Search

The number of long-duration gamma-ray burst (LGRB) host galaxies with measured metallicities and host masses has expanded sufficiently to investigate how the distributions of these properties change with redshift. Using the combined host galaxy metallicity sample from Graham & Fruchter and Krühler et al., we find a surprising lack of evolution in the LGRB metallicity distribution across different redshifts. In particular, the fraction of LGRB hosts with relatively high metallicity (12+log(O/H) ≥ 8.4) remains essentially constant out to z = 2.5. This result is at odds with the evolution in the mass–metallicity relation of typical galaxies, which become progressively more metal poor with increasing redshift. A similar result is found when converting the LGRB host galaxy mass distribution taken from the Swift GRB Host Galaxy Legacy Survey (SHOALS) sample to a corresponding metallicity distribution by applying a redshift-dependent mass–metallicity relation. The SHOALS sample is compiled using an unbiased selection function implying that the observed lack of evolution in the host galaxy high-metallicity distribution is not caused by selection effects. However, the LGRB host galaxy metallicities estimated from the stellar mass are typically a quarter dex higher at all redshifts than the metallicity we measure spectroscopically. This implies that using mass–metallicity relationships to estimate host metallicities will thus produce a substantial systematic bias. [ABSTRACT FROM AUTHOR]

It is well established that magnetars are neutron stars with extreme magnetic fields and young ages, but the evolutionary pathways to their creation are still uncertain. Since most massive stars are in binaries, if magnetars are a frequent result of core-collapse supernovae, some fractions are expected to have a bound companion at the time of observation. In this paper, we utilize literature constraints, including deep Hubble Space Telescope imaging, to search for bound stellar companions to magnetars. The magnitude and colour measurements are interpreted in the context of binary population synthesis predictions. We find two candidates for stellar companions associated with CXOU J171405.7–381031 and SGR 0755–2933, based on their J–H colours and H -band absolute magnitudes. Overall, the proportion of the Galactic magnetar population with a plausibly stellar near-infrared (NIR) counterpart candidate, based on their magnitudes and colours, is between 5 and 10 per cent. This is consistent with a population synthesis prediction of 5 per cent, for the fraction of core-collapse neutron stars arising from primaries that remain bound to their companion after the supernova. These results are therefore consistent with magnetars being drawn in an unbiased way from the natal core-collapse neutron star population, but some contribution from alternative progenitor channels cannot be ruled out. [ABSTRACT FROM AUTHOR]

When massive stars exhaust their fuel, they collapse and often produce the extraordinarily bright explosions known as core-collapse supernovae. On occasion, this stellar collapse also powers an even more brilliant relativistic explosion known as a long-duration [gamma]-ray burst. One would then expect that these long [gamma]-ray bursts and core-collapse supernovae should be found in similar galactic environments. Here we show that this expectation is wrong. We find that the [gamma]-ray bursts are far more concentrated in the very brightest regions of their host galaxies than are the core-collapse supernovae. Furthermore, the host galaxies of the long [gamma]-ray bursts are significantly fainter and more irregular than the hosts of the core-collapse supernovae. Together these results suggest that long-duration [gamma]-ray bursts are associated with the most extremely massive stars and may be restricted to galaxies of limited chemical evolution. Our results directly imply that long [gamma]-ray bursts are relatively rare in galaxies such as our own Milky Way. Not in our back yard In their death throes massive stars often produce supernovae, and occasionally a long-duration [gamma]-ray burst (GRB). That suggests that GRBs and supernovae should be found in similar environments, but work based on more than a thousand hours of Hubble Space Telescope observation time shows that expectation to be wrong. Most long GRBs are found in small, faint, irregular galaxies. Supernovae appear equally divided between spiral and irregular galaxies. GRBs are concentrated in the brightest regions of their host galaxies whereas supernovae occur throughout their host galaxies. A happy conclusion of this finding is that GRBs, which would cause havoc here on Earth if exploding nearby, should be relatively rare in the Milky Way. [gamma]-ray bursts are more concentrated in the very brightest regions of their host galaxies than are supernovae -- in addition, the host galaxies of the [gamma]-ray bursts are significantly fainter and more irregular than the hosts of the supernovae., Author(s): A. S. Fruchter [sup.1] , A. J. Levan [sup.1] [sup.2] [sup.3] , L. Strolger [sup.1] [sup.4] [sup.23] , P. M. Vreeswijk [sup.5] , S. E. Thorsett [sup.6] , D. [...]

