GRB 051028: an intrinsically faint GRB at high redshift? (original) (raw)
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GRB 051028: an intrinsically faint gamma-ray burst at high redshift?
2006
Aims. We present multiwavelength observations of the gamma-ray burst GRB 051028 detected by HETE-2 in order to derive its afterglow emission parameters and to determine the reason for its optical faintness when compared to other events. Methods. Observations were taken in the optical (2.0m Himalayan Chandra Telescope, 1.34m Tautenburg, 4.2m William Herschel Telescope) and in X-rays (Swift/XRT) between 2.7 hours and ∼ 10 days after the onset of the event. Results. The data can be interpreted by collimated emission in a jet with a typical value of p = 2.4 which is moving in an homogeneous interstellar medium and with a cooling frequency ν c still above the X-rays at 0.5 days after the burst onset. GRB 051028 can be classified as a "gray" or "potentially dark" GRB. On the basis of the combined optical and Swift/XRT data, we conclude that the reason for the optical dimness is not extra absorption in the host galaxy, but rather the GRB taking place at high-redshift. We also notice the very striking similarity with the optical lightcurve of GRB 050730, a burst with a spectroscopic redshift of 3.967, although GRB 051028 is ∼ 3 mag fainter. We suggest that the bumps could be explained by multiple energy injection episodes and that the burst is intrinsically faint when compared to the average afterglows detected since 1997. The non-detection of the host galaxy down to R = 25.1 is also consistent with the burst arising at high redshift, compatible with the published pseudo-z of 3.7 ± 1.8.
The search for the host galaxy of the gamma-ray burst GRB 000214
Astronomy & Astrophysics, 2005
We present UBVRI-band observations taken ~300 days after the BeppoSAX gamma-ray burst GRB 000214. This GRB did not show a detectable optical afterglow, however due to the localization of a previously unknown, fading, X-ray source at a tentative redshift in the range 0.37-0.47, we have searched with the ESO 3.6 m telescope for objects with photometric redshifts consistent with the mentioned X-ray redshift range. We report four host galaxy candidates, which might be the subject of future spectroscopic observations in order to confirm their redshifts.
A γ-ray burst at a redshift of z ≈ 8.2
Nature, 2009
It is thought that the first generations of massive stars in the Universe were an important, and quite possibly dominant 1 , source of the ultra-violet radiation that reionized the hydrogen gas in the intergalactic medium (IGM); a state in which it has remained to the present day. Measurements of cosmic microwave background anisotropies suggest that this phase-change largely took place 2 in the redshift range z=10.8 ±1.4, while observations of quasars and Lyman-α galaxies have shown that the process was essentially completed 3,4,5 by z≈6. However, the detailed history of reionization, and characteristics of the stars and proto-galaxies that drove it, remain unknown. Further progress in understanding requires direct observations of the sources of ultra-violet radiation in the era of reionization, and mapping the evolution of the neutral hydrogen (H I) fraction through time. The detection of galaxies at such redshifts is highly challenging, due to their intrinsic faintness and high luminosity distance, whilst bright quasars appear to be rare beyond z≈7 [ref 6]. Here we report the discovery of a gamma-ray burst, GRB 090423, at redshift ! z = 8.26 "0.08 +0.07 . This is well beyond the redshift of the most distant spectroscopically-confirmed galaxy (z=6.96; ref 7) and quasar (z=6.43; ref 8). It establishes that massive stars were being produced, and dying as GRBs, ~625 million years after the Big Bang. In addition, the accurate position of the burst pinpoints the location of the most distant galaxy known to date. Larger samples of
GRB 071028B, a burst behind large amounts of dust in an unabsorbed galaxy
Astronomy & Astrophysics, 2011
Aims. We report on the discovery and properties of the fading afterglow and underlying host galaxy of GRB 071028B, thereby facilitating a detailed comparison between these two. Methods. Observations were performed with the Gamma-ray Burst Optical and Near-infrared Detector at the 2.2 m telescope on the La Silla Paranal Observatory in Chile. We conducted five observations from 1.9 d to 227.2 d after the trigger and obtained deep images in the g ′ r ′ i ′ z ′ and JHK s bands.
