Showing papers by "Steve Schulze published in 2015"
Queen's University Belfast1, Las Cumbres Observatory Global Telescope Network2, University of California, Santa Barbara3, University of Cambridge4, University of Southampton5, Weizmann Institute of Science6, Max Planck Society7, European Southern Observatory8, Liverpool John Moores University9, Pierre-and-Marie-Curie University10, Yale University11, Sapienza University of Rome12, Pontifical Catholic University of Chile13, Space Science Institute14, Millennium Institute15, Andrés Bello National University16, Australian National University17, Aarhus University18, Carnegie Institution for Science19, University of Chile20, Institut d'Astrophysique de Paris21, Spanish National Research Council22, University of Bonn23, Humboldt University of Berlin24, University of Würzburg25, University of Turku26, Stockholm University27, University of Copenhagen28, University of Warwick29, University of Oxford30, University of California, Berkeley31, Lawrence Berkeley National Laboratory32, University of Padua33, University of Warsaw34
TL;DR: The first data release (SSDR1) contains flux calibrated spectra from the first year (April 2012-2013), and a total of 221 confirmed supernovae were classified, and they released calibrated optical spectra and classifications publicly within 24 h of the data being taken as mentioned in this paper.
Abstract: Context. The Public European Southern Observatory Spectroscopic Survey of Transient Objects (PESSTO) began as a public spectroscopic survey in April 2012. PESSTO classifies transients from publicly available sources and wide-field surveys, and selects science targets for detailed spectroscopic and photometric follow-up. PESSTO runs for nine months of the year, January - April and August - December inclusive, and typically has allocations of 10 nights per month. Aims. We describe the data reduction strategy and data products that are publicly available through the ESO archive as the Spectroscopic Survey data release 1 (SSDR1). Methods. PESSTO uses the New Technology Telescope with the instruments EFOSC2 and SOFI to provide optical and NIR spectroscopy and imaging. We target supernovae and optical transients brighter than 20.5(m) for classification. Science targets are selected for follow-up based on the PESSTO science goal of extending knowledge of the extremes of the supernova population. We use standard EFOSC2 set-ups providing spectra with resolutions of 13-18 angstrom between 3345-9995 angstrom. A subset of the brighter science targets are selected for SOFI spectroscopy with the blue and red grisms (0.935-2.53 mu m and resolutions 23-33 angstrom) and imaging with broadband JHK(s) filters. Results. This first data release (SSDR1) contains flux calibrated spectra from the first year (April 2012-2013). A total of 221 confirmed supernovae were classified, and we released calibrated optical spectra and classifications publicly within 24 h of the data being taken (via WISeREP). The data in SSDR1 replace those released spectra. They have more reliable and quantifiable flux calibrations, correction for telluric absorption, and are made available in standard ESO Phase 3 formats. We estimate the absolute accuracy of the flux calibrations for EFOSC2 across the whole survey in SSDR1 to be typically similar to 15%, although a number of spectra will have less reliable absolute flux calibration because of weather and slit losses. Acquisition images for each spectrum are available which, in principle, can allow the user to refine the absolute flux calibration. The standard NIR reduction process does not produce high accuracy absolute spectrophotometry but synthetic photometry with accompanying JHK(s) imaging can improve this. Whenever possible, reduced SOFI images are provided to allow this. Conclusions. Future data releases will focus on improving the automated flux calibration of the data products. The rapid turnaround between discovery and classification and access to reliable pipeline processed data products has allowed early science papers in the first few months of the survey.
286 citations
Weizmann Institute of Science1, University of Copenhagen2, Pontifical Catholic University of Chile3, Millennium Institute4, European Southern Observatory5, University of the Basque Country6, Spanish National Research Council7, Ikerbasque8, Space Science Institute9, Subaru10, Valparaiso University11, Carnegie Institution for Science12, University of Szeged13, University of Texas at Austin14
TL;DR: In this article, the authors present the first results of their project to study SUperluminous supernova host galaxies (SUSHIES), focusing on the sample for which they have obtained spectroscopy.
