AstroNote 2020-107

Primary tabs

DRAFT
2020-05-21 17:09:21
Type: Object/s-Discovery/Classification
Pan-STARRS Search for Kilonovae: discovery of an unusual and intrinsically faint transient in NGC 6106 (26 Mpc)
Authors: M. Fulton, S. J. Smartt, K. W. Smith (QUB), K. C. Chambers, M. Huber (IfA, Hawaii), S. Srivastav, O. McBrien, D. R. Young, J. Gillanders, D. O'Neill, P. Clark, S. Sim (QUB), T. de Boer, J. Bulger, J. Fairlamb, C.-C. Lin, T. Lowe, E. Magnier, A. Schultz, R. J. Wainscoat, M. Willman (IfA), T.-W. Chen (Stockholm), D. E. Wright (University of Minnesota), C. Stubbs (Harvard), A. Rest (STScI)
Source Group: Pan-STARRS1
Abstract:
We are carrying out the "Pan-STARRS Search for Kilonovae" which is a focused search for intrinsically faint transients, or rapidly evolving transients in galaxies which are closer than 200 Mpc in the ongoing Pan-STARRS Near-Earth Object surveys (see Smartt et al. AstroNote 2019-48 for details).  Here we report the discovery of an intrinsically faint transient PS20dgq (AT2020kog) in the host galaxy NGC 6106, at a redshift of z = 0.005 or d = 26 Mpc (from NED). Its discovery magnitude (MJD = 58987.49) is w = 20.30 +/- 0.10, and hence an absolute magnitude of M_w = -11.90 +/- 0.18.

We are carrying out the "Pan-STARRS Search for Kilonovae" which is a focused search for intrinsically faint transients, or rapidly evolving transients in galaxies which are closer than 200 Mpc in the ongoing Pan-STARRS Near-Earth Object surveys (see Smartt et al. AstroNote 2019-48 for details). 

In normal survey mode, Pan-STARRS takes 4 x 45s exposures in w, i or z each night reaching 5 sigma magnitudes of w<22, i<21 and z<20.5 in each frame (see Chambers et al. 2016, 1612.05560). 

We report the discovery of an intrinsically faint transient PS20dgq (AT2020kog) in the host galaxy NGC 6106, at a redshift of z = 0.005 or d = 26 Mpc (from NED). The transient was discovered on MJD = 58987.49 (2019-05-18.49) at mag w = 20.30 +/- 0.10. It is offset from the host by 42.7" N, 9.1" E (a projected 5.8 kpc radius from the galaxy centre). At this distance the absolute magnitude is M_w = -11.90 (assuming m-M = 32.08 and foreground extinction of  A_w = 0.12).

There exists unusual pre-rise activity in the photometry of PS20dgq up to 25 days before discovery. This activity likely rules PS20dgq out as a kilonova candidate, however, combined with the intrinsic faintness this is still a peculiar transient event. A luminous stellar outburst is possible, or a rising supernova that would become detectable with ATLAS and ZTF. Spectroscopic classification is therefore strongly encouraged. A plot of the forced photometry is attached.

We will release AstroNotes for all these candidates and encourage spectroscopic classification or photometric follow-up.  A finder is attached. 

These discoveries are a byproduct of the Pan-STARRS NEO survey observations supported by the NASA Grants, including No. NNX14AM74G issued through the SSO Near-Earth Object Observations Program.

Show current TNS values
CatalogNameReported RAReported DECReported Obj-TypeReported RedshiftHost NameHost RedshiftRemarksTNS RATNS DECTNS Obj-TypeTNS Redshift
TNS2020kog [PS20dgq]16:18:47.655+07:25:16.83NGC 61060.00482916:18:47.652+07:25:16.86