A Possible Massive Asteroid Belt Around zeta Lep

We have used the Keck I telescope to image at 11.7 microns and 17.9 microns the dust emission around zeta Lep, a main sequence A-type star at 21.5 pc from the Sun with an infrared excess. The excess is at most marginally resolved at 17.9 microns. The dust distance from the star is probably less than or equal to 6 AU, although some dust may extend to 9 AU. The mass of observed dust is \~10^22 g. Since the lifetime of dust particles is about 10,000 years because of the Poytning-Robertson effect, we robustly estimate at least 4 10^26 g must reside in parent bodies which may be asteroids if the system is in a steady state and has an age of ~300 Myr. This mass is approximately 200 times that contained within the main asteroid belt in our solar system.Comment: 12 pages, 3 figures, ApJL in pres

New optical and near-infrared Surface Brightness Fluctuations models. A primary distance indicator ranging from Globular Clusters to distant galaxies?

We present new theoretical models for Surface Brightness Fluctuations (SBF) both for optical and near-infrared bands in standard ground-based and Hubble Space Telescope filter systems. Simple Stellar Population simulations are adopted. Models cover the age and metallicity ranges from $t=5$ to $15~Gyr$ and from $Z=0.0001$ to 0.04 respectively. Effects due to the variation of the Initial Mass Function and the stellar color-temperature relations are explored. Particular attention is devoted to very bright stars in the color-magnitude diagram and to investigate the effects of mass loss along the Red Giant Branch (RGB) and the Asymptotic Giant Branch (AGB). It is found that $U$ and $B$ bands SBF amplitudes are powerful diagnostics for the morphology of the Horizontal Branch and the Post-AGB stars population. We point out that a careful treatment of mass loss process along the RGB and AGB is fundamental in determining reliable SBF evaluations. The SBF measurements are used to give robust constraints on the evolution of AGB stars, suggesting that mass loss activity on AGB stars should be twice more efficient than on the RGB stars. Our models are able to reproduce the absolute SBF magnitudes of the Galactic Globular Clusters and of galaxies, and their integrated colors. New calibrations of absolute SBF magnitude in $V$, $R$, $I$, and $K$ photometric filters are provided, which appear reliable enough to directly gauge distances bypassing other distance indicators. The SBF technique is also used as stellar population tracer to derive age and metallicity of a selected sample of galaxies of known distances. Finally, {\it SBF color} versus {\it integrated color} diagrams are proposed as particularly useful in removing the well known {\it age-metallicity degeneracy} affecting our knowledge of remote stellar systems.Comment: AJ accepted, 46 pages, 21 figures, 10 tables, uses aastex.cl

Non-Violent Resistance parent training and adolescent substance misuse

Adolescent substance misuse is increasingly being viewed as a systemic problem and several studies have shown the benefit of increased parental involvement. This article describes the evaluation of a ten-week Non-Violent Resistance (NVR) group parent training programme delivered within a Young People’s Specialist Substance Misuse Treatment Service. Eighteen participants completed questionnaires before and after the programme, and at follow-up. Eight participants also took part in semi-structured interviews. Parents reported experiencing the programme as unique and helpful, and highlighted some challenges. Measures of parental self-efficacy and goal-based outcomes showed significant improvement at the end of the programme, and improvement in parental self-efficacy remained significant at follow-up. This evaluation provides preliminary evidence that NVR parent training may be a useful intervention in this context. However, the generalisability of the data is limited and further research is needed. Practitioner points: Non-Violent Resistance parent training helps parents resist their child’s behaviour, manage their own emotional reactions, and recruit supporters from their wider network Qualitative data suggests that parents who have attended this programme experience additional benefits to those found in qualitative evaluations of other parenting interventions A group training programme delivered within a Young People’s Specialist Substance Misuse Treatment Service improves parents’ self-efficacy and helps them achieve their goals for their children.</p

Non-Violent Resistance parent training and adolescent substance misuse

Adolescent substance misuse is increasingly being viewed as a systemic problem and several studies have shown the benefit of increased parental involvement. This article describes the evaluation of a ten-week Non-Violent Resistance (NVR) group parent training programme delivered within a Young People’s Specialist Substance Misuse Treatment Service. Eighteen participants completed questionnaires before and after the programme, and at follow-up. Eight participants also took part in semi-structured interviews. Parents reported experiencing the programme as unique and helpful, and highlighted some challenges. Measures of parental self-efficacy and goal-based outcomes showed significant improvement at the end of the programme, and improvement in parental self-efficacy remained significant at follow-up. This evaluation provides preliminary evidence that NVR parent training may be a useful intervention in this context. However, the generalisability of the data is limited and further research is needed. Practitioner points: Non-Violent Resistance parent training helps parents resist their child’s behaviour, manage their own emotional reactions, and recruit supporters from their wider network Qualitative data suggests that parents who have attended this programme experience additional benefits to those found in qualitative evaluations of other parenting interventions A group training programme delivered within a Young People’s Specialist Substance Misuse Treatment Service improves parents’ self-efficacy and helps them achieve their goals for their children.</p

