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We present observations of Swift J1112.2-8238, and identify it as a candidate relativistic tidal disruption flare (rTDF). The outburst was first detected by Swift/BAT in June 2011 as an unknown, long-lived (order of days) γ-ray transient source. We show that its position is consistent with the nucleus of a faint galaxy for which we establish a likely redshift of z = 0.89 based on a single emission line that we interpret as the blended [Oii]λ3727 doublet. At this redshift, the peak X/γ-ray luminosity exceeded 1047 ergs s−1, while a spatially coincident optical transient source had i 0∼22 (Mg∼ − 21.4 at z = 0.89) during early observations, ∼20 days after the Swift trigger. These properties place Swift J1112.2-8238 in a very similar region of parameter space to the two previously identified members of this class, Swift J1644+57 and Swift J2058+0516. As with those events the high-energy emission shows evidence for variability over the first few days, while late time observations, almost 3 years postoutburst, demonstrate that it has now switched off. Swift J1112.2-8238 brings the total number of such events observed by Swift to three, interestingly all detected by Swift over a ∼3 month period (< 3% of its total lifetime as of March 2015). While this suggests the possibility that further examples may be uncovered by detailed searches of the BAT archives, the lack of any prime candidates in the years since 2011 means these events are undoubtedly rare., Astronomy

We present rest-frame far-infrared (FIR) and optical observations of the host galaxy of GRB 090423 at z = 8.23 from the Atacama Large Millimeter Array (ALMA) and the Spitzer Space Telescope, respectively. The host remains undetected to 3σ limits of Fν(222GHz) . 33 µJy and Fν(3.6µm) . 81 nJy. The FIR limit is about 20 times fainter than the luminosity of the local ULIRG Arp 220, and comparable to the local starburst M 82. Comparing to model spectral energy distributions we place a limit on the IR luminosity of LIR(8 − 1000µm) . 3×1010 L⊙, corresponding to a limit on the obscured star formation rate of SFRIR . 5 M⊙ yr−1; for comparison, the limit on the unobscured star formation rate from Hubble Space Telescope rest-frame UV observations is SFRUV . 1 M⊙ yr−1. We also place a limit on the host galaxy stellar mass of M∗ . 5×107 M⊙ (for a stellar population age of 100 Myr and constant star formation rate). Finally, we compare our millimeter observations to those of field galaxies at z & 4 (Lyman break galaxies, Lyα emitters, and submillimeter galaxies), and find that our limit on the FIR luminosity is the most constraining to date, although the field galaxies have much larger rest-frame UV/optical luminosities than the host of GRB 090423 by virtue of their selection techniques. We conclude that GRB host galaxies at z & 4, especially those with measured interstellar medium metallicities from afterglow spectroscopy, are an attractive sample for future ALMA studies of high redshift obscured star formation., Astronomy