Spectroscopic Observations of the WZ Sge-Type Dwarf Nova GW Librae during the 2007 Superoutburst

Abstract

We carried out an international spectroscopic observation campaign of the dwarf nova GW Librae (GW Lib) during the 2007 superoutburst. Our observation period covered the rising phase of the superoutburst, maximum, slowly decaying phase (plateau), and long fading tail after the rapid decline from the plateau. The spectral features dramatically changed during the observations. In the rising phase, only absorption lines of H$\alpha$, H$\beta$, and H$\gamma$ were present. Around the maximum, the spectrum showed singly-peaked emission lines of H$\alpha$, He I 5876, He I 6678, He II 4686, and C III/N III as well as absorption lines of Balmer components and He I. These emission lines significantly weakened in the latter part of the plateau phase. In the fading tail, all the Balmer lines and He I 6678 were in emission, as observed in quiescence. We find that the center of the H$\alpha$ emission component was mostly stable over the whole orbital phase, being consistent with the low inclination of the system. Comparing with the observational results of WZ Sge during the 2001 superoutburst, the same type of stars as GW Lib seen with a high inclination angle, we interpret that the change of the H$\alpha$ profile before the fading tail phase is attributed to a photoionized region formed at the outer edge of the accretion disk, irradiated from the white dwarf and inner disk.

10 pages, 9 figures, accepted for publication in PASJ

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• GALEX and Optical Observations of GW Librae During the Long Decline from Superoutburst
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• Unexpected Superoutburst and Rebrightening of AL Comae Berenices in 2015
• Spectroscopic and Photometric Observations of Dwarf Nova Superoutbursts by the 3.8 m Telescope Seimei and the Variable Star Network
• Spectroscopic Observations of V455 Andromedae Superoutburst in 2007: the Most Exotic Spectral Features in Dwarf Nova Outbursts
• Multiwavelength Observations of the Black Hole X-ray Binary MAXI J1820$+$070 in the Rebrightening Phase
• GOTO065054+593624: a 8.5 mag amplitude dwarf nova identified in real time via Kilonova Seekers
• Evolution of Accretion Disk Structure of the Black Hole X-ray Binary MAXI J1820$+$070 during the Rebrightening Phase
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