Saurabh W. Jha

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We have discovered 21 new Type Ia supernovae (SNe Ia) with the Hubble Space Telescope (HST) and have used them to trace the history of cosmic expansion over the last 10 billion yr. These objects, which include 13 spectro-scopically confirmed SNe Ia at z ! 1, were discovered during 14 epochs of reimaging of the GOODS fields North and South over 2 yr with the(More)
We have measured the rest-frame B, V, and I-band light curves of a high-redshift type Ia supernova (SN Ia), SN 1999Q (z = 0.46), using HST and ground-based near-infrared detectors. A goal of this study is the measurement of the color excess, E B−I , which is a sensitive indicator of interstellar or intergalactic dust which could affect recent cosmological(More)
We present constraints on the dark energy equation-of-state parameter, w = P/(ρc 2), using 60 Type Ia supernovae (SNe Ia) from the ESSENCE su-pernova survey. We derive a set of constraints on the nature of the dark energy assuming a flat Universe. By including constraints on (Ω M , w) from baryon acoustic oscillations, we obtain a value for a static(More)
The first cosmological results from the ESSENCE supernova survey (Wood-Vasey et al. 2007) are extended to a wider range of cosmological models including dynamical dark energy and non-standard cosmological models. We fold in a greater number of external data sets such as the recent Higher-z release of high-redshift supernovae (Riess et al. 2007) as well as(More)
This is the second of two papers reporting results from a program to determine the Hubble constant to ∼ 5% precision from a refurbished distance ladder based on extensive use of differential measurements. Here we report observations of 240 Cepheid variables obtained with the Near Infrared Camera and Multi-Object Spectrometer (NIC-MOS) Camera 2 through the F(More)
We present an updated version of the Multicolor Light Curve Shape method to measure distances to type Ia supernovae (SN Ia), incorporating new procedures for K-correction and extinction corrections. We also develop a simple model to disentangle intrinsic color variations and reddening by dust, and expand the method to incorporate U-band light curves and to(More)
We report observations of two nearby Type Ia supernovae (SNe Ia) for which observations of Cepheid variables in the host galaxies have been obtained with the Hubble Space Telescope: SN 1994ae in NGC 3370 and SN 1998aq in NGC 3982. For NCG 3370, we used the Advanced Camera for Surveys to observe 64 Cepheids that yield a distance of 29 Mpc, the farthest(More)
We combine the CfA3 supernova Type Ia (SN Ia) sample with samples from the literature to calculate improved constraints on the dark energy equation of state parameter, w. The CfA3 sample is added to the Union set of Kowalski et al. (2008) to form the Constitution set and, combined with a BAO prior, produces 1 + w = 0.013 +0.066 −0.068 (0.11 syst),(More)
We present BV RIZ photometric observations of HD 209458 during the transit by its planetary companion on UT 1999 November 15 with the University of Hawaii 0.6m and 2.2m telescopes and the High Altitude Observatory STARE telescope. The detailed shape of the transit curve is predicted to vary with color due primarily to the color-dependent limb-darkening of(More)
We report the discovery of near-sinusoidal radial velocity variations of the G0V star ρ CrB, with period 39.6 days and amplitude 67 m s −1. These variations are consistent with the existence of an orbital companion in a circular orbit. Adopting a mass of 1.0 M ⊙ for the primary, the companion has minimum mass about 1.1 Jupiter masses, and orbital radius(More)