Abstract: Superluminous supernovae (SLSNe) were only discovered recently due to their preference for occurring in faint dwarf galaxies. Understanding why stellar evolution yields dierent types of stellar explosions in these environments is fundamental in order to both uncover the elusive progenitors of SLSNe and to study star formation in dwarf galaxies. In this paper, we present the rst results of our project to study SUperluminous Supernova Host galaxIES (SUSHIES), focusing on the sample for which we have obtained spectroscopy. We show that SLSNe-I and SLSNe-R (hydrogen-poor) often ( 50% in our sample) occur in a class of galaxies that is known as Extreme Emission Line Galaxies (EELGs). The probability of this happening by chance is negligible and we therefore conclude that the extreme environmental conditions and the SLSN phenomenon are related. In contrast, SLSNe-II (hydrogen-rich) occur in more massive, more metal-rich galaxies with softer radiation elds. Therefore, if SLSNe-II constitute a uniform class, their progenitor systems must be dierent from those of H-poor SLSNe. Gamma-ray bursts (GRBs) are, on average, not found in as extreme environments as H-poor SLSNe. We propose that H-poor SLSNe result from the very rst stars exploding in a starburst, even earlier than GRBs. This might indicate a bottom-light initial mass function in these systems. SLSNe present a novel method of selecting candidate EELGs independent of their luminosity.
248 citations
European Southern Observatory1, University of Copenhagen2, University of Amsterdam3, University of Iceland4, California Institute of Technology5, INAF6, Max Planck Society7, Millennium Institute8, Pontifical Catholic University of Chile9, University of Leicester10, Janssen Pharmaceutica11, American River College12, Spanish National Research Council13, Czech Technical University in Prague14, Paris Diderot University15, University of Ljubljana16, University of Warwick17, Weizmann Institute of Science18, University of the Basque Country19, Ikerbasque20, University of Calabria21
TL;DR: In this article, the authors 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 2 by 0.4 dex.
Abstract: 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 2 by ~0.4 dex. These properties of GRB hosts and their evolution with redshift can be understood in a cosmological context of star-forming galaxies and a picture in which the hosts’ properties at low redshift are influenced by the tendency of GRBs to avoid the most metal-rich environments.
221 citations
Queen's University Belfast1, INAF2, University of Cambridge3, Weizmann Institute of Science4, European Southern Observatory5, University of Southampton6, Las Cumbres Observatory Global Telescope Network7, University of California, Santa Barbara8, Yale University9, Space Science Institute10, Millennium Institute11, Pontifical Catholic University of Chile12, Centre national de la recherche scientifique13, University of Paris14, Liverpool John Moores University15, Australian National University16, Institut d'Astrophysique de Paris17, Humboldt University of Berlin18, University of Bonn19, University of Chile20, University of Copenhagen21, Stockholm University22
TL;DR: In this article, a sample of 24 hydrogen-poor superluminous supernovae (SLSNe) was assembled and the authors measured the light-curve shape through rise and decline time-scales.
Abstract: We assemble a sample of 24 hydrogen-poor superluminous supernovae (SLSNe). Parameterizing the light-curve shape through rise and decline time-scales shows that the two are highly correlated. Magnetar-powered models can reproduce the correlation, with the diversity in rise and decline rates driven by the diffusion time-scale. Circumstellar interaction models can exhibit a similar rise–decline relation, but only for a narrow range of densities, which may be problematic for these models. We find that SLSNe are approximately 3.5 mag brighter and have light curves three times broader than SNe Ibc, but that the intrinsic shapes are similar. There are a number of SLSNe with particularly broad light curves, possibly indicating two progenitor channels, but statistical tests do not cleanly separate two populations. The general spectral evolution is also presented. Velocities measured from Fe II are similar for SLSNe and SNe Ibc, suggesting that diffusion time differences are dominated by mass or opacity. Flat velocity evolution in most SLSNe suggests a dense shell of ejecta. If opacities in SLSNe are similar to other SNe Ibc, the average ejected mass is higher by a factor 2–3. Assuming κ = 0.1 cm2 g−1, we estimate a mean (median) SLSN ejecta mass of 10 M⊙ (6 M⊙), with a range of 3–30 M⊙. Doubling the assumed opacity brings the masses closer to normal SNe Ibc, but with a high-mass tail. The most probable mechanism for generating SLSNe seems to be the core collapse of a very massive hydrogen-poor star, forming a millisecond magnetar.
