The dust mass in Cassiopeia A from infrared and optical line flux differences

ABSTRACT The large quantities of dust that have been found in a number of high-redshift galaxies have led to suggestions that core-collapse supernovae (CCSNe) are the main sources of their dust and have motivated the measurement of the dust masses formed by local CCSNe. For Cassiopeia A (Cas A), an oxygen-rich remnant of a Type IIb CCSN, a dust mass of 0.6–1.1 M⊙ has already been determined by two different methods, namely (a) from its far-infrared spectral energy distribution and (b) from analysis of the red–blue emission line asymmetries in its integrated optical spectrum. We present a third, independent, method for determining the mass of dust contained within Cas A. This compares the relative fluxes measured in similar apertures from [O iii] far-infrared and visual-region emission lines, taking into account foreground dust extinction, in order to determine internal dust optical depths, from which corresponding dust masses can be obtained. Using this method, we determine a dust mass within Cas A of at least 0.99$^{+0.10}_{-0.09}$ M⊙.

Neutron Star Cooling Within the Equation of State With Induced Surface Tension

We study the thermal evolution of neutron stars described within the equation of state with induced surface tension (IST) that reproduces properties of normal nuclear matter, fulfills the proton flow constraint, provides a high-quality description of hadron multiplicities created during the nuclear-nuclear collision experiments, and it is equally compatible with the constraints from astrophysical observations and the GW170817 event. The model features strong direct Urca processes for the stars above 1.91M⊙. The IST equation of state shows very good agreement with the available cooling data, even without introducing nuclear pairing. We also analysed the effect of the singlet proton/neutron and triplet neutron pairing on the cooling of neutron stars of different mass. We show that the description of the compact object in the center of the Cassiopeia A does not necessarily require an inclusion of neutron superfluidity and/or proton superconductivity. Our results indicate that data of Cassiopeia A can be adequately well reproduced by a 1.66M⊙ star with an atmosphere of light elements. Moreover, the IST EoS reproduces each of the observational datasets for the surface temperature of Cassiopeia A either by a rapidly cooling ∼1.955M⊙ star with paired and unpaired matter or by a 1.91M⊙ star with the inclusion of neutron and proton pairings in the singlet channel.

Formation pathway for lonely stripped-envelope supernova progenitors: implications for Cassiopeia A

ABSTRACT We explore a new scenario for producing stripped-envelope supernova progenitors. In our scenario, the stripped-envelope supernova is the second supernova of the binary, in which the envelope of the secondary was removed during its red supergiant phase by the impact of the first supernova. Through 2D hydrodynamical simulations, we find that ∼50–90 ${{\ \rm per\ cent}}$ of the envelope can be unbound as long as the pre-supernova orbital separation is ≲5 times the stellar radius. Recombination energy plays a significant role in the unbinding, especially for relatively high mass systems (≳18 M⊙). We predict that more than half of the unbound mass should be distributed as a one-sided shell at about ∼10–100 pc away from the second supernova site. We discuss possible applications to known supernova remnants such as Cassiopeia A, RX J1713.7−3946, G11.2−0.3, and find promising agreements. The predicted rate is ∼0.35–1${{\ \rm per\ cent}}$ of the core-collapse population. This new scenario could be a major channel for the subclass of stripped-envelope or type IIL supernovae that lack companion detections like Cassiopeia A.

Trans-Alfvénic magnetohydrodynamic turbulence in the vicinity of supernova remnant Cassiopeia-A shocks

ABSTRACT Statistics of the magnetic field disturbances in supernova remnants (SNRs) can be accessed using the second-order correlation function of the synchrotron intensities. Here we measure the magnetic energy spectra in the supernova remnant Cassiopeia-A by two-point correlation of the synchrotron intensities, using a recently developed unbiased method. The measured magnetic energy spectra in the vicinity of supernova remnant shocks are found to be a 2/3 power law over the decade of range scales, showing the developed trans-Alfvénic magnetohydrodynamic turbulence. Our results are globally consistent with the theoretical prediction of trans-Alfvénic Mach number in developed magnetohydrodynamic turbulence and can be explained by amplification of the magnetic field in the vicinity of SNR shocks. The magnetic energy spectra predict SNR Cassiopeia-A to have an additional subshock in the radio frequency observation along with forward and reverse shocks, with a radial window of the amplified magnetic field of ∼ 0.115 pc near the shocks.