A5033173817- Gamma-ray bursts and supernovae
- SAS software applications and methods
- Astrophysical Phenomena and Observations
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Astrophysics and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Radio Astronomy Observations and Technology
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Advanced X-ray and CT Imaging
- Corneal surgery and disorders
- Cancer Diagnosis and Treatment
- Dark Matter and Cosmic Phenomena
- Atmospheric Ozone and Climate
- Statistical and numerical algorithms
- Cognitive Science and Education Research
- Solar and Space Plasma Dynamics
- Statistics Education and Methodologies
- Particle Accelerators and Free-Electron Lasers
- Historical Studies on Spain
- Chaos, Complexity, and Education
American River College
2011-2023
Escola Superior de Artes e Design
2021
Max Planck Society
2008-2014
Max Planck Institute for Extraterrestrial Physics
2008-2013
We report on the detection by Swift of GRB 080913, and subsequent optical/near-infrared follow-up observations GROND, which led to discovery its optical/NIR afterglow recognition high-z nature via a spectral break between i' z' bands. Spectroscopy obtained at ESO-VLT revealed continuum extending down λ = 9400 Å, zero flux for 7500 Å<λ < we interpret as onset Gunn–Peterson trough z 6.695± 0.025 (95.5% confidence level), making 080913 highest-redshift gamma-ray burst (GRB) date, more distant...
Context. Thirteen years after the discovery of first afterglows, nature dark gamma-ray bursts (GRB) still eludes explanation: while each long-duration GRB typically has an X-ray afterglow, optical/NIR emission is only seen for 40–60% them.
(Abridged) Until recently the information inferred from gamma-ray burst follow-up observations was mostly limited to optically bright afterglows, biasing all demographic studies against sight-lines that contain large amounts of dust. Here, we present GRB afterglow and host for a sample bursts are exemplary previously missed ones because high visual extinction along sight-line. This facilitates an investigation properties, geometry location absorbing dust these poorly-explored galaxies,...
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...
Fermi can measure the spectral properties of gamma-ray bursts over a very large energy range and is opening new window on prompt emission these energetic events. Localizations by instruments in combination with follow-up Swift provide accurate positions for observations at longer wavelengths leading to determination redshifts, true budget, host galaxy facilitate comparison pre-Fermi bursts. Multi-wavelength were performed afterglows four high detected Fermi/LAT : GRB090323, GRB090328,...
We report on the surprisingly high metallicity measured in two absorption systems at redshift, detected Very Large Telescope spectrum of afterglow gamma-ray burst GRB 090323. The systems, redshift z=3.5673 and z=3.5774 (separation Delta v ~ 660 km/s), are dominated by neutral gas interstellar medium parent galaxies. From singly ionized zinc sulfur, we estimate oversolar metallicities [Zn/H] =+0.29+/-0.10 [S/H] = +0.67+/- 0.34, blue red absorber, respectively. These highest ever galaxies z>3....
The detection of GeV photons from gamma-ray bursts (GRBs) has important consequences for the interpretation and modelling these most-energetic cosmological explosions. full exploitation high-energy measurements relies, however, on accurate knowledge distance to events. Here we report discovery afterglow subsequent redshift determination GRB 080916C, first detected by Fermi Gamma-Ray Space Telescope with high significance at >0.1 GeV. Observations were done 7-channel imager GROND 2.2m...
Observations of the gamma-ray sky with Fermi led to significant advances towards understanding blazars, most extreme class Active Galactic Nuclei. A large fraction population detected by is formed BL Lacertae (BL Lac) objects, whose sample has always suffered from a severe redshift incompleteness due quasi-featureless optical spectra. Our goal provide increase number confirmed high-redshift Lac objects contained in 2 LAC Fermi/LAT catalog. For 103 photometric redshifts using spectral energy...
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 observations and analysis of the broadband afterglow Swift GRB 071025. Using optical infrared (RIYJHK) photometry, we derive a photometric redshift 4.4 < z 5.2; at this our simultaneous multicolour begin ~30 s after trigger in host frame during initial rising phase afterglow. associate light curve peak 580 observer with formation forward shock, giving an estimate Lorentz factor Gamma_0 ~ 200. The red spectral energy distribution (even regions not affected by Lyman-alpha break)...
