R. Sánchez-Ramírez
A5084015602- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- SAS software applications and methods
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Galaxies: Formation, Evolution, Phenomena
- Geophysics and Gravity Measurements
- Astrophysics and Star Formation Studies
- Particle Detector Development and Performance
- Solar and Space Plasma Dynamics
- Adaptive optics and wavefront sensing
- Calibration and Measurement Techniques
- Advanced X-ray and CT Imaging
- Nuclear Physics and Applications
- Atmospheric Ozone and Climate
- Radio Astronomy Observations and Technology
- Neutrino Physics Research
- X-ray Diffraction in Crystallography
- High-pressure geophysics and materials
- Isotope Analysis in Ecology
- CCD and CMOS Imaging Sensors
Instituto de Astrofísica de Andalucía
2015-2025
Institute for Space Astrophysics and Planetology
2017-2024
Consejo Superior de Investigaciones Científicas
2011-2024
Universidad Tecnológica de Querétaro
2023
Autonomous University of Queretaro
2023
Aryabhatta Research Institute of Observational Sciences
2021
National Institute for Astrophysics
2019
University of the Basque Country
2015-2016
Ikerbasque
2015-2016
University of California, Santa Cruz
2014
Variable X-ray and gamma-ray emission is characteristic of the most extreme physical processes in Universe, studying sources these energetic photons has been a major driver astronomy for past 50 years. Here we present multiwavelength observations unique selected transient, discovered by Swift, which was accompanied bright across electromagnetic spectrum, whose properties are unlike any previously observed source. We pinpoint event to center small, star-forming galaxy at redshift z=0.3534....
We present comprehensive multiwavelength observations of three gamma-ray bursts (GRBs) with durations several thousand seconds. demonstrate that these events are extragalactic transients; in particular we resolve the long-standing conundrum distance GRB 101225A (the "Christmas-day burst"), finding it to have a redshift z=0.847, and showing two apparently similar (GRB 111209A 121027A) lie at z=0.677 z=1.773 respectively. The systems show extremely unusual X-ray optical lightcurves, very...
We present data and initial results from VLT/X-Shooter emission-line spectroscopy of 96 galaxies selected by long γ-ray bursts (GRBs) at 0.1 <z< 3.6, the largest sample GRB host spectra available to date. Most our GRBs were detected Swift 76% are 0.5 2.5 with a median zmed ~ 1.6. Based on Balmer and/or forbidden lines oxygen, nitrogen, neon, we measure systemic redshifts, star formation rates (SFR), visual attenuations (AV), oxygen abundances (12 + log (O/H)), widths (σ). study hosts up z...
GRB 160821B is a short duration gamma-ray burst (GRB) detected and localized by the Neil Gehrels Swift Observatory in outskirts of spiral galaxy at z=0.1613, projected physical offset 16 kpc from galaxy's center. We present X-ray, optical/nIR radio observations its counterpart model them with two distinct components emission: standard afterglow, arising interaction relativistic jet surrounding medium, kilonova, powered radioactive decay sub-relativistic ejecta. Broadband modeling afterglow...
We report the results of our observing campaign on GRB140903A, a nearby (z=0.351) short duration (T90~0.3 s) gamma-ray burst discovered by Swift. monitored X-ray afterglow with Chandra up to 21 days after burst, and detected steeper decay flux approximately 1 day. Continued monitoring at optical radio wavelengths showed similar in nearly same time, we interpret it as evidence narrowly collimated jet. By using standard fireball model describe evolution, derive jet opening angle 5 deg...
ABSTRACT A significant fraction (30 per cent) of well-localized short gamma-ray bursts (sGRBs) lack a coincident host galaxy. This leads to two main scenarios: (i) that the progenitor system merged outside visible light its host, or (ii) sGRB resided within faint and distant galaxy was not detected by follow-up observations. Discriminating between these scenarios has important implications for constraining formation channels neutron star mergers, rate environments gravitational wave sources,...
Long-duration gamma-ray bursts (GRBs) at z < 1 are found in most cases to be accompanied by bright, broad-lined Type Ic supernovae (SNe Ic-BL). The highest-energy GRBs mostly located higher redshifts, where the associated SNe hard detect observationally. Here, we present early and late observations of optical counterpart very energetic GRB 130427A. Despite its moderate redshift, = 0.3399 ± 0.0002, 130427A is high end energy distribution, with an isotropic-equivalent release Eiso ∼ 9.6 × 1053...
