ATLAS18qqn (AT2018cow) - a bright transient spatially coincident with CGCG 137-068 (60 Mpc)
ATel #11727; S. J. Smartt, P. Clark K. W. Smith, O. McBrien, K. Maguire, D. O'Neil, M. Fulton, M. Magee, S. Prentice, C. Colin (Queen's University Belfast), J. Tonry, L. Denneau, B. Stalder, A. Heinze, H. Weiland, H. Flewelling (IfA, University of Hawaii), A. Rest (STScI),
on 17 Jun 2018; 22:22 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Stephen Smartt (s.smartt@qub.ac.uk)
Subjects: Optical, Cataclysmic Variable, Nova, Supernovae, Transient
Referred to by ATel #: 11729, 11732, 11734, 11736, 11737, 11738, 11740, 11741, 11742, 11743, 11744, 11748, 11749, 11750, 11751, 11752, 11753, 11757, 11758, 11759, 11760, 11761, 11766, 11767, 11772, 11773, 11774, 11775, 11776, 11781, 11782, 11785, 11788, 11789, 11792, 11793, 11794, 11795, 11796, 11799, 11801, 11808, 11809, 11810, 11813, 11818, 11819, 11822, 11836, 11843, 11862, 11868, 11891, 11921, 11950, 11956, 12030, 12067, 14105
ATLAS is a twin 0.5m telescope system on
Haleakala and Mauna Loa. Each unit has a single camera covering
28.9 square degree field of view and is
robotically surveying the sky every night.
Two filters are used, cyan and orange
(denoted c and o, all mags in AB system), more information is on http://www.fallingstar.com. While carrying out the primary mission for NEOs,
we search for and publicly report stationary transients (see
Tonry et al. ATel #8680, Tonry et al. 2018, PASP, 130, 4505).
We report a bright new transient source, which is spatially coincident
with the galaxy CGCG 137-068 (z=0.014145, 60 Mpc).
We discovered ATLAS18qqn (AT2018cow)
on
MJD 58285.441 == 2018-06-16 10:35:02 UTC
at
o = 14.76 +/- 0.10.
ATLAS18qqn
is offset by
3.46 arsec south,
4.86 arcsec west of the core of
CGCG 137-068.
If it were in the galaxy it would be M_o = -19.2.
It has a very fast rise time, with no detection on MJD=58281.5 to
o~19.5. Most likely it is a foreground CV in chance alignment with
the galaxy. There are a number of blue knots (possible foreground
stars or host galaxy features) visible in the Pan-STARRS and SDSS
images. The transient is close to but not coincident with any of
these sources.
There are no previous outbursts in ATLAS or any other survey that we
are aware of.
To rule this out being a very unusual transient in this galaxy
CGCG 137-068, or (more likely) confirm it as a foreground CV,
a spectrum is required.
The object details and pointer to the PS1 finder are available on the
TNS: https://wis-tns.weizmann.ac.il/object/2018cow
Name | ATLAS Name | RA (J2000) | Dec (J2000) | Disc. Date | Disc Mag
AT2018cow | ATLAS18qqn | 16:16:00.22 | +22:16:04.8 | 58285.441 | 14.76 o
