AstroNote 2020-55

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DRAFT
2020-03-01 21:58:02
Type: Object/s-Data/Analysis
AT 2020dih - a fast transient either in M94 (5 Mpc) or at z ~ 0.1
Authors: S. J. Smartt, K. W. Smith, S. Srivastav, J. Gillanders, O. McBrien, M. Fulton (Queen's University Belfast), L. Denneau, H. Flewelling, A. Heinze, J. Tonry, H. Weiland (IfA, University of Hawaii), B. Stalder (LSST) A. Rest (STScI), P. Clark, D. O'Neill, D. R. Young (Queen's University Belfast), D. E. Wright (University of Minnesota)
Source Group: ATLAS
Keywords: Supernova
Abstract:
We draw attention to the fast evolving transient AT2020dih from the combined ZTF and ATLAS survey data and encourage rapid spectroscopic classification (now at r = 19.7). The transient could be associated with the nearby galaxy M94 (at a distance of approximately 5 Mpc it would be 12kpc offset), or a more distant SDSS galaxy with a photometric redshift of z ~ 0.1. It has declined by 1.5 mag in 3 days, and the more distant redshift would be make it very unusual. A nova in M94 is possible, but spectroscopic confirmation is required to determine the redshift and type.

The combination of ATLAS and ZTF data has led to recent discoveries of interesting fast and faint objects (e.g. SN2018kzr: McBrien et al. 2019, ApJ 885, L23,  SN2019gsc : Srivastav et al. ApJL arXiv:2001.09722). 

We draw attention to the fast evolving transient AT2020dih from the combined ZTF and ATLAS survey data and encourage rapid spectroscopic classification.  

AT 2020dih was discovered by ZTF on 2020-02-22 (MJD=58901.429), see TNS Transient Report 62755. It is potentially associated with the nearby galaxy M94, offset by 514" S, 203" W or a projected distance of 12 kpc, assuming a distance to M94 of 5 Mpc (from NED). 

The transient peaked at g =18.6, o = 18.5  between 58905.5 - 58906.5, which would be an absolute mag of M = -10 and has faded by 1.5 mag in 3 days. The ZTF lightcurve is available through Lasair (Smith et al. 2019, RNASS, 3 26)

https://lasair.roe.ac.uk/object/ZTF20aaqhsil/

It is now at r =19.7 (58908.5) , and has reddened considerably. A nova in M95 is a possible explanation. 

The transient is 5 arcsec north of a faint, r=22.3  SDSS galaxy SDSS J125035.04+405833.5 with an uncertain photo z=0.11+/-0.08. At this redshift, it would also be around 12 kpc offset from the host and would have peaked at -19.8. The fast decline would be very unusual for an object of this luminosity. 

Spectroscopic confirmation is required to determine the host and confirm if this is a nova in M94 or other unusually fast evovling transient. A finder is attached. 

 

 

Show current TNS values
CatalogNameReported RAReported DECReported Obj-TypeReported RedshiftHost NameHost RedshiftRemarksTNS RATNS DECTNS Obj-TypeTNS Redshift
TNS2020dih12:50:35.091+40:58:39.1312:50:35.091+40:58:39.13