We report on radio and X-ray observations of the only known repeating Fast Radio Burst (FRB) source, FRB 121102. We have detected six additional radio bursts from this source: five with the Green Bank Telescope at 2 GHz, and one at 1.4 GHz with the Arecibo Observatory for a total of 17 bursts from this source. All have dispersion measures consistent with a single value (∼ 559 pc cm −3 ) that is three times the predicted maximum Galactic contribution. The 2-GHz bursts have highly variable spectra like those at 1.4 GHz, indicating that the frequency structure seen across the individual 1.4 and 2-GHz bandpasses is part of a wideband process. X-ray observations of the FRB 121102 field with the Swift and Chandra observatories show at least one possible counterpart; however, the probability of chance superposition is high. A radio imaging observation of the field with the Jansky Very Large Array at 1.6 GHz yields a 5σ upper limit of 0.3 mJy on any point-source continuum emission. This upper limit, combined with archival WISE 22-µm and IPHAS Hα surveys, rules out the presence of an intervening Galactic H II region. We update our estimate of the FRB detection rate in the PALFA survey to be 1.1 +3.7 −1.0 × 10 4 FRBs sky −1 day −1 (95% confidence) for peak flux density at 1.4 GHz above 300 mJy. We find that the intrinsic widths of the 12 FRB 121102 bursts from Arecibo are, on average, significantly longer than the intrinsic widths of the 13 single-component FRBs detected with the Parkes telescope.

We present an analysis of the final data release of the Carnegie Supernova Project I, focusing on the absolute calibration of the luminosity-decline-rate relation for Type Ia supernovae (SNe Ia) using new intrinsic color relations with respect to the color-stretch parameter, s BV , enabling improved dust extinction corrections. We investigate to what degree the so-called fast-declining SNe Ia can be used to determine accurate extragalactic distances. We estimate the intrinsic scatter in the luminositydecline-rate relation, and find it ranges from ±0.13 mag to ±0.18 mag with no obvious dependence on wavelength. Using the Cepheid variable star data from the SH0ES project (Riess et al. 2016), the SN Ia distance scale is calibrated and the Hubble constant is estimated using our optical and near-infrared sample, and these results are compared to those determined exclusively from a nearinfrared sub-sample. The systematic effect of the supernova's host galaxy mass is investigated as a function of wavelength and is found to decrease toward redder wavelengths, suggesting this effect may be due to dust properties of the host. Using estimates of the dust extinction derived from optical and NIR wavelengths, and applying these to H band, we derive a Hubble constant H 0 = 73.2 + / − 2.3 km s −1 Mpc −1 , whereas using a simple B − V color-correction applied to B band yields H 0 = 72.7 + / − 2.1 km s −1 Mpc −1 . Photometry of two calibrating SNe Ia from the CSP-II sample, SN 2012ht and SN 2015F, is presented and used to improve the calibration of the SN Ia distance ladder.

We report the discovery and initial follow-up of a double neutron star (DNS) system, PSR J1946+2052, with the Arecibo L-Band Feed Array pulsar (PALFA) survey. PSR J1946+2052 is a 17-ms pulsar in a 1.88-hour, eccentric (e = 0.06) orbit with a 1.2 M companion. We have used the Jansky Very Large Array to localize PSR J1946+2052 to a precision of 0. 09 using a new phase binning mode. We have searched multiwavelength catalogs for coincident sources but did not find any counterparts. The improved position enabled a measurement of the spin period derivative of the pulsar (Ṗ = 9 ± 2 × 10 −19 ); the small inferred magnetic field strength at the surface (B S = 4 × 10 9 G) indicates that this pulsar has been recycled. This and the orbital eccentricity lead to the conclusion that PSR J1946+2052 is in a DNS system. Among all known radio pulsars in DNS systems, PSR J1946+2052 has the shortest orbital period and the shortest estimated merger timescale, 46 Myr; at that time it will display the largest spin effects on gravitational wave waveforms of any such system discovered to date. We have measured the advance of periastron passage for this system, ω = 25.6 ± 0.3 deg yr −1 , implying a total system mass of only 2.50 ± 0.04 M , so it is among the 2 lowest mass DNS systems. This total mass measurement combined with the minimum companion mass constrains the pulsar mass to 1.3 M .

We present bolometric light curves constructed from multi-wavelength photometry of Type Ia supernovae (SNe Ia) from the Carnegie Supernova Project and the CfA Supernova Group, using near-infrared observations to provide robust constraints on host galaxy dust extinction. This set of light curves form a well-measured reference set for comparison with theoretical models. Ejected mass and synthesized 56 Ni mass are inferred for each SN Ia from its bolometric light curve using a semi-analytic Bayesian light curve model, and fitting formulae provided in terms of light curve width parameters from the SALT2 and SNOOPY light curve fitters. A weak bolometric width-luminosity relation is confirmed, along with a correlation between ejected mass and the bolometric light curve width. SNe Ia likely to have sub-Chandrasekhar ejected masses belong preferentially to the broad-line and cool-photosphere spectroscopic subtypes, and have higher photospheric velocities and populate older, highermass host galaxies than SNe Ia consistent with Chandrasekhar-mass explosions. Two peculiar events, SN 2006bt and SN 2006ot, have normal peak luminosities but appear to have super-Chandrasekhar ejected masses.