100 research outputs found
Multi-epoch Doppler tomography and polarimetry of QQ Vul
We present multi-epoch high-resolution spectroscopy and photoelectric polarimetry of the long-period polar (AM Herculis star) QQ Vul. The blue emission lines show several distinct components, the sharpest of which can unequivocally be assigned to the illuminated hemisphere of the secondary star and used to trace its orbital motion. This narrow emission line can be used in combination with Nai-absorption lines from the photosphere of the companion to build a stable long-term ephemeris for the star: inferior conjunction of the companion occurs at HJD = 244 8446.4710(5)+E×0. d 15452011(11). The polarization curves are dissimilar at different epochs, thus supporting the idea of fundamental changes of the accretion geometry, e.g. between one- and two-pole accretion modes. The linear polarization pulses display a random scatter by 0.2 phase units and are not suitable for the determination of the binary period. The polarization data suggest that the magnetic (dipolar) axis has a co-latitude of 23 ◦ , an azimuth of −50 ◦, and an orbital inclination between 50 ◦ and 70 ◦. Doppler images of blue emission and red absorption lines show a clear separatio
X-Ray Emission and Optical Polarization of V1432 Aquilae: An Asynchronous Polar
A detailed analysis of X-ray data from ROSAT, ASCA, XMM and RXTE for the
asynchronous polar V1432 Aql along with Stokes polarimetry data from SAAO, is
presented. Power spectra from long-baseline ROSAT data show a spin period of
12150s along with several system related frequency components. However, the
second harmonic of the spin period dominates power spectrum in the XMM data.
For the optical circular polarization, the dominant period corresponds to half
the spin period. The ROSAT data can be explained as due to accretion onto two
hot spots that are not anti-podal. The variations seen in the optical
polarization and the ASCA and XMM data suggest the presence of at least three
accretion foot prints on the white dwarf surface. Two spectral models, a
multi-temperature plasma and a photo-ionized plasma model, are used for
spectral study. The RXTE PCA data are used to constrain the white dwarf mass to
1.20.1 M_odot using the multi-temperature plasma model. A strong soft
X-ray excess (<0.8 keV) in the XMM MOS data is well modeled by a blackbody
component having a temperature of 80-90 eV. The plasma emission lines seen at
6.7 and 7.0 keV are well fitted using the multi-temperature plasma model,
however an additional Gaussian is needed for the 6.4 keV line. The
multi-temperature plasma model requires a homogeneous absorber fully covering
the source and a partial absorber covering 65% of the source. The photo-ionized
plasma model, with a range of Fe column densities, gives a slightly better
overall fit and fits all emission lines. The presence of a strong blackbody
component, a spin period of 12150s, modulation of the 6.4 keV line flux with
spin period, and a very hard X-ray component suggest that V1432 Aql is a polar
with X-ray spectral properties similar to that of a soft intermediate polar.Comment: 46 pages, including 13 figures and 4 tables, To appear in The
Astrophysical Journal, 20 May 2005 issue, vol. 625, Added Report-no and
Journal-ref, no change in the text of the pape
The Three Dimensional Structure of EUV Accretion Regions in AM Herculis Stars: Modeling of EUV Photometric and Spectroscopic Observations
We have developed a model of the high-energy accretion region for magnetic
cataclysmic variables and applied it to {\it Extreme Ultraviolet Explorer}
observations of 10 AM Herculis type systems. The major features of the EUV
light curves are well described by the model. The light curves exhibit a large
variety of features such as eclipses of the accretion region by the secondary
star and the accretion stream, and dips caused by material very close to the
accretion region. While all the observed features of the light curves are
highly dependent on viewing geometry, none of the light curves are consistent
with a flat, circular accretion spot whose lightcurve would vary solely from
projection effects. The accretion region immediately above the WD surface is a
source of EUV radiation caused by either a vertical extent to the accretion
spot, or Compton scattering off electrons in the accretion column, or, very
likely, both. Our model yields spot sizes averaging 0.06 R, or the WD surface area, and average spot heights of 0.023
R. Spectra extracted during broad dip phases are softer than spectra
during the out-of-dip phases. This spectral ratio measurement leads to the
conclusion that Compton scattering, some absorption by a warm absorber,
geometric effects, an asymmetric temperature structure in the accretion region
and an asymmetric density structure of the accretion columnare all important
components needed to fully explain the data. Spectra extracted at phases where
the accretion spot is hidden behind the limb of the WD, but with the accretion
column immediately above the spot still visible, show no evidence of emission
features characteristic of a hot plasma.Comment: 30 Pages, 11 Figure
