High-resolution spectroscopy of Nova Cyg 2014

ATel #6181; Ashish Raj (Korea Astronomy and Space Science Institute), U. Munari (INAF Padova-Asiago), Byeong-Cheol Lee and Sang Chul KIM (Korea Astronomy and Space Science Institute), Sang-Joon Kim and Chae-Kyung Sim (Kyung Hee University, South Korea)
on 28 May 2014; 10:05 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Ashish Raj (ashish@kasi.re.kr)

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We report about high-resolution spectroscopy (resolving power 40,000) of Nova Cyg 2014 (PNV J20214234+3103296) that we obtained on May 1.78 and May 22.72 UT over the wavelength range 3800-8900 Angstrom with the BOES (Bohyunsan Observatory Echelle Spectrograph) attached to the 1.8 m telescope at Bohyunsan Optical Astronomy Observatory.

On May 1.78 spectrum, all permitted emission lines display the same two blue-shifted absorption components: one at low velocity, which is remarkably sharp and displays a Gaussian-like profile; the other at twice larger velocity is much broader, with a trapezoidal profile. The FWHM of the sharp components ranges from the 45 km/s for OI 7774 (triplet line fully resolved) to 52 km/s for NaI, 60 for FeII 42, 100 for H-beta and 130 km/s for H-alpha. The width at half intensity of the broad trapezoidal absorption component ranges from 185 km/s for NaI, 200 for FeII 42, 220 for Balmer lines and OI 8446, and 400 km/s for OI 7774. The heliocentric radial velocity of the narrow component is remarkably similar for all lines, -585 km/s (rms=7 km/s). The same occurs for the heliocentric radial velocity of the photocenter of the broad component, which is -1125 km/s (rms=13 km/s). The profile of permitted emission lines (except for CaII triplet) is Gaussian-like, with a FWHM ranging from 855 km/s for OI 8446 to 1050 km/s for higher Balmer lines. The profile of forbidden [OI] 5577, 6300, 6364 emission lines and permitted CaII triplet is instead rectangular, of 805 km/s width, with superimposed two feeble peaks separated by 530 km/s. The interstellar absorption lines from NaI and KI appear composed by several components, some of them saturated for NaI, at -37, -12, -2, +15 and +30 km/s heliocentric radial velocities. The total equivalent width of the optically thin KI 7699 indicates a reddening E(B-V) = 0.63 following the calibration by Munari and Zwitter (1997, A&A 318, 269).

The appearance of the May 22.72 spectrum is similar, with both absorption components wider and shifted to bluer wavelengths. The sharp component moved to -690 km/s, the broad one to -1380 km/s. Their profile changed too. While the sharp component developed a double peaked minimum (separation 30 km/s), the broad one developed into a series of sub-components different among the various lines. The forbidden [OI] emission lines retained the overall rectangular shape (width 900 km/s) on top of which six distinct peaks now appear. The CaII triplet is this rectangular with the two superimposed peaks now stronger and separated by 650 km/s.