Measurement of polarized light provides a direct probe of magnetic fields in collimated outflows (jets) of relativistic plasma from accreting stellar-mass black holes at cosmological distances. These ...outflows power brief and intense flashes of prompt gamma-rays known as Gamma Ray Bursts (GRBs), followed by longer-lived afterglow radiation detected across the electromagnetic spectrum. Rapid-response polarimetric observations of newly discovered GRBs have probed the initial afterglow phase. Linear polarization degrees as high as Π∼30% are detected minutes after the end of the prompt GRB emission, consistent with a stable, globally ordered magnetic field permeating the jet at large distances from the central source. In contrast, optical and gamma-ray observations during the prompt phase led to discordant and often controversial results, and no definitive conclusions on the origin of the prompt radiation or the configuration of the magnetic field could be derived. Here we report the detection of linear polarization of a prompt optical flash that accompanied the extremely energetic and long-lived prompt gamma-ray emission from GRB 160625B. Our measurements probe the structure of the magnetic field at an early stage of the GRB jet, closer to the central source, and show that the prompt GRB phase is produced via fast cooling synchrotron radiation in a large-scale magnetic field advected from the central black hole and distorted from dissipation processes within the jet.
Abstract
Gamma-ray bursts (GRBs) are fascinating events due to their panchromatic nature. We study optical plateaus in GRB afterglows via an extended search into archival data. We comprehensively ...analyze all published GRBs with known redshifts and optical plateaus observed by many ground-based telescopes (e.g., Subaru Telescope, RATIR) around the world and several space-based observatories such as the Neil Gehrels Swift Observatory. We fit 500 optical light curves, showing the existence of the plateau in 179 cases. This sample is 75% larger than the previous one, and it is the largest compilation so far of optical plateaus. We discover the 3D fundamental plane relation at optical wavelengths using this sample. This correlation is between the rest-frame time at the end of the plateau emission,
T
opt
*
, its optical luminosity,
L
opt
, and the peak in the optical prompt emission,
L
peak,opt
, thus resembling the three-dimensional (3D) X-ray fundamental plane (the so-called 3D Dainotti relation). We correct our sample for redshift evolution and selection effects, discovering that this correlation is indeed intrinsic to GRB physics. We investigate the rest-frame end-time distributions in X-rays and optical (
T
opt
*
,
T
X
*
), and conclude that the plateau is achromatic only when selection biases are not considered. We also investigate if the 3D optical correlation may be a new discriminant between optical GRB classes and find that there is no significant separation between the classes compared to the Gold sample plane after correcting for evolution.
Abstract
We present the first data release of the James Clerk Maxwell Telescope Plane Survey (JPS), the JPS Public Release 1. JPS is an 850-μm continuum survey of six fields in the northern inner ...Galactic plane in a longitude range of ℓ = 7°–63°, made with the Submillimetre Common-User Bolometer Array 2. This first data release consists of emission maps of the six JPS regions with an average pixel-to-pixel noise of 7.19 mJy beam−1, when smoothed over the beam, and a compact source catalogue containing 7813 sources. The 95 per cent completeness limits of the catalogue are estimated at 0.04 Jy beam−1 and 0.3 Jy for the peak and integrated flux densities, respectively. The emission contained in the compact source catalogue is 42 ± 5 per cent of the total and, apart from the large-scale (greater than 8 arcmin) emission, there is excellent correspondence with features in the 500-μm Herschel maps. We find that, with two-dimensional matching, 98 ± 2 per cent of sources within the fields centred at ℓ = 20°, 30°, 40° and 50° are associated with molecular clouds, with 91 ± 3 per cent of the ℓ = 30° and 40° sources associated with dense molecular clumps. Matching the JPS catalogue to Herschel 70-μm sources, we find that 38 ± 1 per cent of sources show evidence of ongoing star formation. The JPS Public Release 1 images and catalogue will be a valuable resource for studies of star formation in the Galaxy and the role of environment and spiral arms in the star formation process.
