Near-infrared K-band Spectroscopic Investigation of Seyfert 2 Nuclei in the CfA and 12 Micron Samples

We present near-infrared K-band slit spectra of the nuclei of 25 Seyfert 2 galaxies in the CfA and 12 micron samples. The strength of the CO absorption features at 2.3-2.4 micron produced by stars is measured in terms of a spectroscopic CO index. A clear anti-correlation between the observed CO index and the nuclear K-L color is present, suggesting that a featureless hot dust continuum heated by an AGN contributes significantly to the observed K-band fluxes in the nuclei of Seyfert 2 galaxies. After correction for this AGN contribution, we estimate nuclear stellar K-band luminosities for all sources, and CO indices for sources with modestly large observed CO indices. The corrected CO indices for 10 (=40%) Seyfert 2 nuclei are found to be as high as those observed in star-forming or elliptical (=spheroidal) galaxies. We combine the K-band data with measurements of the L-band 3.3 micron polycyclic aromatic hydrocarbon (PAH) emission feature, another powerful indicator for star-formation, and find that the 3.3 micron PAH to K-band stellar luminosity ratios are substantially smaller than those of starburst galaxies. Our results suggest that the 3.3 micron PAH emission originates in the putative nuclear starbursts in the dusty tori surrounding the AGNs, because of its high surface brightness, whereas the K-band CO absorption features detected at the nuclei are dominated by old bulge (=spheroid) stars, and thus may not be a powerful indicator for the nuclear starbursts. We see no clear difference in the strength of the CO absorption and PAH emission features between the CfA and 12 micron Seyfert 2s.Comment: 28 pages, 6 figures, accepted for publication in ApJ (10 October 2004, v614 issue

Imprints of massive inverse seesaw model neutrinos in lepton flavor violating Higgs boson decays

In this paper we consider a Higgs boson with mass and other properties compatible with those of the recently discovered Higgs particle at the LHC, and explore the possibility of new Higgs leptonic decays, beyond the standard model, with the singular feature of being lepton flavor violating (LFV). We study these LFV Higgs decays, $H \to l_k\bar l_m$, within the context of the inverse seesaw model (ISS) and consider the most generic case where three additional pairs of massive right-handed singlet neutrinos are added to the standard model particle content. We require in addition that the input parameters of this ISS model are compatible with the present neutrino data and other constraints, like perturbativity of the neutrino Yukawa couplings. We present a full one-loop computation of the BR($H \to l_k\bar l_m$) rates for the three possible channels, $l_k\bar l_m=\mu \bar \tau,\, e \bar \tau,\, e \bar \mu$, and analyze in full detail the predictions as functions of the various relevant ISS parameters. We study in parallel the correlated one-loop predictions for the radiative decays, $l_m \to l_k \gamma$, within this same ISS context, and require full compatibility of our predictions with the present experimental bounds for the three radiative decays, $\mu \to e \gamma$, $\tau \to \mu \gamma$, and $\tau \to e \gamma$. After exploring the ISS parameter space we conclude on the maximum allowed LFV Higgs decay rates within the ISS.Comment: 29 pages, 13 figures, 1 table, 1 appendix: v4 matches the manuscript published in PR

Sensitivity to SUSY Seesaw Parameters and Lepton Flavour Violation

We address the constraints on the SUSY seesaw parameters arising from Lepton Flavour Violation observables. Working in the Constrained Minimal Supersymmetric Standard Model extended by three right-handed (s)neutrinos, we study the predictions for the branching ratios of $l_j \to l_i \gamma$ and $l_j \to 3 l_i$ channels. We impose compatibility with neutrino data, electric dipole moment bounds, and further require a successful baryon asymmetry of the Universe (via thermal leptogenesis). We emphasise the interesting interplay between $\theta_{13}$ and the LFV muon decays, pointing out the hints on the SUSY seesaw parameters that can arise from measurements of $\theta_{13}$ and LFV branching ratios. This is a brief summary of the work of Ref. \cite{Antusch:2006vw}.Comment: 6 pages, 4 figures. Presented at 5th Flavor Physics and CP Violation Conference (FPCP 2007), Bled, Slovenia, 12-16 May 200

Photospheric activity, rotation and magnetic interaction in LHS 6343 A

Context. The Kepler mission has recently discovered a brown dwarf companion transiting one member of the M4V+M5V visual binary system LHS 6343 AB with an orbital period of 12.71 days. Aims. The particular interest of this transiting system lies in the synchronicity between the transits of the brown dwarf C component and the main modulation observed in the light curve, which is assumed to be caused by rotating starspots on the A component. We model the activity of this star by deriving maps of the active regions that allow us to study stellar rotation and the possible interaction with the brown dwarf companion. Methods. An average transit profile was derived, and the photometric perturbations due to spots occulted during transits are removed to derive more precise transit parameters. We applied a maximum entropy spot model to fit the out-of-transit optical modulation as observed by Kepler during an uninterrupted interval of 500 days. It assumes that stellar active regions consist of cool spots and bright faculae whose visibility is modulated by stellar rotation. Results. Thanks to the extended photometric time series, we refine the determination of the transit parameters and find evidence of spots that are occulted by the brown dwarf during its transits. The modelling of the out-of-transit light curve of LHS 6343 A reveals several starspots rotating with a slightly longer period than the orbital period of the brown dwarf, i.e., 13.13 +- 0.02 days. No signature attributable to differential rotation is observed. We find evidence of a persistent active longitude on the M dwarf preceding the sub- companion point by 100 deg and lasting for at least 500 days. This can be relevant for understanding how magnetic interaction works in low-mass binary and star-planet systems.Comment: 14 pages, 16 figure

3He-Rich Solar Energetic Particles in Helical Jets on the Sun

Particle acceleration in stellar flares is ubiquitous in the Universe, however, our Sun is the only astrophysical object where energetic particles and their source flares can both be observed. The acceleration mechanism in solar flares, tremendously enhancing (up to a factor of ten thousand) rare elements like 3He and ultra-heavy nuclei, has been puzzling for almost 50 years. Here we present some of the most intense 3He- and Fe-rich solar energetic particle events ever reported. The events were accompanied by non-relativistic electron events and type III radio bursts. The corresponding high-resolution, extreme-ultraviolet imaging observations have revealed for the first time a helical structure in the source flare with a jet-like shape. The helical jets originated in relatively small, compact active regions, located at the coronal hole boundary. A mini-filament at the base of the jet appears to trigger these events. The events were observed with the two Solar Terrestrial Relations Observatories STEREO on the backside of the Sun, during the period of increased solar activity in 2014. The helical jets may be a distinct feature of these intense events that is related to the production of high 3He and Fe enrichments.Comment: accepted for publication in The Astrophysical Journa