The Remarkable Be Star HD110432

HD110432 has gained considerable attention because it is a hard, variable X-ray source similar to gamma Cas. From time-serial echelle data obtained over two weeks during 2005 January and February, we find several remarkable characteristics in the star's optical spectrum. The line profiles show rapid variations on some nights which can be most likely be attributed to irregularly occurring and short-lived migrating subfeatures. Such features have only been observed to date in gamma Cas and AB Dor, two stars for which it is believed magnetic fields force circumstellar clouds to corotate over the stellar surface. The star's optical spectrum also exhibits a number of mainly FeII and HeI emission features with profiles typical of an optically thin disk viewed edge-on. Using spectral synthesis techniques, we find that its temperature is 9800K +/-300K, that its projected area is a remarkably large 100 stellar areas, and its emitting volume resides at a distance of 1 AU from the star. We also find that the star's absorption profiles extend to +/-1000 km/s, a fact which we cannot explain. Otherwise, HD110432 and gamma Cas share similarly peculiar X-ray and optical characteristics such as high X-ray temperature, erratic X-ray variability on timescales of a few hours, optical emission lines, and submigrating features in optical line profiles. Because of these similarities, we suggest that this star is a new member of a select class of "gamma Cas analogs."Comment: 31 pages, 9 figures, accepted by ApJ (3/20/06

US 708 - An unbound hyper-velocity subluminous O star

We report the discovery of an unbound hyper-velocity star, US 708, in the Milky Way halo, with a heliocentric radial velocity of +708+-15km/s. A quantitative NLTE model atmosphere analysis of optical spectra obtained with LRIS at the Keck I telescope shows that US 708 is an extremely helium-rich (N(He)/N(H)=10) subluminous O type star with Teff=44500K, log g=5.23 at a distance of 19kpc. Its Galactic rest frame velocity is at least 751km/s, much higher than the local Galactic escape velocity indicating that the star is unbound to the Galaxy. It has been suggested that such hyper-velocity stars can be formed by the tidal disruption of a binary through interaction with the super-massive black hole (SMBH) at the Galactic centre (GC). Numerical kinematical experiments are carried out to reconstruct the path from the GC.U S 708 needs about 32Myrs to travel from the GC to its present position, less than its evolutionary lifetime. Its predicted proper motion mue(alpha) cos(delta)=-2.3mas/y and mue(delta)=-2.4mas/y should be measurable by future space missions. We conjecture that US 708 is formed by the merger of two helium white dwarfs in a close binary induced by the interaction with the SMBH in the GC and then escaped.Comment: 4 pages, 3 figure

Three ways to solve the orbit of KIC11558725: a 10 day beaming sdB+WD binary with a pulsating subdwarf

The recently discovered subdwarf B (sdB) pulsator KIC11558725 features a rich g-mode frequency spectrum, with a few low-amplitude p-modes at short periods, and is a promising target for a seismic study aiming to constrain the internal structure of this star, and of sdB stars in general. We have obtained ground-based spectroscopic Balmer-line radial-velocity measurements of KIC11558725, spanning the 2010 and 2011 observing seasons. From these data we have discovered that KIC11558725 is a binary with period P=10.05 d, and that the radial-velocity amplitude of the sdB star is 58 km/s. Consequently the companion of the sdB star has a minimum mass of 0.63 M\odot, and is therefore most likely an unseen white dwarf. We analyse the near-continuous 2010-2011 Kepler light curve to reveal orbital Doppler-beaming light variations at the 238 ppm level, which is consistent with the observed spectroscopic orbital radial-velocity amplitude of the subdwarf. We use the strongest 70 pulsation frequencies in the Kepler light curve of the subdwarf as clocks to derive a third consistent measurement of the orbital radial-velocity amplitude, from the orbital light-travel delay. We use our high signal-to-noise average spectra to study the atmospheric parameters of the sdB star, deriving Teff = 27 910K and log g = 5.41 dex, and find that carbon, nitrogen and oxygen are underabundant relative to the solar mixture. Furthermore, we extract more than 160 significant frequencies from the Kepler light curve. We investigate the pulsation frequencies for expected period spacings and rotational splittings. We find period-spacing sequences of spherical-harmonic degrees \ell=1 and \ell=2, and we associate a large fraction of the g-modes in KIC11558725 with these sequences. From frequency splittings we conclude that the subdwarf is rotating subsynchronously with respect to the orbit