We present optical and near-infrared (NIR) photometry of 28 gamma-ray bursts (GRBs) detected by the Swift satellite and rapidly observed by the Reionization and Transients Infrared/Optical (RATIR) ...camera. We compare the optical flux at fiducial times of 5.5 and 11 h after the high-energy trigger to that in the X-ray regime to quantify optical darkness. 46 ± 9 per cent (13/28) of all bursts in our sample and 55 ± 10 per cent (13/26) of long GRBs are optically dark, which is statistically consistently with previous studies. Fitting RATIR optical and NIR spectral energy distributions of 19 GRBs, most (6/7) optically dark GRBs either occur at high redshift (z > 4.5) or have a high dust content in their host galaxies (A
V > 0.3). Performing Kolmogorov–Smirnov tests, we compare the RATIR sample to those previously presented in the literature, finding our distributions of redshift, optical darkness, host dust extinction and X-ray-derived column density to be consistent. The one reported discrepancy is with host galaxy dust content in the BAT6 sample, which appears inconsistent with our sample and other previous literature. Comparing X-ray-derived host galaxy hydrogen column densities to host galaxy dust extinction, we find that GRBs tend to occur in host galaxies with a higher metal-to-dust ratio than our own Galaxy, more akin to the Large and Small Magellanic Clouds. Finally, to mitigate time evolution of optical darkness, we measure βOX, rest at a fixed rest-frame time, t
rest = 1.5 h and fixed rest-frame energies in the X-ray and optical regimes. Choosing to evaluate optical flux at λrest = 0.25 μm, we remove high redshift as a source of optical darkness, demonstrating that optical darkness must result from either high redshift, dust content in the host galaxy along the GRB sight line, or a combination of the two.
We present observations of the possible short GRB 180418A in γ-rays, X-rays, and in the optical. Early optical photometry with the TAROT and RATIR instruments shows a bright peak ( 14.2 AB mag) ...between T + 28 and T + 90 s that we interpret as the signature of a reverse shock. Later observations can be modeled by a standard forward shock model and show no evidence of a jet break, allowing us to constrain the jet collimation to θj > 7°. Using deep late-time optical observations, we place an upper limit of r > 24 AB mag on any underlying host galaxy. The detection of the afterglow in the Swift UV filters constrains the GRB redshift to z < 1.3 and places an upper bound on the γ-ray isotropic equivalent energy Eγ,iso < 3 × 1051 erg. The properties of this GRB (e.g., duration, hardness ratio, energy, and environment) lie at the intersection between short and long bursts, and we cannot conclusively identify its type. We estimate that the probability that it is drawn from the population of short GRBs is 10%-30%.
We present early results from the JCMT (James Clerk Maxwell Telescope) Plane Survey (JPS), which has surveyed the northern inner Galactic plane between longitudes ... = 7... and ... = 63... in the ...850-...m continuum with SCUBA-2 (Submm Common-User Bolometer Array 2), as part of the JCMT Legacy Survey programme. Data from the ... = 30... survey region, which contains the massive-star-forming regions W43 and G29.96, are analysed after approximately 40 per cent of the observations had been completed. The pixel-to-pixel noise is found to be 19 mJy beam... after a smooth over the beam area, and the projected equivalent noise levels in the final survey are expected to be around 10 mJy beam... An initial extraction of compact sources was performed using the FellWalker method, resulting in the detection of 1029 sources above a 5... surface-brightness threshold. The completeness limits in these data are estimated to be around 0.2 Jy beam... (peak flux density) and 0.8 Jy (integrated flux density) and are therefore probably already dominated by source confusion in this relatively crowded section of the survey. The flux densities of extracted compact sources are consistent with those of matching detections in the shallower APEX (Atacama Pathfinder Experiment) Telescope Large Area Survey of the Galaxy (ATLASGAL) survey. We analyse the virial and evolutionary state of the detected clumps in the W43 star-forming complex and find that they appear younger than the Galactic-plane average. (ProQuest: ... denotes formulae/symbols omitted.)