We report the discovery of six new magnetar counterpart candidates from deep near-infrared Hubble Space Telescope (HST) imaging. The new candidates are among a sample of 19 magnetars for which we present HST data obtained between 2018 and 2020. We confirm the variability of previously established near-infrared counterparts, and newly identify candidates for PSR J1622−4950, Swift J1822.3−1606, CXOU J171405.7−381031, Swift J1833−0832, Swift J1834.9−0846, and AX J1818.8−1559 based on their proximity to X-ray localizations. The new candidates are compared with the existing counterpart population in terms of their colours, magnitudes, and near-infrared to X-ray spectral indices. We find two candidates for AX J1818 that are both consistent with previously established counterparts. The other new candidates are likely to be chance alignments, or otherwise have a different origin for their near-infrared emission not previously seen in magnetar counterparts. Further observations and studies of these candidates are needed to firmly establish their nature. [ABSTRACT FROM AUTHOR]

This study examines the possibility that nondechlorinating microorganisms can contribute to the transformation of carbon tetrachloride (CT) in Fe(III)-bearing minerals such as goethite. In several experiments, Fe(III)-reducing bacterium Shewanella Alga, strain BrY, dechlorinated CT was used to from biogenic Fe(II) by means of enzymatic reduction of goethite. Chloroform was formed when the CT was degraded by abiotic and biogentic Fe(II) on goethite.

We present deep Hubble Space Telescope (HST) near-infrared (NIR) observations of the magnetar SGR 1935+2154 from 2021 June, approximately 6 yr after the first HST observations, a year after the discovery of fast-radio-burst-like emission from the source, and in a period of exceptional high-frequency activity. Although not directly taken during a bursting period the counterpart is a factor of ∼1.5–2.5 brighter than seen at previous epochs with F140W(AB) = 24.65 ± 0.02 mag. We do not detect significant variations of the NIR counterpart within the course of any one orbit (i.e., on minutes to hour timescales), and contemporaneous X-ray observations show SGR 1935+2154 to be at the quiescent level. With a time baseline of 6 yr from the first identification of the counterpart we place stringent limits on the proper motion (PM) of the source, with a measured PM of μ = 3.1 ± 1.5 mas yr−1. The direction of PM indicates an origin of SGR 1935+2154 very close to the geometric center of SNR G57.2+08, further strengthening their association. At an adopted distance of 6.6 ± 0.7 kpc, the corresponding tangential space velocity is νT = 97 ± 48 km s−1 (corrected for differential Galactic rotation and peculiar solar motion), although its formal statistical determination may be compromised owing to few epochs of observation. The current velocity estimate places it at the low end of the kick distribution for pulsars, and makes it among the lowest known magnetar kicks. When collating the few-magnetar kick constraints available, we find full consistency between the magnetar kick distribution and the much larger pulsar kick sample. [ABSTRACT FROM AUTHOR]

We present deep Hubble Space Telescope (HST) near-infrared (NIR) observations of the magnetar SGR 1935+2154 from 2021 June, approximately 6 yr after the first HST observations, a year after the discovery of fast-radio-burst-like emission from the source, and in a period of exceptional high-frequency activity. Although not directly taken during a bursting period the counterpart is a factor of ∼1.5â€"2.5 brighter than seen at previous epochs with F140W(AB) = 24.65 ± 0.02 mag. We do not detect significant variations of the NIR counterpart within the course of any one orbit (i.e., on minutes to hour timescales), and contemporaneous X-ray observations show SGR 1935+2154 to be at the quiescent level. With a time baseline of 6 yr from the first identification of the counterpart we place stringent limits on the proper motion (PM) of the source, with a measured PM of ÎĽ = 3.1 ± 1.5 mas yrâˆ'1. The direction of PM indicates an origin of SGR 1935+2154 very close to the geometric center of SNR G57.2+08, further strengthening their association. At an adopted distance of 6.6 ± 0.7 kpc, the corresponding tangential space velocity is ν T = 97 ± 48 km sâˆ'1 (corrected for differential Galactic rotation and peculiar solar motion), although its formal statistical determination may be compromised owing to few epochs of observation. The current velocity estimate places it at the low end of the kick distribution for pulsars, and makes it among the lowest known magnetar kicks. When collating the few-magnetar kick constraints available, we find full consistency between the magnetar kick distribution and the much larger pulsar kick sample. [ABSTRACT FROM AUTHOR]

