT.
The nova has been discovered well before maximum brightness, as shown by the comparison of our BVI photometry for Aug 10 and 11, with that by S. Kiyota as reported on the CBAT "Transient Object Followup Reports" web page:
| UT | B | V | I |
|---|
| Aug 9.359 | 11.29 | 10.69 | 10.07 | S. Kiyota |
| Aug 10.018 | 10.97 | 10.11 | 8.90 | ANS |
| Aug 11.014 | 10.37 | 9.45 | 8.26 | ANS |
The red colors above suggest significant reddening, as confirmed by the saturated interstellar NaI doublet and the rich assortment of diffuse interstellar bands (DIBs) we have measured on an high resolution Echelle spectrum (4400-9100 Ang, res. pow. 15,000) that we have obtained with the
Varese 84cm telescope on Aug 10.839 UT, at the same time when we also recorded a low resolution spectrum (3200-7900 Ang, 2.31 Ang/pix) with the Asiago 1.22m telescope. The equivalent width (E.W.) for interstellar KI 7699 corresponds to E(B-V)=0.94 adopting the calibration of Munari and Zwitter
(1997, A&A 318, 269), and the E.W. of DIB 6614 provides E(B-V)=1.01 from Munari (2014, ASPC 490, 183). The E.W. of DIBs at 5780 and 5797 correspond, respectively, to E(B-V)=0.92 and 1.04 applying Kos and Zwitter (2013, ApJ 774, 72) relations. The overall average is E(B-V)=0.98 +/- 0.02.
Significant evolution has occurred since the spectral observation by Williams et al. (ATel #11928), primarily a reduction in excitation and in line width and velocity, as usual during the rise to maximum. The HeI lines are gone, and now a greater number of low-excitation emission lines are present over the whole spectral range, all displaying P-Cyg profiles, with the equivalent width of the absorption component rivaling or surpassing the emission one. Lines from a large number of FeII multiplets are present, CaII H and K, near-IR CaII triplet, Balmer and Paschen series, NaI, OI 7772 and 8446 (not yet Bowen pumped). The P-Cyg profiles are now perfectly fitted by a combination of two Gaussians, with no extended wings. The velocity shift from emission of P-Cyg absorptions range now from about -580 km/s for FeII, to -650 for Hbeta, to -710 for OI. The width of emission and absorption components also vary among ions and lines, from 1100 and 760 km/s (respectively) for Hbeta to 730 and 460 km/s for OI.
