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GROND followup of DLT17h/SN 2017ahn

ATel #10067; Ting-Wan Chen, Patricia Schady (MPE)
on 10 Feb 2017; 11:00 UT
Credential Certification: Ting-Wan Chen (jchen@mpe.mpg.de)

Subjects: Infra-Red, Optical, Supernovae, Transient

Referred to by ATel #: 10147

On behalf of the GROND SN team we observed the field of a Type II supernova DLT17h/SN 2017ahn in NGC3318 (Tartaglia et al. ATel #10058; Hosseinzadeh et al. ATel #10059) 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).

Observations started at 03:58 UT on 2017-02-09 (MJD = 57793.141), 1.2 days after the discovery and 2.3 days after the non-detection time reported by Tartaglia et al. (ATel #10058). We derive the following preliminary magnitudes (all in the AB system):

g' = 17.0 +- 0.1 mag,
r' = 17.2 +- 0.1 mag,
i' = 17.4 +- 0.1 mag,
z' = 17.5 +- 0.1 mag,
J = 17.3 +- 0.1 mag,
H = 17.8 +- 0.1 mag, and
K = 18.0 +- 0.2 mag.

The spectral energy distribution is very blue, which is consistent with bright UVOT detection (Tartaglia et al. ATel #10066).

Given magnitudes are calibrated against GROND zeropoint as well as 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.07 mag in the direction of the SN (Schlafly & Finkbeiner 2011).

We acknowledge excellent help in obtaining these data from the supporting astronomer and observer on La Silla, Sam Kim and Simon Steinmassl.