We examine a sample of 21 gamma-ray burst (GRB) afterglow light curves at radio frequencies and compare them to the X-ray and/or optical properties of the afterglows and to the predictions of the standard jet/fireball model. Our sample includes every Swift GRB with an X-ray light curve indicating a jet break and with a published radio light curve, as well as several other targets with observed X-ray or and/optical jet breaks. We examine the late-time decline of each burst and attempt to fit an analytical model based on the standard GRB afterglow equations to each data set. We show that most of the events in our Swift GRB sample are incompatible with the radio light-curve behavior predicted by conventional afterglow theory. Many exhibit a late-time radio decline incompatible with the post-break X-ray or optical afterglow. Only one radio afterglow in this sample, at any time, shows the eventually expected decline of ∼t−2, although two others show it in their millimeter light curve. Several others remain consistent with the standard model if such a decline began after the observations. The radio behavior alone does not, however, indicate whether a GRB can be fit by our modeling code. Indeed, several of the well-fit GRBs may only appear so due to a lack of multiwavelength data. While a second source of emission can account for some of the anomalous radio behavior, our tests indicate this is often not the case unless the main jet component is simultaneously suppressed. [ABSTRACT FROM AUTHOR]

We present multiwavelength modeling of the afterglow from the long γ-ray burst (GRB) 160625B using Markov Chain Monte Carlo techniques of the afterglowpy Python package. GRB 160625B is an extremely bright burst with a rich set of observations spanning from radio to γ-ray frequencies. These observations range from ∼0.1 days to >1000 days, thus making this event extremely well suited to such modeling. In this work we compare top-hat and Gaussian jet structure types in order to find best-fit values for the GRB jet collimation angle, viewing angle, and other physical parameters. We find that a Gaussian-shaped jet is preferred (2.7σ–5.3σ) over the traditional top-hat model. Our estimate for the opening angle of the burst ranges from 1.°26 to 3.°90, depending on jet-shape model. We also discuss the implications that assumptions on jet shape, viewing angle, and particularly the participation a fraction of electrons have on the final estimation of GRB intrinsic energy release and the resulting energy budget of the relativistic outflow. Most notably, allowing the participation fraction to vary results in an estimated total relativistic energy of ∼1053 erg. This is two orders of magnitude higher than when the total fraction is assumed to be unity; thus, this parameter has strong relevance for placing constraints on long GRB central engines, details of the circumburst media, and host environment. [ABSTRACT FROM AUTHOR]

We present post-jet-break Hubble Space Telescope, Very Large Array, and Chandra observations of the afterglow of the long γ-ray bursts GRB 160625B (between 69 and 209 days) and GRB 160509A (between 35 and 80 days). We calculate the post-jet-break decline rates of the light curves and find the afterglow of GRB 160625B is inconsistent with a simple t−3/4 steepening over the break, expected from the geometric effect of the jet edge entering our line of sight. However, the favored optical post-break decline () is also inconsistent with the fν ∝ t−p decline (where p ≈ 2.3 from the pre-break light curve), which is expected from exponential lateral expansion of the jet; perhaps suggesting lateral expansion that only affects a fraction of the jet. The post-break decline of GRB 160509A is consistent with both the t−3/4 steepening and with fν ∝ t−p. We also use boxfit to fit afterglow models to both light curves and find both to be energetically consistent with a millisecond magnetar central engine, but the magnetar parameters need to be extreme (i.e., E ∼ 3 × 1052 erg). Finally, the late-time radio light curves of both afterglows are not reproduced well by boxfit and are inconsistent with predictions from the standard jet model; instead, both are well represented by a single power-law decline (roughly fν ∝ t−1) with no breaks. This requires a highly chromatic jet break () and possibly a two-component jet for both bursts. [ABSTRACT FROM AUTHOR]

The number of long gamma-ray bursts (GRBs) known to have occurred in the distant Universe (z > 5) is small (∼15); however, these events provide a powerful way of probing star formation at the onset of galaxy evolution. In this paper, we present the case for GRB 100205A being a largely overlooked high-redshift event. While initially noted as a high- z candidate, this event and its host galaxy have not been explored in detail. By combining optical and near-infrared Gemini afterglow imaging (at t < 1.3 d since burst) with deep late-time limits on host emission from the Hubble Space Telescope , we show that the most likely scenario is that GRB 100205A arose in the range 4 < z < 8. GRB 100205A is an example of a burst whose afterglow, even at ∼1 h post burst, could only be identified by 8-m class IR observations, and suggests that such observations of all optically dark bursts may be necessary to significantly enhance the number of high-redshift GRBs known. [ABSTRACT FROM AUTHOR]

