Four GRB supernovae at redshifts between 0.4 and 0.8

Abstract

Twenty years ago, GRB 980425/SN 1998bw revealed that long Gamma-Ray Bursts (GRBs) are physically associated with broad-lined type Ic supernovae. Since then more than 1000 long GRBs have been localized to high angular precision, but only in ∼ 50 cases the underlying supernova (SN) component was identified. Using the multi-channel imager GROND (Gamma-Ray Burst Optical Near-Infrared Detector) at ESO/La Silla, during the last ten years we have devoted a substantial amount of observing time to reveal and to study SN components in long-GRB afterglows.Here we report on four more GRB-SNe (associated with GRBs 071112C, 111228A, 120714B, and 130831A) which were discovered and/or followed-up with GROND and whose redshifts lie between z = 0.4 and 0.8. We study their afterglow light curves, follow the associated SN bumps over several weeks, and characterize their host galaxies. Using SN 1998bw as a template, the derived SN explosion parameters are fully consistent with the corresponding properties of the so-far known GRB-SN ensemble, with no evidence for an evolution of their properties as a function of redshift. In two cases (GRB 120714B/SN 2012eb at z = 0.398 and GRB 130831A/SN 2013fu at z = 0.479) additional Very Large Telescope (VLT) spectroscopy of the associated SNe revealed a photospheric expansion velocity at maximum light of about 40 000 and 20 000 km s −1 , respectively. For GRB 120714B, which was an intermediate-luminosity burst, we find additional evidence for a blackbody component in the light of the optical transient at early times, similar to what has been detected in some GRB-SNe at lower redshifts.

GRB 171010A/SN 2017htp: a GRB-SN at z = 0.33

“…We analysed the optical photometry and spectroscopy of GRB 171010A and SN 2017htp spanning nearly four months since its discovery. The supernova is confirmed both photometrically and spectroscopically and this event represents an example of the GRB-SN connection at moderately high redshift (Cano et al 2017;Klose et al 2019). We find that 0.33 M of nickel is required to reproduce the peak luminosity of SN 2017htp, with an ejecta mass of M ej = 4.1 ± 0.7 M and a kinetic energy of E K = 8.1 ± 2.5 × 10 51 erg.…”

Highly luminous supernovae associated with gamma-ray bursts

“…In this scenario, the optical afterglow behaves completely differently, of which prime examples are GRBs 070110 (Troja et al 2007) and 130831A (De Pasquale et al 2016b). These GRBs were otherwise completely unremarkable; GRB 130831A was also followed by a garden-variety Type Ic-BL SN, SN 2013fu (Cano et al 2014;Klose et al 2019). Therefore, even though this paper, together with G15 and K18B, shows strong evidence for a GRB central engine not involving a rapidly spinning BH, the exact connection between the ultra-long duration and the spectrally deviant, luminous SN remains a topic for further research.…”

“…We perform the SN fitting together with that of the late afterglow with the method of Zeh et al (2004) and give the results in the k, s formalism (see below). Those authors used the light curves of SN 1998bw as given by Galama et al (1998) as a template, and derived an analytical equation which is able to fit the data well (Klose et al 2019). We create SN 1998bw template light curves in the GROND bandpasses (as well as J from L14) and at the redshift of GRB 111209A, i.e.…”

Searching for Fermi GRB optical counterparts with the prototype Gravitational-wave Optical Transient Observer (GOTO)

“…where F is the afterglow flux, t is the time after the trigger and α is the power-law index with a typical value of ∼ 1.2 , we expect that they become too faint to be detected in one to two days after the trigger. However, as long GRBs are typically associated with supernovae, they rise long after the optical afterglow has faded and show much longer decay timescales in a few tens of days once the supernova has peaked in its emission (Woosley et al 1999;Klose et al 2019). We define a GRB-associated period as [t0,t0 +100,days], where t0 is the GRB trigger time.…”