Rapid Response Mode observations of GRB 160203A: Looking for fine-structure line variability at z = 3.52
Context.
Gamma-ray bursts are the most energetic known explosions. Although they fade rapidly, they give us the opportunity to measure redshift and important properties of their host galaxies. We report the photometric and spectroscopic study of the Swift GRB 160203A at z = 3.518, and its host galaxy. Fine-structure absorption lines, detected in the afterglow at different epochs, allow us to investigate variability due to the strong fading background source.
Aims.
We obtained two optical to near-infrared spectra of the GRB afterglow with X-shooter on ESO/VLT, 18 minutes and 5.7 hours after the burst, allowing us to investigate temporal changes of fine-structure absorption lines.
Methods.
We measured H I column density log N(HI/cm–2) = 21.75 ± 0.10, and several heavy-element ions along the GRB sightline in the host galaxy, among which Si II, Al II, Al III, C II, Ni II, Si IV, C IV, Zn II and Fe II, and Fe II∗ and Si II∗ fine-structure transitions from energetic levels excited by the afterglow, at the common redshift z = 3.518. We measured [M/H]TOT = –0.78 ± 0.13 and a [Zn/Fe]FIT = 0.69 ± 0.15, representing the total (dust corrected) metallicity and dust depletion, respectively. We detected additional intervening systems along the line of sight at ɀ = 1.03, ɀ = 1.26, ɀ = 1.98, ɀ = 1.99, ɀ = 2.20, and ɀ = 2.83. We could not measure significant variability in the strength of the fine-structure lines throughout all the observations and determined an upper limit for the GRB distance from the absorber of d < 300 pc, adopting the canonical UV pumping scenario. However, we note that the quality of our data is not sufficient to conclusively rule out collisions as an alternative mechanism.
Results.
GRB 160203A belongs to a growing sample of GRBs with medium resolution spectroscopy, provided by the Swift/X-shooter legacy programme, which enables a detailed investigation of the interstellar medium in high-redshift GRB host galaxies. In particular, this host galaxy shows relatively high metal enrichment and dust depletion already in place when the universe was only 1.8 Gyr old.
Funding
Carlsberg Foundation Reintegration Fellowship Grant CF21-0103
Interstellar one: one vision for the Interstellar Medium at all cosmic times
Swiss National Science Foundation
Find out more...Spanish National Research Project RTI2018-098104-J-I00 (GRBPhot)
History
Citation
Rapid Response Mode observations of GRB 160203A: Looking for fine-structure line variability at z = 3.52 G. Pugliese, A. Saccardi, V. D’Elia, S. D. Vergani, K. E. Heintz, S. Savaglio, L. Kaper, A. de Ugarte Postigo, D. H. Hartmann, A. De Cia, S. Vejlgaard, J. P. U. Fynbo, L. Christensen, S. Campana, D. van Rest, J. Selsing, K. Wiersema, D. B. Malesani, S. Covino, D. Burgarella, M. De Pasquale, P. Jakobsson, J. Japelj, D. A. Kann, C. Kouveliotou, A. Rossi, N. R. Tanvir, C. C. Thöne and D. Xu A&A, 690 (2024) A35Author affiliation
College of Science & Engineering/Physics & AstronomyVersion
- VoR (Version of Record)
Published in
Astronomy & AstrophysicsVolume
690Pagination
A35 - A35Publisher
EDP Sciencesissn
0004-6361eissn
1432-0746Acceptance date
2024-06-24Copyright date
2024Available date
2024-10-30Publisher DOI
Language
enPublisher version
Deposited by
Professor Nial TanvirDeposit date
2024-10-24Rights Retention Statement
- No