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Spectroscopic confirmation of ASASSN-17mt as a classical nova in the optically thick (Fe curtain) stage

ATel #10795; Paul Luckas, International Centre for Radio Astronomy Research, University of Western Australia -17mt Confirmed as a Classical Nova in the Iron Curtain Phase
on 28 Sep 2017; 19:59 UT
Distributed as an Instant Email Notice Novae
Credential Certification: S. N. Shore (shore@df.unipi.it)

Subjects: Optical, Nova

Referred to by ATel #: 10977

ASASSN-17mt (ATel #10772, #10785) has recently been announced as a nova candidate. We obtained a medium resolution spectrum (0.82A/px) using an Alpy600 spectrograph (single exposure, 600 sec, S/N of about 20 in the continuum from 5200-5600A) on 2017 Sept.28.77 UT that confirm this identification and show that the ejecta are optically thick and at moderately high velocity. Fe II 4923, 5018, 5169 have maximum absorption (P Cyg) radial velocities of -1600+/-100 km/s with red wings extending to -1000 km/s while the Balmer lines (Halpha-Hepsilon) show similar values for the absorption but broader red wings, reaching nearly the same velocity with a perceptible Balmer progression (a decrease of order 150 km/s passing to higher series lines). Neither He I nor Na ID are seen in emission although there is weak (resolution limited) IS absorption at low velocity. Si II 6347,6374 are present with weaker absorption (no terminal edge is seen on any P Cyg profile) with maximum velocity of about -1000 km/s. More precisely, the Si II absorption minimum is shifted from that of the Fe II lines by +300 km/s, similarly seen on all metal ion absorption troughs. No strong forbidden metal ion lines were detected, nor is there (yet) C I or C II, and [O I] is absent. The spectrum is typical of the opaque stage of the ejecta around or a bit after optical maximum. Spectroscopic monitoring is continuing.

A.R.A.S. Spectral Data Base