216 citations
European Southern Observatory1, Yale University2, INAF3, University of Hawaii4, University of Bonn5, Humboldt University of Berlin6, University of Cambridge7, University of Chile8, Millennium Institute9, University of Turku10, Pontifical Catholic University of Chile11, University of Southampton12, Las Cumbres Observatory Global Telescope Network13, University of California, Santa Barbara14
TL;DR: In this article, a hydrogen-poor super-luminous supernova (SLSN) was discovered by the La Silla QUEST survey and classified by the Public ESO Spectroscopic Survey of Transient Objects.
Abstract: We present data for LSQ14bdq, a hydrogen-poor super-luminous supernova (SLSN) discovered by the La Silla QUEST survey and classified by the Public ESO Spectroscopic Survey of Transient Objects. The spectrum and light curve are very similar to slow-declining SLSNe such as PTF12dam. However, detections within ~1 day after explosion show a bright and relatively fast initial peak, lasting for ~15 days, prior to the usual slow rise to maximum light. The broader, main peak can be fit with either central engine or circumstellar interaction models. We discuss the implications of the precursor peak in the context of these models. It is too bright and narrow to be explained as a normal 56Ni-powered SN, and we suggest that interaction models may struggle to fit the two peaks simultaneously. We propose that the initial peak may arise from the post-shock cooling of extended stellar material, and reheating by a central engine drives the second peak. In this picture, we show that an explosion energy of $\sim 2\times {10}^{52}$ erg and a progenitor radius of a few hundred solar radii would be required to power the early emission. The competing engine models involve rapidly spinning magnetars (neutron stars) or fallback onto a central black hole. The prompt energy required may favor the black hole scenario. The bright initial peak may be difficult to reconcile with a compact Wolf–Rayet star as a progenitor since the inferred energies and ejected masses become unphysical.
127 citations
University of Iceland1, Weizmann Institute of Science2, University of Copenhagen3, European Southern Observatory4, Ikerbasque5, Spanish National Research Council6, University of the Basque Country7, University of Leicester8, Max Planck Society9, University of North Carolina at Chapel Hill10, Instituto Politécnico Nacional11, INAF12, Heidelberg University13, Paris Diderot University14, University of Amsterdam15, Millennium Institute16, Pontifical Catholic University of Chile17
TL;DR: The first reported case of the simultaneous metallicity determination of a gamma-ray burst (GRB) host galaxy, from both afterglow absorption lines as well as strong emission-line diagnostics, was reported in this paper.
Abstract: We present the first reported case of the simultaneous metallicity determination of a gamma-ray burst (GRB) host galaxy, from both afterglow absorption lines as well as strong emission-line diagnostics. Using spectroscopic and imaging observations of the afterglow and host of the long-duration Swift GRB 121024A at z = 2.30, we give one of the most complete views of a GRB host/environment to date. We observe a strong damped Lyα absorber (DLA) with a hydrogen column density of log N(HI)=21.88±0.10, H2 absorption in the Lyman-Werner bands (molecular fraction of log(f) ≈−1.4; fourth solid detection of molecular hydrogen in a GRB-DLA), the nebular emission lines Hα, Hβ, [O ii], [O iii] and [N ii], as well as metal absorption lines. We find a GRB host galaxy that is highly star forming (SFR ∼ 40 M⊙ yr−1), with a dust-corrected metallicity along the line of sight of [Zn/H]corr = −0.6 ± 0.2 ([O/H] ∼ −0.3 from emission lines), and a depletion factor [Zn/Fe] = 0.85 ± 0.04. The molecular gas is separated by 400 km s−1 (and 1-3 kpc) from the gas that is photoexcited by the GRB. This implies a fairly massive host, in agreement with the derived stellar mass of log(M★/M⊙) = 9.9+0.2−0.3. We dissect the host galaxy by characterizing its molecular component, the excited gas, and the line-emitting star-forming regions. The extinction curve for the line of sight is found to be unusually flat (RV ∼ 15). We discuss the possibility of an anomalous grain size distributions. We furthermore discuss the different metallicity determinations from both absorption and emission lines, which gives consistent results for the line of sight to GRB 121024A.
