Calibrating hydrogen-rich core-collapse supernovae for their use as distance indicators independently of type Ia supernovae

Using our new general-relativistic, radiation hydrodynamics, Lagrangian code, we computed a rather extended grid of hydrogen-rich core-collapse supernova (CC-SN) models and explored the potentials of their "standardization" as distance indicators. We discuss the properties of some calibrations previously reported in the literature and present new correlations based on the behavior of the light curve, that can be employed for calibrating hydrogen-rich CC-SNe using only photometric data.Comment: 2 pages, 3 figures, to appear in Proceedings of IAU Symp. 281, Binary Paths to Type Ia Supernovae Explosions, ed. R. Di Stefano and M. Ori

Simulated Gamma-Ray Pulse Profile of the Crab Pulsar with the Cherenkov Telescope Array

We present simulations of the very high energy (VHE) gamma-ray light curve of the Crab pulsar as observed by the Cherenkov Telescope Array (CTA). The CTA pulse profile of the Crab pulsar is simulated with the specific goal of determining the accuracy of the position of the interpulse. We fit the pulse shape obtained by the MAGIC telescope with a three-Gaussian template and rescale it to account for the different CTA instrumental and observational configurations. Simulations are performed for different configurations of CTA and for the ASTRI mini-array. The northern CTA configuration will provide an improvement of a factor of ~3 in accuracy with an observing time comparable to that of MAGIC (73 hours). Unless the VHE spectrum above 1 TeV behaves differently from what we presently know, unreasonably long observing times are required for a significant detection of the pulsations of the Crab pulsar with the high-energy-range sub-arrays. We also found that an independent VHE timing analysis is feasible with Large Size Telescopes (LSTs). CTA will provide a significant improvement in determining the VHE pulse shape parameters necessary to constrain theoretical models of the gamma-ray emission of the Crab pulsar. One of such parameters is the shift in phase between peaks in the pulse profile at VHE and in other energy bands that, if detected, may point to different locations of the emission regions.Comment: 11 pages, 11 figures, 5 table

On the Mathematical Character of the Relativistic Transfer Moment Equations

General--relativistic, frequency--dependent radiative transfer in spherical, differentially--moving media is considered. In particular we investigate the character of the differential operator defined by the first two moment equations in the stationary case. We prove that the moment equations form a hyperbolic system when the logarithmic velocity gradient is positive, provided that a reasonable condition on the Eddington factors is met. The operator, however, may become elliptic in accretion flows and, in general, when gravity is taken into account. Finally we show that, in an optically thick medium, one of the characteristics becomes infinite when the flow velocity equals $\pm c/\sqrt 3$. Both high--speed, stationary inflows and outflows may therefore contain regions which are ``causally'' disconnected.Comment: 16 pages, PlainTex, accepted for publication in MNRA

XMM-Newton detects the beginning of the X-ray decline of SN 1995N

We present the results of a new XMM-Newton observation of the interacting supernova 1995N, performed on July 27, 2003. We find that the 0.2-10.0 keV flux has dropt at a level of 1.44e-13 erg cm^-2 s^-1, about one order of magnitude lower than that of a previous ASCA observation performed on January 1998. The X-ray spectral analysis shows statistically significant evidence for the presence of two distinct components, that can be modeled with emission from optically thin, thermal plasmas at different temperatures. From these temperatures we derive that the exponent of the ejecta density distribution is n ~ 6.5.Comment: 3 pages, 2 figures. To appear in proceedings of the International Conference "1604-2004: Supernovae as Cosmological Lighthouses" (Padova, Italy, June 16-19, 2004), eds. M. Turatto, W. Shea, S. Benetti and L. Zampieri, ASP conference Serie

Dynamical Comptonization in spherical flows: black hole accretion and stellar winds

The transport of photons in steady, spherical, scattering flows is investigated. The moment equations are solved analytically for accretion onto a Schwarzschild black hole, taking into full account relativistic effects. We show that the emergent radiation spectrum is a power law at high frequencies with a spectral index smaller (harder spectrum) than in the non--relativistic case. Radiative transfer in an expanding envelope is also analyzed. We find that adiabatic expansion produces a drift of injected monochromatic photons towards lower frequencies and the formation of a power--law, low--energy tail with spectral index $-3$.Comment: 11 pages with 3 ps figures, MNRAS to appea