63 research outputs found
Four New Delta Scuti Pulsators from a Variability Survey of 131 Stars
In a photometric variability survey of 131 stars with B < 14 mag, we have
found four new Delta Scuti stars. We were sensitive to oscillation amplitudes
as low as a few mmag. The detection rate of short-period (P < 0.1 d) pulsating
variable stars, which may be relevant for planned large variability surveys
such as GAIA, POI, and even the LSST, was therefore 3%. All four new variable
stars have low pulsation amplitude (tens of mmag), and one has a very short
period (0.0198 d). This star is one of the fastest known Delta Scuti pulsators.
The short period of this variable star makes it observationally tractable, and
it may therefore be a particularly good candidate for asteroseismological
studies. All four new variable stars will add to the cadre of low-amplitude and
relatively short-period Delta Scuti stars that are potentially useful for
learning about the structure of stars on or near the main sequence, slightly
more massive than the Sun.Comment: To appear in the June 2002 issue of PASP, 9 pages, 6 figure
A Case of Primary Amyloidosis Involving Liver, Stomach, Intestines, and Heart without Evident Kidney Involvement
Aim. Systemic amyloidosis caused by the synthesis and deposition of immunoglobulin light chains (AL amyloidosis) is a relatively rare disease that involves heart, kidneys, peripheral nervous system, gastrointestinal tract, and has a large number of various clinical manifestations. We present a clinical case of systemic AL amyloidosis with a predominant involvement of liver, stomach, intestines, and heart in a Caucasian female.Key points. A Caucasian woman presented to clinic with severe general weakness, abdominal pain, diarrhea, sudden weight loss, and palpitation. Initial examination revealed a duodenal bulb ulcer complicated by bleeding and polyps in the retrobulbar part of duodenum. Decreased hemoglobin levels, elevated levels of alkaline phosphatase, gamma-glutamyltransferase, and N-terminal prohormone of brain natriuretic peptide, signs of heart failure with preserved ejection fraction, and hepatomegaly became the basis for a clinical suspicion of AL amyloidosis and puncture liver biopsy. Histochemical and immunohistochemical studies of liver, stomach, and duodenum biopsy specimens confirmed AL amyloidosis. Timely diagnosis made it possible to conduct a specific therapy with melphalan plus dexamethasone, get a satisfactory response and improve the patient’s condition.Conclusion. A thorough examination of patients along with a pathomorphological and immunohistochemical study of the biopsy specimens is the basis for confirming the diagnosis of AL amyloidosis, selecting the proper therapy, improving the condition of patients and their survival
Infrared Spectroscopy of Symbiotic Stars. IV. V2116 Ophiuchi/GX 1+4, The Neutron Star Symbiotic
We have computed, based on 17 infrared radial velocities, the first set of
orbital elements for the M giant in the symbiotic binary V2116 Ophiuchi. The
giant's companion is a neutron star, the bright X-ray source GX 1+4. We find an
orbital period of 1161 days by far the longest of any known X-ray binary. The
orbit has a modest eccentricity of 0.10 with an orbital circularization time of
less than 10^6 years. The large mass function of the orbit significantly
restricts the mass of the M giant. Adopting a neutron-star mass of 1.35M(Sun),
the maximum mass of the M giant is 1.22M(Sun), making it the less massive star.
Derived abundances indicate a slightly subsolar metallicity. Carbon and
nitrogen are in the expected ratio resulting from the red-giant first dredge-up
phase. The lack of O-17 suggests that the M-giant has a mass less than
1.3M(Sun), consistent with our maximum mass. The red giant radius is 103R(Sun),
much smaller than the estimated Roche lobe radius. Thus, the mass loss of the
red giant is via a stellar wind. Although the M giant companion to the neutron
star has a mass similar to the late-type star in low-mass X-ray binaries, its
near-solar abundances and apparent runaway velocity are not fully consistent
with the properties of this class of stars.Comment: In press to The Astrophysical Journal (10 April 2006 issue). 23 page
In Search of Possible Associations between Planetary Nebulae and Open Clusters
We consider the possibility of cluster membership for 13 planetary nebulae
that are located in close proximity to open clusters lying in their lines of
sight. The short lifetimes and low sample size of intermediate-mass planetary
nebulae with respect to nearby open clusters conspire to reduce the probability
of observing a true association. Not surprisingly, line of sight coincidences
almost certainly exist for 7 of the 13 cases considered. Additional studies are
advocated, however, for 6 planetary nebula/open cluster coincidences in which a
physical association is not excluded by the available evidence, namely M
1-80/Berkeley 57, NGC 2438/NGC 2437, NGC 2452/NGC 2453, VBRC 2 & NGC 2899/IC
2488, and HeFa 1/NGC 6067. A number of additional potential associations
between planetary nebulae and open clusters is tabulated for reference
purposes. It is noteworthy that the strongest cases involve planetary nebulae
lying in cluster coronae, a feature also found for short-period cluster
Cepheids, which are themselves potential progenitors of planetary nebulae.Comment: Accepted for publication in PASP (December 2007
Optical Multicolor Photometry of Spectrophotometric Standard Stars
Photoelectric data on the Johnson-Kron-Cousins UBVRI broadband photometric
system are provided for a set of stars which have been used as
spectrophotometric standard stars at the Hubble Space Telescope.Comment: 76 pages, 48 figures - published version available here:
http://www.journals.uchicago.edu/AJ/journal/issues/v133n3/205588/205588.html
. Also see ERRATUM at:
http://www.journals.uchicago.edu/AJ/journal/issues/v133n5/205838/205838.htm
Clinical and epidemiological characteristics of cancers associated with human papillomavirus in the regions of North-West Russia
Introduction. The leading role of the human papillomavirus in the etiopathogenesis of malignant neoplasms of some localizations is generally recognized. Vaccines that are used in the world and in Russia for the prevention of papillomavirus infection create the basis for the elimination of diseases associated with the human papillomavirus in the future.