91 citations
Pontifical Catholic University of Chile1, Millennium Institute2, University of Iceland3, University of Hertfordshire4, University of Copenhagen5, University of Warwick6, California Institute of Technology7, European Southern Observatory8, Ikerbasque9, Spanish National Research Council10, University of the Basque Country11, University of Leicester12
TL;DR: The Optically Unbiased GRB Host (Tough) survey as mentioned in this paper includes observations of all GRB hosts (69) in an optically unbiased sample of Swift GRBs; they utilize these to constrain the evolution of the UV GRB-host-galaxy luminosity function (LF) between z = 0 and z = 4.5, and compare this with LFs derived from both Lyman break galaxy (LBG) surveys and simulation modeling.
Abstract: Gamma-ray bursts (GRBs) offer a route to characterizing star-forming galaxies and quantifying high-z star formation that is distinct from the approach of traditional galaxy surveys: GRB selection is independent of dust and probes even the faintest galaxies which can evade detection in flux-limited surveys. However, the exact relation between the GRB rate and the star formation rate (SFR) throughout all redshifts is controversial. The Optically Unbiased GRB Host (TOUGH) survey includes observations of all GRB hosts (69) in an optically unbiased sample of Swift GRBs; we utilize these to constrain the evolution of the UV GRB-host-galaxy luminosity function (LF) between z = 0 and z = 4.5, and compare this with LFs derived from both Lyman-break galaxy (LBG) surveys and simulation modeling. At all redshifts we find the GRB hosts to be most consistent with an LF derived from SFR weighted models incorporating GRB production via both metallicity-dependent and independent channels with a relatively high level of bias toward low metallicity hosts. In the range 1 < z < 3 an SFR weighted LBG derived (i.e., non-metallicity biased) LF is also a reasonable fit to the data. Between z ~ 3 and z ~ 6, we observe an apparent lack of UV bright hosts in comparison with LBGs, though the significance of this shortfall is limited by nine hosts of unknown redshift.
87 citations
European Southern Observatory1, Yale University2, INAF3, University of Hawaii4, University of Bonn5, Humboldt University of Berlin6, University of Cambridge7, Millennium Institute8, University of Chile9, University of Turku10, Pontifical Catholic University of Chile11, University of Southampton12, Las Cumbres Observatory Global Telescope Network13, University of California, Santa Barbara14
TL;DR: In this article, a hydrogen-poor super-luminous supernova (SLSN) was discovered by the La Silla QUEST survey and classified by the Public ESO Spectroscopic Survey of Transient Objects.