Short duration gamma-ray bursts (SGRBs) are thought to be related the violent merger of compact objects, such as neutron stars or black holes, which makes them promising sources gravitational waves. The detection a 'kilonova'-like signature associated Swift-detected GRB 130603B has suggested that this event is result object merger. Our knowledge on SGRB been, until now, mostly based absence supernova signatures and analysis host galaxies they cannot always securely associated. Further...
At low redshift, a handful of gamma-ray bursts (GRBs) have been discovered with peak luminosities ($L_{\rm iso} < 10^{48.5}~\rm{erg\,s}^{-1}$) substantially lower than the average more distant ones > 10^{49.5}~\rm{erg\,s}^{-1}$). The properties several low-luminosity (low-$L$) GRBs indicate that they can be due to shock break-out, as opposed emission from ultrarelativistic jets. Owing this, it is highly debated how both populations are connected, and whether there continuum between them....
GRB 130925A was an unusual gamma ray burst (GRB), consisting of three distinct episodes high-energy emission spanning ∼20 ks, making it a member the proposed category ‘ultralong’ bursts. It also in that its late-time X-ray observed by Swift very soft, and showed strong hard-to-soft spectral evolution with time. This evolution, rarely seen afterglows, can be well modelled as dust-scattered echo prompt emission, stringent limits on contribution from normal afterglow (i.e. external shock)...
Observations of the afterglows long gamma-ray bursts (GRBs) allow study star-forming galaxies across most cosmic history. Here we present observations GRB 111008A from which can measure metallicity, chemical abundance patterns, dust-to-metals ratio and extinction host galaxy at z=5.0. The absorption system is a damped Lyman-alpha absorber (DLA) with very large neutral hydrogen column density log N(HI)/cm^(-2) = 22.30 +/- 0.06, metallicity [S/H]= -1.70 0.10. It highest redshift such precise...
We present the discovery of molecular hydrogen (H_2), including presence vibrationally-excited H_2^* in optical spectrum afterglow GRB 120815A at z=2.36 obtained with X-shooter VLT. Simultaneous photometric broad-band data from GROND and X-ray observations by Swift/XRT place further constraints on amount nature dust along sightline. The galactic environment is characterized a strong DLA log(N(H)/cm^-2) = 21.95 +/- 0.10, prominent H_2 absorption Lyman-Werner bands (log(N(H_2)/cm^-2) 20.53...
We present optical and near-infrared (NIR) photometry for three gamma-ray burst supernovae (GRB-SNe): GRB 120729A, 130215A / SN 2013ez 130831A 2013fu. In the case of 2013ez, we also spectroscopy at t-t0=16.1 d, which covers rest-frame 3000-6250 Angstroms. Based on Fe II (5169) Si (II) (6355), our spectrum indicates an unusually low expansion velocity 4000-6350 km/s, lowest ever measured a GRB-SN. Additionally, determined brightness shape each accompanying relative to template supernova (SN...
The short gamma-ray burst (GRB) 170817A was the first GRB associated with a gravitational-wave event. Due to exceptionally low luminosity of prompt $\gamma$-ray and afterglow emission, origin both radiation components is highly debated. most discussed models for include regular jet seen off-axis emission from cocoon encompassing "choked" jet. Here, we report radio-frequency observations at 610 1390~MHz obtained Giant Metrewave Radio Telescope (GMRT). Our span range $\sim7$ $\sim152$ days...
We present a sample of 38 intervening Damped Lyman $\alpha$ (DLA) systems identified towards 100 $z>3.5$ quasars, observed during the XQ-100 survey. The DLA is combined with major surveys in literature. final consists 742 DLAs over redshift range approximately $1.6 < z_{\rm abs} 5.0$. develop novel technique for computing $\Omega_{\rm HI}^{\rm DLA}$ as continuous function redshift, and we thoroughly assess quantify sources error therein, including fitting errors incomplete sampling high...
Whether stars could have driven the reionization of intergalactic medium depends critically on proportion ionizing radiation that escapes galaxies in which it is produced. Spectroscopy gamma-ray burst (GRB) afterglows can be used to estimate opacity extreme ultraviolet (EUV) along lines-of-sight bursts. Assuming long-duration GRBs trace locations massive dominating EUV production, average escape fraction calculated independently galaxy size or luminosity. Here we present a compilation H i...