Discovery of Multiple High-Velocity Narrow Circumstellar Na I D Lines in Nova V1280 Sco

TL;DR

This study reports the discovery of multiple high-velocity, narrow Na I D absorption lines in Nova V1280 Sco, indicating cool clumpy circumstellar gas interactions, with detailed spectral analysis over two months.

Contribution

First detection of multiple high-velocity narrow Na I D absorption components in Nova V1280 Sco, revealing complex circumstellar gas dynamics post-explosion.

Findings

Discovered at least 11 distinct Na I D absorption components.

High-velocity components remained nearly constant in wavelength over two months.

Na I D lines showed narrow, deepening absorption features, unlike Fe II and Balmer lines.

Abstract

We discovered multiple high-velocity (ranging from -900 to -650 km/s) and narrow (FWHM = 15 km/s) absorption components corresponding to both the D2 and the D1 lines of Na I on a high dispersion spectrum of V1280 Sco observed on 2009 May 9 (UT), 814 d after the V-band maximum. Subsequent observations carried out on 2009 June and July confirmed at least 11 distinct absorption components in both systems. Some components had deepened during the two months period while their HWHMs and wavelengths remained nearly constant. We suggest these high velocity components originate in cool clumpy gas clouds moving on the line of sight, produced in interactions between pre-existing cool circumstellar gas and high velocity gas ejected in the nova explosion. The optical region spectrum of V1280 Sco in 2009 is dominated by the continuum radiation and exhibits no forbidden line characterizing the nebular phase of typical novae. Permitted Fe II lines show doubly peaked emission profiles and some strong Fe II lines are accompanied by a blue shifted (about -255 km/s) absorption component. However, no high-velocity and narrow components corresponding to those of Na I could be detected in Fe II lines nor in the Balmer lines. The 255 km/s low velocity absorption component is most probably originating in the wind from the nova.