SALT high resolution optical spectroscopy of Nova Mus 2018 = PNV J11261220-6531086

ATel #11221; E. Aydi (South African Astronomical Observatory, University of Cape Town), D. A. H. Buckley (SAAO), S. Mohamed (SAAO, UCT), P. A. Whitelock (SAAO, UCT)
on 24 Jan 2018; 17:59 UT
Credential Certification: David Buckley (dibnob@saao.ac.za)

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The High Resolution Spectrograph (HRS; Crause et al. 2014, Proc SPIE, 91476) mounted on the Southern African Large Telescope (SALT) was used to obtain observations of nova Muscae 2018 (PNV J11261220-6531086) on 2018 January 21 .36 (UTC; HJD 2458139.86). The observations were taken in the MR mode of HRS, covering a spectral range of 3800-8900 Å at a resolution of R ~ 40000. The nova was discovered on 2018 January 14 .5 (CBET #4472) at V = 7.0. On the same day a low resolution spectrum was obtained confirming the nova classification and showing features of the Fe II spectroscopic class. The SALT data reported here were reduced with the SALT HRS MIDAS pipeline (Kniazev et al. 2016, MNRAS 459, 3068).

The SALT HRS spectrum is consistent with the Fe II classification, showing strong permitted lines of H I, Fe II, O I, Ca II, Na I, Mg II, and forbidden lines of O I (see below a full list of the line identification). The lines have rounded profiles accompanied with P Cygni absorption features, characteristic of an optically thick ejecta and typical for Fe II class novae. The Balmer (Hβ and Hα) lines consist of: (1) a main emission, moderately broad, component with a FWHM = 1700 ± 100 km/s; (2) two absorption components at -750 ± 50 km/s and -1700 ± 50 km/s where the higher velocity absorption component is broader; (3) a second blue-emission-component with a FWHM = 320 ± 30 km/s at around -1100 ± 50 km/s; (4) a red emission wing extending to more than 2600 km/s. The features and their velocities are consistent with the measurements reported in ATel #11183. These features are also easily identifiable in the Fe II (42) multiplet (the strongest Fe II emissions) and in the O I 7773 line.

Line identifications:

H I: 3970, 4102, 4340, 4861 , and 6563Å
Ca II: 3934, 3968, 8498, 8542 , and 8662Å
Na I: 5686 and 5892Å
O I: 7773 and 8446Å
[O I]: 5577, 6300, and 6364Å
Mg I: 5528Å
Mg II: 4481 and 8232Å

Fe II:
Multiplet (27): 4233, 4303, 4352 , and 4417Å
Multiplet (28): 4179 and 4297Å
Multiplet (37): 4491, 4515, 4556 , and 4629Å
Multiplet (38): 4508, 4523, 4549 , and 4584Å
Multiplet (42): 4924, 5018, and 5169Å
Multiplet (46): 5991 and 6084Å
Multiplet (48): 5265, 5317, 5363 and 5414Å
Multiplet (49): 5198, 5235, 5276, 5317 and 5425Å
Multiplet (55): 5535Å
Multiplet (73): 7462Å while 7308Å might be blended with atmospheric absorption.
Multiplet (74): 6148, 6248, 6417 and 6456Å

Possible lines: Al II4663Å, Si II 5958/79Å, N I 6486Å
Unidentified features at: 4660, 6715, 6810 and 8717Å