Quasi-Periodic Oscillations and energy spectra from the two brightest Ultra-Luminous X-ray sources in M82

Ultra-Luminous X-ray sources are thought to be accreting black holes that might host Intermediate Mass Black Holes (IMBH), proposed to exist by theoretical studies, even though a firm detection (as a class) is still missing. The brightest ULX in M82 (M82 X-1) is probably one of the best candidates to host an IMBH. In this work we analyzed the data of the recent release of observations obtained from M82 X-1 taken by XMM-Newton. We performed a study of the timing and spectral properties of the source. We report on the detection of (46+-2) mHz Quasi-Periodic Oscillations (QPOs) in the power density spectra of two observations. A comparison of the frequency of these high-frequency QPOs with previous detections supports the 1:2:3 frequency distribution as suggested in other studies. We discuss the implications if the (46+-2) mHz QPO detected in M82 X-1 is the fundamental harmonic, in analogy with the High-Frequency QPOs observed in black hole binaries. For one of the observations we have detected for the first time a QPO at 8 mHz (albeit at a low significance), that coincides with a hardening of the spectrum. We suggest that the QPO is a milli-hertz QPO originating from the close-by transient ULX M82 X-2, with analogies to the Low-Frequency QPOs observed in black hole binaries.Comment: 9 pages (with 4 figures and 4 tables). Accepted for publication in MNRAS (26/09/13

Non-analyticities in three-dimensional gauge theories

Quantum fluctuations generate in three-dimensional gauge theories not only radiative corrections to the Chern-Simons coupling but also non-analytic terms in the effective action. We review the role of those terms in gauge theories with massless fermions and Chern-Simons theories. The explicit form of non-analytic terms turns out to be dependent on the regularization scheme and in consequence the very existence of phenomena like parity and framing anomalies becomes regularization dependent. In particular we find regularization regimes where both anomalies are absent. Due to the presence of non-analytic terms the effective action becomes not only discontinuous but also singular for some background gauge fields which include sphalerons. The appearence of this type of singularities is linked to the existence of nodal configurations in physical states and tunneling suppression at some classical field configurations. In the topological field theory the number of physical states may also become regularization dependent. Another consequence of the peculiar behaviour of three-dimensional theories under parity odd regularizations is the existence of a simple mechanism of generation of a mass gap in pure Yang-Mills theory by a suitable choice of regularization scheme. The generic value of this mass does agree with the values obtained in Hamiltonian and numerical analysis. Finally, the existence of different regularization regimes unveils the difficulties of establishing a Zamolodchikov c-theorem for three-dimensional field theories in terms of the induced gravitational Chern-Simons couplings.Comment: 21 pages; Contribution to Ian Kogan Memorial Collection, ``From Fields to Strings: Circumnavigating Theoretical Physics'

A new Lyropecten (Pectinidae, Bivalvia, Mollusca) from the central California Miocene, USA

A new pectinid, Lyropecten terrysmithae n. sp., has been recognized in middle to late Miocene rock units referred to as the Monterey Formation and Santa Margarita Sandstone in the southern Salinas Valley, central California. Previously, L. terrysmithae had been identified as a flat form belonging to either L. estrellanus or L. catalinae, then more recently to Argopecten sp. The earlier assignments were based on its moderate size and a radial rib count nearly identical to these taxa. However, its hinge, flat unledged valves, looped lamellar growth lines, and hinge crura set L. terrysmithae apart from Argopecten and all species of Lyropecten. Localities where it occurs in the Salinas Valley that can be accurately dated are from the late middle to middle late Miocene “Margaritan” California provincial molluscan stage. While L. terrysmithae has been collected at other sites, those localities lack diagnostic age-specific species necessary to determine an accurate geological age and maybe older