Modeling the Radio and X-ray Emission of SN 1993J and SN 2002ap

Modeling of radio and X-ray observations of supernovae interacting with their circumstellar media are discussed, with special application to SN 1993J and SN 2002ap. We emphasize the importance of including all relevant physical mechanisms, especially for the modeling of the radio light curves. The different conclusions for the absorption mechanism (free-free or synchrotron self-absorption), as well as departures from an $\rho \propto r^{-2}$ CSM, as inferred by some authors, are discussed in detail. We conclude that the evidence for a variation in the mass loss rate with time is very weak. The results regarding the efficiencies of magnetic field generation and relativistic particle acceleration are summarized.Comment: 10 pages, 2 figures. Uses svmult.cls. To appear in proceedings of IAU Colloquium 192 "Supernovae (10 years of SN 1993J)", April 2003, Valencia, Spain, eds. J. M. Marcaide and K. W. Weile

Circumstellar interaction in supernovae in dense environments - an observational perspective

In a supernova explosion, the ejecta interacting with the surrounding circumstellar medium (CSM) give rise to variety of radiation. Since CSM is created from the mass lost from the progenitor star, it carries footprints of the late time evolution of the star. This is one of the unique ways to get a handle on the nature of the progenitor star system. Here, I will focus mainly on the supernovae (SNe) exploding in dense environments, a.k.a. Type IIn SNe. Radio and X-ray emission from this class of SNe have revealed important modifications in their radiation properties, due to the presence of high density CSM. Forward shock dominance of the X-ray emission, internal free-free absorption of the radio emission, episodic or non-steady mass loss rate, asymmetry in the explosion seem to be common properties of this class of SNe.Comment: Fixed minor typos. 31 pages, 9 figures, accepted for publication in Space Science Reviews. Chapter in International Space Science Institute (ISSI) Book on "Supernovae" to be published in Space Science Reviews by Springe

A First Search for coincident Gravitational Waves and High Energy Neutrinos using LIGO, Virgo and ANTARES data from 2007

We present the results of the first search for gravitational wave bursts associated with high energy neutrinos. Together, these messengers could reveal new, hidden sources that are not observed by conventional photon astronomy, particularly at high energy. Our search uses neutrinos detected by the underwater neutrino telescope ANTARES in its 5 line configuration during the period January - September 2007, which coincided with the fifth and first science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed for candidate gravitational-wave signals coincident in time and direction with the neutrino events. No significant coincident events were observed. We place limits on the density of joint high energy neutrino - gravitational wave emission events in the local universe, and compare them with densities of merger and core-collapse events.Comment: 19 pages, 8 figures, science summary page at http://www.ligo.org/science/Publication-S5LV_ANTARES/index.php. Public access area to figures, tables at https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=p120000

Supernova Interaction with a Circumstellar Medium

The explosion of a core collapse supernova drives a powerful shock front into the wind from the progenitor star. A layer of shocked circumstellar gas and ejecta develops that is subject to hydrodynamic instabilities. The hot gas can be observed directly by its X-ray emission, some of which is absorbed and re-radiated at lower frequencies by the ejecta and the circumstellar gas. Synchrotron radiation from relativistic electrons accelerated at the shock fronts provides information on the mass loss density if free-free absorption dominates at early times or the size of the emitting region if synchrotron self-absorption dominates. Analysis of the interaction leads to information on the density and structure of the ejecta and the circumstellar medium, and the abundances in these media. The emphasis here is on the physical processes related to the interaction.Comment: 22 pages, 7 figures, to appear as a Chapter in "Supernovae and Gamma-Ray Bursts," edited by K. W. Weiler (Springer-Verlag

The Physics of Star Cluster Formation and Evolution

© 2020 Springer-Verlag. The final publication is available at Springer via https://doi.org/10.1007/s11214-020-00689-4.Star clusters form in dense, hierarchically collapsing gas clouds. Bulk kinetic energy is transformed to turbulence with stars forming from cores fed by filaments. In the most compact regions, stellar feedback is least effective in removing the gas and stars may form very efficiently. These are also the regions where, in high-mass clusters, ejecta from some kind of high-mass stars are effectively captured during the formation phase of some of the low mass stars and effectively channeled into the latter to form multiple populations. Star formation epochs in star clusters are generally set by gas flows that determine the abundance of gas in the cluster. We argue that there is likely only one star formation epoch after which clusters remain essentially clear of gas by cluster winds. Collisional dynamics is important in this phase leading to core collapse, expansion and eventual dispersion of every cluster. We review recent developments in the field with a focus on theoretical work.Peer reviewe

Mass-loading in Galactic Winds: the Role of Photoevaporation and Wind Ablation

We present a dynamical scenario of instantaneous dense gas entrainment by stellar winds in a wind-dominated HII region. Stellar winds and radiation pressure will become more important in an HII region as the central star or cluster is sufficiently luminous, therefore the region is windswept instead of photoevaporation-dominated. In our model, a cloud is smaller than the region as a whole, hence its mass injection occurs through either ordinary photoevaporation or wind ablation. We predict that the instantaneous wind ablation will cause strong mixing between hot winds and warm gas, and the mass injection rate of the wind-confined photoevaporated flow is higher than that of the ionizing source

Evolution and precession of accretion disk in tidal disruption events

In a supermassive black hole (BH) tidal disruption event (TDE), the tidally disrupted star feeds the BH via an accretion disk. Most often it is assumed that the accretion rate history, hence the emission light curve, tracks the rate at which new debris mass falls back onto the disk, notably the t−5/3 power law. But this is not the case when the disk evolution due to viscous spreading - the driving force for accretion - is carefully considered. We construct a simple analytical model that comprehensively describes the accretion rate history across 4 different phases of the disk evolution, in the presence of mass fallback and disk wind loss. Accretion rate evolves differently in those phases which are governed by how the disk heat energy is carried away, early on by advection and later by radiation. The accretion rate can decline as steeply as t−5/3 only if copious disk wind loss is present during the early advection-cooled phase. Later, the accretion rate history is t−8/7 or shallower. These have great implications on the TDE flare light curve. A TDE accretion disk is most likely misaligned with the equatorial plane of the spinning BH. Moreover, in the TDE the accretion rate is super- or near-Eddington thus the disk is geometrically thick, for which case the BH’s frame dragging effect may cause the disk precess as a solid body, which may manifest itself as quasi-periodic signal in the TDE light curve. Our disk evolution model predicts the disk precession period increases with time, typically as ∝ t. The results are applied to the recently jetted TDE flare Swift transient J1644 + 57 which shows numerous, quasi-periodic dips in its long-term X-ray light curve. As the current TDE sample increases, the identification of the disk precession signature provides a unique way of measuring BH spin and studying BH accretion physics