Reynald Pain

The type Ia supernova SNLS-03D3bb from a super-Chandrasekhar-mass white dwarf star

The accelerating expansion of the Universe, and the need for dark energy, were inferred from observations of type Ia supernovae. There is a consensus that type Ia supernovae are thermonuclear explosions that destroy carbon–oxygen white dwarf stars that have accreted matter from a companion star, although the nature of this companion remains uncertain. These supernovae are thought to be reliable distance indicators because they have a standard amount of fuel and a uniform trigger: they are predicted to explode when the mass of the white dwarf nears the Chandrasekhar mass of 1.4 solar masses (M[circdot]). Here we show that the high-redshift supernova SNLS-03D3bb has an exceptionally high luminosity and low kinetic energy that both imply a super-Chandrasekhar-mass progenitor. Super-Chandrasekhar-mass supernovae should occur preferentially in a young stellar population, so this may provide an explanation for the observed trend that overluminous type Ia supernovae occur only in ‘young’ environments. As this supernova does not obey the relations that allow type Ia supernovae to be calibrated as standard candles, and as no counterparts have been found at low redshift, future cosmology studies will have to consider possible contamination from such events.

SNIFS: a wideband integral field spectrograph with microlens arrays

SNIFS is an integral field spectrograph devoted to the observation of supernovae. This instrument is today in the manufacturing phase and should be able to observe supernovae at the end of this year (2003) on the 2.2m telescope of University Hawaii. The concept of SNIFS is to split the 6” x 6” field of view into 225 samples of 0.4” x 0.4” through a microlens array. Then the spectral decomposition of each sample is imaged on a 2k x 4k CCD. In order to cover all the large spectral range with a high resolution, the spectrograph is composed of two modules, one for the blue wavelengths (320 nm to 560nm)with a resolution around 1000 at 430 nm and one for the red wavelengths (520 nm to 1 µm) with a resolution around 1300 at 760 nm. First we will present the optical design and detail the function of each optical component. Then the mechanical design will be shown with some maps of the structure. Finally the first pictures taken during the alignments will be displayed.

MAX: a gamma-ray lens for nuclear astrophysics

The mission concept MAX is a space borne crystal diffraction telescope, featuring a broad-band Laue lens optimized for the observation of compact sources in two wide energy bands of high astrophysical relevance. For the first time in this domain, gamma-rays will be focused from the large collecting area of a crystal diffraction lens onto a very small detector volume. As a consequence, the background noise is extremely low, making possible unprecedented sensitivities. The primary scientific objective of MAX is the study of type Ia supernovae by measuring intensities, shifts and shapes of their nuclear gamma-ray lines. When finally understood and calibrated, these profoundly radioactive events will be crucial in measuring the size, shape, and age of the Universe. Observing the radioactivities from a substantial sample of supernovae and novae will significantly improve our understanding of explosive nucleosynthesis. Moreover, the sensitive gamma-ray line spectroscopy performed with MAX is expected to clarify the nature of galactic microquasars (e+e- annihilation radiation from the jets), neutrons stars and pulsars, X-ray Binaries, AGN, solar flares and, last but not least, gamma-ray afterglow from gamma-burst counterparts.

The Nearby Supernova Factory dataset-improving SNe Ia as dark energy probes

During the 2004–2008 period the Nearby Supernova Factory discovered ∼1000 supernovae, and obtained detailed spectrophotometric time series of ∼190 SNe Ia with the SuperNova Integral Field Spectrograph. These supernovae are located in the nearby Hubble flow (0.03<z<0.08), allowing relative distance measurements with minimal uncertainties from peculiar velocities and bulk flows. Each supernova was spectrophotometrically observed over a period of ∼50 days, with a median number of 15 observations per target. The first spectrum is typically obtained at ‐4 days, and in some instances as early as ‐14 days before maximum light. Each spectrum (3200A–10000A) is photometrically calibrated, with simultaneous observations of field stars used to correct for atmospheric extinction variability.The first results, impacting the use of SNe Ia as dark energy probes, are presented. We discuss how the SNfactory dataset can be used to find correlations between spectroscopic and photometric properties of SNe Ia, and demonstrate a ...