We present a study of 21 dark gamma-ray burst (GRB) host galaxies, predominantly using X-ray afterglows obtained with the Chandra X-Ray Observatory (CXO) to precisely locate the burst in deep Hubble Space Telescope (HST) imaging of the burst region. The host galaxies are well-detected in F160W in all but one case and in F606W imaging in 60 per cent of cases. We measure magnitudes and perform a morphological analysis of each galaxy. The asymmetry, concentration, and ellipticity of the dark burst hosts are compared against the host galaxies of optically bright GRBs. In agreement with other studies, we find that dark GRB hosts are redder and more luminous than the bulk of the GRB host population. The distribution of projected spatial offsets for dark GRBs from their host galaxy centroids is comparable to that of optically bright bursts. The dark GRB hosts are physically larger, more massive and redder, but are morphologically similar to the hosts of bright GRBs in terms of concentration and asymmetry. Our analysis constrains the fraction of high redshift (z > 5) GRBs in the sample to 14 per cent, implying an upper limit for the whole long-GRB population of ≤4.4 per cent. If dust is the primary cause of afterglow darkening amongst dark GRBs, the measured extinction may require a clumpy dust component in order to explain the observed offset and ellipticity distributions. [ABSTRACT FROM AUTHOR]

We present the late-time Hubble Space Telescope observations of two Gamma Ray Burst (GRB) associated supernovae (SNe), GRB 030329/SN 2003dh and XRF 060218/SN 2006aj. Using the multi-color data up to ~320 days after the burst, we constrain the late-time decay nature of these SNe. The decay rates of SN 2003dh are steeper than SN 2006aj. A comparison with two other GRB SNe, GRB 980425/SN 1998bw and the SN associated with XRF 020903, shows that the decay rates of SN 2003dh are similar to XRF 020903 and those of SN 2006aj are similar to SN 1998bw. The late-time decay rates are steeper than the 56Co→56Fe radioactive decay rate indicating that there is some leakage of gamma-rays. We also compare the late-time decay rates of nine type Ic SNe, including the SNe of long GRBs, Ic broad lined and normal Ics. The decay rates of the SNe sample show a remarkable similarity in I band at late-times with a scatter of ~10%. [ABSTRACT FROM PUBLISHER]

We present Hubble Space Telescope (HST)Wide Field Camera 3UVand near-IR (nIR) imaging of 21 Superluminous Supernovae (SLSNe) host galaxies, providing a sensitive probe of star formation and stellar mass within the hosts. Comparing the photometric and morphological properties of these host galaxies with those of core-collapse supernovae (CCSNe) and longduration gamma-ray bursts (LGRBs), we find SLSN hosts are fainter and more compact at both UV and nIR wavelengths, in some cases we barely recover hosts with absolute magnitude aroundMV≈-14.With the addition of ground based optical observations and archival results, we produce spectral energy distribution fits to these hosts, and show that SLSN hosts possess lower stellar mass and star formation rates. This is most pronounced for the hydrogen deficient Type-I SLSN hosts, although Type-II H-rich SLSN host galaxies remain distinct from the bulk of CCSNe, spanning a remarkably broad range of absolute magnitudes, with ~30 per cent of SLSNe-II arising from galaxies fainter than MnIR ~-14. The detection of our faintest SLSN hosts increases the confidence that SLSNe-I hosts are distinct from those of LGRBs in star formation rate and stellar mass, and suggests that apparent similarities in metallicity may be due to the limited fraction of hosts for which emission line metallicity measurements are feasible. The broad range of luminosities of SLSN-II hosts is difficult to describe by metallicity cuts, and does not match the expectations of any reasonable UV-weighted luminosity function, suggesting additional environmental constraints are likely necessary to yield hydrogen rich SLSNe. [ABSTRACT FROM AUTHOR]

