Palomar Gattini-IR classification of a new highly reddened symbiotic star in outburst

ATel #14475; K. De (Caltech), D. Stern (JPL), L. Hillenbrand (Caltech), M. M. Kasliwal (Caltech), M. Hankins (Arkansas Tech), 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 (NAOC), T. Travouillon (ANU) on behalf of the Palomar Gattini-IR team
on 19 Mar 2021; 19:59 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Kishalay De (kde@astro.caltech.edu)

Tweet

We report the classification of a highly reddened transient detected by the Palomar Gattini-IR survey (Moore & Kasliwal 2019; De et al. 2020). The source was identified as part of an ongoing campaign to find large amplitude Galactic plane transients (De et al. 2021).

The source PGIR 20djo was first saved as a nova candidate in April 2020 at a magnitude of J = 13.1 +/- 0.2 Vega mag, and at coordinates

RA = 19:03:56.2; Dec = +09:01:58.5

following a brightness increase of ~ 1.5 mag from the template image. Low amplitude variability is detected dating back to the start of the survey in 2019. The source is coincident with a red source in PS1 images, with a r-band magnitude of ~ 20 mag. The source did not brighten subsequently during 2020.

The source re-appeared significantly brighter after solar conjunction in 2021 as a magnitude of J = 11.3 Vega mag, assigned for follow-up and reported to the Transient Name Server as AT 2019aajn. The 2021 brightening was also detected in ZTF data (Bellm et al. 2019; Masci et al. 2019) as ZTF18aaywchl, which shows a long lived outburst starting as early as 2018. The source was also reported in ATel #14376 as DDE 175, and is characterized by a red color of g - J ~ 7 mags.

We obtained an optical spectrum of the source with the Double Spectrograph on the Palomar 200-inch telescope. The spectrum shows a very red continuum superimposed with strong Balmer emission lines, and emission lines of He II, O I, Fe II and Ca II. We also detect likely absorption features of TiO near 8500 - 9000 Angstroms. Overall, the spectrum and light curve is consistent with a new reddened symbiotic star in outburst.

We encourage follow-up in all bands, in particular, the near-infrared given the highly reddened nature of the source.