Fermi-LAT upper limits on gamma-ray emission from colliding wind binaries

Context: Colliding wind binaries (CWBs) are thought to give rise to a plethora of physical processes including acceleration and interaction of relativistic particles. Observation of synchrotron radiation in the radio band confirms there is a relativistic electron population in CWBs. Accordingly, CWBs have been suspected sources of high-energy gamma-ray emission since the COS-B era. Theoretical models exist that characterize the underlying physical processes leading to particle acceleration and quantitatively predict the non-thermal energy emission observable at Earth. Aims: We strive to find evidence of gamma-ray emission from a sample of seven CWB systems: WR 11, WR 70, WR 125, WR 137, WR 140, WR 146, and WR 147. Theoretical modelling identified these systems as the most favourable candidates for emitting gamma-rays. We make a comparison with existing gamma-ray flux predictions and investigate possible constraints. Methods: We used 24 months of data from the Large Area Telescope (LAT) on-board the Fermi Gamma Ray Space Telescope to perform a dedicated likelihood analysis of CWBs in the LAT energy range. Results: We find no evidence of gamma-ray emission from any of the studied CWB systems and determine corresponding flux upper limits. For some CWBs the interplay of orbital and stellar parameters renders the Fermi-LAT data not sensitive enough to constrain the parameter space of the emission models. In the cases of WR140 and WR147, the Fermi-LAT upper limits appear to rule out some model predictions entirely and constrain theoretical models over a significant parameter space. A comparison of our findings to the CWB eta Car is made.Comment: 9 pages, 3 figure

Child psychology as revealed in Wordsworth's "The prelude"

Thesis (M.A.)--Boston Universit

Citations and Allusions to Jewish Scripture in Early Christian and Jewish Writings through 180 CE

Reviewed Book: McLean, Bradley H. Citations and Allusions to Jewish Scripture in Early Christian and Jewish Writings through 180 CE. Lewiston, NY: Edwin Mellen Press, 1992

Introduction to the Talmud and Midrash

Reviewed Book: Stemberger, Günter . Introduction to the Talmud and Midrash. London: T & T Clark, 1991

The Book of Ruth, Nahum, Habakkuk, and Zephaniah

Reviewed Book: Hubbard, Robert L. The Book of Ruth. Grand Rapids: Eerdmans, 1989. New international commentary on the Old Testament. Reviewed Book: Robertson, O Palmer. The Books of Nahum, Habakkuk, and Zephaniah. Grand Rapids: Eerdmans, 1990. New international commentary on the Old Testament

Civil religion and political theology

Reviewed Book: Rouner, Leroy S. Civil religion and political theology. Notre Dame, Ind: University of Notre Dame Press, 1986. Boston University studies in philosophy and religio

High-energy particle transport in 3D hydrodynamic models of colliding-wind binaries

Massive stars in binary systems (as WR140, WR147 or $\eta$ Carinae) have long been regarded as potential sources of high-energy $\gamma$-rays. The emission is thought to arise in the region where the stellar winds collide and produce relativistic particles which subsequently might be able to emit $\gamma$-rays. Detailed numerical hydrodynamic simulations have already offered insight in the complex dynamics of the wind collision region (WCR), while independent analytical studies, albeit with simplified descriptions of the WCR, have shed light on the spectra of charged particles. In this paper, we describe a combination of these two approaches. We present a 3D-hydrodynamical model for colliding stellar winds and compute spectral energy distributions of relativistic particles for the resulting structure of the WCR. The hydrodynamic part of our model incorporates the line-driven acceleration of the winds, gravity, orbital motion and the radiative cooling of the shocked plasma. In our treatment of charged particles we consider diffusive shock acceleration in the WCR and the subsequent cooling via inverse Compton losses (including Klein-Nishina effects), bremsstrahlung, collisions and other energy loss mechanisms.Comment: 28 pages, 9 figures / accepted for publication in The Astrophysical Journa

Josephus and the New Testament

Reviewed Book: Mason, Steve. Josephus and the New Testament. Peabody, Mass: Hendrickson Pubs, 1992

Divine Disclosure: An Introduction to Jewish Apocalyptic

Reviewed Book: Russell, D S. (David Syme). Divine Disclosure: An Introduction to Jewish Apocalyptic. Minneapolis: Augsburg Fortress; London: SCM Press, 1992