A Photometric and Spectroscopic Study of the Cataclysmic Variable ST LMi during 2005-2006
We present orbit-resolved spectroscopic and photometric observations of the
polar ST LMi during its recent low and high states. In the low state spectra,
we report the presence of blue and red satellites to the H-alpha emission line;
the velocities and visibility of the satellites vary with phase. This behavior
is similar to emission line profile variations recently reported in the low
state of AM Her, which were interpreted as being due to magnetically-confined
gas motions in large loops near the secondary. Our low-state spectroscopy of ST
LMi is discussed in terms of extreme chromospheric activity on the secondary
star. Concurrent photometry indicates that occasional low-level accretion may
be present, as well as cool regions on the secondary near L1. Furthermore, we
report a new ``extreme low-state'' of the system at V~18.5mag. Our orbital
high-state spectroscopy reveals changes in the emission line profiles with
orbital phases that are similar to those reported by earlier high-state
studies. The complicated emission line profiles generally consist of two main
components. The first has radial velocity variations identical to that of the
major emission H-alpha component seen in the low state. The second is an
additional red-shifted component appearing at the phases of maximum visibility
of the accreting column of the white dwarf; it is interpreted as being due to
infall velocities on the accreting magnetic pole of the white dwarf. At the
opposite phases, an extended blue emission wing appears on the emission line
profiles. We confirm the presence of a broad absorption feature near 6275Ang
which has been previously identified as Zeeman sigma(-) absorption component to
H-alpha. This feature appears at just those phases when the accretion pole
region is mostly directly visible and most nearly face-on to the observer.Comment: 16 pages, 1 table, 17 figures. To appear in the Astronomical Journa
New Low Accretion-Rate Magnetic Binary Systems and their Significance for the Evolution of Cataclysmic Variables
Discoveries of two new white dwarf plus M star binaries with striking optical
cyclotron emission features from the Sloan Digital Sky Survey (SDSS) brings to
six the total number of X-ray faint, magnetic accretion binaries that accrete
at rates < 10^{-13} Msun/yr, or <1% of the values normally encountered in
cataclysmic variables. This fact, coupled with donor stars that underfill their
Roche lobes and very cool white dwarfs, brand the binaries as post
common-envelope systems whose orbits have not yet decayed to the point of
Roche-lobe contact. They are pre-magnetic CVs, or pre-Polars. The systems
exhibit spin/orbit synchronism and apparently accrete by efficient capture of
the stellar wind from the secondary star, a process that has been dubbed a
``magnetic siphon''. Because of this, period evolution of the binaries will
occur solely by gravitational radiation, which is very slow for periods >3 hr.
Optical surveys for the cyclotron harmonics appear to be the only means of
discovery, so the space density of pre-Polars could rival that of Polars, and
the binaries provide an important channel of progenitors (in addition to the
asynchronous Intermediate Polars). Both physical and SDSS observational
selection effects are identified that may help to explain the clumping of all
six systems in a narrow range of magnetic field strength around 60 MG.Comment: 25 pages, 13 figures, Accepted to Ap
Two Rare Magnetic Cataclysmic Variables with Extreme Cyclotron Features Identified in the Sloan Digital Sky Survey
Two newly identified magnetic cataclysmic variables discovered in the Sloan
Digital Sky Survey (SDSS), SDSSJ155331.12+551614.5 and SDSSJ132411.57+032050.5,
have spectra showing highly prominent, narrow, strongly polarized cyclotron
humps with amplitudes that vary on orbital periods of 4.39 and 2.6 hrs,
respectively. In the former, the spacing of the humps indicates the 3rd and 4th
harmonics in a magnetic field of ~60 MG. The narrowness of the cyclotron
features and the lack of strong emission lines imply very low temperature
plasmas and very low accretion rates, so that the accreting area is heated by
particle collisions rather than accretion shocks. The detection of rare systems
like these exemplifies the ability of the SDSS to find the lowest accretion
rate close binaries.Comment: Accepted for publication in the Astrophysical Journal, vol. 583,
February 1, 2003; slight revisions and additions in response to referee's
comments; 17 pages, 6 figures, AASTeX v4.
Phase-Resolved Infrared H- and K-band Spectroscopy of EF Eridani
We present new phase-resolved H and K-band spectroscopy of the ultra-short
period magnetic cataclysmic variable EF Eri in its current, prolonged ``low''
state obtained using NIRI on Gemini-North, and NIRSPEC on Keck II. These new
data show that the H-band spectrum of EF Eri appears to be dominated by
cyclotron emission during the entire orbital cycle. The {\it K}-band spectrum
of EF Eri is likewise dominated by cyclotron emission during most of an orbital
period, but near binary phase 0.0, the secondary star spectrum may be visible.
