B. L. Jensen
A5068204153- Gamma-ray bursts and supernovae
- SAS software applications and methods
- Stellar, planetary, and galactic studies
- Astronomical Observations and Instrumentation
- Astronomy and Astrophysical Research
- Astrophysical Phenomena and Observations
- Astro and Planetary Science
- Astrophysics and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- CCD and CMOS Imaging Sensors
- Microbial Metabolites in Food Biotechnology
- Adaptive optics and wavefront sensing
- Medical Imaging Techniques and Applications
- Experimental and Theoretical Physics Studies
- Calibration and Measurement Techniques
- Laser Design and Applications
- Enzyme Structure and Function
- Manufacturing Process and Optimization
- Spectroscopy and Chemometric Analyses
- Spectroscopy Techniques in Biomedical and Chemical Research
- Advanced X-ray and CT Imaging
- Ocular and Laser Science Research
- Embedded Systems and FPGA Design
- Astrophysics and Star Formation Studies
- Optical Systems and Laser Technology
University of Copenhagen
2001-2010
Netherlands Institute for Radio Astronomy
2004
European Space Research and Technology Centre
2003
Knox College
1998
We have gathered optical photometry data from the literature on a large sample of Swift-era gamma-ray burst (GRB) afterglows including GRBs up to September 2009, for total 76 GRBs, and present an additional three pre-Swift not included in earlier sample. Furthermore, we publish 840 new points 42 GRB afterglows, sets 050319, 050408, 050802, 050820A, 050922C, 060418, 080413A 080810. analyzed light curves all derived spectral energy distributions with best quality, allowing us estimate host...
(Abridged). We present a sample of 77 optical afterglows (OAs) Swift detected GRBs for which spectroscopic follow-up observations have been secured. provide linelists and equivalent widths all lines redward Ly-alpha. discuss to what extent the current bursts with OA spectroscopy is biased subsample GRBs. For that purpose we define an X-ray selected optimal conditions ground-based follow up from period March 2005 September 2008; 146 fulfill our criteria. derive redshift distribution this...
The exceptionally high luminosities of gamma-ray bursts (GRBs), gradually emerging as extremely useful probes star formation, make them promising tools for exploration the high-redshift Universe. Here we present a carefully selected sample Swift GRBs, intended to estimate in an unbiased way GRB mean redshift (), constraints on fraction and upper limit heavily obscured afterglows. We find that at least 7% GRBs originate . In addition, consistent with pre-Swift observations, most 20%...
Aims.We present early optical spectroscopy of the afterglow gamma-ray burst GRB 060206 with aim determining metallicity absorber and physical conditions in circumburst medium. We also discuss how GRBs may be important complementary probes cosmic chemical evolution.
We present photometry and spectroscopy of the afterglow GRB 030323. VLT spectra show damped Lyα (DLA) absorption low- high-ionization lines at a redshift . The inferred neutral hydrogen column density, , is larger than any (GRB- or QSO-) DLA density directly from in absorption. From photometry, we derive conservative upper limit to host-galaxy extinction: mag. iron abundance while metallicity gas as measured sulphur an on H2 molecular fraction In trough, emission line detected, which...
Context.Before the launch of Swift satellite, majority gamma-ray burst (GRB) afterglows for which Lyα was redshifted into observable spectrum showed evidence a damped absorber. This small sample indicated that GRBs explode either in galaxies, or regions within them, having high neutral hydrogen column densities.
We have studied the afterglow of gamma-ray burst (GRB) February 18, 2006. This is a nearby long GRB, with very low peak energy, and therefore classified as an X-ray Flash (XRF). XRF 060218 clearly associated supernova -- dubbed SN 2006aj. present early spectra for 2006aj well optical lightcurves reaching out to 50 days past explosion. Our define rise times, lightcurve shapes absolute magnitudes in U, V R bands, we compare these data other relevant supernovae. evolved quite fast, somewhat...
The optical afterglow spectrum of GRB050401 (at z=2.8992+/-0.0004) shows the presence a DLA, with log(nHI)=22.6+/-0.3. This is highest column density ever observed in and about five times larger than strongest DLA detected so far any QSO spectrum. From spectrum, we also find very large Zn density, allowing us to infer an abundance [Zn/H]=-1.0+/-0.4. These columns are supported by X-ray from Swift-XRT which (in excess Galactic) log(nH)=22.21^{+0.06}_{-0.08} assuming solar abundances z=2.9)....
We present the discovery of optical transient long-duration gamma-ray burst GRB 000630. The was detected with Nordic Optical Telescope 21.1 hours after burst. At time magnitude . displayed a power-law decline characterized by decay slope A deep image obtained 25 days shows no indication contribution from supernova or host galaxy at position transient. closest is 2.0 arcsec north magnitudes afterglows 980329, 980613 and 000630 were all less than 24 epoch. discuss implications this for our...
We report the discovery of optical afterglow (OA) long-duration gamma-ray burst GRB 030429, and present a comprehensive optical/near-infrared dataset used to probe matter at different distance scales, i.e. in environment, host galaxy an intervening absorber. A break light curve is seen approximately 1 day from onset burst. The displays significant deviation simple broken power-law with bright 1.5 magnitude bump duration 2-3 days. spectral energy distribution best fit index beta = -0.36 +/-...
We have obtained deep optical images with the Very Large Telescope at ESO of first well-localized short-duration gamma-ray burst, GRB 050509B. From V and R imaging, initiated ~2 days after trigger lasting up to three weeks, we detect no variable object inside small Swift XRT X-ray error circle down 2 σ limits = 26.5 25.1. The includes a giant elliptical galaxy z 0.225, which has been proposed as likely host this GRB. Our indicate that if originated any supernova-like event accompanying would...
