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GTC and Swift observations of SN 2017dcc: Revised redshift & X-ray upper limit

ATel #10319; D. A. Kann, L. Izzo, Z. Cano, A de Ugarte Postigo, C. C. Thoene (all IAA-CSIC), and S. Schulze (Weizmann)
on 24 Apr 2017; 20:29 UT
Credential Certification: David Alexander Kann (kann@tls-tautenburg.de)

Subjects: Supernovae

We obtained observations of the broad-lined type Ic SN 2017dcc (Guiterrez et al., ATel #10313) with the 10.4m GTC on La Palma, Canary Islands, Spain, as well as with XRT and UVOT on the Swift space telescope.

We obtained GTC spectroscopy (exposure time 3 x 180 s) starting at 23:04:07 UT on April 23, 2017 with grism 1000B. In the spectrum, taken at the parallactic angle, we detect multiple emission lines from the host galaxy (Halpha, [OIII] 5007, Hbeta) at a redshift z = 0.0245. We note that this is significantly closer than the redshift given in ATel #10313 (z = 0.043, 107 Mpc vs. 191 Mpc; Delta(m-M) = 1.26 mag). No emission lines are detected at z = 0.043. We confirm the classification as a broad-lined type Ic SN, finding similarities to SN 1998bw and SN 2003jd around peak light. Spectral classifications were performed with SNID (Blondin & Tonry, 2007, ApJ, 666, 1024) and GELATO (Harutyunyan et al., 2008, A&A, 488, 383).

We obtained 964 s of Swift XRT and UVOT DDT observations starting at 07:31 UT on April 23, 2017. The SN is not detected in X-rays to a limit of 1.17E-02 ct/s. Assuming a power-law spectral function with photon index gamma=2 and Galactic absorption of NH=3.58E+20 cm^-2, this implies a limit of < 6.4E+41 erg/s.

The SN is clearly detected in five of the six UVOT filters, we find:

Filter Exptime(s) Mag(Vega) Significance(sigma)
v 78.52 15.98 +/- 0.07 16.7
b 78.52 16.72 +/- 0.06 21.9
u 78.51 16.69 +/- 0.07 15.7
uvw1 157.26 17.42 +/- 0.11 9.8
uvm2 30.74 > 17.82 2.9
uvw2 314.73 17.58 +/- 0.09 12.9

Further observations are planned.