iPTF17cw: An Engine-driven Supernova Candidate Discovered Independent of a Gamma-Ray Trigger

• Published in: The Astrophysical journal Vol. 847; no. 1; pp. 54 - 67
• Main Authors: Corsi, A., Cenko, S. B., Kasliwal, M. M., Quimby, R., Kulkarni, S. R., Frail, D. A., Goldstein, A. M., Blagorodnova, N., Connaughton, V., Perley, D. A., Singer, L. P., Copperwheat, C. M., Fremling, C., Kupfer, T., Piascik, A. S., Steele, I. A., Taddia, F., Vedantham, H., Kutyrev, A., Palliyaguru, N. T., Roberts, O., Sollerman, J., Troja, E., Veilleux, S.
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 20-09-2017; IOP Publishing
• Subjects: Astrophysics; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BOLOMETERS; BY-PRODUCTS; CLASSIFICATION; CONFIGURATION; COSMIC GAMMA BURSTS; Ejecta; GAMMA RADIATION; Gamma ray bursts; Gamma rays; gamma-ray burst: individual (GRB 161228B); GRAVITATIONAL WAVES; Gravity waves; Light curve; LUMINOSITY; Radio; Radio observation; Relativism; Relativistic effects; RELATIVISTIC RANGE; Supernova; supernovae: individual (iPTF17cw); TYPE I SUPERNOVAE; VISIBLE RADIATION; X RADIATION; X-RAY DETECTION
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.3847/1538-4357/aa85e5

We present the discovery, classification, and radio-to-X-ray follow-up observations of iPTF17cw, a broad-lined (BL) type Ic supernova (SN) discovered by the intermediate Palomar Transient Factory (iPTF). Although it is unrelated to the gravitational wave trigger, this SN was discovered as a happy by-product of the extensive observational campaign dedicated to the follow-up of Advanced LIGO event GW 170104. The spectroscopic properties and inferred peak bolometric luminosity of iPTF17cw are most similar to the gamma-ray-burst (GRB)-associated SN, SN 1998bw, while the shape of the r-band light curve is most similar to that of the relativistic SN, SN 2009bb. Karl G. Jansky Very Large Array (VLA) observations of the iPTF17cw field reveal a radio counterpart 10 times less luminous than SN 1998bw, and with a peak radio luminosity comparable to that of SN 2006aj/GRB 060218 and SN 2010bh/GRB 100316D. Our radio observations of iPTF17cw imply a relativistically expanding outflow. However, further late-time observations with the VLA in its most extended configuration are needed to confirm fading of the iPTF17cw radio counterpart at all frequencies. X-ray observations carried out with Chandra reveal the presence of an X-ray counterpart with a luminosity similar to that of SN 2010bh/GRB 100316D. Searching the Fermi catalog for possible γ-rays reveals that GRB 161228B is spatially and temporally compatible with iPTF17cw. The similarity to SN 1998bw and SN 2009bb, the radio and X-ray detections, and the potential association with GRB 161228B all point to iPTF17cw being a new candidate member of the rare sample of optically discovered engine-driven BL-Ic SNe associated with relativistic ejecta.