Palomar Gattini-IR archival discovery of the bright NIR transient PGIR20ekz/AT2019aafo: Spectroscopic confirmation of a highly reddened Galactic nova missed in 2019
ATel #14014; K. De (Caltech), M. Hankins (Caltech), I. Andreoni (Caltech), S. Anand (Caltech), M. M. Kasliwal (Caltech), 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 (NAOC), T. Travouillon (ANU) on behalf of the Palomar Gattini-IR team
on 15 Sep 2020; 19:15 UT
Credential Certification: Kishalay De (kde@astro.caltech.edu)
Subjects: Infra-Red, Optical, Cataclysmic Variable, Nova, Transient
During an archival search of early commissioning data of the Palomar Gattini-IR all-sky NIR survey (De et al. 2020; Moore & Kasliwal 2019), we discovered a bright NIR transient PGIR20ekz (AT2019aafo) at J = 8.6 +/- 0.02 Vega mag, first detected on 2019-07-21 at J2000 coordinates
RA 17:38:35.0
Dec -25:19:03.5
corresponding to a Galactic latitude of 3.2 degrees. The integrated extinction along this line of sight is ~ 7 mags in g band, ~4.5 mags in r band and ~1.5 mags in J band (Schlafly et al. 2011). No source was detected on 2019-07-08 to a depth of 11.5 Vega mag.
The transient was also detected in the public ZTF alert stream (Bellm et al. 2019) as ZTF19abgnhzj at g = 15 mag on UT 2019-07-16, and faded to g = 18 mag in 40 days, suggesting a fast evolving and highly reddened Galactic transient.
On UT 2020-09-15, we obtained an optical spectrum of the source using LRIS on the Keck-I telescope (Oke et al. 1995). In the extracted spectrum, we find broadened emission lines of H alpha, [O III] and [Ca II] with FWHM widths of ~ 2600 km/s. The large amplitude, fast evolution and late-time spectroscopic properties of the source are consistent with a highly reddened and fast Galactic nova missed in 2019.
Given the late phase of the source, we encourage multi-wavelength follow-up in other wavebands.
