Insight into atmospheres of extrasolar planets through plasma processes

Extrasolar planets appear in a chemical diversity unseen in our own solar system. Despite their atmospheres being cold, continuous and transient plasma processes do affect these atmosphere where clouds form with great efficiency. Clouds can be very dynamic due to winds for example in highly irradiated planets like HD 189733b, and lightning may emerge. Lightning, and discharge events in general, leave spectral fingerprints, for example due to the formation of HCN. During the interaction, lightning or other flash--ionisation events also change the electromagnetic field of a coherent, high energy emission which results a characteristic damping of the initial, unperturbed (e.g. cyclotron emission) radiation beam. We summarise this as 'recipe for observers'. External ionisation by X-ray or UV e.g. from within the interstellar medium or from a white dwarf companion will introduce additional ionisation leading to the formation of a chromosphere. Signatures of plasma processes therefore allow for an alternative way to study atmospheres of extrasolar planets and brown dwarfs.Comment: refereed proceeding (3 referees) for 'Planetary Radio Emissions VIII', Austrian Academy of Sciences Pres

The impact of M-dwarf atmosphere modelling on planet detection

Being able to accurately estimate stellar parameters based on spectral observations is important not only for understanding the stars themselves but it is also vital for the determination of exoplanet parameters. M dwarfs are discussed as targets for planet detection as these stars are less massive, less luminous and have smaller radii making it possible to detect smaller and lighter planets. Therefore M-dwarfs could prove to be a valuable source for examining the lower mass end of planet distribution, but in order to do that, one must first take care to understand the characteristics of the host stars well enough. Up to date, there are several families of stellar model atmospheres. We focus on the ATLAS9, MARCS and Drift-Phoenix families in the M-dwarf parameter space. We examine the differences in the (Tgas, pgas) structures, synthetic photometric fluxes and related colour indices.We find discrepancies in the hotter regions of the stellar atmosphere between the ATLAS and MARCS models. The MARCS and Drift-Phoenix models appear to agree to a better extend with variances of less than 300K. We have compiled the broad-band synthetic photometric fluxes of all models for the Johnson UBVRI and 2MASS JHKs. The fluxes of MARCS differ from both ATLAS and Drift-Phoenix models in the optical range.Comment: submitted to the proceedings of the conference 'Brown dwarfs come of age', May 20-24 2013, Memorie della Societa Astronomica Italian

Sexual abuse risk in sport: Testing the ‘stage of imminent achievement’ hypothesis

The purpose of this study was to assess the hypothetical model outlined by Brackenridge and Kirby in IRSS in 1997 (32(4): 407-418) which suggested that athlete susceptibility to grooming and sexual abuse in sport coincides with a defined stage of athletic development just prior to peak success: this period they called the ‘stage of imminent achievement’ (SIA). The model was assessed by investigating 83 cases of criminally-defined child sexual abuse within the sport context that had been reported in the print media over a period of 15 years. SIA-related hypotheses were examined in relation to athlete performance level, sex and early- and late-specialisation sport types. The majority of cases of child abuse in the sample occurred below the SIA for both males and females and with sexually abused males being three times more likely to be aged below the SIA than their female athlete victim counterparts. Age below the SIA thus appears to be a stronger predictor of the timing of sexual abuse among male athletes than females: this suggests that much more research is needed on both age and gender differences in sport-related sexual victimisation. Several limitations of the data are discussed. It is recommended that the SIA be reconceived as both a relational and a developmental construct and examined more closely in relation to the increased dependence of the athlete on their coach just as they approach a performance goal

Planetary host stars: Evaluating uncertainties in ultra-cool model atmospheres

M-dwarfs are emerging in the literature as promising targets for detecting low-mass, Earth-like planets. An important step in this process is to determine the stellar parameters of the M-dwarf host star as accurately as possible. Different well-tested stellar model atmosphere simulations from different groups are widely applied to undertake this task. This paper provides a comparison of different model atmosphere families to allow a better estimate of systematic errors on host-star stellar parameter introduced by the use of one specific model atmosphere family only. We present a comparison of the ATLAS9, MARCS, Phoenix and Drift-Phoenix model atmosphere families including the M-dwarf parameter space (T$_{\rm eff}=2500$K$\,...\,$4000K, log(g)=3.0$\,...\,$5.0, [M/H]=$-2.5\,...\,0.5$). We examine the differences in the (T$_{\rm gas}$, p$_{\rm gas}$)-structures, in synthetic photometric fluxes and in colour indices. Model atmospheres results for higher log(g) deviate considerably less between different models families than those for lower log(g) for all T$_{\rm eff}=2500$K$\,...\,$4000K examined. We compiled the broad-band synthetic photometric fluxes for all available model atmospheres (incl. M-dwarfs and brown dwarfs) for the UKIRT WFCAM ZYJHK, 2MASS JHKs and Johnson UBVRI filters, and calculated related colour indices. Synthetic colours in the IR wavelengths diverge by no more than 0.15 dex amongst all model families. For all spectral bands considered, model discrepancies in colour diminish for higher T$_{\rm eff}$ atmosphere simulations. We notice differences in synthetic colours between all model families and observed example data (incl. Kepler 42 and GJ1214).Comment: accepted for publication in MNRA

Connected Lie groups and property RD

For a locally compact group, property RD gives a control on the convolution norm of any compactly supported measure in terms of the $L^2$-norm of its density and the diameter of its support. We give a complete classification of those Lie groups with property RD.Comment: 29 page

A Spin-Isospin Dependent 3N Scattering Formalism in a 3D Faddeev Scheme

We have introduced a spin-isospin dependent three-dimensional approach for formulation of the three-nucleon scattering. Faddeev equation is expressed in terms of vector Jacobi momenta and spin-isospin quantum numbers of each nucleon. Our formalism is based on connecting the transition amplitude $T$ to momentum-helicity representations of the two-body $t$-matrix and the deuteron wave function. Finally the expressions for nucleon-deuteron elastic scattering and full breakup process amplitudes are presented.Comment: 17 page

Tuning nonlinearity, dynamic range, and frequency of nanomechanical resonators

We explore an electrostatic mechanism for tuning the nonlinearity of nanomechanical resonators and increasing their dynamic range for sensor applications. We also demonstrate tuning the resonant frequency of resonators both upward and downward. A theoretical model is developed that qualitatively explains the experimental results and serves as a simple guide for design of tunable nanomechanical devices