Abstract: We present data for LSQ14bdq, a hydrogen-poor super-luminous supernova (SLSN) discovered by the La Silla QUEST survey and classified by the Public ESO Spectroscopic Survey of Transient Objects. The spectrum and light curve are very similar to slow-declining SLSNe such as PTF12dam. However, detections within ~1 day after explosion show a bright and relatively fast initial peak, lasting for ~15 days, prior to the usual slow rise to maximum light. The broader, main peak can be fit with either central engine or circumstellar interaction models. We discuss the implications of the precursor peak in the context of these models. It is too bright and narrow to be explained as a normal 56Ni-powered SN, and we suggest that interaction models may struggle to fit the two peaks simultaneously. We propose that the initial peak may arise from the post-shock cooling of extended stellar material, and reheating by a central engine drives the second peak. In this picture, we show that an explosion energy of ~2x10^{52} erg and a progenitor radius of a few hundred solar radii would be required to power the early emission. The competing engine models involve rapidly spinning magnetars (neutron stars) or fall-back accretion onto a central black hole. The prompt energy required may favour the black hole scenario. The bright initial peak effectively rules out a compact Wolf-Rayet star as a progenitor, since the inferred energies and ejected masses become unphysical.
70 citations
University of Copenhagen1, Weizmann Institute of Science2, European Southern Observatory3, University of Sheffield4, Aarhus University5, Florida State University6, Pontifical Catholic University of Chile7, Millennium Institute8, Carnegie Institution for Science9, Spanish National Research Council10, Stockholm University11, University of Texas at Austin12, University of the Basque Country13
TL;DR: The first polarimetric observations of a Type I superluminous supernova (SLSN) was presented in this paper, where LSQ14mo was observed with VLT/FORS2 at five different epochs in the V band, with the observations starting before maximum light and spanning 26 days in the rest frame.
Abstract: We present the first polarimetric observations of a Type I superluminous supernova (SLSN). LSQ14mo was observed with VLT/FORS2 at five different epochs in the V band, with the observations starting before maximum light and spanning 26 days in the rest frame (z. = 0.256). During this period, we do not detect any statistically significant evolution (<2 sigma) in the Stokes parameters. The average values we obtain, corrected for interstellar polarization in the Galaxy, are Q = -0.01% (+/- 0.15%) and U = -0.50% (+/- 0.14%). This low polarization can be entirely due to interstellar polarization in the SN host galaxy. We conclude that, at least during the period of observations and at the optical depths probed, the photosphere of LSQ14mo does not present significant asymmetries, unlike most lower-luminosity hydrogen-poor SNe Ib/c. Alternatively, it is possible that we may have observed LSQ14mo from a special viewing angle. Supporting spectroscopy and photometry confirm that LSQ14mo is a typical SLSN I. Further studies of the polarization of Type I SLSNe are required to determine whether the low levels of polarization are a characteristic of the entire class and to also study the implications for the proposed explosion models.
55 citations
University of Iceland1, Spanish National Research Council2, Niels Bohr Institute3, California Institute of Technology4, European Southern Observatory5, Harvard University6, University of the Basque Country7, Ikerbasque8, Millennium Institute9, Pontifical Catholic University of Chile10, University of Leicester11, Chinese Academy of Sciences12
TL;DR: In this paper, optical and near-infrared photometry of GRB 140606B (z = 0.384), and optical photometry and spectroscopy of its associated supernova (SN).
Abstract: We present optical and near-infrared photometry of GRB 140606B (z = 0.384), and optical photometry and spectroscopy of its associated supernova (SN). The results of our modelling indicate that the bolometric properties of the SN (M_(Ni) = 0.4 ± 0.2 M_⊙, M_(ej) = 5 ± 2 M_⊙, and E_K = 2 ± 1 × 10^(52) erg) are fully consistent with the statistical averages determined for other γ-ray burst (GRB)-SNe. However, in terms of its γ-ray emission, GRB 140606B is an outlier of the Amati relation, and occupies the same region as low luminosity (ll) and short GRBs. The γ-ray emission in llGRBs is thought to arise in some or all events from a shock breakout (SBO), rather than from a jet. The measured peak photon energy (E_p ≈ 800 keV) is close to that expected for γ-rays created by an SBO (≳ 1 MeV). Moreover, based on its position in the M_(V, p)-L_(iso, γ) plane and the E_K–Γβ plane, GRB 140606B has properties similar to both SBO-GRBs and jetted-GRBs. Additionally, we searched for correlations between the isotropic γ-ray emission and the bolometric properties of a sample of GRB-SNe, finding that no statistically significant correlation is present. The average kinetic energy of the sample is E¯_K = 2.1×10^(52) erg. All of the GRB-SNe in our sample, with the exception of SN 2006aj, are within this range, which has implications for the total energy budget available to power both the relativistic and non-relativistic components in a GRB-SN event.