We present Ulysses and NEAR data from the detection of short or intermediate duration (2 s) gamma-ray burst GRB 000301C (2000 March 1.41 UT). The (GRB) was localised by Inter Planetary Network (IPN) RXTE to an area ~50 arcmin2. A fading optical counterpart subsequently discovered with Nordic Optical Telescope (NOT) about 42 h after burst. lies at border between long-soft short-hard classes GRBs. If belongs latter class, this would be first afterglow a UBRI photometry time discovery until 11...
The gamma-ray burst GRB000210 had the highest peak flux of any event localized by BeppoSAX as yet but it did not have a detected optical afterglow. It is therefore one events recently classified dark GRBs or GHOST (GRB Hiding Optical Source Transient), whose origin still unclear. Chandra observations allowed us to localize this GRB within ~1" and radio transient was with VLA. We identify likely (P=0.01) host galaxy at z=0.846. X-ray spectrum afterglow shows intrinsic absorption N_H=5x10**21...
We report the result of a search for Ly-alpha emission from host galaxies gamma-ray bursts (GRBs) 030226 (z = 1.986), 021004 2.335) and 020124 3.198). find that galaxy GRB is an extended (around 8 kpc) strong emitter with restframe equivalent width (EW) 68^{+12}_{-11} AA, star-formation rate 10.6 +/- 2.0 M_sun/yr. do not detect hosts 020124, but upper limits on their fluxes rule out large EWs. In fields we seven five other galaxies, respectively, excess in narrow-band filter. These are...
Observations of the extraordinarily bright optical afterglow (OA) GRB 991208 started 2.1 d after event. The flux decay constant OA in R-band is -2.30 +/- 0.07 up to 5 d, which very likely due jet effect, and that it followed by a much steeper with -3.2 0.2, fastest one ever seen OA. A negative detection several all-sky films taken simultaneously event implies either previous additional break prior 2 occurrence (as expected from effect). existence second might indicate steepening electron...
We present optical and near-infrared follow-up observations of the X-Ray Flash (XRF) July 23 2003. Our in R-band cover temporal range from 4.2 h to 64 days after high energy event. also results multicolor imaging extending K-band on three epochs. The lightcurve afterglow first week burst is similar for long duration Gamma-Ray Bursts (GRBs), i.e., a broken power-law with late time slope alpha=-2.0 (F_nu propto t^alpha). Furthermore, spectral distribution (SED) has nu^beta) shape beta=-1.0....
We report on a 3600 s spectrum of GRB 021004 obtained with the Nordic Optical Telecope La Palma 10.71 hours after burst. identify absorption lines from five systems at redshifts 1.3806, 1.6039, 2.2983, 2.3230, and 2.3292. In addition we find an emission line which, if due to Lyα host galaxy, gives redshift 2.3351. The nearest absorber is blueshifted by 530 km s-1 respect this line, consistent shifts seen in Damped Lyman-Break galaxies similar redshifts. flux erg cm-2. Some are “line-locked”,...
We present the discovery of Optical Transient (OT) long-duration gamma-ray burst GRB 000926. The optical transient was detected independently with Nordic Telescope and at Calar Alto 22.2 hours after burst. At this time magnitude . faded a decay slope about 1.7 during first two days which increased abruptly (within few hours) to 2.4. light-curve started flatten off week indicating presence an underlying extended object. This object in deep image obtained one month consists several compact...
The X-Ray Flash (XRF), 031203 with a host galaxy at , is, apart from GRB 980425, the closest γ-Ray Burst (GRB) or XRF known to date. We have monitored its 1–100 days after burst. In spite of high extinction source and bright host, significant increase subsequent decrease has been detected in apparent brightness peaking between 10 33 GRB. only convincing explanation is supernova (SN) associated XRF, SN2003lw. This earliest time which SN signal clearly discernible GRB/XRF (apart SN1998bw)....
We report on follow-up observations of the gamma-ray burst GRB 060927 using robotic ROTSE-IIIa telescope and a suite larger aperture ground-based telescopes. An optical afterglow was detected 20 s after burst, earliest rest-frame detection emission from any GRB. Spectroscopy performed with VLT about 13 hr trigger shows continuum break at λ ≈ 8070 Å, produced by neutral hydrogen absorption z 5.6. also detect an line 8158 which we interpret as Si II λ1260 = 5.467. Hence, is second most distant...
We report on the results of deep narrow-band Lyα and broad-band U I imaging fields two Gamma-Ray bursts at redshift (GRB 000301C GRB 000926). find that host galaxy 000926 is an extended (more than 2 arcsec), strong emitter with a rest-frame equivalent width 71 Å. The consists main components several fainter knots. occurred in western component, whereas most luminosity (about 65%) originates eastern component. Using archival HST images we measure spectral slopes () to (east) (west). This...
We present UBVRCIC photometry of the optical afterglow gamma-ray burst GRB 021004 taken at Nordic Optical Telescope between approximately 8 hours and 30 days after burst. These data are combined with an analysis 87 ks Chandra X-ray observations a mean epoch 33 hr to investigate nature this GRB. find intrinsic spectral slope wavelengths βUH = 0.39 ± 0.12 βX 0.94 0.03. There is no evidence for color evolution 8.5 5.5 The decay becomes steeper 5 This appears be gradual break due onset sideways...
We present comprehensive photometric R-band observations of the fading optical afterglow X-Ray Flash XRF050824, from 11 minutes to 104 days after burst. The lightcurve resembles lightcurves long duration Gamma-Ray Bursts (GRBs), i.e., a power-law albeit with rather shallow slope alpha=0.6. Our late images reveal host galaxy rest-frame B-band luminosity corresponding roughly 0.5 Lstar. star-formation rate as determined [O II] emission line is about 1.8 Msun per year. When accounting for...