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We report the results of our observing campaign on GRB140903A, a nearby (z=0.351) short duration (T90~0.3 s) gamma-ray burst discovered by Swift. We monitored the X-ray afterglow with Chandra up to 21 days after the burst, and detected a steeper decay of the X-ray flux after approximately 1 day. Continued monitoring at optical and radio wavelengths showed a similar decay in flux at nearly the same time, and we interpret it as evidence of a narrowly collimated jet. By using the standard fireball model to describe the afterglow evolution, we derive a jet opening angle of 5 deg and a collimation-corrected total energy release of 2E50 erg. We further discuss the nature of the GRB progenitor system. Three main lines disfavor a massive star progenitor: the properties of the prompt gamma-ray emission, the age and low star-formation rate of the host galaxy, and the lack of a bright supernova. We conclude that this event was likely originated by a compact binary merger., Comment: 12 pages, 7 figures, accepted for publication in ApJ

New Zealand’s Alpine Fault is a site of global importance for the study of active geological faults. The Alpine Fault provides an opportunity to study a major fault late in the cycle of stress accumulation ahead of a future earthquake, to search for precursors to large earthquakes, and to understand the long-term evolution of faults and the formation of fault rocks. The fault’s self-exhuming geometry, relative geological simplicity, and rapid and precisely-known slip rates, mean its accessible surface exposures have already been the subject of >40 years of intensive research. The goal of the Alpine Fault, Deep Fault Drilling Project (DFDP) is to go beneath the surface, to sample and make observations of the fault rocks and physical conditions at a range of depths, and monitor these over coming decades. To date, no active fault drilling experiment has targeted the mid-crustal roots of a long-lived active fault, or addressed fault zone evolution throughout the seismogenic zone and towards the brittle-ductile transition. DFDP-2A drilling started in August 2014 and DFDP-2B was completed in January 2015, having reached a maximum depth of 893 m. Technical problems, most notably the loss (and recovery) of the bottom-hole assembly on two occasions, caused delays in the drilling schedule, and the failure of a casing string ultimately caused drilling to be terminated at a shallower depth than planned and before the fault had been intersected. A very extensive data set was collected including geological, geophysical, geochemical and hydraulic measurements extending the length of the DFDP-2B borehole. Samples of rocks and fluids were collected, and a long-term observatory installed. Of particular significance are the observations that the geothermal gradient is extremely high, exceeding 140°C/km in the upper part of the borehole, and that the hangingwall is overpressured, as predicted prior to drilling. This report documents the technical planning and execution of DFDP-2 drilling, summarizes the scientific methods and types of data collected, and describes the observatory constructed.

The first phase of the Deep Fault Drilling Project (DFDP-1), Alpine Fault, was carried out in January and February 2011 at Gaunt Creek, South Westland, New Zealand. Two boreholes, DFDP-1A and DFDP-1B, were drilled to depths of 101 m and 151 m respectively. DFDP-1A cored a hangingwall mylonite sequence containing cataclasite zones that increase in frequency downward; 20–30 m of cemented and hydrothermally altered cataclasites; a >5 cm-thick principal slip surface of ultracatalasite and gouge at 90 m; and footwall fluvial gravels to a total depth of 100.6 m. DFDP-1B cored a similar hangingwall sequence; encountered a principal slip surface with a thickness of about 20 cm at depth of 128 m; penetrated a footwall sequence of quartz- and feldspar-rich, extensively altered and variably cataclased rock including a significant fault at 130 m; and reached a total depth of 151.4 m. A broad suite of downhole geophysical logs was collected using acoustic televiewer, neutron, full-waveform sonic, density, dipmeter, and electromagnetic flowmeter sondes. A fault zone observatory was installed in the DFDP-1B borehole, consisting of a seismometer near the base; a 25 mm internal diameter alkathene fluid sampling tube (perforated above the seismometer in the footwall); four vibrating-wire piezometers with inbuilt temperature sensors; 20 platinum RTD temperature sensors on two separate strings; and surface infrastructure providing security and housing the power supply and recording equipment. DFDP-1A was cased to 81 m depth and had a seismometer installed at the base of the casing, connected to the observatory equipment mounted above DFDP-1B.

We present a sample of 45 Damped Ly-Alpha system [DLA; H I-N is greater than or equal to 2 x 10(exp. 20) cm(exp. -2)] counterparts (33 detections, 12 upper limits) which host gamma-ray bursts (GRB-DLAs) in order to investigate star formation and metallicity within galaxies hosting DLAs. Our sample spans z is approx. 2 - 6 and is nearly three times larger than any previously detected DLA counterparts survey based on quasar line-of-sight searches (QSO-DLAs). We report star formation rates (SFRs) from rest-frame UV photometry and spectral energy distribution modeling. We find that DLA counterpart SFRs are not correlated with either redshift or H I column density. Thanks to the combination of Hubble Space Telescope and ground-based observations, we also investigate DLA host star formation efficiency. Our GRB-DLA counterpart sample spans both higher efficiency and low efficiency star formation regions compared to the local Kennicutt-Schmidt relation, local star formation laws, and z is approximately 3 cosmological simulations. We also compare the depletion times of our DLA hosts sample to other objects in the local universe; our sample appears to deviate from the star formation efficiencies measured in local spiral and dwarf galaxies. Furthermore, we find similar efficiencies as local inner disks, SMC, and Lyman-break galaxy outskirts. Finally, our enrichment time measurements show a spread of systems with under- and over-abundance of metals, which may suggest that these systems had episodic star formation and a metal enrichment/depletion as a result of strong stellar feedback and/or metal inflow/outflow.