182 research outputs found
H-alpha Emission Variability in the gamma-ray Binary LS I +61 303
LS I +61 303 is an exceptionally rare example of a high mass X-ray binary
(HMXB) that also exhibits MeV-TeV emission, making it one of only a handful of
"gamma-ray binaries". Here we present H-alpha spectra that show strong
variability during the 26.5 day orbital period and over decadal time scales. We
detect evidence of a spiral density wave in the Be circumstellar disk over part
of the orbit. The H-alpha line profile also exhibits a dramatic emission burst
shortly before apastron, observed as a redshifted shoulder in the line profile,
as the compact source moves almost directly away from the observer. We
investigate several possible origins for this red shoulder, including an
accretion disk, mass transfer stream, and a compact pulsar wind nebula that
forms via a shock between the Be star's wind and the relativistic pulsar wind.Comment: Accepted to Ap
A Binary Orbit for the Massive, Evolved Star HDE 326823, a WR+O System Progenitor
The hot star HDE 326823 is a candidate transition-phase object that is
evolving into a nitrogen-enriched Wolf-Rayet star. It is also a known
low-amplitude, photometric variable with a 6.123 d period. We present new, high
and moderate resolution spectroscopy of HDE 326823, and we show that the
absorption lines show coherent Doppler shifts with this period while the
emission lines display little or no velocity variation. We interpret the
absorption line shifts as the orbital motion of the apparently brighter star in
a close, interacting binary. We argue that this star is losing mass to a mass
gainer star hidden in a thick accretion torus and to a circumbinary disk that
is the source of the emission lines. HDE 326823 probably belongs to a class of
objects that produce short-period WR+O binaries.Comment: 32 pages, 10 figures, accepted to the Astronomical Journa
The ejection of runaway massive binaries
The runaway O-type stars HD 14633 and HD 15137 are both SB1 systems that were probably ejected from the open cluster NGC 654. Were these stars dynamically ejected by close gravitational encounters in the dense cluster, or did the binaries each receive a kick from a supernova in one member? We present new results from our investigation of the optical, X-ray, and radio properties of these binary systems to discuss the probable ejection scenarios. We argue that these binaries may have been ejected via dynamical interactions in the dense cluster environment. © 2007 International Astronomical Union
The Orbits of the Gamma-ray Binaries LS I +61 303 and LS 5039
LS I +61 303 and LS 5039 are two of only a handful of known high mass X-ray
binaries (HMXBs) that exhibit very high energy emission in the MeV-TeV range,
and these "gamma-ray binaries" are of renewed interest due to the recent launch
of the Fermi Gamma-ray Space Telescope. Here we present new radial velocities
of both systems based on recent red and blue optical spectra. Both systems have
somewhat discrepant orbital solutions available in the literature, and our new
measurements result in improved orbital elements and resolve the disagreements.
The improved geometry of each orbit will aid in studies of the high energy
emission region near each source.Comment: Accepted to ApJ, 13 pages, preprint2 styl
The Full Spectrum Galactic Terrarium: MHz to TeV Observations of Various Critters
Multi-wavelength studies at radio, infrared, optical, X-ray, and TeV
wavelengths have discovered probable counterparts to many Galactic sources of
GeV emission detected by EGRET. These include pulsar wind nebulae, high mass
X-ray binaries, and mixed morphology supernova remnants. Here we provide an
overview of the observational properties of Galactic sources which emit across
19 orders of magnitude in energy. We also present new observations of several
sources.Comment: 4 pages, 5 figures, Proceedings of the The 4th Heidelberg
International Symposium on High Energy Gamma-Ray Astronomy, eds. Aharonian,
Hofmann, Riege
Radial Velocities of Six OB Stars
We present new results from a radial velocity study of six bright OB stars
with little or no prior measurements. One of these, HD 45314, may be a
long-period binary, but the velocity variations of this Be star may be related
to changes in its circumstellar disk. Significant velocity variations were also
found for HD 60848 (possibly related to nonradial pulsations) and HD 61827
(related to wind variations). The other three targets, HD 46150, HD 54879, and
HD 206183, are constant velocity objects, but we note that HD 54879 has
H emission that may originate from a binary companion. We illustrate
the average red spectrum of each target.Comment: Accepted for publication in PASP July 2007 issu
Runaway Massive Binaries and Cluster Ejection Scenarios
The production of runaway massive binaries offers key insights into the
evolution of close binary stars and open clusters. The stars HD 14633 and HD
15137 are rare examples of such runaway systems, and in this work we
investigate the mechanism by which they were ejected from their parent open
cluster, NGC 654. We discuss observational characteristics that can be used to
distinguish supernova ejected systems from those ejected by dynamical