The spiral host galaxy of the Swift GRB 060505 at z = 0.089 was the site of a puzzling long duration burst without an accompanying supernova. Studies of the burst environment by Thöne et al. suggested that this Gamma-ray Burst (GRB) came from the collapse of a massive star and that the GRB site was a region with properties different from the rest of the galaxy. We reobserved the galaxy in high spatial resolution using the VIMOS integral-field unit at the VLT with a spaxel size of 0.67 arcsec. Furthermore, we use long-slit high-resolution data from HIRES/Keck at two different slit positions covering the GRB site, the centre of the galaxy and an H ii region next to the GRB region. We compare the properties of different H ii regions in the galaxy with the GRB site and study the global and local kinematic properties of this galaxy. The resolved data show that the GRB site has the lowest metallicity in the galaxy with ∼1/3 Z⊙, but its specific star formation rate (SSFR) of 7.4 M⊙ yr−1/L/L* and age (determined by the Hα EW) are similar to other H ii regions in the host. The galaxy shows a gradient in metallicity and SSFR from the bulge to the outskirts as it is common for spiral galaxies. This gives further support to the theory that GRBs prefer regions of higher star formation and lower metallicity, which, in S-type galaxies, are more easily found in the spiral arms than in the centre. Kinematic measurements of the galaxy do not show evidence for large perturbations but a minor merger in the past cannot be excluded. This study confirms the collapsar origin of GRB 060505 but reveals that the properties of the H ii region surrounding the GRB were not unique to that galaxy. Spatially resolved observations are key to know the implications and interpretations of unresolved GRB hosts observations at higher redshifts. [ABSTRACT FROM AUTHOR]

An injectable permeable reactive barrier ( PRB) technology was developed to sequester 90Sr in groundwater through the in situ formation of calcium-phosphate mineral phases, specifically apatite that incorporates 90Sr into the chemical structure. This injectable barrier technology extends the PRB concept to sites where groundwater contaminants are too deep or where site conditions otherwise preclude the application of more traditional trench-emplaced barriers. An integrated, multiscale development and testing approach was used that included laboratory bench-scale experiments, an initial pilot-scale field test, and the emplacement and evaluation of a 300-feet-long treatability-test-scale PRB. The apatite amendment formulation uses two separate precursor solutions, one containing a Ca-citrate complex and the other a Na-phosphate solution, to form apatite precipitate in situ. Citrate is needed to keep calcium in solution long enough to achieve a more uniform and areally extensive distribution of precipitate formation. In the summer of 2008, the apatite PRB technology was applied as a 91-m-long (300 feet) PRB on the downgradient edge of a 90Sr plume beneath the Hanford Site in Washington State. The technology was deployed to reduce 90Sr flux discharging to the Columbia River. Performance assessment monitoring data collected to date indicate that the barrier is meeting treatment objectives (i.e., 90% reduction in 90Sr concentration). The average reduction in 90Sr concentrations at four downgradient compliance monitoring locations was 95% relative to the high end of the baseline range approximately 1 year after treatment, and continues to meet remedial objectives more than 4 years after treatment. [ABSTRACT FROM AUTHOR]

We present comprehensive multiwavelength observations of three gamma-ray bursts (GRBs) with durations of several thousand seconds. We demonstrate that these events are extragalactic transients; in particular, we resolve the long-standing conundrum of the distance of GRB 101225A (the “Christmas-day burst”), finding it to have a redshift z = 0.847 and showing that two apparently similar events (GRB 111209A and GRB 121027A) lie at z = 0.677 and z = 1.773, respectively. The systems show extremely unusual X-ray and optical light curves, very different from classical GRBs, with long-lasting, highly variable X-ray emission and optical light curves that exhibit little correlation with the behavior seen in the X-ray. Their host galaxies are faint, compact, and highly star-forming dwarf galaxies, typical of “blue compact galaxies.” We propose that these bursts are the prototypes of a hitherto largely unrecognized population of ultra-long GRBs, which while observationally difficult to detect may be astrophysically relatively common. The long durations may naturally be explained by the engine-driven explosions of stars of much larger radii than normally considered for GRB progenitors, which are thought to have compact Wolf-Rayet progenitor stars. However, we cannot unambiguously identify supernova signatures within their light curves or spectra. We also consider the alternative possibility that they arise from the tidal disruption of stars by massive black holes and conclude that the associated timescales are only consistent with the disruption of compact stars (e.g., white dwarfs) by black holes of relatively low mass (<105M☼). [ABSTRACT FROM AUTHOR]

