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Supernova Constraints on a Superlight Gravitino

In supergravity models with low supersymmetry breaking scale the gravitinos can be superlight, with mass in the 10[sup -6] eV to few keV range. In such a case, gravitino emission provides a new cooling mechanism for protoneutron stars and therefore can provide constraints on the mass of a superlight gravitino. This happens because the coupling to matter of superlight gravitinos is dominated by its goldstino component, whose coupling to matter of superlight gravitinos is dominated by its goldstino component, whose coupling to matter is inversely proportional to the scale of supersymmetry breaking and increases as the gravitino mass decreases. Present observations therefore provide lower limits on the gravitino mass. Using the recently revised goldstino couplings, we find that the two dominant processes in supernova cooling are e[sup+] e[sup -][yields] GG and[gamma]+e[sup -][yields] e[sup -] GG. They lead to a lower limit on the supersymmetry breaking scale[Lambda][sub s] from 160 to 500 GeV for core temperatures 30 to 60 MeV and electron chemical potentials 200 to 300 MeV. The corresponding lower limits on the gravitino mass are .6 - 6 x 10[sup -6] eV.

In supergravity models with low supersymmetry breaking scale the gravitinos can be superlight, with mass in the 10[sup -6] eV to few keV range.

Overview of the SuperNova

The SuperNova/Acceleration Probe (SNAP) is a space-based experiment to measure the expansion history of the Universe and study both its dark energy and the dark matter. The experiment is motivated by the startling discovery that the expansion of the Universe is accelerating. A 0.7 square-degree imager comprised of 36 large format fully-depleted n-type CCD's sharing a focal plane with 36 HgCdTe detectors forms the heart of SNAP, allowing discovery and lightcurve measurements simultaneously for many supernovae. The imager and a high-efficiency low-resolution integral field spectrograph are coupled to a 2-m three mirror anastigmat wide-field telescope, which will be placed in a high-earth orbit. The SNAP mission can obtain high-signal-to-noise calibrated light-curves and spectra for over 2000 Type Ia supernovae at redshifts between z = 0.1 and 1.7. The resulting data set can not only determine the amount of dark energy with high precision, but test the nature of the dark energy by examining its equation of state. In particular, dark energy due to a cosmological constant can be differentiated from alternatives such as ''quintessence'', by measuring the dark energy's equation of state to an accuracy of ± 0.05, and by studying its time dependence.

The SuperNova/Acceleration Probe (SNAP) is a space-based experiment to measure the expansion history of the Universe and study both its dark energy and the dark matter.

Radio Polarisation Study of the Snail Pulsar Wind Nebula in Supernova Remnant G327.1-1.1

This dissertation, "Radio Polarisation Study of the Snail Pulsar Wind Nebula in Supernova Remnant G327.1-1.1" by Yik-ki, Ma, 馬奕騏, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Pulsar wind nebulae (PWNe) are believed to be acceleration sites of cosmic rays in the Galaxy. In the acceleration process, magnetic field plays an important role. Radio polarisation measurements offer a direct probe of the magnetic field geometry of astronomical objects, but such experiments have rarely been conducted on PWNe, especially for evolved systems. PWNe can be crushed by the supernova reverse shock at an age of 10 kyr. Previous hydrodynamical simulations show that such interactions can result in a turbulent environment in the nebula interior, suggesting a tangled magnetic field. In this thesis, I present a radio study of the Snail PWN in the composite supernova remnant G327.1-1.1 using the Australia Telescope Compact Array. This PWN is believed to have already interacted with the supernova reverse shock. The study reveals a highly ordered magnetic field configuration in the Snail, which can be explained if either the shockwave could not penetrate into the PWN interior to drive the turbulence, or the characteristic turbulence scale is large. A toy model is built to estimate the turbulence scale assuming the latter scenario. It is found that a simulated PWN with a turbulence scale of one-eighth to one-sixth of the nebula radius and a pulsar wind filling factor of 50-75% can match the observation results. This suggests significant mixing between supernova ejecta and pulsar wind material in this system. In addition, the Snail exhibits a subsonic comet-like protrusion extending from the putative neutron star. Cometary PWNe were found to exhibit a variety of magnetic field configurations but the exact reason remains unclear. The polarisation observations of this system revealed a magnetic field parallel to the nebula elongation, similar to what was found in the Mouse (G359.23-0.82) and the handle of the Frying Pan (G315.78-0.23). This adds an important sample to cometary PWNe for future MHD modelling. Subjects: Supernova remnants Pulsars

This dissertation, "Radio Polarisation Study of the Snail Pulsar Wind Nebula in Supernova Remnant G327.1-1.1" by Yik-ki, Ma, 馬奕騏, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to ...

Preliminary Estimates of Core-collapse Supernova Rates from the Berkeley Automated Supernova Search

Over the last few years, the Berkeley Automated Supernova Search has discovered 19 supernova. We present here preliminary measurements of supernova rates from a subset of these supernovae, which were found from a sample of well-monitored galaxies. Two effects are apparent: a surprising number of the supernovae are Type Ic supernovae, and most (17 out of 19) of the supernovae are in late spiral galaxies. Less luminous supernovae may still be escaping our attention. If the Milky Way galaxy is a late spiral, the core-collapse supernova rate (i.e., for supernovae of types II, Ib, and Ic) should be at least one supernova every 44 {plus minus} 9 years (assuming H = 75 km/sec/Mpc). A crude estimate of the core collapse supernova rate in Sc and Sbc galaxies within 5 Mpc would be one supernova every 7 years. These rates have important implications for the design of supernova neutrino, gamma-ray, and gravity-wave detectors. Plans have been developed to extend our search to a better site with more sensitivity to understand the true core-collapse supernova rate in nearby galaxies. 13 refs.

Two effects are apparent: a surprising number of the supernovae are Type Ic supernovae, and most (17 out of 19) of the supernovae are in late spiral galaxies. Less luminous supernovae may still be escaping our attention.

Supernova

Can anything save you at the end of the universe? This upcoming major motion picture from United Artists, features James Spader, Angela Bassett, & Lou Diamond Phillips.

Can anything save you at the end of the universe? This upcoming major motion picture from United Artists, features James Spader, Angela Bassett, & Lou Diamond Phillips.

Supernova

When you're reaching for the stars, nothing can hold you back. Star Calloway is fourteen years old, and she's the most famous pop star in the world. Her album has topped the charts, her video is all the rage, and she's about to start her world tour. There's only one thing that keeps her life from being perfect: Star's parents and baby brother have been missing for two years, and no one knows what happened to them. Still, Star knows her family would want her to be happy, and performing means everything to her. But with so many mysterious things going wrong in preparation for the tour, could the show be over before it begins?

When you're reaching for the stars, nothing can hold you back.