Photometry of SN 2017cts/ASASSN-17em
ATel #10251; R. Konyves-Toth, J. Vinko (Konkoly Obs)
on 8 Apr 2017; 08:12 UT
Credential Certification: Jozsef Vinko (vinko@astro.as.utexas.edu)
Subjects: Optical, Supernovae
We report photometric observations of the recently discovered
Type Ia supernova SN 2017cts/ASASSN-17em (ATel #10241, #10242)
taken with the 60/90 cm Schmidt telescope through Bessell B,V,R,I filters
at Konkoly Observatory, Piszkesteto, Hungary on 2017 Apr 06.9 UT.
Photometry on the SN and several local comparison stars was computed
via PSF-fitting. The magnitudes of the local comparison stars were tied
to their PS1-photometry after
transforming the PS1 griz magnitudes to the Johnson-Cousins BVRI system
(Magnier et al. arXiv:1612.05242).
The following Vega-magnitudes have been obtained for SN 2017cts:
MJD B eB V eV R eR I eI
57849.94 16.107 0.059 16.165 0.011 16.043 0.029 16.079 0.027
Our data indicate that the SN has brightened by about 1 mag since its discovery
on 2017-04-02.46 UT (ATel #10241), confirming its pre-maximum phase reported by
D. Bersier (ATel #10242).
The color indices of SN 2017cts, after correcting for Milky-Way extinction,
are B-V = -0.086, V-R = 0.104 and V-I = 0.048, suggesting a normal Type Ia
supernova close to maximum light.
Adopting the Hubble-flow distance
D(3K CMB) = 80.7 +/- 5.7 Mpc for the presumed host galaxy
CGCG 299-048 NED01, the extinction-corrected absolute magnitudes of the SN are
M_B = -18.54 (+/-0.16), M_V = -18.45 (0.15), M_R = -18.55 (0.15) and M_I = -18.50 (0.15) mag,
consistent with those of a Type Ia supernova before maximum light.