interactions, and we present the results of a new radio pulsar search of these
systems as well as estimates of their predicted X-ray flux assuming that each
binary contains a compact object. Since neither pulsars nor X-ray emission are
observed in these systems, we cannot conclude that these binaries contain
compact companions. We also consider whether they may have been ejected by
dynamical interactions in the dense environment where they formed, and our
simulations of four-body interactions suggest that a dynamical origin is
possible but unlikely. We recommend further X-ray observations that will
conclusively identify whether HD 14633 or HD 15137 contain neutron stars.Comment: Accepted to ApJ, 11 page
The Long Period, Massive Binaries HD 37366 and HD 54662: Potential Targets for Long Baseline Optical Interferometry
We present the results from an optical spectroscopic analysis of the massive
stars HD 37366 and HD 54662. We find that HD 37366 is a double-lined
spectroscopic binary with a period of 31.8187 +/- 0.0004 days, and HD 54662 is
also a double lined binary with a much longer period of 557.8 +/- 0.3 days. The
primary of HD 37366 is classified as O9.5 V, and it contributes approximately
two-thirds of the optical flux. The less luminous secondary is a broad-lined,
early B-type main-sequence star. Tomographic reconstruction of the individual
spectra of HD 37366 reveals absorption lines present in each component,
enabling us to constrain the nature of the secondary and physical
characteristics of both stars. Tomographic reconstruction was not possible for
HD 54662; however, we do present mean spectra from our observations that show
that the secondary component is approximately half as bright as the primary.
The observed spectral energy distributions (SEDs) were fit with model SEDs and
galactic reddening curves to determine the angular sizes of the stars. By
assuming radii appropriate for their classifications, we determine distance
ranges of 1.4 - 1.9 and 1.2 - 1.5 kpc for HD 37366 and HD 54662, respectively.Comment: 27 pages, 8 figures, Accepted for publication in Ap
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Assessment of Maternal Posttraumatic Stress Disorder Following Childbirth: Psychometric Properties of the Swedish Version of City Birth Trauma Scale
Objective: City Birth Trauma Scale is an instrument designed to evaluate and diagnose postpartum posttraumatic stress disorder (PTSD) according to the 5th edition of Diagnostic and Statistical Manual of Mental Disorders (DSM-5). No validated Swedish instrument exists to measure postpartum PTSD according to DSM-5. Therefore, the objective of this study was to assess the psychometric properties of the Swedish version of the City BiTS (City BiTS-Swe) and to examine the latent factor structure of postpartum PTSD.
Method: A total of 619 women, who had given birth at five clinics in the past six to 16 weeks, completed an online version of City BiTS-Swe and the Edinburgh Postnatal Depression Scale (EPDS). Additionally, sociodemographic and medical data was collected. A second questionnaire was answered by 110 women to examine reliability over time.
Results: The confirmatory factor analysis using the two-factor model gave best fit to the data. We found a high internal consistency (α = 0.89-0.87) and good test-retest reliability (ICC = 0.53 - 0.90). Divergent reliability with EPDS showed significant correlations with satisfying results for the subscale birth-related symptoms (r=0.41). We also found discriminant validity concerning mode of birth, parity, gestational age, mental illness, history of traumatic childbirth and history of traumatic event as expected.
Conclusions: The City BiTS-Swe is a valid and reliable instrument to assess and diagnose PTSD following childbirth.
Clinical impact statement: PTSD following childbirth can cause considerable suffering for the affected woman, her partner and the child. Having a valid and reliable instrument to assess and diagnose childbirth-related PTSD is of great importance for the detection and treatment of the disease. The results of this study confirms that the Swedish version of City BiTS is a reliable and valid instrument that can be recommended for use in daily clinical practice and for research purposes
A Spectroscopic Study of Field and Runaway OB Stars
Identifying binaries among runaway O- and B-type stars offers valuable
insight into the evolution of open clusters and close binary stars. Here we
present a spectroscopic investigation of 12 known or suspected binaries among
field and runaway OB stars. We find new orbital solutions for five single-lined
spectroscopic binaries (HD 1976, HD 14633, HD 15137, HD 37737, and HD 52533),
and we classify two stars thought to be binaries (HD 30614 and HD 188001) as
single stars. In addition, we reinvestigate their runaway status using our new
radial velocity data with the UCAC2 proper motion catalogs. Seven stars in our
study appear to have been ejected from their birthplaces, and at least three of
these runaways are spectroscopic binaries and are of great interest for future
study.Comment: 21 pages, 1 figure, 7 tables; Accepted to Ap
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