Very Large Telescope and [ITAL]Hubble Space Telescope[/ITAL] Observations of the Host Galaxy of GRB 990705 (original) (raw)

Very Large Telescope and Hubble Space Telescope Observations of the Host Galaxy of GRB 990705

The Astrophysical Journal, 2002

We present Very Large Telescope spectroscopic observations of the GRB 990705 host galaxy and highlight the benefits provided by the prompt phase features of gamma-ray bursts (GRBs) to derive the redshifts of the latter. In the host spectrum, we indeed detect an emission feature that we attribute to the [O ii] ll3726, 3729 doublet and derive an unambiguous redshift for this galaxy. This is in full agreement with z p 0.8424 ‫ע‬ 0.0002 the value previously derived using a transient absorption edge discovered in the X-ray spectrum z ∼ 0.86 ‫ע‬ 0.17 of GRB 990705. This burst is therefore the first GRB for which a reliable redshift was derived from the prompt phase emission itself, as opposed to redshift determinations performed using putative host galaxy emission lines or interstellar absorption lines in the GRB afterglows. Deep and high-resolution images of the host of GRB 990705 with the Space Telescope Imaging Spectrograph camera on board the Hubble Space Telescope reveal that the burst occurred in a nearly face-on Sc spiral galaxy typical of disk-dominated systems at . 0.75 ≤ z ≤ 1 Assuming a cosmology with km s Ϫ1 Mpc Ϫ1 , , and , we derive an absolute B magnitude H p 65 Q p 0.3 Q p 0.7 0 m l for this galaxy and a star formation rate yr Ϫ1 . Finally, we discuss the implications M p Ϫ21.75 SFR ≈ 5-8 M B ,

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.

GRB 070714B—Discovery of the Highest Spectroscopically Confirmed Short Burst Redshift

2009

We detect the optical afterglow and host galaxy of GRB 070714B. Our observations of the afterglow show an initial plateau in the lightcurve for approximately the first 5 to 25 minutes, then steepening to a powerlaw decay with index α = 0.86±0.10 for the period between 1 to 24 hours post burst. This is consistent with the X-ray light-curve which shows an initial plateau followed by a similar subsequent decay. At late time, we detect a host galaxy at the location of the optical transient. Gemini Nod & Shuffle spectroscopic observations of the host show a single emission line at 7167Å which, based on a grizJHK photometric redshift, we conclude is the 3727Å [O II] line. We therefore find a redshift of z = 0.923. This redshift, as well as a subsequent probable spectroscopic redshift determination of GRB 070429B at z = 0.904 by two other groups, significantly exceeds the previous highest spectroscopically confirmed short burst redshift of z = 0.546 for GRB 051221. This dramatically moves back the time at which we know short bursts were being formed, and suggests that the present evidence for an old progenitor population may be observationally biased.

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.

GRB 051028: an intrinsically faint GRB at high redshift?

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.

GRBâ090426: the environment of a rest-frame 0.35-s gamma-ray burst at a redshift of 2.609

Monthly Notices of the Royal Astronomical Society, 2010

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 (GRB) 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 per cent confidence) a member of the short/hard phenomenological class of GRBs. From analysis of the opticalafterglow spectrum we find that the burst originated along a very low H I column density sightline, with N H I < 3.2 × 10 19 cm −2. Our GRB 090426 afterglow spectrum also appears to have weaker low-ionization absorption (Si II, C II) than ∼95 per cent of previous afterglow spectra. Finally, we also report the discovery of a blue, very luminous, star-forming putative host galaxy (∼2L *) 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.

Very Large Telescope and [ITAL]Hubble Space Telescope[/ITAL] Observations of the Host Galaxy of GRB 990705 (original) (raw)

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