We conclude that strong, and highly variable cyclotron emission is responsible
for the photometric variation previously reported for EF Eri. The nature of
this cyclotron emission is complex: the H-band spectra show that the dominant
cyclotron harmonic at phase 0.5 peaks at 1.65 m, but at phase 0.0, the
harmonic peaks near 1.72 m. At phase 0.5, there is another cyclotron
feature present that peaks in between the H and K bands (near 1.93 m), but
at phase 0.0, no such feature is present. These data suggest that cyclotron
emission from both poles is occurring.Comment: 23 pages of text, 8 figure
A Turke turn'd Quaker: conversion from Islam to radical dissent in early modern England
The study of the relationship between the anglophone and Islamic
worlds in the seventeenth century has been the subject of increas-
ing interest in recent years, and much attention has been given to
the cultural anxiety surrounding “Turning Turke”, conversion from
Christianity to Islam, especially by English captives on the Barbary
coast. Conversion in the other direction has attracted far less
scrutiny, not least because it appears to have been far less com-
mon. Conversion from Islam to any form of radical dissent has
attracted no scholarship whatsoever, probably because it has been
assumed to be non-existent. However, the case of Bartholomew
Cole provides evidence that such conversions did take place, and
examining the life of this “Turke turn’d Quaker” provides an insight
into the dynamics of cross-cultural conversion of an exceptional
kind
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Recent Developments Affecting Golf Course Design (page 1) From the Editor (3) Five Year Results (3) Turf Management Club News (4) Quotes from 1960 Seniors (5) Poa annua - - Friend or Foe (6) The Horticulture Show (7) Cartoons (8) Message from the Winter School President of 1960 (10) The Most Outstanding Turf Senior for 1959 (10) The Value of the Proper Use of Lime (11) Summer Placement (12) A Greenhouse on the Golf Course (13) More Opportunities in the Future for the Aggressive Superintendent at Country Clubs (14) Soil, Sawdust and Turfgrass (15) Picture - Senior Stockbridge Turf majors (16) Picture - Freshman Stockbridge Turf majors (17) Susceptibility of Merion Bluegrass to Stripe Smut (18) Bents in the South (19) Picture - Honorary Members of Turf Management Club (20) Picture - Graduates of Winter School for Turf mangers- 1960 (21) Weather - We are Going to Have Weather, Whether or Not - What Should we Expect by O. Tennebaum & R. E. Lautzenheiser (A-1) The Nature of Winter Injury to Plants by Dr. Johnson Parker (A-1) Turf Problems: You Name it and We\u27ve Had It in \u2759 by Alexander Radko ad T.T. Taylor (A-3) Topdressing Experiences with Greens at Century by James Fulwider (A-5) Poa annua - Fairway Rennovation at winged Foot by Sherwood A. Moore (A-6) Winter Problems at Ekwanaok by Paul O\u27Leary (A-8) Progress Through Drainage by Kayem Ovian (A-10) Winter Injury on Home Lawns by Orlando Capizzi (A-12) The Status of Pre-emergence Chemicals for the Control of Crabgrass by Dr. E. Engel (A-12) Turf Nurseries - Establishment, Maintenance & Utilization by Robert Grant (A-14) Soil Compaction by Dr. R. B. Alderfer (A-16) Water Management Practices on Turf Areas by Dr. J.R. Watson (A-18) Getting to Know Your Members by Owen Griffith (A-23) New Trends in Clubhouse Landscaping by Alfred Boicourt (A-26) General Lawn Management (Alternate Session) Conserving Soil for a good Lawn by Dr. William G. Colby (A-27) Fertilizting and Liming by Dr. Joseph Steckel (A-28) Grasses and Grass Mixtures for New England Lawns by Dr. Robert Schery (A-29) The Care and Maintenance of Establishment Lawns by Dr. John R. Davi
Novel systemic therapies in atopic dermatitis : what do we need to fulfil the promise of a treatment revolution?
Patients with atopic dermatitis (AD) who do not adequately respond to topical therapy and phototherapy often need systemic immunomodulatory treatment to control their symptoms. Conventional systemic agents, such as ciclosporin, azathioprine, and methotrexate, have been used for decades, but there are concerns about their safety profile. There are now many novel systemic agents emerging through clinical trials, which may have great potential in the treatment of AD. Despite this, there are very few data comparing the performance of these drugs against each other. The purpose of this article is to review the current systemic therapies in AD and present an indirect comparison of systemic AD treatments using effectiveness and safety data from published randomised controlled trials, highlighting important remaining gaps in knowledge. Although the latest developments in systemic AD treatments are exciting and dearly needed, further work is required before the promise of a therapeutic revolution becomes reality
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