Bruno Leibundgut

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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)
The High-z Supernova Search Team has discovered and observed 8 new supernovae in the redshift interval z = 0.3–1.2. These independent observations, analyzed by similar but distinct methods, confirm the result of Riess et al. (1998a) and Perlmutter et al. (1999) that supernova luminosity distances imply an accelerating universe. More importantly, they extend(More)
– 2 – We report and interpret HST /Space Telescope Imaging Spectrograph (STIS) long-slit observations of the optical and ultraviolet (UV) (1150 − 10270Å) emission-line spectra of the rapidly brightening Spot 1 on the equatorial ring of SN 1987A between 1997 September and 1999 October (days 3869 – 4606 after outburst). The emission is caused by radiative(More)
We have started a large survey for radial velocity variations in white dwarfs (PI R. Napiwotzki) with the aim of finding close double degenerates, which could be precursor systems for SNe Ia. The UVES spectrograph at the ESO VLT is used to obtain high resolution spectra with good S/N. During this project 1500 white dwarfs will be observed. This unique data(More)
We present photometric and spectroscopic observations of 23 high redshift supernovae spanning a range of z = 0.34 − 1.03, 9 of which are unambiguously classified as Type Ia. These supernovae were discovered during the IfA Deep Survey, which began in September 2001 and observed a total of 2.5 square degrees to a depth of approximately m ≈ 25 − 26 in RIZ over(More)
3 Based in part on observations taken with the Very Large Telescope under ESO program 170.A-0519. – 3 – We present broad-band light curves of nine supernovae ranging in redshift from 0.5 to 0.8. The supernovae were discovered as part of the ESSENCE project, and the light curves are a combination of Cerro Tololo 4-m and Hubble Space Telescope (HST)(More)
Type Ia Supernovae are in many aspects still enigmatic objects. Their observational and theoretical exploration is in full swing, but we still have plenty to learn about these explosions. Recent years have already witnessed a bonanza of supernova observations. The increased samples from dedicated searches have allowed the statistical investigation of Type(More)