On the protection of extrasolar Earth-like planets around K/M stars against galactic cosmic rays

Previous studies have shown that extrasolar Earth-like planets in close-in habitable zones around M-stars are weakly protected against galactic cosmic rays (GCRs), leading to a strongly increased particle flux to the top of the planetary atmosphere. Two main effects were held responsible for the weak shielding of such an exoplanet: (a) For a close-in planet, the planetary magnetic moment is strongly reduced by tidal locking. Therefore, such a close-in extrasolar planet is not protected by an extended magnetosphere. (b) The small orbital distance of the planet exposes it to a much denser stellar wind than that prevailing at larger orbital distances. This dense stellar wind leads to additional compression of the magnetosphere, which can further reduce the shielding efficiency against GCRs. In this work, we analyse and compare the effect of (a) and (b), showing that the stellar wind variation with orbital distance has little influence on the cosmic ray shielding. Instead, the weak shielding of M star planets can be attributed to their small magnetic moment. We further analyse how the planetary mass and composition influence the planetary magnetic moment, and thus modify the cosmic ray shielding efficiency. We show that more massive planets are not necessarily better protected against galactic cosmic rays, but that the planetary bulk composition can play an important role.Comment: 7 figure

Kepler observations of variability in B-type stars

The analysis of the light curves of 48 B-type stars observed by Kepler is presented. Among these are 15 pulsating stars, all of which show low frequencies characteristic of SPB stars. Seven of these stars also show a few weak, isolated high frequencies and they could be considered as SPB/beta Cep hybrids. In all cases the frequency spectra are quite different from what is seen from ground-based observations. We suggest that this is because most of the low frequencies are modes of high degree which are predicted to be unstable in models of mid-B stars. We find that there are non-pulsating stars within the beta Cep and SPB instability strips. Apart from the pulsating stars, we can identify stars with frequency groupings similar to what is seen in Be stars but which are not Be stars. The origin of the groupings is not clear, but may be related to rotation. We find periodic variations in other stars which we attribute to proximity effects in binary systems or possibly rotational modulation. We find no evidence for pulsating stars between the cool edge of the SPB and the hot edge of the delta Sct instability strips. None of the stars show the broad features which can be attributed to stochastically-excited modes as recently proposed. Among our sample of B stars are two chemically peculiar stars, one of which is a HgMn star showing rotational modulation in the light curve.Comment: 19 pages, 11 figures, 4 table

Well-being of Canadian Veterans during the COVID-19 pandemic: cross-sectional results from the COVID-19 Veteran well-being study

Background: The impacts of the COVID-19 pandemic have disproportionally affected different population groups. Veterans are more likely to have pre-existing mental health conditions compared to the general Canadian population, experience compounded stressors resulting from disruptions to familial, social, and occupational domains, and were faced with changes in health-care delivery (e.g. telehealth). The objectives of this study are to assess (a) the mental health impact of COVID-19 and related life changes on the well-being of Veterans and (b) perceptions of and satisfaction with changes in health-care treatments and delivery during the pandemic. Methods: A total of 1136 Canadian Veterans participated in an online survey. Participants completed questions pertaining to their mental health and well-being, lifestyle changes, and concerns relating to the COVID-19 pandemic, as well as experiences and satisfaction with health-care treatments during the pandemic. Results: Results showed that 55.9% of respondents reported worse mental health functioning compared to before the pandemic. The frequency of probable posttraumatic stress disorder, major depressive disorder, generalized anxiety disorder, alcohol use disorder, and suicidal ideation were 34.2%, 35.3%, 26.8%, 13.0%, and 22.0%, respectively. Between 38.6% and 53.1% of respondents attributed their symptoms as either directly related to or exacerbated by the pandemic. Approximately 18% of respondents reported using telehealth for mental health services during the pandemic, and among those, 72.8% indicated a choice to use telehealth even after the pandemic. Conclusions: This study found that Veterans experienced worsening mental health as a result of the COVID-19 pandemic. The use of telehealth services was widely endorsed by mental health treatment-seeking Veterans who transitioned to virtual care during the pandemic. Our findings have important clinical and programmeadministrator implications, emphasizing the need to reach out to support veterans, especially those with pre-existing mental health conditions and to enhance and maintain virtual care even post-pandemic

