Palomar Gattini-IR confirmation of a highly reddened Galactic nova PGIR20fbe/Gaia19buy/AT2019flb missed in 2019

ATel #14657; K. De (Caltech), D. Perley (LJMU), I. Andreoni (Caltech), M. M. Kasliwal (Caltech), M. Hankins (Caltech), J. Jencson (Arizona), J. Sokoloski (Columbia), M. Ashley (UNSW), A. Babul (Columbia), V. Karambelkar (Caltech), R. M. Lau (ISAS/JAXA), A. Moore (ANU), E. O. Ofek (Weizmann), M. Sharma (Columbia), J. Soon (ANU), R. Soria (UCAS/Sydney), T. Travouillon (ANU) on behalf of the Palomar Gattini-IR team
on 23 May 2021; 21:28 UT
Credential Certification: Kishalay De (kde@astro.caltech.edu)

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We report spectroscopic confirmation of a highly reddened nova missed in 2019. The source was identified as part of an archival search for large amplitude Galactic plane transients in data from the Palomar Gattini-IR survey (PGIR; Moore & Kasliwal 2019; De et al. 2020), using the methods described in De et al. (2021).

In early commissioning data of PGIR, we identified the source PGIR 20fbe detected at a magnitude of J ~ 11.9 mag on UT 2019-06-07, which faded to J ~ 12.9 mag on UT 2019-06-10. The source did not pass the criteria defined for the nova search in De et al. (2021) since it was detected during the period of reference image generation, and before the official start of the survey (UT 2019-07-02). The source was first reported to the Transient Name Server by Gaia as AT2019flb on UT 2019-05-16 without spectroscopic follow-up. The source was also detected in ZTF data as ZTF19aaontsz with the eruption detected from UT 2019-04-02. The source was detected in ZTF at a magnitude of r ~ 17.6 mag at the time of the PGIR detection, suggesting a r - J color of ~ 5.6 mag and A_V ~ 9 mag (see De et al. 2021). There is no source at this position in archival 2MASS images, and the integrated line of sight extinction is A_V ~ 9.5 mag (Schalfly et al. 2011).

On UT 2021-05-10, we obtained a spectrum of the source using the Low Resolution Imaging Spectrometer (Oke et al. 1995) on the Keck-I telescope. A source is detected only on the red side of the spectrum, showing broad emission lines of H alpha, [O II] 7325, [S III] 9069 and [S III] 9532, similar to novae in the nebular phase (e.g. Williams et al. 1994). We measure a full-width-half-maximum (FWHM) of ~ 800 km/s, although we caution that the signal-to-noise ratio is poor. Overall, the light curve and spectrum are consistent with a highly reddened nova missed in 2019.