Spectroscopic classification of Gaia19dum as a highly reddened classical nova
ATel #13068; E. Aydi, J. Strader, L. Chomiuk, A. Kawash, K. V. Sokolovsky (MSU), Georgios Dimitriadis, Cesar Rojas-Bravo, Ryan Foley (UCSC), K. Z. Stanek, C. S. Kochanek (OSU), and B. J. Shappee (Univ. of Hawaii)
on 2 Sep 2019; 19:44 UT
Credential Certification: Elias Aydi (eaydi@saao.ac.za)
Subjects: Optical, Binary, Cataclysmic Variable, Nova, Star, Transient, Variables
We report on spectroscopic follow up of the optical transient Gaia19dum, which was was discovered by Gaia on 2019 Aug 24.89, at coordinates of 19:52:08.25 +27:42:20.88.
On 2019-08-02.14UT, we obtained a 450 s spectrum using the Kat Double spectrograph on the 3.0 m C. Donald Shane telescope at Lick observatory. The spectrum shows broad emission lines of H I, Fe II, and O I. We measure a FWHM of around 1800 km/s for Halpha. The overall spectrum is that of a classical nova eruption.
The nova was recovered in ASAS-SN (Shappee et al. 2014; Kochanek et al. 2017) with a first detection on Aug 18.45 at g=16.3, before fading to g=18.0 on Aug 23.43. The source is also detected in ZTF as ZTF19abqknsv, with a first detection on Aug 19.36 at r=13.3 and a most recent detection on Aug 28.26 with g=18.6. The nova is undetected in ZTF on Aug 15.22 and in Gaia on Aug 15.73, which constraints the nova to have occurred between Aug 15.73 and Aug 18.45. The ZTF color of the nova on Aug 22 is g-r = 3.3, suggesting the nova is highly reddened. The ZTF photometry came from the Lasair broker (Smith et al, 2019, RNAAS, 3, 26)
This is the 4th confirmed Galactic nova in 2019, yet the expected rate of novae in the Miky Way ranges somewhere between 20 to more than 50 novae per year (della Valle & Livio 1994, A&A, 286, 786, Darnley et al., 2006, MNRAS, 369, 257, Shafter 2017, ApJ, 834, 196). Peaking at g > 16 and declining rapidly, Gaia19dum makes a prototype of highly reddened, fast declining Galactic novae which can go undetected or confused with dwarf nova outbursts by the current all-sky surveys or individual observers. Detecting and classifying more similar novae has the potential to bridge the gap between the predicted and observed nova rates in the Galaxy.
