Chandra Observations of SN 2004et and the X-ray Emission of Type IIp Supernovae

We report the X-ray detection of the Type II-plateau supernova SN 2004et in the spiral galaxy NGC 6946, using the Chandra X-Ray Observatory. The position of the X-ray source was found to agree with the optical position within ~0.4 arcsec. Chandra also surveyed the region before the 2004 event, finding no X-ray emission at the location of the progenitor. For the post-explosion observations, a total of 202, 151, and 158 photons were detected in three pointings, each ~29 ks in length, on 2004 October 22, November 6, and December 3, respectively. The spectrum of the first observation is best fit by a thermal model with a temperature of kT=1.3 keV and a line-of-sight absorption of N_H=1.0 x 10^{22} cm^{-2}. The inferred unabsorbed luminosity (0.4-8 keV) is ~4x10^{38} erg/s, adopting a distance of 5.5 Mpc. A comparison between hard and soft counts on the first and third epochs indicates a softening over this time, although there is an insufficient number of photons to constrain the variation of temperature and absorption by spectral fitting. We model the emission as arising from the reverse shock region in the interaction between the supernova ejecta and the progenitor wind. For a Type IIP supernova with an extended progenitor, the cool shell formed at the time of shock wave breakout from the star can affect the initial evolution of the interaction shell and the absorption of radiation from the reverse shock. The observed spectral softening might be due to decreasing shell absorption. We find a pre-supernova mass loss rate of (2-2.5)x 10^{-6} M_{\odot} /yr for a wind velocity of 10 kms, which is in line with expectations for a Type IIP supernova.Comment: total 19 pages including 7 figures. ApJ, in press. See http://spider.ipac.caltech.edu/staff/rho/preprint/SN2004etms.ps for the paper including full resolution image

Dark matter inner slope and concentration in galaxies: from the Fornax dwarf to M87

We apply two new state-of-the-art methods that model the distribution of observed tracers in projected phase space to lift the mass / velocity anisotropy (VA) degeneracy and deduce constraints on the mass profiles of galaxies, as well as their VA. We first show how a distribution function based method applied to the satellite kinematics of otherwise isolated SDSS galaxies shows convincing observational evidence of age matching: red galaxies have more concentrated dark matter (DM) halos than blue galaxies of the same stellar or halo mass. Then, applying the MAMPOSSt technique to M87 (traced by its red and blue globular clusters) we find that very cuspy DM is favored, unless we release priors on DM concentration or stellar mass (leading to unconstrained slope). For the Fornax dwarf spheroidal (traced by its metal-rich and metal-poor stars), the inner DM slope is unconstrained, with weak evidence for a core if the stellar mass is fixed. This highlights how priors are crucial for DM modeling. Finally, we find that blue GCs around M87 and metal-rich stars in Fornax have tangential outer VA.Comment: 4 pages, 4 figures, to appear in proceeding of IAU 311 meeting on Galaxy Masses as Constraints for Formation Model

Highly ionized atoms in cooling gas

The ionization of low density gas cooling from a high temperature was calculated. The evolution during the cooling is assumed to be isochoric, isobaric, or a combination of these cases. The calculations are used to predict the column densities and ultraviolet line luminosities of highly ionized atoms in cooling gas. In a model for cooling of a hot galactic corona, it is shown that the observed value of N(N V) can be produced in the cooling gas, while the predicted value of N(Si IV) falls short of the observed value by a factor of about 5. The same model predicts fluxes of ultraviolet emission lines that are a factor of 10 lower than the claimed detections of Feldman, Brune, and Henry. Predictions are made for ultraviolet lines in cooling flows in early-type galaxies and clusters of galaxies. It is shown that the column densities of interest vary over a fairly narrow range, while the emission line luminosities are simply proportional to the mass inflow rate

1.6 GHz VLBI Observations of SN 1979C: almost-free expansion

We report on 1.6 GHz Very-Long-Baseline-Interferometry (VLBI) observations of supernova SN 1979C made on 18 November 2002. We derive a model-dependent supernova size. We also present a reanalysis of VLBI observations made by us on June 1999 and by other authors on February 2005. We conclude that, contrary to our earlier claim of strong deceleration in the expansion, SN 1979C has been undergoing almost-free expansion ($m = 0.91\pm0.09$; $R \propto t^m$) for over 25 years.Comment: 4 pages, 4 figures; submitted to A&A on 14 May 2009. Accepted on 7 Jul 200