The aim of the study is to determine the regional, gender and age-specific features of cancers associated with the human papillomavirus to substantiate the development of a unified system of epidemiological surveillance and vaccination.
Materials and methods. The retrospective epidemiological analysis of the incidence of cancers associated with the human papillomavirus and mortality due to these neoplasms in the regions of the North-Western Federal District of Russia in 20112020 was carried out based on data from Statistic Form 7 "Information on malignant neoplasms" and the Population cancer Registers of St. Petersburg (13,117 cases), Leningrad region (3204 cases) and the Kaliningrad region (2898 cases).
Results. In the structure of cancers associated with the human papillomavirus in St. Petersburg, Leningrad and Kaliningrad regions, more than 90% of men had tumors of the oral cavity, oropharynx and larynx, more than 60% of women had cervical cancer. Regional and age-specific features of the incidence of cervical cancer and mortality from this pathology have been established. Statistically significant differences in the incidence of cancer of the head and neck, anus and anal canal in different age groups of the male and female population were revealed.
Conclusion. As a result of the study, regional, gender and age-specific features of the incidence of human papillomavirus-associated malignant neoplasms in the North-West of Russia were established. These data should be used to develop a system of epidemiological surveillance of papillomavirus infection and vaccination program
Size-dependent properties of dithallium selenide
We report on size-dependent properties of dithallium selenide, Tl2Se. We have
carried out a comparative nuclear magnetic resonance (NMR) study of Tl2Se
nanorods and bulk samples, measuring NMR spectra and spin-lattice relaxation
rate of 203Tl and 205Tl isotopes. Though bulk Tl2Se was reported to be a metal,
the Korringa-like spin-lattice relaxation behavior is observed only at low
temperatures and is transformed to an activation regime above ~200 K. This
finding is interpreted assuming a two-band model in the semimetallic compound.
Our measurements show significant difference in the Knight shift and indirect
nuclear exchange coupling for the bulk and nanorod Tl2Se samples, reflecting
noticeable distinction in their electronic structure. At that, Tl2Se nanorods
are semiconductors and exhibit a characteristic activation behavior in the
spin-lattice relaxation rate due to the thermal excitation of carriers to the
conduction band. The obtained size dependence of the Tl2Se properties is
interpreted in terms of the semimetal-semiconductor transformation due to the
quantum confinement.Comment: 15 pages, 4 figure
4U 0115+63 from RXTE and INTEGRAL Data: Pulse Profile and Cyclotron Line Energy
We analyze the observations of the transient X-ray pulsar 4U 0115+63 with the
RXTE and INTEGRAL observatories in a wide X-ray (3-100 keV) energy band during
its intense outbursts in 1999 and 2004. The energy of the fundamental harmonic
of the cyclotron resonance absorption line near the maximum of the X-ray flux
from the source (luminosity range 5x10^{37} - 2x10^{38} erg/s) is ~11 keV. When
the pulsar luminosity falls below ~5x10^{37} erg/s, the energy of the
fundamental harmonic is displaced sharply toward the high energies, up to ~16
keV. Under the assumption of a dipole magnetic field configuration, this change
in cyclotron harmonic energy corresponds to a decrease in the height of the
emitting region by ~2 km, while other spectral parameters, in particular, the
cutoff energy, remain essentially constant. At a luminosity ~7x10^{37} erg/s,
four almost equidistant cyclotron line harmonics are clearly seen in the
spectrum. This suggests that either the region where the emission originates is
compact or the emergent spectrum from different (in height) segments of the
accretion column is uniform. We have found significant pulse profile variations
with energy, luminosity, and time. In particular, we show that the profile
variations from pulse to pulse are not reduced to a simple modulation of the
accretion rate specified by external conditions.Comment: 30 pages, 13 figures, Astronomy Letters, 33, 368 (2007
The Swift Ultra-Violet/Optical Telescope
The UV/Optical Telescope (UVOT) is one of three instruments flying aboard the
Swift Gamma-ray Observatory. It is designed to capture the early (approximately
1 minute) UV and optical photons from the afterglow of gamma-ray bursts in the
170-600 nm band as well as long term observations of these afterglows. This is
accomplished through the use of UV and optical broadband filters and grisms.
The UVOT has a modified Ritchey-Chretien design with micro-channel plate
intensified charged-coupled device detectors that record the arrival time of
individual photons and provide sub-arcsecond positioning of sources. We discuss
some of the science to be pursued by the UVOT and the overall design of the
instrument.Comment: 55 Pages, 28 Figures, To be published in Space Science Review
The first spectroscopically confirmed Mira star in M33
We present photometry and moderate-resolution spectroscopy of the luminous
red variable [HBS2006] 40671 originally detected as a possible nova in the
galaxy M33. We found that the star is a pulsating Mira-type variable with a
long period of 665 days and an amplitude exceeding 7 mag in the R band.
[HBS2006] 40671 is the first confirmed Mira-type star in M33. It is one of the
most luminous Mira-type variables. In the K band its mean absolute magnitude is
M_K = -9.5, its bolometric magnitude measured in the maximum light is also
extreme, M_bol = -7.4. The spectral type of the star in the maximum is M2e -
M3e. The heliocentric radial velocity of the star is -475 km/s. There is a big
negative excess (-210~km/s) in radial velocity of [HBS2006] 40671 relative to
the average radial velocity of stars in its neighborhood pointing at an
exceptional peculiar motion of the star. All the extreme properties of the new
Mira star make it important for further studies.Comment: 7 pages, 4 figures, accepted by MNRA
- …