Recently, it has been suggested that the metallicity aversion of Long-duration Gamma Ray Bursts (LGRBs) is not intrinsic to their formation, but rather a consequence of the anti-correlation between star formation and metallicity seen in the general galaxy population. To investigate this proposal, we compare the metallicity of the hosts of LGRBs, broad-lined Type Ic (Ic-bl) supernovae (SNe), and Type II SNe to each other and to the metallicity distribution of star-forming galaxies using the Sloan Digital Sky Survey (SDSS) to represent galaxies in the local universe and the Team Keck Redshift Survey (TKRS) for galaxies at intermediate redshifts. The differing metallicity distributions of LGRB hosts and the star formation in local galaxies forces us to conclude that the low-metallicity preference of LGRBs is not primarily driven by the anti-correlation between star formation and metallicity, but rather must be overwhelmingly due to the astrophysics of the LGRBs themselves. Three quarters of our LGRB sample are found at metallicities below 12+log(O/H)<8.6, while less than a one-tenth of local star formation is at similarly low metallicities. However, our SN samples are statistically consistent with the metallicity distribution of the general galaxy population. Additionally, we show that the star formation rate distribution of the LGRB and SNe host populations are consistent with the star formation rate distribution of the SDSS galaxy sample. This provides further evidence that the low-metallicity distribution of LGRBs is not caused by the general properties of star-forming galaxies. Using the TKRS population of galaxies, we can exclude the possibility that the LGRB host metallicity aversion is caused by the decrease in galaxy metallicity with redshift, as this effect is clearly much smaller than the observed LGRB host metallicity bias over the redshift span of our sample. The presence of the strong metallicity difference between LGRBs and Type Ic-bl SNe largely eliminates the possibility that the observed LGRB metallicity bias is a byproduct of a difference in the initial mass functions of the galaxy populations. Rather, metallicity below half-solar must be a fundamental component of the evolutionary process that separates LGRBs from the vast majority of Type Ic-bl SNe and from the bulk of local star formation. [ABSTRACT FROM AUTHOR]

Recently, it has been suggested that the metallicity aversion of long-duration gamma-ray bursts (LGRBs) is not intrinsic to their formation, but rather a consequence of the anti-correlation between star-formation and metallicity seen in the general galaxy population. To investigate this proposal, we compare the metallicity of the hosts of LGRBs, broad-lined Type Ic (Ic-bl) supernovae (SNe), and Type II SNe to each other and to the metallicity distribution of star-forming galaxies using the SDSS to represent galaxies in the local universe and the TKRS for galaxies at intermediate redshifts. The differing metallicity distributions of the LGRB hosts and the star-formation in local galaxies forces us to conclude that the low-metallicity preference of LGRBs is not primarily driven by the anti-correlation between star-formation and metallicity, but rather must be overwhelmingly due to the astrophysics of the LGRBs themselves. Three quarters of our LGRB sample are found at metallicities below 12+log(O/H) < 8.6, while less than a tenth of local star-formation is at similarly low metallicities. However, our SN samples are statistically consistent with the metallicity distribution of the general galaxy population. Using the TKRS population of galaxies, we are able to exclude the possibility that the LGRB host metallieity aversion is caused by the decrease in galaxy metallicity with redshift. The presence of the strong metallicity difference between LGRBs and Ie-bl SNe largely eliminates the possibility that the observed LGRB metallicity bias is a byproduct of a difference in the initial mass functions of the galaxy populations. Rather, metallicity below half-solar must be a fundamental component of the evolutionary process that separates LGRBs from the vast majority of Ic-bl SNe and from the bulk of local star-formation. [ABSTRACT FROM AUTHOR]

