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A. Nebot Gomez-Moran,
C. Motch,
X. Barcons,
F. J. Carrera,
M. T. Ceballos,
M. Cropper,
N. Grosso,
P. Guillout,
O. Herent,
S. Mateos,
L. Michel,
J. P. Osborne,
M. Pakull,
F. -X. Pineau,
J. P. Pye,
T. P. Roberts, S. R. Rosen,
A. D. Schwope,
M. G. Watson,
N. Webb
[show abstract]
[hide abstract]
ABSTRACT: Many different classes of X-ray sources contribute to the Galactic landscape
at high energies. Although the nature of the most luminous X-ray emitters is
now fairly well understood, the population of low-to-medium X-ray luminosity
(Lx = 10^27-10^34 erg/s) sources remains much less studied, our knowledge being
mostly based on the observation of local members. The advent of wide field and
high sensitivity X-ray telescopes such as XMM-Newton now offers the opportunity
to observe this low-to-medium Lx population at large distances. We report on
the results of a Galactic plane survey conducted by the XMM-Newton Survey
Science Centre (SSC). Beyond its astrophysical goals, this survey aims at
gathering a representative sample of identified X-ray sources at low latitude
that can be used later on to statistically identify the rest of the
serendipitous sources discovered in the Milky Way. The survey is based on 26
XMM-Newton observations, obtained at |b| < 20 deg, distributed over a large
range in Galactic longitudes and covering a summed area of 4 deg2. The flux
limit of our survey is 2 x 10-15 erg/cm^2/s in the soft (0.5 - 2 keV) band and
1 x 10^-14 erg/cm^2/s in the hard (2 - 12 keV) band. We detect a total of 1319
individual X-ray sources. Using optical follow-up observations supplemented by
cross-correlation with a large range of multi-wavelength archival catalogues we
identify 316 X-ray sources. This constitutes the largest group of
spectroscopically identified low latitude X-ray sources at this flux level. The
majority of the identified X-ray sources are active coronae with spectral types
in the range A - M at maximum distances of ~ 1 kpc. The number of identified
active stars increases towards late spectral types, reaching a maximum at K.
(abridged)
02/2013;
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P. Esquej,
M. Page,
F. J. Carrera,
S. Mateos,
J. Tedds,
M. G. Watson,
A. Corral,
J. Ebrero,
M. Krumpe, S. R. Rosen,
M. T. Ceballos,
A. Schwope,
C. Page,
A. Alonso-Herrero,
A. Caccianiga,
R. Della Ceca,
O. Gonzalez-Martín,
G. Lamer,
P. Severgnini
[show abstract]
[hide abstract]
ABSTRACT: This programme is aimed at obtaining one of the largest X-ray selected
samples of identified active galactic nuclei to date in order to characterise
such a population at intermediate fluxes, where most of the Universe's
accretion power originates. We present the XMM-Newton Wide Angle Survey (XWAS),
a new catalogue of almost a thousand X-ray sources spectroscopically identified
through optical observations. A sample of X-ray sources detected in 68
XMM-Newton pointed observations was selected for optical multi-fibre
spectroscopy. Optical counterparts and corresponding photometry of the X-ray
sources were obtained from the SuperCOSMOS Sky Survey. Candidates for
spectroscopy were initially selected with magnitudes down to R~21, with
preference for X-ray sources having a flux F(0.5-4.5 keV) >10^-14 erg s^-1
cm^-2. Optical spectroscopic observations performed at the Anglo Australian
Telescope Two Degree Field were analysed, and the derived spectra were
classified based on optical emission lines. We have identified through optical
spectroscopy 940 X-ray sources over ~11.8 deg^2 of the sky. Source populations
in our sample can be summarised as 65% broad line active galactic nuclei
(BLAGN), 16% narrow emission line galaxies (NELGs), 6% absorption line galaxies
(ALGs) and 13% stars. An active nucleus is likely to be present also in the
large majority of the X-ray sources spectroscopically classified as NELGs or
ALGs. Sources lie in high-galactic latitude (|b| > 20 deg) XMM-Newton fields
mainly in the southern hemisphere. Due to the large parameter space in redshift
(0 < z < 4.25) and flux (10^-15 < F(0.5-4.5 keV) < 10^-12 erg s^-1 cm^-2)
covered by the XWAS this work provides an excellent resource to further study
subsamples and particular cases. The overall properties of the extragalactic
objects are presented in this paper.
