The Transiting Exoplanet Survey Satellite (TESS) will be conducting a nearly all-sky photometric survey over two years, with a core mission goal to discover small transiting exoplanets orbiting nearby bright stars. It will obtain 30 minute cadence observations of all objects in the TESS fields of view, along with two-minute cadence observations of 200,000-400,000 selected stars. The choice of which stars to observe at the two-minute cadence is driven by the need to detect small transiting planets, which leads to the selection of primarily bright, cool dwarfs. We describe the catalogs assembled and the algorithms used to populate the TESS Input Catalog (TIC), including plans to update the TIC with the incorporation of the Gaia second data release in the near future. We also describe a ranking system for prioritizing stars according to the smallest transiting planet detectable, and assemble a Candidate Target List (CTL) using that ranking. We discuss additional factors that affect the ability to photometrically detect and dynamically confirm small planets, and we note additional stellar populations of interest that may be added to the final target list. The TIC is available on the STScI MAST server, and an enhanced CTL is available through the Filtergraph data visualization portal system at the URL http://filtergraph.com/tess_ctl.

Gamma-ray bursts (GRBs) fall into two classes: short-hard and long-soft bursts. The latter are now known to have X-ray and optical afterglows, to occur at cosmological distances in star-forming galaxies, and to be associated with the explosion of massive stars. In contrast, the distance scale, the energy scale and the progenitors of the short bursts have remained a mystery. Here we report the discovery of a short-hard burst whose accurate localization has led to follow-up observations that have identified the X-ray afterglow and (for the first time) the optical afterglow of a short-hard burst; this in turn led to the identification of the host galaxy of the burst as a late-type galaxy at z = 0.16 (ref. 10). These results show that at least some short-hard bursts occur at cosmological distances in the outskirts of galaxies, and are likely to be caused by the merging of compact binaries.

We report on X-ray, optical, and infrared follow-up observations of GRB 980703. We detect a previously unknown X-ray source in the GRB error box ; assuming a power-law decline, we Ðnd for its decay index a \ [0.91 (3 p). We invoke host-galaxy extinction to match the observed spectral slope with the slope expected from "" Ðreball ÏÏ models. We Ðnd no evidence for a spectral break in the infrared to X-ray spectral range on 1998 July 4.4, and determine a lower limit of the cooling break frequency, Hz. For this epoch we obtain an extinction of From the X-ray data we l c [ 1.3 ] 1017 A V \ 1.50^0.11. estimate the optical extinction to be inconsistent with the former value. Our optical A V \ 20.2~7 .3 12.3, spectra conÐrm the redshift of z \ 0.966. We compare the afterglow of GRB 980703 with that of GRB 970508 and Ðnd that the fraction of the energy in the magnetic Ðeld, is much lower in the v B \ 6 ] 10~5, case of GRB 980703, as a consequence of the high frequency of the cooling break.

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