Context: The link between the duration of GRBs and nature their progenitors remains disputed. Short bursts (with durations less than ~2 s) are frequently observed, technically more difficult to localize, exhibit significantly fainter afterglows. Aims: It is critical importance establish whether burst can reliably distinguish different GRB population models collapsars compact stellar mergers. Swift 090426 provides an unique opportunity address this question. Its (T_90=1.28 places firmly in...
We present the first uniform treatment of long duration gamma-ray burst (GRB) host galaxy detections and upper limits over redshift range , a key epoch for observational theoretical efforts to understand processes, environments, consequences early cosmic star formation (SF). contribute deep imaging observations 13 GRB positions yielding discovery 8 new galaxies. use this data set in tandem with previously published 31 further estimate or constrain rest-frame ultraviolet (UV; Å) absolute...
We present extensive optical and near-infrared photometric spectroscopic observations of the stripped-envelope (SE) supernova SN 2010as. Spectroscopic peculiarities, such as initially weak helium features low expansion velocities with a nearly flat evolution, place this object in small family events previously identified transitional Type Ib/c supernovae (SNe). There is ubiquitous evidence hydrogen, albeit weak, SNe, indicating that they are fact peculiar kind IIb SNe we name "flat-velocity...
The quick and precise localization of GRBs by the Swift telescope allows early evolution afterglow light curve to be captured ground-based telescopes. With GROND measurements we can investigate optical/near-infrared gamma-ray burst 080413B in context late rebrightening. Multi-wavelength follow-up observations were performed on GRB 080413B. X-ray emission was detected onboard satellite obtained from public archive. Optical near-infrared photometry with seven-channel imager mounted at MPG/ESO...
We present VLT/FORS2 spectroscopy and Gamma-ray Optical/Near-Infrared Detector optical/near-IR photometry of the afterglow bright Fermi/LAT GRB 090926A. The spectrum shows prominent Lyman-α absorption with cm−2 a multitude metal lines at common redshift z = 2.1062 ± 0.0004, which we associate gamma-ray burst (GRB). metallicity derived from S ii is log(Z/Z☉) ≈ −1.9, one lowest values ever found in Damped (DLA) system. This confirms that spread GRB-DLAs 2 least two orders magnitude. argue this...
We present a framework to obtain photometric redshifts (photo-zs) for gamma-ray burst afterglows. Using multi-band photometry from GROND and Swift/UVOT, photo-zs are derived five GRBs which spectroscopic not available. use UV/optical/NIR data synthetic based on afterglow observations theory derive the of their accuracy. Taking into account synchrotron emission properties, we investigate application in theoretical range between z~1 z~12. The measurement GRB afterglows provides quick, robust...
Context. After the launch of Swift satellite, Gamma-Ray Burst (GRB) optical light-curve smoothness paradigm has been questioned thanks to faster and better sampled follow-up, which unveiled a very complex behaviour. This complexity is triggering interest whole GRB community. The GROND multi-channel imager used study near-infrared (NIR) afterglows GRBs with unprecedented temporal spectral resolution. 081029 prominent rebrightening event an outstanding example application afterglows. Aims....
We present the results of a comprehensive study gamma-ray burst 080928 and its afterglow. GRB was long detected by Swift/BAT Fermi/GBM. It is one exceptional cases where optical emission had already been when itself still radiating in band. For nearly 100 s simultaneous optical, X-ray data provide coverage spectral energy distribution transient source from about 1 eV to 150 keV. In particular, we show that SED during main prompt phase agrees with synchrotron radiation. constructed...
We report on follow-up observations of 20 short-duration gamma-ray bursts performed in g'r'i'z'JHKs with the seven-channel imager GROND between mid-2007 and end 2010. This is one most comprehensive data sets GRB afterglow short published so far. In three cases was target within less than 10 min after trigger, leading to discovery 081226A its faint underlying host galaxy. addition, able image optical follow light-curve evolution further five cases, GRBs 090305, 090426, 090510, 090927,...
(...) Since 1998, only half a dozen spectroscopically confirmed associations have been discovered and XRF 100316D associated with the type-Ic SN 2010bh at z = 0.059 is among latest. We began observations GROND 12 hours after GRB trigger continued until 80 days burst. provided excellent photometric data in six filter bands covering wavelength range from approx. 350 to 1800 nm, significantly expanding pre-existing set for this event. Combining Swift data, early broad-band SED modelled...