02/2013;
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M. J. Page,
C. Brindle,
A. Talavera,
M. Still, S. R. Rosen,
V. N. Yershov,
H. Ziaeepour,
K. O. Mason,
M. S. Cropper,
A. A. Breeveld,
N. Loiseau,
R. Mignani,
A. Smith,
P. Murdin
[show abstract]
[hide abstract]
ABSTRACT: The XMM-Newton Serendipitous Ultraviolet Source Survey (XMM-SUSS) is a
catalogue of ultraviolet (UV) sources detected serendipitously by the Optical
Monitor (XMM-OM) on-board the XMM-Newton observatory. The catalogue contains
ultraviolet-detected sources collected from 2,417 XMM-OM observations in 1-6
broad band UV and optical filters, made between 24 February 2000 and 29 March
2007. The primary contents of the catalogue are source positions, magnitudes
and fluxes in 1 to 6 passbands, and these are accompanied by profile
diagnostics and variability statistics. The XMM-SUSS is populated by 753,578 UV
source detections above a 3 sigma signal-to-noise threshold limit which relate
to 624,049 unique objects. Taking account of substantial overlaps between
observations, the net sky area covered is 29-54 square degrees, depending on UV
filter. The magnitude distributions peak at 20.2, 20.9 and 21.2 in UVW2, UVM2
and UVW1 respectively. More than 10 per cent of sources have been visited more
than once using the same filter during XMM-Newton operation, and > 20 per cent
of sources are observed more than once per filter during an individual visit.
Consequently, the scope for science based on temporal source variability on
timescales of hours to years is broad. By comparison with other astrophysical
catalogues we test the accuracy of the source measurements and define the
nature of the serendipitous UV XMM-OM source sample. The distributions of
source colours in the UV and optical filters are shown together with the
expected loci of stars and galaxies, and indicate that sources which are
detected in multiple UV bands are predominantly star-forming galaxies and stars
of type G or earlier.
07/2012;
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[show abstract]
[hide abstract]
ABSTRACT: We describe here a new full 2-D parameterization of the PSFs of the three
XMM-Newton EPIC telescopes as a function of instrument, energy, off-axis angle
and azimuthal angle, covering the whole field-of-view of the three EPIC
detectors. It models the general PSF envelopes, the primary and secondary
spokes, their radial dependencies, and the large-scale azimuthal variations.
This PSF model has been constructed via the stacking and centering of a large
number of bright, but not significantly piled-up point sources from the full
field-of-view of each EPIC detector, and azimuthally filtering the resultant
PSF envelopes to form the spoke structures and the gross azimuthal shapes
observed. This PSF model is available for use within the XMM-Newton Science
Analysis System via the usage of Current Calibration Files XRTi_XPSF_0011.CCF
and later versions. Initial source-searching tests showed substantial
reductions in the numbers of spurious sources being detected in the wings of
bright point sources. Furthermore, we have uncovered a systematic error in the
previous PSF system, affecting the entire mission to date, whereby returned
source RA and Dec values are seen to vary sinusoidally about the true position
(amplitude ~0.8") with source azimuthal position. The new PSF system is now
available and is seen as a major improvement with regard to the detection of
spurious sources. The new PSF also largely removes the discovered astrometry
error and is seen to improve the positional accuracy of EPIC. The modular
nature of the PSF system allows for further refinements in the future.
