625 research outputs found
PHOEBE 2.0 – Where no model has gone before
phoebe 2.0 is an open source framework bridging the gap between stellar observations and models. It allows to create and fit models simultaneously and consistently to a wide range of observational data such as photometry, spectroscopy, spectrapolarimetry, interferometry and astrometry. To reach the level of precision required by the newest generation of instruments such as Kepler, GAIA and the arrays of large telescopes, the code is set up to handle a wide range of phenomena such as multiplicity, rotation, pulsations and magnetic fields, and to model the involved physics to a new level
Photometric Analysis of Recently Discovered Eclipsing Binary GSC 00008-00901
Photometric analysis of light curves of newly discovered eclipsing
binary GSC 0008-00901 is presented. The orbital period is improved to
0.28948(11) days. Photometric parameters are determined, as well. The analysis
yielded to conclusion that system is an over-contact binary of W UMa type with
components not in thermal contact. The light curves from 2005 show the presence
of a spot on the surface of one of the components, while light curves from 2006
are not affected by maculation.Comment: Accepted for publication in Astrophysics & Space Scienc
Physics of Eclipsing Binaries: Heartbeat Stars and Tidally Induced Pulsations
Heartbeat stars are a relatively new class of eccentric ellipsoidal variable first discovered by Kepler. An overview of the current field is given with details of some of the interesting objects identified in our current Kepler sample of 135 heartbeats stars. Three objects that have recently been or are undergoing detailed study are described along with suggestions for further avenues of research. We conclude by discussing why heartbeat stars are an interesting new tool to study tidally induced pulsations and orbital dynamics
The economic case for investing in the prevention of mental health conditions in the UK
This report provides an overview of the economic case for the prevention of mental health conditions. To do this, we first estimated the societal costs of living with mental health conditions in the UK in 2019 and then reviewed what is known about the cost-effectiveness of wellevidenced actions to prevent these mental health conditions. To estimate costs, we used a prevalencebased costing approach. This measures the number of people living with mental health conditions over a specific short time period (usually one year) and estimates the average costs associated with these conditions over this time period. Our prevalencebased costing model makes use of data on prevalence from the 2019 Institute of Health Metrics and Evaluation Global Burden of Disease (GBD) study. The GBD study quantifies the impact of all health conditions, both infectious and non-communicable, including mental health conditions, as well as the impacts on injury, including intentional self-harm. As part of the study, the GBD systematically searches for and assesses mental health surveys around the globe. To allow for comparability in measurement, case definitions used by GBD predominantly adhered to international diagnostic criteria guidance, either the DSM-IV-TR, mainly used in the United States or the ICD-10 criteria used mainly elsewhere, as these are used by the majority of mental health surveys included in the GBD. The GBD study estimates are periodically updated, apply a common methodology, are subject to peer review, and are routinely used by the World Health Organization (WHO) when looking at the global impact of mental health conditions. Furthermore, GBD estimates are provided separately for all four nations of the UK, as well as at English Region level. These estimates are conservative, as the GBD does not include the impact of sub-diagnostic threshold mental health conditions, as well as risk factors such as undue stress which do not fit into diagnostic criteria, all of which will also have economic costs. We included 11 of 12 broad categories of mental disorder meeting diagnosable thresholds used in the GBD1. These were depressive disorders (major depressive disorder and dysthymia), anxiety disorders, bipolar affective disorder, schizophrenia, autism spectrum disorders, conduct disorder, attention-deficit hyperactivity disorder (ADHD), eating disorders (anorexia nervosa and bulimia nervosa), and a final category of other mental disorders (which mainly covers personality disorders). A detailed list of conditions is listed in Table A-2 in the appendix. We excluded the idiopathic intellectual disabilities category in the GBD. Neurological conditions such as dementia, as well as alcohol and substance use disorders, are not included. Although not all intentional self-harm is linked with a mental health condition, we also separately provide an estimate of the health and intangible costs associated with intentional self-harm, including suicide, reported in the GBD. All costs are calculated and reported in 2020 pounds sterling
A photometric and spectroscopic study of NSVS 14256825: the second sdOB+dM eclipsing binary
We present an analysis of UBVRIJH photometry and
phase-resolved optical spectroscopy of NSVS 14256825, an HW Vir type binary.
