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Observations of ATLAS17grw/AT2017eod with GROND

ATel #10483; T.-W. Chen (MPE), S. J. Smartt, K. W. Smith, D. Young (QUB), J. Tonry, B. Stalder, L. Denneau., A. Heinze, H. Weiland (IfA, Univ. of Hawaii), A. Rest (STScI)
on 11 Jun 2017; 22:45 UT
Credential Certification: Ting-Wan Chen (jchen@mpe.mpg.de)

Subjects: Infra-Red, Optical, Supernovae, Transient

As part of the broad ePESSTO (www.pessto.org) collaboration we observed ATLAS17grw/AT2017eod (Tonry et al. AT #11916) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m MPG telescope at the ESO La Silla Observatory (Chile). Targets were supplied by the ATLAS survey, see Tonry et al. (2011, PASP, 123, 58) and Tonry et al. (ATel #8680), and additional details can be obtained from the IAU Transient Name Server.

Observations started at 07:16 UT on 2017-06-10 (MJD = 57914.303), 2.7 days after the ATLAS discovery. We derive the following magnitudes (all in the AB system):

ATLAS17grw/AT2017eod:
g' = 17.08 +/- 0.01 mag,
r' = 16.96 +/- 0.02 mag,
i' = 17.31 +/- 0.04 mag,
z' = 17.14 +/- 0.03 mag,
J = 17.74 +/- 0.02 mag,
H = 17.84 +/- 0.05 mag, and
K = 17.91 +/- 0.10 mag.

Given magnitudes are calibrated against PS1 field stars as well as 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.02 mag in the direction of the transients (Schlafly & Finkbeiner 2011).

We fitted our colour SED assuming a black body, which indicates a temperature of 8900 +/- 800 K. If the underlying galaxy (2dFGRS S006Z051) is the host of ATLAS17grw/AT2017eod at the redshift of 0.039400 (via NED), which indicates an absolute magnitudes of the host is -16.7 mag and the transient is -19.1 mag. However, there is no close pre-discovery non-detection date from ATLAS and thus no good explosion constraint.

We acknowledge excellent help in obtaining these data from Simona Ciceri on La Silla.