48 citations
TL;DR: In this paper, a resolved long-slit study of the host of the hydrogen-poor SLSN PTF12dam probing the kpc environment of the SN site to determine the age of the progenitor was presented.
Abstract: The progenitors of super luminous supernovae (SLSNe) are still a mystery. Hydrogen-poor SLSN hosts are often highly star-forming dwarf galaxies and the majority belongs to the class of extreme emission line galaxies hosting young and highly star-forming stellar populations. Here we present a resolved long-slit study of the host of the hydrogen-poor SLSN PTF12dam probing the kpc environment of the SN site to determine the age of the progenitor. The galaxy is a "tadpole" with uniform properties and the SN occurred in a star-forming region in the head of the tadpole. The galaxy experienced a recent star-burst superimposed on an underlying old stellar population. We measure a very young stellar population at the SN site with an age of ~3 Myr and a metallicity of 12+log(O/H)=8.0 at the SN site but do not observe any WR features. The progenitor of PTF12dam must have been a massive star of at least 60 M_solar and one of the first stars exploding as a SN in this extremely young starburst.
INAF1, University of Cambridge2, University of Warsaw3, Las Cumbres Observatory Global Telescope Network4, University of California, Santa Barbara5, Diego Portales University6, Millennium Institute7, Institut de Ciències de l'Espai8, European Southern Observatory9, National University of La Plata10, Institute for the Physics and Mathematics of the Universe11, National Scientific and Technical Research Council12, Weizmann Institute of Science13, University of Birmingham14, Max Planck Society15, University of Würzburg16, Queen's University Belfast17, Dartmouth College18, University of Concepción19, Ohio State University20
TL;DR: The OGLE-2012-SN-006 was discovered and monitored by the Optical Gravitational Lensing Experiment-IV survey, and spectroscopically followed by Public ESO Spectroscopic Survey of Transient Objects (PESSTO) at late phases as discussed by the authors.
Abstract: We present optical observations of the peculiar Type Ibn supernova (SN Ibn) OGLE-2012-SN-006, discovered and monitored by the Optical Gravitational Lensing Experiment-IV survey, and spectroscopically followed by Public ESO Spectroscopic Survey of Transient Objects (PESSTO) at late phases. Stringent pre-discovery limits constrain the explosion epoch with fair precision to JD = 245 6203.8 ± 4.0. The rise time to the I-band light-curve maximum is about two weeks. The object reaches the peak absolute magnitude MI = −19.65 ± 0.19 on JD = 245 6218.1 ± 1.8. After maximum, the light curve declines for about 25 d with a rate of 4 mag (100 d)−1. The symmetric I-band peak resembles that of canonical Type Ib/c supernovae (SNe), whereas SNe Ibn usually exhibit asymmetric and narrower early-time light curves. Since 25 d past maximum, the light curve flattens with a decline rate slower than that of the 56Co–56Fe decay, although at very late phases it steepens to approach that rate. However, other observables suggest that the match with the 56Co decay rate is a mere coincidence, and the radioactive decay is not the main mechanism powering the light curve of OGLE-2012-SN-006. An early-time spectrum is dominated by a blue continuum, with only a marginal evidence for the presence of He i lines marking this SN type. This spectrum shows broad absorptions bluewards than 5000 A, likely O ii lines, which are similar to spectral features observed in superluminous SNe at early epochs. The object has been spectroscopically monitored by PESSTO from 90 to 180 d after peak, and these spectra show the typical features observed in a number of SN 2006jc-like events, including a blue spectral energy distribution and prominent and narrow (vFWHM ≈ 1900 km s−1) He i emission lines. This suggests that the ejecta are interacting with He-rich circumstellar material. The detection of broad (104 km s−1) O i and Ca ii features likely produced in the SN ejecta (including the [O i] λλ6300,6364 doublet in the latest spectra) lends support to the interpretation of OGLE-2012-SN-006 as a core-collapse event.
