AstroNote 2020-106

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DRAFT
2020-05-18 22:46:44
Type: Object/s-Discovery/Classification
Pan-STARRS Search for Kilonovae: discovery of an intrinsically faint transient in GALEXASC J143604.85-025300.6 (185 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 PS20dfb (AT2020kfr) in the host galaxy GALEXASC J143604.85-025300.6, at a redshift of z = 0.043 or d = 185 Mpc (from NED). Its discovery magnitude (MJD = 58985.42) is w = 21.03 +/- 0.17, and hence an absolute magnitude of M_w = -15.51 +/- 0.23.

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 PS20dfb (AT2020kfr) in the host galaxy GALEXASC J143604.85-025300.6, at a redshift of z = 0.043 or d = 185 Mpc (from NED). The transient was discovered on MJD = 58985.42 (2020-05-16.42) at mag m_w = 21.03 +/- 0.17. There was no detection by Pan-STARRS on MJD = 58960.49 (2020-04-21.49) suggesting this is not an old supernova. It is offset from the host by 8.6" N, 9.7" W (a projected 12.0 kpc radius from the galaxy centre). At this distance, the absolute magnitude is M_w = -15.51 (assuming m-M = 36.34 and foreground extinction of A_w = 0.20). 

PS20dfb was followed up by Pan-STARRS on MJD = 58987.33 (2020-05-18.33) and observed at mag m_w = 21.13 +/- 0.15. This small change in magnitude two days after discovery rules the transient out as a kilonova candidate. However, spectroscopic classification is still encouraged. 

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
TNS2020kfr [PS20dfb]14:36:04.400-02:52:52.43GALEXASC J143604.85-025300.60.042914:36:04.400-02:52:52.43