BATSE Soft Gamma-Ray Observations of GROJ0422+32

We report results of a comprehensive study of the soft gamma-ray (30 keV to 1.7 MeV) emission of GROJ0422+32 during its first known outburst in 1992. These results were derived from the BATSE earth-occultation database with the JPL data analysis package, EBOP (Enhanced BATSE Occultation Package). Results presented here focus primarily on the long-term temporal and spectral variability of the source emission associated with the outburst. The light curves with 1-day resolution in six broad energy-bands show the high-energy flux (>200 keV) led the low-energy flux (<200 keV) by ~5 days in reaching the primary peak, but lagged the latter by ~7 days in starting the declining phase. We confirm the "secondary maximum" of the low-energy (<200 keV) flux at TJD 8970-8981, ~120 days after the first maximum. Our data show that the "secondary maximum" was also prominent in the 200-300 keV band, but became less pronounced at higher energies. During this 200-day period, the spectrum evolved from a power-law with photon index of 1.75 on TJD 8839, to a shape that can be described by a Comptonized model or an exponential power law below 300 keV, with a variable power-law tail above 300 keV. The spectrum remained roughly in this two-component shape until ~9 November (TJD 8935) and then returned to the initial power-law shape with an index of ~2 until the end of the period. The correlation of the two spectral shapes with the high and low luminosities of the soft gamma-ray emission is strongly reminiscent of that seen in Cygnus X-1. We interpret these results in terms of the Advection Dominated Accretion Flow (ADAF) model with possibly a "jet-like" region that persistently produced the non-thermal power-law gamma rays observed throughout the event.Comment: 40 pages total, including 10 figures and 2 table

Radio Supernova SN 1998bw and Its Relation to GRB 980425

SN 1998bw is an unusual Type Ic supernova that may be associated with the $\gamma$-ray burst GRB 980425. We use a synchrotron self-absorption model for its radio emission to deduce that the synchrotron-emitting gas is expanding into a circumstellar medium of approximately $r^{-2}$ density profile, at a speed comparable to the speed of light. We assume that the efficiencies of production of relativistic electrons and magnetic field are constant through the evolution. The circumstellar density is consistent with that expected around the massive star core thought to be the progenitor of SN 1998bw. The explosion energy in material moving with velocity $>0.5c$ is $\sim 10^{49}- 3\times 10^{50}$ ergs, with some preference for the high values. The rise in the radio light curves observed at days 20-40 is inferred to be the result of a rise in the energy of the blast wave by a factor $\sim 2.5$. Interaction with a jump in the ambient density is not consistent with the observed evolution. We infer that the boost in energy is from a shell of matter from the explosion that catches up with the decelerating shock front. Both the high explosion energy and the nature of the energy input to the blast wave are difficult to reconcile with energy input from the shock-accelerated high velocity ejecta from a supernova. The implication is that there is irregular energy input from a central engine, which is the type of model invoked for normal $\gamma$-ray bursts. The link between SN 1998bw and GRB 980425 is thus strengthened.Comment: 21 pages, 9 figures, revised version to appear in Ap

Remote optical addressing of single nano-objects

We present a scheme for remotely addressing single nano-objects by means of near-field optical microscopy that makes only use of one of the most fundamental properties of electromagnetic radiation: its polarization. A medium containing optically active nano-objects is covered with a thin metallic film presenting sub-wavelength holes. When the optical tip is positioned some distance away from a hole, surface plasmons in the metal coating are generated which, by turning the polarization plane of the excitation light, transfer the excitation towards a chosen hole and induce emission from the underlying nano-objects. The method, easily applicable to other systems, is demonstrated for single quantum dots (QDs) at low temperature. It may become a valuable tool for future optical applications in the nanoworld

An adjustable law of motion for relativistic spherical shells

A classical and a relativistic law of motion for an advancing shell are deduced applying the thin layer approximation. A new parameter connected with the quantity of absorbed matter in the expansion is introduced; this allows of matching theory and observation.Comment: 15 pages, 10 figures and article in press; Central European Journal of Physics 201

Moderate Asphericity of the SN 2002ic Circumstellar Envelope

The polarization of SN 2002ic interacting with a dense circumstellar envelope is calculated in the context of the asymmetric version of a previously proposed spherical interaction model. The circumstellar envelope is taken to be oblate. The observed polarization (Wang et al. 2004) can be reproduced for an aspect ratio of 0.65-0.7 assuming inclination angles >60 degrees. This model predicts a weak sensitivity of the line profiles to the orientation, in agreement with the absence of significant variations of the line profiles among SN 2002ic-like supernovae. We propose a test for distinguishing between the binary and single star progenitor scenarios based upon the polarization distribution function for the growing sample of these events.Comment: 13 pages, 4 figs., ApJ, accepte