Inference for bounded parameters

The estimation of signal frequency count in the presence of background noise has had much discussion in the recent physics literature, and Mandelkern [1] brings the central issues to the statistical community, leading in turn to extensive discussion by statisticians. The primary focus however in [1] and the accompanying discussion is on the construction of a confidence interval. We argue that the likelihood function and $p$-value function provide a comprehensive presentation of the information available from the model and the data. This is illustrated for Gaussian and Poisson models with lower bounds for the mean parameter

Photometric analysis of Magellanic Cloud R Coronae Borealis Stars in the recovery phase of their declines

This paper presents the initial results of a multi-site photometric programme to examine the extraordinary behaviour displayed by 18 R Coronae Borealis (RCB) stars in the Magellanic Clouds (MCs). RCB stars exhibit a unique variability whereby they undergo rapid declines of up to several magnitudes. These are thought to be caused by the formation of dust in the stellar environment which reduces the brightness. The monitoring programme comprised the collection of UBVRI photometric data using five telescopes located at three different southern hemisphere longitudes (Las Campanas Observatory in Chile, Mount Joun University Observatory in New Zealand, and the Southern African Large Telescope (SALT) in South Africa). Examination of the data acquired in the V and I filters resulted in the identification of a total of 18 RCB declines occurring in four stars. Construction of colour-magnitude diagrams (V vs V-I), during the recovery to maximum light were undertaken in order to study the unique colour behaviour associated with the RCB declines. The combined recovery slope for the four stars was determined to be 3.37+/-0.24, which is similar to the value of 3.1+/-0.1 calculated for galactic RCB stars (Skuljan et al. 2003). These results may imply that the nature of the dust (i.e. the particle size) is similar in both our Galaxy and the MCs.Comment: accepted for publication in the Publications of the Astronomical Society of Australi

Spectroscopy and Time Variability of Absorption Lines in the Direction of the Vela Supernova Remnant

We present high resolution (R~75,000), high signal-to-noise (S/N~100) Ca II $\lambda$3933.663 and Na I $\lambda\lambda$5889.951, 5895.924 spectra of 68 stars in the direction of the Vela supernova remnant. The spectra comprise the most complete high resolution, high S/N, optical survey of early type stars in this region of the sky. A subset of the sight lines has been observed at multiple epochs, 1993/1994 and 1996. Of the thirteen stars observed twice, seven have spectra revealing changes in the equivalent width and/or velocity structure of lines, most of which arise from remnant gas. Such time variability has been reported previously for the sight lines towards HD 72089 and HD 72997 by Danks & Sembach (1995) and for HD 72127 by Hobbs et al. (1991). We have confirmed the ongoing time variability of these spectra and present new evidence of variability in the spectra of HD 73658, HD 74455, HD 75309 and HD 75821. We have tabulated Na I and Ca II absorption line information for the sight lines in our sample to serve as a benchmark for further investigations of the dynamics and evolution of the Vela SNR.Comment: 8 pages of text, 4 tables, 16 pages of figures Accepted and to be published in ApJ

HST Observations of Chromospheres in Metal Deficient Field Giants

HST high resolution spectra of metal-deficient field giants more than double the stars in previous studies, span about 3 magnitudes on the red giant branch, and sample an abundance range [Fe/H]= -1 to -3. These stars, in spite of their age and low metallicity, possess chromospheric fluxes of Mg II (2800 Angstrom) that are within a factor of 4 of Population I stars, and give signs of a dependence on the metal abundance at the lowest metallicities. The Mg II k-line widths depend on luminosity and correlate with metallicity. Line profile asymmetries reveal outflows that occur at lower luminosities (M_V = -0.8) than detected in Ca K and H-alpha lines in metal-poor giants, suggesting mass outflow occurs over a larger span of the red giant branch than previously thought, and confirming that the Mg II lines are good wind diagnostics. These results do not support a magnetically dominated chromosphere, but appear more consistent with some sort of hydrodynamic, or acoustic heating of the outer atmospheres.Comment: 36 pages, 12 figures, 7 tables, and accepted for publication in The Astronomical Journa

The Palomar Testbed Interferometer Calibrator Catalog

The Palomar Testbed Interferometer (PTI) archive of observations between 1998 and 2005 is examined for objects appropriate for calibration of optical long-baseline interferometer observations - stars that are predictably point-like and single. Approximately 1,400 nights of data on 1,800 objects were examined for this investigation. We compare those observations to an intensively studied object that is a suitable calibrator, HD217014, and statistically compare each candidate calibrator to that object by computing both a Mahalanobis distance and a Principal Component Analysis. Our hypothesis is that the frequency distribution of visibility data associated with calibrator stars differs from non-calibrator stars such as binary stars. Spectroscopic binaries resolved by PTI, objects known to be unsuitable for calibrator use, are similarly tested to establish detection limits of this approach. From this investigation, we find more than 350 observed stars suitable for use as calibrators (with an additional $\approx 140$ being rejected), corresponding to $\gtrsim 95$ sky coverage for PTI. This approach is noteworthy in that it rigorously establishes calibration sources through a traceable, empirical methodology, leveraging the predictions of spectral energy distribution modeling but also verifying it with the rich body of PTI's on-sky observations.Comment: 100 pages, 7 figures, 7 tables; to appear in the May 2008ApJS, v176n