Using the sample of Type Ia supernovae (SNe Ia) discovered by the Hubble Space Telescope (HST) Cluster Supernova Survey and augmented with HST-observed SNe Ia in the Great Observatories Origins Deep Survey (GOODS) fields, we search for correlations between the properties of SNe and their host galaxies at high redshift. We use galaxy color and quantitative morphology to determine the red sequence in 25 clusters and develop a model to distinguish passively evolving early-type galaxies from star-forming galaxies in both clusters and the field. With this approach, we identify 6 SN Ia hosts that are early-type cluster members and 11 SN Ia hosts that are early-type field galaxies. We confirm for the first time at z > 0.9 that SNe Ia hosted by early-type galaxies brighten and fade more quickly than SNe Ia hosted by late-type galaxies. We also show that the two samples of hosts produce SNe Ia with similar color distributions. The relatively simple spectral energy distributions expected for passive galaxies enable us to measure stellar masses of early-type SN hosts. In combination with stellar mass estimates of late-type GOODS SN hosts from Thomson & Chary, we investigate the correlation of host mass with Hubble residual observed at lower redshifts. Although the sample is small and the uncertainties are large, a hint of this relation is found at z > 0.9. By simultaneously fitting the average cluster galaxy formation history and dust content to the red-sequence scatters, we show that the reddening of early-type cluster SN hosts is likely E(B - V) ≲ 0.06. The similarity of the field and cluster early-type host samples suggests that field early-type galaxies that lie on the red sequence may also be minimally affected by dust. Hence, the early-type-hosted SNe Ia studied here occupy a more favorable environment to use as well-characterized high-redshift standard candles than other SNe Ia. [ABSTRACT FROM AUTHOR]

We report a measurement of the Type Ia supernova (SN Ia) rate in galaxy clusters at 0.9 < ɀ < 1.46 from the Hubble Space Telescope Cluster Supernova Survey. This is the first cluster SN Ia rate measurement with detected ɀ > 0.9 SNe. Finding 8 ± 1 cluster SNe Ia, we determine an SN Ia rate of 0.50 Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. (stat) Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. (sys) Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. SNuB (SNUB ≡ 10-12 SNe Lʘ-1 yr-1). In units of stellar mass, this translates to. 0.13 Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. (stat) Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. (sys) Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. SNuM (SNuM ≡ 10-12 SNe Mʘ-1 yr-1 ). This represents a factor of ≈5 ± 2 increase over measurements of the cluster rate at ɀ < 0.2. We parameterize the late-time SN Ia delay time distribution (DTD) with a power law: ψ (t) t Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. 5 Under the approximation of a single-burst cluster formation redshift of ɀf = 3, our rate measurement in combination with lower-redshift cluster SN Ia rates constrains s = - 1.41 Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. consistent with measurements of the DTD in the field. This measurement is generally consistent with expectations for the "double degenerate" scenario and inconsistent with some models for the "single degenerate" scenario predicting a steeper DTD at large delay times. We check for environmental dependence and the influence of younger stellar populations by calculating the rate specifically in cluster red-sequence galaxies and in morphologically early-type galaxies, finding results similar to the full cluster rate. Finally, the upper limit of one hostless cluster SN Ia detected in the survey implies that the fraction of stars in the intra-cluster medium is less than 0.47 (95% confidence), consistent with measurements at lower redshifts. [ABSTRACT FROM AUTHOR]

We present a measurement of the volumetric Type Ia supernova (SN la) rate out to ɀ ≃ 1.6 from the Hubble Space Telescope Cluster Supernova Survey. In observations spanning 189 orbits with the Advanced Camera for Surveys we discovered 29 SNe, of which approximately 20 are SNe Ia. Twelve of these SNe Ia are located in the foregrounds and backgrounds of the clusters targeted in the survey. Using these new data, we derive the volumetric SN la rate in four broad redshift bins, finding results consistent with previous measurements at ɀ ≳1 and strengthening the case for an SN Ia rate that is ≳0.6 x 10-4 Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. yr-1 Mpc-3 at ɀ ~ 1 and flattening out at higher redshift. We provide SN candidates and efficiency calculations in a form that makes it easy to rebin and combine these results with other measurements for increased statistics. Finally, we compare the assumptions about host-galaxy dust extinction used in different high-redshift rate measurements, finding that different assumptions may induce significant systematic differences between measurements. [ABSTRACT FROM AUTHOR]

