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Spectroscopic classification of ASASSN-18ds as a classical nova

ATel #11360; L. Schmidtobreick (ESO), R. Ahumada (UNAB, Santiago), M. Dennefeld (IAP), A. Melo (Univ. de Valparaiso), J. Nascimento (UFRGS, Porto Alegre), G. Navarro (UNAB, Santiago), P. Pessi (Inst. de Astrofisica, La Plata), J. Quirola (PUC, Santiago), E. Sani (ESO), F. Surot (ESO), M. J. Ubeira (ESO)
on 26 Feb 2018; 23:09 UT
Credential Certification: Linda Schmidtobreick (lschmidt@eso.org)

Subjects: Optical, Nova

Referred to by ATel #: 11364, 11365

We report the classification of the transient ASASSN-18ds, detected by the All Sky Automated Survey for SuperNovae (ASAS-SN, Shappee et al. 2014) on 2018-02-24.36 at V~14.3 (Stanek et al. 2018, ATel #11348). Three consecutive observations of 180s, 60s and 80s starting on 2018-02-25 at 09:47 UT were performed with EFOSC2 and Grism 13 (3985-9315, 18 A resolution) mounted on the ESO New Technology Telescope at La Silla. The spectrum is dominated by the strong emission blend of Halpha and [NII]. In addition to the Balmer lines, strong FeII emission lines are present, blended with their respective blue-shifted absorption lines. We interpret the spectrum as that of an FeII-class nova during the pre-maximum phase. Unfortunately, the object is slightly saturated on the R acquisition image. Comparing with the brightest star in the field, USNO 0450.26357218, which is not saturated, we find that the nova is brighter than R=12.4mag during our observation. This confirms that it is still on the rise to maximum. The observations were taken and reduced by students of the ESO/NEON observing school 2018.