arXiv subjects

Christina C. Thone

Publications and source records attributed to Christina C. Thone.

3 recordsLinked to original sources

arXiv2026

GRB 220706A: a gamma-ray burst with a month-long engine and a luminous supernova

While the progenitors of many long gamma-ray bursts (GRBs) are well established as the core collapse of very massive, envelope-stripped, rapidly-rotating stars, it has been suggested that bursts at the extremely long end of the duration distribution may be a separate population of `ultra-long' GRBs. With durations of thousands of seconds or more, these bursts are difficult to reconcile with the engine timescales expected from the compact Wolf-Rayet stars that are typically assumed to produce more `standard' long GRBs. Here, we present observations of GRB~220706A, where X-ray follow-up reveals flaring episodes that last until $\approx 51$ days after trigger. At the measured redshift of $z = 0.8577$, this corresponds to 27 days in the GRB rest frame, and represents the latest central engine activity ever observed in a GRB by a margin of $\approx 21$ rest-frame days. We also identify a likely supernova (SN) which, when accounting for the inferred optical extinction of $0.9 \leq A_V \leq 3.6$ mag (constrained by indirect arguments), has a peak absolute magnitude of $M_r \leq -20.25$, resembling the energetic SN\,2011kl found accompanying ultra-long GRB\,111209A, and consistent with super-luminous SNe. We discuss the implications GRB~220706A has for ultra-long GRB progenitor models and possible powering mechanisms for the extremely late central engine activity.

astro-ph.HE↗

arXiv2012

The properties of the 2175AA extinction feature discovered in GRB afterglows

The unequivocal, spectroscopic detection of the 2175 bump in extinction curves outside the Local Group is rare. To date, the properties of the bump have been examined in only two GRB afterglows (GRB 070802 and GRB 080607). In this work we analyse in detail the detections of the 2175 extinction bump in the optical spectra of the two further GRB afterglows: GRB 080605 and 080805. We gather all available optical/NIR photometric, spectroscopic and X-ray data to construct multi-epoch SEDs for both GRB afterglows. We fit the SEDs with the Fitzpatrick & Massa (1990) model with a single or broken PL. We also fit a sample of 38 GRB afterglows, known to prefer a SMC-type extinction curve, with the same model. We find that the SEDs of GRB 080605 and GRB 080805 at two epochs are fit well with a single PL with a derived extinction of A_V = 0.52(+0.13 -0.16) and 0.50 (+0.13 -0.10), and 2.1(+0.7-0.6) and 1.5+/-0.2 respectively. While the slope of the extinction curve of GRB 080805 is not well-constrained, the extinction curve of GRB 080605 has an unusual very steep far-UV rise together with the 2175 bump. Such an extinction curve has previously been found in only a small handful of sightlines in the MW. One possible explanation of such an extinction curve may be dust arising from two different regions with two separate grain populations, however we cannot distinguish the origin of the curve. We finally compare the four 2175 bump sightlines to the larger GRB afterglow sample and to Local Group sightlines. We find that while the width and central positions of the bumps are consistent with what is observed in the Local Group, the relative strength of the detected bump (A_bump) for GRB afterglows is weaker for a given A_V than for almost any Local Group sightline. Such dilution of the bump strength may offer tentative support to a dual dust-population scenario.

astro-ph.CO↗

arXiv2012

VLT/X-shooter spectroscopy of the candidate black-hole X-ray binary MAXI J1659-152 in outburst

We present the optical to near-infrared spectrum of MAXI J1659-152, during the onset of its 2010 X-ray outburst. The spectrum was obtained with X-shooter on the ESO - Very Large Telescope (VLT) early in the outburst simultaneous with high quality observations at both shorter and longer wavelengths. At the time of the observations, the source was in the low-hard state. The X-shooter spectrum includes many broad (~2000 km/s), double-peaked emission profiles of H, HeI, HeII, characteristic signatures of a low-mass X-ray binary during outburst. We detect no spectral signatures of the low-mass companion star. The strength of the diffuse interstellar bands results in a lower limit to the total interstellar extinction of Av ~ 0.4 mag. Using the neutral hydrogen column density obtained from the X-ray spectrum we estimate Av ~1 mag. The radial-velocity structure of the interstellar NaI D and CaII H & K lines results in a lower limit to the distance of ~ 4 +/- 1 kpc, consistent with previous estimates. With this distance and Av, the dereddened spectral energy distribution represents a flat disk spectrum. The two subsequent 10 minute X-shooter spectra show significant variability in the red wing of the emission-line profiles, indicating a global change in the density structure of the disk, though on a timescale much shorter than the typical viscous timescale of the disk.

astro-ph.HE↗