Program: GN-2018B-Q-106

The discovery and study of the optical source SSS17a/AT2017gfo associated with the binary neutron star merger GW170817 (Coulter et al 2017, Cannon et al., 2017, Smartt et al, 2017, see summary of campaign in Abbott et al., 2017)) has forever changed the field of astronomy. The r-process isotopes appear to be formed in binary neutron star mergers (Abbott et al 2017). The primary evidence for this is the rapidly decaying light curve (1.5mag/day) consistent with the radioactive decay of a kilonova. But our collaboration alone detected spectroscopic features of light r-process elements, specifically Cesium and Tellurium indicative of a blue or low opacity kilonova (Smartt et al 2017). Advanced LIGO (aLIGO) and Advance Virgo (AdV) are scheduled to begin the third LIGO observing run, O3 in November of 2018. The sensitivities to Binary Neutron Star mergers (BNS) are such that they can detect the gravitational waves from a nominal BNS at a distance of 120 - 170 Mpc for aLIGO, or 65 to 48 Mpc for AdV(Abbott et al. 2018) This is an increase in search volume by a factor of 2 to 3 over the brief period in O2 when the Virgo detector was brought online and helped constrain the discovery of GW170817 (Abbott et al., 2018).The O3 run is intended to last for one year. The rate of BNS is still poorly understood, but range expected by the LIGO Virgo Consoritum is between 1 and 50 per year (Abbott et al. 2018). O3 will only last a year, and then LIGO will be shut down for improvements until late 2020. A reasonable expection would be around 10 in the sky available to Pan-STARRS (Chambers et al 2016) and Gemini. The median 90% Credible Region is expected to be 120 to 180 square degrees. This is very well suited to the combined survey power of Pan-STARRS1 and Pan-STARRS2. Furthermore, Pan-STARRS has pre-existing imaging in the grizy bands over more than 80It was our ability to do precision photometry on difference images with Pan-STARRS that reliably determined the fast fade of SSS17a (Chambers et al. 2017a,2017b,2017c,2017d). To advance our understanding of kilonova, we need optical and infrared high signal-to-noise spectra as a function of time. These are not symmetric objects, and what we see spectroscopically is likely to vary from object to object depending strongly on the angle with respect to the merger axis and the opacity along the line of sight and how the opacity evolves in time (Metzger 2017). This proposal is for optical and infrared spectroscopy with GMOS and GNIRS on Gemini of kilonova from aLIGO/AdVIRGO. We also propose to observe other rare transients discoverd by Pan-STARRS, such as the recent Tidal Disruption Event PS18kh (Tucker et al., 2018), superluminous supernova (e.g. Luannan et al. 2018 and Nicholl 2016) and peculiar supernova like SN2016bdu (Pastorello 2018), and capitalize on fast transients by leveraging our geographical position with respect to the Zwicky Transient Factory, ZTF at Palomar.