The members of this class consist of a hot subdwarf and a main-sequence
low-mass star in a close orbit ( d). Using the
primary-eclipse timings, we refine the ephemeris for the system, which has an
orbital period of 0.11037 d. From the spectroscopic data analysis, we derive
the effective temperature, K, the surface gravity, , and the helium abundance, , for the hot component. Simultaneously modelling the
photometric and spectroscopic data using the Wilson-Devinney code, we obtain
the geometrical and physical parameters of NSVS 14256825. Using the fitted
orbital inclination and mass ratio (i = 82\fdg5\pm0\fdg3 and , respectively), the components of the system have , , , and . From its spectral
characteristics, the hot star is classified as an sdOB star.Comment: 8 pages, 7 figures, accepted for publication in MNRA
TYC 2675-663-1: A newly discovered W UMa system in an active state
The recently discovered eclipsing binary system TYC 2675-663-1 is a X-ray
source, and shows properties in the optical that are similar to the W UMa
systems, but are somewhat unusual compared to what is seen in other contact
binary systems. The goal of this work is to characterize its properties and
investigate its nature by means of detailed photometric and spectroscopic
observations. We have performed extensive V-band photometric measurements with
the INTEGRAL satellite along with ground-based multi-band photometric
observations, as well as high-resolution spectroscopic monitoring from which we
have measured the radial velocities of the components. These data have been
analysed to determine the stellar properties, including the absolute masses and
radii. Additional low-resolution spectroscopy was obtained to investigate
spectral features. From the measured eclipse timings we determine an orbital
period for the binary of P=0.4223576+-0.0000009 days. The light-curve and
spectroscopic analyses reveal the observations to be well represented by a
model of an overcontact system composed of main-sequence F5 and G7 stars
(temperature difference of nearly 1000 K), with the possible presence of a
third star. Low-resolution optical spectroscopy reveals a complex H alpha
emission, and other features that are not yet understood. The unusually large
mass ratio of q=0.81+-0.05 places it in the rare "H" (high mass ratio) subclass
of the W UMa systems, which are presumably on their way to coalescence.Comment: 12 pages in double column format. Accepted for publication in
Astronomy and Astrophysic
Rotational velocities of A-type stars. III. Velocity distributions
Aim - In this work, a sample of vsini of B9 to F2-type main sequence single
stars has been built from highly homogeneous vsini parameters determined for a
large sample cleansed from objects presenting the Am and Ap phenomenon as well
as from all known binaries. The aim is to study the distributions of rotational
velocities in the mass range of A-type stars for normal single objects.
Methods - Robust statistical methods are used to rectify the vsini
distributions from the projection effect and the error distribution. The
equatorial velocity distributions are obtained for an amount of about 1100
stars divided in six groups defined by the spectral type, under the assumption
of randomly orientated rotational axes.
Results - We show that late B and early A-type main-sequence stars have
genuine bimodal distributions of true equatorial rotational velocities due
probably to phenomena of angular momentum loss and redistribution the star
underwent before reaching the main sequence. A striking lack of slow rotators
is noticed among intermediate and late A-type stars. The bimodal-like shape of
their true equatorial rotational velocity distributions could be due to
evolutionary effects.Comment: 16 pages, 10 figures, accepted in A&
NSVS06507557; a low-mass double-lined eclipsing binary
In this paper we present the results of a detailed spectroscopic and
photometric analysis of the V=13.4 low-mass eclipsing binary NSVS 06507557
with an orbital period of 0.515 d. We obtained a series of mid-resolution
spectra covering nearly entire orbit of the system. In addition we obtained
simultaneous VRI broadband photometry using a small aperture telescope. From
these spectroscopic and photometric data we have derived the system's orbital
parameters and determined the fundamental stellar parameters of the two
components. Our results indicate that NSVS 06507557 consists of a K9 and an M3
pre-main-sequence stars with masses of 0.660.09 \Msun and 0.280.05
\Msun and radii of 0.600.03 and 0.440.02 \Rsun, located at a distance
of 1119 pc. The radius of the less massive secondary component is larger
than that of the zero-age main-sequnce star having the same mass. While the
radius of the primary component is in agreement with ZAMS the secondary
component appers to be larger by about 35 % with respect to its ZAMS
counterpart. Night-to-night intrinsic light variations up to 0.2 have been
observed. In addition, the H, H lines and the forbidden
line of [O{\sc i}] are seen in emission. The Li{\sc i} 6708 \AA absorption line
is seen in most of the spectra. These features are taken to be the signs of the
classic T Tauri stars' characteristics. The parameters we derived are
consistent with an age of about 20 Myr according to the stellar evolutionary
models. The spectroscopic and photometric results are in agreement with those
obtained by theoretical predictions.Comment: 21 pages, 9 figures. Accepted by MNRA
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