Gamma-ray burst host galaxies at low and high redshift
Astronomische Nachrichten, 2012
The galaxies hosting the most energetic explosions in the universe, the gamma-ray bursts (GRBs), are generally found to be low-mass, metal poor, blue and star forming galaxies. However, the majority of the targets investigated so far (less than 100) are at relatively low redshift, z < 2. We know that at low redshift, the cosmic star formation is predominantly in small galaxies. Therefore, at low redshift, long-duration GRBs, which are associated with massive stars, are expected to be in small galaxies. Preliminary investigations of the stellar mass function of z < 1.5 GRB hosts does not indicate that these galaxies are different from the general population of nearby star-forming galaxies. At high-z, it is still unclear whether GRB hosts are different. Recent results indicate that a fraction of them might be associated with dusty regions in massive galaxies. Remarkable is the a super-solar metallicity measured in the interstellar medium of a z = 3.57 GRB host.
The Astrophysical Journal, 2006
We present near-infrared (nIR) and optical observations of the afterglow of GRB 030115. Discovered in an infrared search at Kitt Peak 5 hours after the burst trigger, this afterglow is amongst the faintest observed in the R-band at an early epoch, and exhibits very red colors, with R−K ≈ 6. The magnitude of the optical afterglow of GRB 030115 is fainter than many upper limits for other bursts, suggesting that without early nIR observations it would have been classified as a "dark" burst. Both the color and optical magnitude of the afterglow are likely due to dust extinction and indicate that at least some optical afterglows are very faint due to dust along the line of sight. Multicolor Hubble Space Telescope observations were also taken of the host galaxy and the surrounding field. Photometric redshifts imply that the host, and a substantial number of faint galaxies in the field are at z ∼ 2.5. The overdensity of galaxies is sufficiently great that GRB 030115 may have occurred in a rich high-redshift cluster. The host galaxy shows extremely red colors (R-K=5) and is the first GRB host to be classified as an Extreme Red Object (ERO). Some of the galaxies surrounding the host also show very red colors, while the majority of the cluster are much bluer, indicating ongoing unobscured star formation. As it is thought that much of high redshift star formation occurs in highly obscured environments it may be that GRB 030115 represents a transition object, between the relatively unobscured afterglows seen to date and a population which are very heavily extinguished, even in the nIR. Subject headings: gamma rays: bursts 1 Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs 9074 and 9405.
GRB 090426: The Environment of a Rest-Frame 0.35-second Gamma-Ray Burst at Redshift z=2.609
Monthly Notices of The Royal Astronomical Society, 2009
We present the discovery of an absorption-line redshift of z = 2.609 for GRB 090426, establishing the first firm lower limit to a redshift for a gamma-ray burst with an observed duration of <2 s. With a rest-frame burst duration of T_90z = 0.35 s and a detailed examination of the peak energy of the event, we suggest that this is likely (at >90% confidence) a member of the short/hard phenomenological class of GRBs. From analysis of the optical-afterglow spectrum we find that the burst originated along a very low HI column density sightline, with N_HI < 3.2 x 10^19 cm^-2. Our GRB 090426 afterglow spectrum also appears to have weaker low-ionisation absorption (Si II, C II) than ~95% of previous afterglow spectra. Finally, we also report the discovery of a blue, very luminous, star-forming putative host galaxy (~2 L*) at a small angular offset from the location of the optical afterglow. We consider the implications of this unique GRB in the context of burst duration classification and our understanding of GRB progenitor scenarios.
The host galaxy and optical light curve of the gamma-ray burst GRB 980703
Astronomy and Astrophysics, 2001
We present deep HST/STIS and ground-based photometry of the host galaxy of the gamma-ray burst GRB 980703 taken 17, 551, 710, and 716 days after the burst. We find that the host is a blue, slightly over-luminous galaxy with V gal = 23.00 ± 0.10, (V −R) gal = 0.43 ± 0.13, and a centre that is ≈ 0.2 mag bluer than the outer regions of the galaxy. The galaxy has a star-formation rate of 8-13 M ⊙ yr −1 , assuming no extinction in the host. We find that the galaxy is best fit by a Sersic R 1/n profile with n ≈ 1.0 and a half-light radius of 0. ′′ 13 (= 0.72h −1 100 proper kpc). This corresponds to an exponential disk with a scale radius of 0. ′′ 22 (= 1.21h −1 100 proper kpc). Subtracting a fit with elliptical isophotes leaves large residuals, which suggests that the host galaxy has a somewhat irregular morphology, but we are unable to connect the location of GRB 980703 with any special features in the host.