Parametric studies of cosmic ray acceleration in supernova remnants

We present a library of numerical models of cosmic-ray accelerating supernova remnants (SNRs) evolving through a homogeneous ambient medium. We analyse distributions of the different energy components and diffusive shock acceleration time-scales for the models in various conditions. The library comprises a variety of SNR evolutionary scenarios and is used to map remnants with sufficiently known properties. This mapping constrains the respective ambient medium properties and the acceleration efficiency. Employing the library, we derive the ambient medium density, ambient magnetic field strength and the cosmic-ray acceleration efficiency for models of Tycho and SN 1006 remnants and refine the ages of SNR 0509-67.5 and SNR 0519-69.0.Comment: 13 pages, 9 figures, MNRAS accepte

Progenitor's signatures in Type Ia supernova remnants

The remnants of Type Ia supernovae can provide important clues about their progenitor-histories. We discuss two well-observed supernova remnants (SNRs) that are believed to result from a Type Ia SN and use various tools to shed light on the possible progenitor history. We find that Kepler's SNR is consistent with a symbiotic binary progenitor consisted of a white dwarf and an AGB star. Our hydrosimulations can reproduce the observed kinematic and morphological properties. For Tycho's remnant we use the characteristics of the X-ray spectrum and the kinematics to show that the ejecta has likely interacted with dense circumstellar gas.Comment: 4 pages, 9 figures, proceedings for IAU Symposium 281, Padova, July 201

Modeling the interaction of thermonuclear supernova remnants with circumstellar structures: The case of Tycho's supernova remnant

The well-established Type Ia remnant of Tycho's supernova (SN 1572) reveals discrepant ambient medium density estimates based on either the measured dynamics or on the X-ray emission properties. This discrepancy can potentially be solved by assuming that the supernova remnant (SNR) shock initially moved through a stellar wind bubble, but is currently evolving in the uniform interstellar medium with a relatively low density. We investigate this scenario by combining hydrodynamical simulations of the wind-loss phase and the supernova remnant evolution with a coupled X-ray emission model, which includes non-equilibrium ionization. For the explosion models we use the well-known W7 deflagration model and the delayed detonation model that was previously shown to provide good fits to the X-ray emission of Tycho's SNR. Our simulations confirm that a uniform ambient density cannot simultaneously reproduce the dynamical and X-ray emission properties of Tycho. In contrast, models that considered that the remnant was evolving in a dense, but small, wind bubble reproduce reasonably well both the measured X-ray emission spectrum and the expansion parameter of Tycho's SNR. Finally, we discuss possible mass loss scenarios in the context of single- and double-degenerate models which possible could form such a small dense wind bubble.Comment: 12 pages, 7 figures, accepted for publication in MNRA

Oxygen emission in remnants of thermonuclear supernovae as a probe for their progenitor system

Recent progress in numerical simulations of thermonuclear supernova explosions brings up a unique opportunity in studying the progenitors of Type Ia supernovae. Coupling state-of-the-art explosion models with detailed hydrodynamical simulations of the supernova remnant evolution and the most up-to-date atomic data for X-ray emission calculations makes it possible to create realistic synthetic X-ray spectra for the supernova remnant phase. Comparing such spectra with high quality observations of supernova remnants could allow to constrain the explosion mechanism and the progenitor of the supernova. The present study focuses in particular on the oxygen emission line properties in young supernova remnants, since different explosion scenarios predict a different amount and distribution of this element. Analysis of the soft X-ray spectra from supernova remnants in the Large Magellanic Cloud and confrontation with remnant models for different explosion scenarios suggests that SNR 0509-67.5 could originate from a delayed detonation explosion and SNR 0519-69.0 from an oxygen-rich merger.Comment: 8 pages, 4 figures, MNRAS accepte

The kinematics and chemical stratification of the Type Ia supernova remnant 0519-69.0

We present an analysis of the XMM-Newton and Chandra X-ray data of the young Type Ia supernova remnant 0519-69.0 in the Large Magellanic Cloud. We used data from both the Chandra ACIS and XMM-Newton EPIC-MOS instruments, and high resolution X-ray spectra obtained with the XMM-Newton Reflection Grating Spectrometer. The Chandra data show that there is a radial stratification of oxygen, intermediate mass elements and iron, with the emission from more massive elements more toward the center. Using a deprojection technique we measure a forward shock radius of 4.0(3) pc and a reverse shock radius of 2.7(4) pc. We took the observed stratification of the shocked ejecta into account in the modeling of the X-ray spectra with multi-component NEI models, with the components corresponding to layers dominated by one or two elements. An additional component was added in order to represent the ISM, which mostly contributed to the continuum emission. This model fits the data well, and was also employed to characterize the spectra of distinct regions extracted from the Chandra data. From our spectral analysis we find that the fractional masses of shocked ejecta for the most abundant elements are: M(O)=32%, M(Si/S)=7%/5%, M(Ar+Ca)=1%, and M(Fe) = 55%. From the continuum component we derive a circumstellar density of nH= 2.4(2)/cm^3. This density, together with the measurements of the forward and reverse shock radii suggest an age of 450+/-200 yr,somewhat lower than, but consistent with the estimate based on the optical light echo (600+/-200 yr). From the RGS spectra we measured a Doppler broadening of sigma=1873+/-50 km/s, from implying a forward shock velocity of vS = 2770+/-500 km/s. We discuss the results in the context of single degenerate explosion models, using semi-analytical and numerical modeling, and compare the characteristics of 0519-69.0 with those of other Type Ia supernova remnants.Comment: Astronomy and Astrophysics in press. This version is the A&A accepted version, which contains improved figures and an extended discussion sectio

Gravitational wave background from binary systems

Basic aspects of the background of gravitational waves and its mathematical characterization are reviewed. The spectral energy density parameter $\Omega(f)$, commonly used as a quantifier of the background, is derived for an ensemble of many identical sources emitting at different times and locations. For such an ensemble, $\Omega(f)$ is generalized to account for the duration of the signals and of the observation, so that one can distinguish the resolvable and unresolvable parts of the background. The unresolvable part, often called confusion noise or stochastic background, is made by signals that cannot be either individually identified or subtracted out of the data. To account for the resolvability of the background, the overlap function is introduced. This function is a generalization of the duty cycle, which has been commonly used in the literature, in some cases leading to incorrect results. The spectra produced by binary systems (stellar binaries and massive black hole binaries) are presented over the frequencies of all existing and planned detectors. A semi-analytical formula for $\Omega(f)$ is derived in the case of stellar binaries (containing white dwarfs, neutron stars or stellar-mass black holes). Besides a realistic expectation of the level of background, upper and lower limits are given, to account for the uncertainties in some astrophysical parameters such as binary coalescence rates. One interesting result concerns all current and planned ground-based detectors (including the Einstein Telescope). In their frequency range, the background of binaries is resolvable and only sporadically present. In other words, there is no stochastic background of binaries for ground-based detectors.Comment: 30 pages, 16 figure