The PR-A and PR-B isoforms of progesterone receptors (PR) have different physiological functions, and their ratio varies widely
in breast cancers. To determine whether the two PR regulate different ...genes, we used human breast cancer cell lines engineered
to express one or the other isoform. Cells were treated with progesterone in triplicate, time-separated experiments, allowing
statistical analyses of microarray gene expression data. Of 94 progesterone-regulated genes, 65 are uniquely regulated by
PR-B, 4 uniquely by PR-A, and only 25 by both. Almost half the genes encode proteins that are membrane-bound or involved in
membrane-initiated signaling. We also find an important set of progesterone-regulated genes involved in mammary gland development
and/or implicated in breast cancer. This first, large scale study of PR gene regulation has important implications for the
measurement of PR in breast cancers and for the many clinical uses of synthetic progestins. It suggests that it is important
to distinguish between the two isoforms in breast cancers and that isoform-specific genes can be used to screen for ligands
that selectively modulate the activity of PR-A or PR-B. Additionally, use of natural target genes, rather than âconsensusâ
response elements, for transcription studies should improve our understanding of steroid hormone action.
Childhood brain tumors have suspected prenatal origins. To identify vulnerable developmental states, we generated a single-cell transcriptome atlas of >65,000 cells from embryonal pons and forebrain, ...two major tumor locations. We derived signatures for 191 distinct cell populations and defined the regional cellular diversity and differentiation dynamics. Projection of bulk tumor transcriptomes onto this dataset shows that WNT medulloblastomas match the rhombic lip-derived mossy fiber neuronal lineage and embryonal tumors with multilayered rosettes fully recapitulate a neuronal lineage, while group 2a/b atypical teratoid/rhabdoid tumors may originate outside the neuroectoderm. Importantly, single-cell tumor profiles reveal highly defined cell hierarchies that mirror transcriptional programs of the corresponding normal lineages. Our findings identify impaired differentiation of specific neural progenitors as a common mechanism underlying these pediatric cancers and provide a rational framework for future modeling and therapeutic interventions.
We identify a sample of 14 planetary nebulae in the nearby starburst disc galaxy NGC 253, using broad- and narrow-band imaging. A simple model of the stellar and dust layers in the galaxy shows that ...planetary nebula magnitudes are not statistically affected much by extinction. The luminosity function of the planetary nebulae is fitted with models accounting for dust, which leads to a distance to NGC 253 of μ0= 27.62+0.16−0.26 mag (d= 3.34+0.26−0.38 Mpc). This new estimate is found to be in agreement with the few existing distance estimates for this galaxy when they are all set to a common Large Magellanic Cloud distance of 18.50 mag. A weighted average of the most reliable distance estimates yields a distance of μ0= 27.7 ± 0.2 mag (d= 3.5 ± 0.2 Mpc).
Gamma-ray bursts (GRBs) are the most luminous explosions in the Universe, yet the nature and physical properties of their energy sources are far from understood. Very important clues, however, can be ...inferred by studying the afterglows of these events. We present optical and X-ray observations of GRB 130831A obtained by Swift, Chandra, Skynet, Reionization And Transients Infra-Red camera, Maidanak, International Scientific Optical-Observation Network, Nordic Optical Telescope, Liverpool Telescope and Gran Telescopio Canarias. This burst shows a steep drop in the X-ray light curve at ≃105 s after the trigger, with a power-law decay index of α ∼ 6. Such a rare behaviour cannot be explained by the standard forward shock (FS) model and indicates that the emission, up to the fast decay at 105 s, must be of ‘internal origin’, produced by a dissipation process within an ultrarelativistic outflow. We propose that the source of such an outflow, which must produce the X-ray flux for ≃1 d in the cosmological rest frame, is a newly born magnetar or black hole. After the drop, the faint X-ray afterglow continues with a much shallower decay. The optical emission, on the other hand, shows no break across the X-ray steep decrease, and the late-time decays of both the X-ray and optical are consistent. Using both the X-ray and optical data, we show that the emission after ≃105 s can be explained well by the FS model. We model our data to derive the kinetic energy of the ejecta and thus measure the efficiency of the central engine of a GRB with emission of internal origin visible for a long time. Furthermore, we break down the energy budget of this GRB into the prompt emission, the late internal dissipation, the kinetic energy of the relativistic ejecta, and compare it with the energy of the associated supernova, SN 2013 fu.
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