Further Optical Spectroscopic Observations of V1674 Herculis
ATel #14723; C. E. Woodward (U. Minnesota), R. M. Wagner (Ohio State U.), S. Starrfield (Arizona State U.), V. Kumar, M. Srivastava, D. P.K. Banerjee, V. Joshi (PRL, India), I. IIyin, K. G. Strassmeier (AIP Potsdam), A. Evans (Keele U., UK)
on 16 Jun 2021; 17:53 UT
Credential Certification: C.E. Woodward (chickw024@gmail.com)
We report optical spectroscopic observations of the very fast nova V1674 Her (TCP J18573095+1653396) between 2021 June 13 to 15, obtained at R = 1700 using the Blue Channel spectrograph (Schmidt et al. 1989, PASP 101, 713) on the 6.5-m MMT, Mt. Hopkins, AZ, at high resolution (R = 220 000) using PEPSI (Strassmeier et al. 2015, Aston. Nachr. 336, 325) which is fiber-fed from the 1.8-m Vatican Telescope, Mt. Graham, AZ, and at R = 500 and 2000 using the MFOSC-P spectrograph at Mt Abu (Srivastava at al. 2018, Proc. SPIE, 10702-163). Most of the spectral features seen in the low-resolution spectra are consistent with the findings of other spectroscopic reports made at around the same time as our observations (ATel# 14720, #14710, #14704). It has not been explicitly stated so far, but the nova is of the Fe II class, despite the lines being much broader than expected for this class. In the low-resolution MMT and MFOSC-P spectra, several FeII lines are seen, most prominent of which are the FeII (42) multiplet. Of particular interest is the rapid variation displayed by the Halpha line profile. Within a period of 1.36 days between June 14.334 UT to June 15.710 UT, a series of 4 spectra (2 with PEPSI and 2 with MFOSC-P at R = 2000) were obtained. The high-resolution PEPSI spectra show that the peak of the Halpha profile is corrugated, comprising of around 9 to 10 distinct sub-peaks separated from each other in velocity by amounts ranging from 180 to 770 km/s. The overall shape of the top of the profile is that the blue side is distinctly stronger in intensity than the red side on June 14.344. But as time progresses the redside is seen to strengthen and by June 15.710 there is a striking reversal with the redside of the peak being stronger than the blue. Further monitoring of these rapid changes are encouraged. The Halpha line is broad; the FWHMs on June 14.344 and 14.727 are similar and measured to be 5850 km/s while the FWZI, which is difficult to accurately estimate due to blending with other lines in the wings, is conservatively estimated to be 10750 km/s or larger. The OI 8446 line, presumably dominantly excited by Lyman beta fluorescence, is prominent and has an FWHM of 5650 km/s. The 6613 angstrom DIB is clearly evident on the red wing of Halpha, with an measured EQW = 0.1158 Angstrom (from the PEPSI data) implying a reddening of 0.52 - 0.58 (Kos and Zwitter, 2013, ApJ, 774, 72). This value of reddening matches well the value of E(B-V) = 0.55 that we estimate at two magnitudes below maximum light (t2) from AAVSO B, V magnitudes and the relations of van den Bergh and Younger (1987, A&AS, 70, 125).