Implications for the Hubble constant from the first seven supernovae at z greater than or equal to 0.35

The Supernova Cosmology Project has discovered over 28 supernovae (SNs) at 0.35 < z < 0.65 in an ongoing program that uses Type Ia SNs (SN Ias) as high-redshift distance indicators. Here we present measurements of the ratio between the locally observed and global Hubble constants, HL0/HG0, based on the first seven SNs of this high-redshift data set compared with 18 SNs at z ≤ 0.1 from the Calan/Tololo survey. If ΩM ≤ 1, then light-curve width corrected SN magnitudes yield HL0/HG0 < 1.10 (95% confidence level) in both a Λ = 0 and a flat universe. The analysis using the SN Ias as standard candles without a light-curve width correction yields similar results. These results rule out the hypothesis that the discrepant ages of the Universe derived from globular clusters and recent measurements of the Hubble constant are attributable to a locally underdense bubble. Using the Cepheid-distance-calibrated absolute magnitudes for SN Ias of Sandage et al., we can also measure the global Hubble constant, HG0. If ΩM ≥ 0.2, we find that HG0 < 70 km s-1 Mpc-1 in a Λ = 0 universe and HG0 < 78 km s-1 Mpc-1 in a flat universe, correcting the distant and local SN apparent magnitudes for light-curve width. Lower results for HG0 are obtained if the magnitudes are not width-corrected.

The type Ia supernova rate at z similar to 0.4

We present the first measurement of the rate of Type Ia supernovae at high redshift. The result is derived by using a large subset of data from the Supernova Cosmology Project. Three supernovae were discovered in a surveyed area of 1.7 deg2. The survey spanned a ~3 week baseline and used images with 3 σ limiting magnitudes of R ~ 23. We present our methods for estimating the numbers of galaxies and the number of solar luminosities to which the survey is sensitive, as well as the supernova detection efficiency, which is used to determine the control time, the effective time for which the survey is sensitive to a Type Ia event. We derive a rest-frame Type Ia supernova (SN) rate at z ~ 0.4 of 0.82−0.37–0.25+0.54 + 0.37 h2 SNu (1 SNu = 1 SN per century per 1010LB☉), where the first uncertainty is statistical and the second includes systematic effects. For the purposes of observers, we also determine the rate of SNe, per sky area surveyed, to be 34.4+23.9−16.2 SNe yr −1 deg −2 for SN magnitudes in the range 21.3 < R < 22.3.We present the first measurement of the rate of Type Ia supernovae at high redshift. The result is derived by using a large subset of data from the Supernova Cosmology Project. Three supernovae were discovered in a surveyed area of 1.7 deg{sup 2}. The survey spanned a {approximately}3 week baseline and used images with 3 {sigma} limiting magnitudes of {ital R}{approximately}23. We present our methods for estimating the numbers of galaxies and the number of solar luminosities to which the survey is sensitive, as well as the supernova detection efficiency, which is used to determine the control time, the effective time for which the survey is sensitive to a Type Ia event. We derive a rest-frame Type Ia supernova (SN) rate at {ital z}{approximately}0.4 of 0.82{sub {minus}0.37{minus}0.25}{sup +0.54+0.37} {ital h}{sup 2} SNu (1 SNu=1 SN per century per 10{sup 10} {ital L}{sub {ital B}{circle_dot}}), where the first uncertainty is statistical and the second includes systematic effects. For the purposes of observers, we also determine the rate of SNe, per sky area surveyed, to be 34.4{sub {minus}16.2}{sup +23.9} SNe yr{sup {minus}1} deg{sup {minus}2} for SN magnitudes in the range 21.3{lt}{ital R}{lt}22.3. {copyright} {ital 1996 The American Astronomical Society.}

Determination of αs from jet production rates and energy-energy correlations on the Z0 resonance

Abstract This presentation uses data obtained from the DELPHI experiment at LEP. The strong coupling constant α s is determined in two different analyses of the Z° decay into multi-hadronic final states. The first uses the jet production rates and the second the asymmetry of energy-energy correlations. Both methods compare experimental data with second order of perturbative QCD predictions. The results are α s (M z )=0.114±0.003±0.004±0.012 using the jet rates method and α s (M z )=0.106±0.003±0.003+0.003 from the energy-energy correlations method.