We present ground-based and Hubble Space Telescope optical and infrared observations of Swift XRF 100316D/SN 2010bh. It is seen that the optical light curves of SN 2010bh evolve at a faster rate than the archetype gamma-ray burst supernova (GRB-SN) 1998bw, but at a similar rate to SN 2006aj, an SN that was spectroscopically linked with XRF 060218, and at a similar rate to the non-GRB associated Type Ic SN 19941. We estimate the rest-frame extinction of this event from our optical data to be E(B - V) = 0.18 ± 0.08 mag. We find the V-band absolute magnitude of SN 2010bh to be Mv = -18.62 ± 0.08, which is the faintest peak V-band magnitude observed to date for spectroscopically confirmed GRB-SNe. When we investigate the origin of the flux at t - t0 = 0.598 days, it is shown that the light is not synchrotron in origin, but is likely coming from the SN shock breakout. We then use our optical and infrared data to create a quasi-bolometric light curve of SN 2010bh, which we model with a simple analytical formula. The results of our modeling imply that SN 2010bh synthesized a nickel mass of MNi ≈ 0.1 M⊙, ejected Mej ≈ 2.2 M⊙, and has an explosion energy of Ek ≈ 1.4 x 1052 erg. Thus, while SN 2010bh is an energetic explosion, the amount of nickel created during the explosion is much less than that of SN 1998bw and only marginally more than SN 1994I. Finally, for a sample of 22 GRB-SNe we check for a correlation between the stretch factors and luminosity factors in the R band and conclude that no statistically significant correlation exists. [ABSTRACT FROM AUTHOR]

It has been suggested that the apparent bias of long-duration GRBs (LGRBs) to low metallicity environments might be a result of the fact that star-formation is anti-correlated with metallicity. However, if this were the cause, one would expect other indicators of star formation, such as Type II and Type Ic SNe to demonstrate a similar bias. Here we show that local Type Ic and Type II SNe track the star-formation weighted metallicity distribution of the SDSS galaxies. In contrast LGRBs are typically found at far-lower metallicities than would be expected based on the distribution of star-formation. This is true even when one takes into account so-called “dark bursts”. Indeed, while we will present data that show that some LGRBs form at very high metallicities, these objects enter the sample because of the large effective search volume produced by their bright hosts. The bias of LGRBs to low metallicity is real and must be related to a mechanism which is crucial in their formation. [ABSTRACT FROM PUBLISHER]

The majority of short gamma-ray bursts (SGRBs) are thought to originate from the merger of compact binary systems collapsing directly to form a black hole. However, it has been proposed that both SGRBs and long gamma-ray bursts (LGRBs) may, on rare occasions, form an unstable millisecond pulsar (magnetar) prior to final collapse. GRB 090515, detected by the Swift satellite was extremely short, with a T of 0.036 ± 0.016 s, and had a very low fluence of erg cm and faint optical afterglow. Despite this, the 0.3-10 keV flux in the first 200 s was the highest observed for an SGRB by the Swift X-ray Telescope (XRT). The X-ray light curve showed an unusual plateau and steep decay, becoming undetectable after ∼500 s. This behaviour is similar to that observed in some long bursts proposed to have magnetars contributing to their emission. In this paper, we present the Swift observations of GRB 090515 and compare it to other gamma-ray bursts (GRBs) in the Swift sample. Additionally, we present optical observations from Gemini, which detected an afterglow of magnitude at T+ 1.7 h after the burst. We discuss potential causes of the unusual 0.3-10 keV emission and suggest it might be energy injection from an unstable millisecond pulsar. Using the duration and flux of the plateau of GRB 090515, we place constraints on the millisecond pulsar spin period and magnetic field. [ABSTRACT FROM AUTHOR]

We present a comparative study of the galactic and small-scale environments of gamma-ray bursts (GRBs) and core-collapse supernovae (CCSNe). We use a sample of 34 GRB hosts at , and a comparison sample of 58 supernova hosts located within the Great Observatories Origins Deep Survey footprint. We fit template spectra to the available photometric data, which span the range 0.45–24 μm, and extract absolute magnitudes, stellar masses and star formation rates from the resulting fits. Our results broadly corroborate previous findings, but offer significant enhancements in spectral coverage and a factor 2–3 increase in sample size. Specifically, we find that CCSNe occur frequently in massive spirals (spiral fraction ∼50 per cent). In contrast GRBs occur in small, relatively low mass galaxies with high specific and surface star formation rates, and have a spiral fraction of only ∼10 per cent. A comparison of the rest-frame absolute magnitudes of the GRB and CCSN sample is less conclusive than found in previous work, suggesting that while GRB hosts are typically both smaller and bluer than those of CCSN their total blue light luminosities are only slightly lower. We suggest this is likely due to rapid periods of intensified star formation activity, as indicated by the high specific SFRs, which both create the GRB progenitors and briefly significantly enhance the host galaxy blue luminosity. Finally, our analysis of local environments of GRBs and CCSNe shows that GRBs are highly concentrated on their host light, and further occur in regions of higher absolute surface luminosity than CCSNe. [ABSTRACT FROM AUTHOR]