University of Nevada, Las Vegas1, INAF2, University College London3, Spanish National Research Council4, Millennium Institute5, University of Iceland6, Pontifical Catholic University of Chile7, Liverpool John Moores University8, University of Ferrara9, University of Leicester10, University of the Basque Country11, Ikerbasque12, Goddard Space Flight Center13, Russian Academy of Sciences14, Ariès15, Seoul National University16, Tata Institute of Fundamental Research17, University of Michigan18, National Taiwan Normal University19, Kyung Hee University20, Korea Astronomy and Space Science Institute21, University of Ljubljana22, Brera Astronomical Observatory23, Technion – Israel Institute of Technology24, Space Telescope Science Institute25, National Central University26
TL;DR: In this paper, a wide data set of gamma-ray, X-ray and UVOIR observations of the Swift GRB100814A burst is presented, which shows a sudden and prominent rebrightening in the optical band only, followed by a fast decay in both bands.
Abstract: We present a wide data set of gamma-ray, X-ray, UV/Opt/IR (UVOIR), and radio observations of the Swift GRB100814A. At the end of the slow decline phase of the X-ray and optical afterglow, this burst shows a sudden and prominent rebrightening in the optical band only, followed by a fast decay in both bands. The optical rebrightening also shows chromatic evolution. Such a puzzling behaviour cannot be explained by a single component model. We discuss other possible interpretations, and we find that a model that incorporates a long-lived reverse shock and forward shock fits the temporal and spectral properties of GRB100814 the best.
INAF1, Max Planck Society2, University of Edinburgh3, University of Copenhagen4, University of Calabria5, Millennium Institute6, Pontifical Catholic University of Chile7, American River College8, Spanish National Research Council9, Czech Technical University in Prague10, Clemson University11, European Southern Observatory12, Andrés Bello National University13, Roger Williams University14
TL;DR: In this paper, the authors used the multi-colour imager GROND at the ESO/La Silla MPG 2.2 m telescope, VLT/FORS2 spectroscopy, and deep Australia Telescope Compact Array (ATCA) radio-continuum observations together with publicly available Gemini imaging data to study the putative host and the galaxies in the field of GRB 100628A.
Abstract: We report on the results of a comprehensive observing campaign to reveal the host galaxy of the short GRB 100628A. This burst was followed by a faint X-ray afterglow but no optical counterpart was discovered. However, inside the X-ray error circle a potential host galaxy at a redshift of z = 0.102 was soon reported in the literature. If this system is the host, then GRB 100628A was the cosmologically most nearby unambiguous short burst with a measured redshift so far. We used the multi-colour imager GROND at the ESO/La Silla MPG 2.2 m telescope, ESO/VLT spectroscopy, and deep Australia Telescope Compact Array (ATCA) radio-continuum observations together with publicly available Gemini imaging data to study the putative host and the galaxies in the field of GRB 100628A. We confirm that inside the X-ray error circle the most probable host-galaxy candidate is the morphologically disturbed, interacting galaxy system at z = 0.102. The interacting galaxies are connected by a several kpc long tidal stream, which our VLT/FORS2 spectroscopy reveals strong emission lines of [O ii], [O iii], Hα and Hβ , characteristic for the class of extreme emission-line galaxies and indicative of ongoing star formation. The latter leaves open the possibility that the GRB progenitor was a member of a young stellar population. However, we indentify a second host-galaxy candidate slightly outside the X-ray error circle. It is a radio-bright, luminous elliptical galaxy at a redshift z = 0.311. With a K -band luminosity of 2 × 1011 L ⊙ this galaxy resembles the probable giant elliptical host of the first well-localized short burst, GRB 050509B. If this is the host, then the progenitor of GRB 100628A was a member of an old stellar population.
