Detection of a Wind in the Fast Nova V1674 Her

ATel #15386; R. M. Wagner (LBTO and Ohio State U.), C. E. Woodward (U. Minnesota), S. Starrfield (Arizona State U.)
on 19 May 2022; 23:42 UT
Credential Certification: R. Mark Wagner (rmw@as.arizona.edu)

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We report further optical spectroscopic observations of the fast nova V1674 Her (range: 310-950 nm; resolution 0.34 nm) obtained on 2022 April 30.414 UT with the 2 x 8.4 m Large Binocular Telescope (+MODS) on Mount Graham, Arizona. This spectrum covers a broader spectral range at higher signal-to-noise ratio than we obtained previously on 2022 March 27 UT (ATel #15312) with the 2.4 m Hiltner telescope (+OSMOS) at the MDM Observatory.

The LBT spectrum exhibits permitted emission lines of the H I Balmer series of Hα, Hβ, Hγ, and Hδ, He II 320.3, 454.2, 468.6, 541.1, and 823.7 nm, He I 667.8 nm, C III 465.0 nm, Fe II 771.2 nm, and H I Paschen series lines at 922.9, 901.5, 886.3, 875.0, 866.5, and 859.8 nm. Narrow permitted emission lines arising from O VI 381.1, 383.4, and 529.2 nm may also be present. He II 468.6 nm emission continues to be as strong as reported in ATel #15312, with a resolution corrected FWHM of about 1550 km/s.

In contrast to the earlier spectrum (ATel #15312), broad forbidden emission lines are still evident and include those of [Ne V] 342.6 and 334.6 nm, [Ne III] 386.9 and 396.8 nm, and a broad feature between 491 and 506 nm that could be residual [O III] 495.9 and 500.7 nm emission. The latter feature exhibits many subcomponents as well. The FWHM of [Ne V] 342.6 nm emission is about 4900 km/s compared to 5900 km/s observed on 2021 June 30 (ATel #14746). The integrated intensity of [Ne V] 342.6 nm emission has declined by a factor of about 3100 compared to the spectrum reported in ATel #14746. V1674 Her was classified as a neon nova based on the exceptionally strong [Ne V] and [Ne III] emission lines (ATel #14746), and the continued presence of neon emission bolsters this classification.

In the 2022 March 27 spectrum (ATel #15312), Hα was described as having an emission line profile exhibiting multiple components, but asymmetric to the blue. In the 2022 April 30 UT LBT spectrum, the Hα line profile exhibits a striking P Cygni-like line profile. The absorption component is centered at -1206 km/s and the terminal velocity is about -1930 km/s relative to the line center. The deconvolved Hα emission line exhibits two relatively narrow components at -490 km/s (FWHM 390 km/s) and +32 km/s (FWHM 630 km/s), and in addition, a much broader but considerably weaker emission component is also evident with a FWHM of about 3430 km/s.

The appearance of a P Cygni-like line profile of Hα in the spectrum of V1674 Her is reminiscent of similar line profiles observed in the UV resonance lines of some cataclysmic variable stars implying mass loss in a stellar or an accretion driven disk wind (see Mauche and Raymond 1987, ApJ, 323, 690; Drew 1987, MNRAS, 224, 595). P Cygni line profiles are generally seen in some cataclysmic variables with high accretion rates and relatively low inclination angles suggesting a bipolar line forming region. Continued optical spectroscopy extending over the binary orbital period might constrain the geometry of the line emitting regions of V1674 Her.