New optical spectroscopy of the Galactic nova V659 Sct = Nova Sct 2019

ATel #13819; S. N. Shore (Univ. of Pisa, Pisa, IT), F. Sims (Desert Celestial Obs, AZ USA)
on 20 Jun 2020; 01:38 UT
Distributed as an Instant Email Notice Novae
Credential Certification: S. N. Shore (shore@df.unipi.it)

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We report optical (3830 - 7250A) low resolution (R approx 1050) spectroscopic observations of V659 Sct (see ATel #13241, ATel #13245) contemporaneously with the recent report by Woodward et al, (ATel #13815). The spectra were obtained on 2020 Jun 19 UT 06:16:38 (MJD 59019.806) in a sequence of 12x600 sec with a Shelyak LISA spectrograph and 355.5mm aperture PlaneWave CDK. We report all lines with S/N > 5, the strongest lines all have S/N > 50. We obtained a simultaneous V filter photometric measurement of V = 14.83 +/-0.04. The principal lines are [Ne III] 3869, 3968 A; H-delta 4101; [O III] 4363(bl. with H-gamma); N III 4636; He II 4686; H-beta 4861; [O III] 4959,5007; [Fe VII] 5158, [Fe VI] 5176; [Fe VII] 5276; [Ca V] 5309 (wk); [Fe VII] 5721 (wk); [N II] 5755; He I 5876; [Fe VII] 6086 ([Ca V] 6087, blend?); [O I] 6300; [Fe X] 6376; H-alpha 6563; He I 6678; [Ar V] 7009; He I 7065; [Ar III] 7135. At the end of the spectrum, there is a hint of [Ar IV] 7236. The Balmer lines show double profiles at -630 and +650 km/s (+/-40 km/s), the peaks are narrow and the bulk of the profile is flat. The red peak is stronger in H-alpha but more nearly equal for H-beta. The He I lines show nearly identical multiple peak profiles with velocities of -640, -50, and +590 km/s (+/-30 km/s); the two extreme peaks are about equal and about 20% stronger than the middle peak. The [O III] lines show almost round-topped profile, although the extreme peaks are there as is the peak at -50 km/s but at low relative contrast. The line halfwidth at zero intensity is -1480 km/s. The [O III] 4959/5007 ratio is 2.9, consistent with the reported nebular phase (ATel #13815). The most striking features are the high ionization Fe lines. All have strongly double peaked profiles with almost no emission in the interval between the peaks, unlike the lower ionization [[Ne III], [O III] and [N II] lines. The Ar lines are similar to the [O III] lines. The ejecta appear to be strongly ionization stratified (see, for example, the appendix in Mason et al. 2018, ApJ, 853, 27; Shore et al. 2018, A&A, 619, A104). The [Fe X] profile has HWZI of about 900 km/s, somewhat narrower than the nebular lines. The lack of any ionization state above Fe^+9 suggests the hardest incident X-ray spectrum was around 0.3 keV (see also the non-detection described in ATel #13252). We thank David Boyd for discussions and guidance.

ARAS Nova Database