University of Copenhagen1, California Institute of Technology2, European Southern Observatory3, Millennium Institute4, Pontifical Catholic University of Chile5, Spanish National Research Council6, Harvard University7, Goddard Space Flight Center8, University of Maryland, College Park9, University of Arizona10, Max Planck Society11, University of Iceland12, University of Warwick13, University of Edinburgh14, University of Leicester15
TL;DR: The Swift Gamma-Ray Burst Host Galaxy Legacy Survey (SHOALS) as mentioned in this paper is a multi-observatory high-redshift galaxy survey targeting the largest unbiased sample of long-duration gamma-ray burst hosts yet assembled (119 in total).
Abstract: We introduce the Swift Gamma-Ray Burst Host Galaxy Legacy Survey ("SHOALS"), a multi-observatory high-redshift galaxy survey targeting the largest unbiased sample of long-duration gamma-ray burst hosts yet assembled (119 in total). We describe the motivations of the survey and the development of our selection criteria, including an assessment of the impact of various observability metrics on the success rate of afterglow-based redshift measurement. We briefly outline our host-galaxy observational program, consisting of deep Spitzer/IRAC imaging of every field supplemented by similarly-deep, multi-color optical/NIR photometry, plus spectroscopy of events without pre-existing redshifts. Our optimized selection cuts combined with host-galaxy follow-up have so far enabled redshift measurements for 110 targets (92%) and placed upper limits on all but one of the remainder. About 20% of GRBs in the sample are heavily dust-obscured, and at most 2% originate from z>5.5. Using this sample we estimate the redshift-dependent GRB rate density, showing it to peak at z~2.5 and fall by about an order of magnitude towards low (z=0) redshift, while declining more gradually towards high (z~7) redshift. This behavior is consistent with a progenitor whose formation efficiency varies modestly over cosmic history. Our survey will permit the most detailed examination to date of the connection between the GRB host population and general star-forming galaxies, directly measure evolution in the host population over cosmic time and discern its causes, and provide new constraints on the fraction of cosmic star-formation occurring in undetectable galaxies at all redshifts.
Journal Article•
University of Copenhagen1, Weizmann Institute of Science2, European Southern Observatory3, University of Sheffield4, Aarhus University5, Florida State University6, Pontifical Catholic University of Chile7, Millennium Institute8, Carnegie Institution for Science9, Spanish National Research Council10, Stockholm University11, University of Texas at Austin12, University of the Basque Country13
TL;DR: The first polarimetric observations of a Type I superluminous supernova (SLSN) was presented in this paper, where LSQ14mo was observed with VLT/FORS2 at five different epochs in the V band, with the observations starting before maximum light and spanning 26 days in the rest frame (z=0.256).
Abstract: We present the first polarimetric observations of a Type I superluminous supernova (SLSN). LSQ14mo was observed with VLT/FORS2 at five different epochs in the V band, with the observations starting before maximum light and spanning 26 days in the rest frame (z=0.256). During this period, we do not detect any statistically significant evolution (< 2$\sigma$) in the Stokes parameters. The average values we obtain, corrected for interstellar polarisation in the Galaxy, are Q = -0.01% ($\pm$ 0.15%) and U = - 0.50% ($\pm$ 0.14%). This low polarisation can be entirely due to interstellar polarisation in the SN host galaxy. We conclude that, at least during the period of observations and at the optical depths probed, the photosphere of LSQ14mo does not present significant asymmetries, unlike most lower-luminosity hydrogen-poor SNe Ib/c. Alternatively, it is possible that we may have observed LSQ14mo from a special viewing angle. Supporting spectroscopy and photometry confirm that LSQ14mo is a typical SLSN I. Further studies of the polarisation of Type I SLSNe are required to determine whether the low levels of polarisation are a characteristic of the entire class and to also study the implications for the proposed explosion models.