Relativistic Turbulence with Strong Synchrotron and Synchrotron-Self-Compton Cooling

Many relativistic plasma environments in high-energy astrophysics, including pulsar wind nebulae, hot accretion flows onto black holes, relativistic jets in active galactic nuclei and gamma-ray bursts, and giant radio lobes, are naturally turbulent. The plasma in these environments is often so hot that synchrotron and inverse-Compton (IC) radiative cooling becomes important. In this paper we investigate the general thermodynamic and radiative properties (and hence the observational appearance) of an optically thin relativistically hot plasma stirred by driven magnetohydrodynamic (MHD) turbulence and cooled by radiation. We find that if the system reaches a statistical equilibrium where turbulent heating is balanced by radiative cooling, the effective electron temperature tends to attain a universal value $theta = kT_e/m_e c^2 sim 1/sqrt{tau_T}$, where $tau_T=n_esigma_T L ll 1$ is the systems Thomson optical depth, essentially independent of the strength of turbulent driving or magnetic field. This is because both MHD turbulent dissipation and synchrotron cooling are proportional to the magnetic energy density. We also find that synchrotron self-Compton (SSC) cooling and perhaps a few higher-order IC components are automatically comparable to synchrotron in this regime. The overall broadband radiation spectrum then consists of several distinct components (synchrotron, SSC, etc.), well separated in photon energy (by a factor $sim tau_T^{-1}$) and roughly equal in power. The number of IC peaks is checked by Klein-Nishina effects and depends logarithmically on $tau_T$ and the magnetic field. We also examine the limitations due to synchrotron self-absorption, explore applications to Crab PWN and blazar jets, and discuss links to radiative magnetic reconnection.

Spectral and Photometric Diagnostics of Giant Planet Formation Scenarios

Gas-giant planets that form via core accretion might have very different characteristics from those that form via disk-instability. Disk-instability objects are typically thought to have higher entropies, larger radii, and (generally) higher effective temperatures than core-accretion objects. We provide a large set of models exploring the observational consequences of high-entropy (hot) and low-entropy (cold) initial conditions, in the hope that this will ultimately help to distinguish between different physical mechanisms of planet formation. However, the exact entropies and radii of newly-formed planets due to these two modes of formation cannot, at present, be precisely predicted. We introduce a broad range of Warm Start gas-giant planet models. Between the hottest and the coldest models that we consider, differences in radii, temperatures, luminosities, and spectra persist for only a few million to a few tens of millions of years for planets that are a few times Jupiters mass or less. For planets that are ~five times Jupiters mass or more, significant differences between hottest-start and coldest-start models persist for on the order of 100 Myrs. We find that out of the standard infrared bands (J, H, K, L, M, N) the K and H bands are the most diagnostic of the initial conditions. A hottest-start model can be from ~4.5 magnitudes brighter (at Jupiters mass) to ~9 magnitudes brighter (at ten times Jupiters mass) than a coldest-start model in the first few million years. In more massive objects, these large differences in luminosity and spectrum persist for much longer than in less massive objects. We consider the influence of atmospheric conditions on spectra, and find that the presence or absence of clouds, and the metallicity of an atmosphere, can affect an objects apparent brightness in different bands by up to several magnitudes.

Life Products of Stars

We attempt to document complete energetic transactions of stars in their life. We calculate photon and neutrino energies that are produced from stars in their each phase of evolution from 1 to 8 M_sun, using the state-of-the-art stellar evolution code, tracing the evolution continuously from pre-main sequence gravitational contraction to white dwarfs. We also catalogue gravitational and thermal energies and helium, and heavier elements that are stored in stars and those ejected into interstellar space in each evolutionary phase.