Hot DB White Dwarfs from the Sloan Digital Sky Survey

We present ugriz photometry and optical spectroscopy for 28 DB and DO white dwarfs with temperatures between 28,000K and 45,000K. About 10 of these are particularly well-observed; the remainder are candidates. These are the hottest DB stars yet found, and they populate the "DB gap" between the hotter DO stars and the familiar DB stars cooler than 30,000K. Nevertheless, after carefully matching the survey volumes, we find that the ratio of DA stars to DB/DO stars is a factor of 2.5 larger at 30,000 K than at 20,000 K, suggesting that the "DB gap" is indeed deficient and that some kind of atmospheric transformation takes place in roughly 10% of DA stars as they cool from 30,000 K to 20,000 K.Comment: Accepted by the Astronomical Journal. 34 pages, 10 figures, LaTe

Well-being of Canadian Armed Forces Veterans and Spouses of Veterans during the COVID-19 Pandemic: Protocol for a Prospective Longitudinal Survey

Background: The COVID-19 pandemic has resulted in significant changes to everyday life, including social distancing mandates, changes to health care, and a heightened risk of infection. Previous research has shown that Canadian Armed Forces (CAF) veterans are at higher risk of developing mental and physical health conditions. Veterans and their families may face unique social challenges that can compound with pandemic-related disruptions to negatively impact well-being. Objective: This study aims to longitudinally characterize the mental health of CAF veterans and spouses of CAF veterans throughout the pandemic and to understand the dynamic influences of pandemic-related stressors on psychological health over time. Methods: We employed a prospective longitudinal panel design using an online data collection platform. Study participation was open to all CAF veterans and spouses of CAF veterans residing in Canada. Participants were asked to complete a comprehensive battery of assessments representing psychological well-being, chronic pain, health care access patterns, physical environment, employment, social integration, and adjustment to pandemic-related lifestyle changes. Follow-up assessments were conducted every 3 months over an 18-month period. This study was approved by the Western University Health Sciences and Lawson Health Research Institute Research Ethics Boards. Results: Baseline data were collected between July 2020 and February 2021. There were 3 population segments that participated in the study: 1047 veterans, 366 spouses of veterans, and 125 veterans who are also spouses of veterans completed baseline data collection. As of November 2021, data collection is ongoing, with participants completing the 9-or 12-month follow-up surveys depending on their date of self-enrollment. Data collection across all time points will be complete in September 2022. Conclusions: This longitudinal survey is unique in its comprehensive assessment of domains relevant to veterans and spouses of veterans during the COVID-19 pandemic, ranging from occupational, demographic, social, mental, and physical domains, to perceptions and experiences with health care treatments and access. The results of this study will be used to inform policy for veteran and veteran family support, and to best prepare for similar emergencies should they occur in the future

1958: Abilene Christian College Bible Lectures - Full Text

“GOD” Being the Abilene Christian College Annual Bible Lectures 1958 Price: $3.00 Published by FIRM FOUNDATION PUBLISHING HOUSE Box 77 Austin, Texa

The medical student

The Medical Student was published from 1888-1921 by the students of Boston University School of Medicine