08/2011;
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M. R. Goad,
L. G. Tyler,
A. P. Beardmore,
P. A. Evans, S. R. Rosen,
J. P. Osborne,
R. L. C. Starling,
F. E. Marshall,
V. Yershov,
D. N. Burrows,
N. Gehrels,
P. Roming,
A. Moretti,
M. Capalbi,
J. E. Hill,
J. Kennea,
S. Koch,
D. Vanden Berk
[show abstract]
[hide abstract]
ABSTRACT: Here we describe an autonomous way of producing more accurate prompt XRT positions for Swift-detected GRBs and their afterglows, based on UVOT astrometry and a detailed mapping between the XRT and UVOT detectors. The latter significantly reduces the dominant systematic error -- the star-tracker solution to the World Coordinate System. This technique, which is limited to times when there is significant overlap between UVOT and XRT PC-mode data, provides a factor of 2 improvement in the localisation of XRT refined positions on timescales of less than a few hours. Furthermore, the accuracy achieved is superior to astrometrically corrected XRT PC mode images at early times (for up to 24 hours), for the majority of bursts, and is comparable to the accuracy achieved by astrometrically corrected X-ray positions based on deep XRT PC-mode imaging at later times (abridged). Comment: 12 pages, 8 figures, 1 table, submitted to Astronomy and Astrophysics, August 7th 2007
08/2007;
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F. J. Carrera,
J. Ebrero,
S. Mateos,
M. T. Ceballos,
A. Corral,
X. Barcons,
M. J. Page, S. R. Rosen,
M. G. Watson,
J. Tedds,
R. Della Ceca,
T. Maccacaro,
H Brunner,
M. Freyberg,
G. Lamer,
F. E. Bauer,
Y Ueda
[show abstract]
[hide abstract]
ABSTRACT: AXIS (An XMM-Newton International Survey) is a survey of 36 high Galactic latitude XMM-Newton observations covering 4.8 deg2 and containing 1433 serendipitous X-ray sources detected with 5-sigma significance. We have studied the X-ray source counts in four energy bands soft (0.5-2 keV), hard (2-10 keV), XID (0.5-4.5 keV) and ultra-hard (4.5-7.5 keV). We have combined this survey with shallower and deeper surveys. Our source counts results are compatible with most previous samples in the soft, XID, ultra-hard and hard bands. The fractions of the XRB resolved in the surveys used in this work are 87%, 85%, 60% and 25% in the soft, hard, XID and ultra-hard bands, respectively. Extrapolation of our source counts to zero flux are not enough to saturate the XRB intensity. Only galaxies and/or absorbed AGN may be able contribute the remaining unresolved XRB intensity. Our results are compatible, within the errors, with recent revisions of the XRB intensity in the soft and hard bands. The maximum fractional contribution to the XRB comes from fluxes within about a decade of the break in the source counts (~1e-14 cgs), reaching ~50% of the total in the soft and hard bands. Using only AXIS sources, we have studied the angular correlation in those bands using a novel robust technique. Angular clustering (widely distributed over the sky and not confined to a few deep fields) is detected at 99-99.9% significance in the soft and XID bands, with no detection in the hard and ultra-hard band (probably due to the smaller number of sources). We cannot confirm the detection of significantly stronger clustering in the hard-spectrum hard sources. Medium depth surveys such as AXIS are essential to determine the evolution of the X-ray emission in the Universe below 10 keV. Comment: 28 pages, 10 figures, A&A accepted
03/2007;
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Massimiliano De Pasquale,
Dirk Grupe,
T. S. Poole,
A. A. Breeveld,
S. Zane, S. R. Rosen,
M. J. Page,
K. O. Mason,
D. N. Burrows,
H. A. Krimm,
N. Gehrels,
J. A. Nousek,
P. W. A. Roming,
S. Kobayashi,
B. Zhang
[show abstract]
[hide abstract]
ABSTRACT: We present the results of X-ray and optical observations of GRB 050712 performed by Swift. The X-ray light curve of this burst exhibits episodes of flares in the first 1000 s, the same epoch at which the UVOT detected an optical counterpart. A shallow X-ray decay, with a decay slope of α=−0.73, followed and lasted ∼70 ks. This behaviour can be explained in terms of activity of the gamma-ray burst ‘inner engine’, with the possibility that the last flare is caused by the interaction of the ejecta with the surrounding medium.We also find interesting spectral parameters for the X-ray emission. In particular, data suggest the presence of an intrinsic absorption in the first 1000 s, which can be explained if circumburst medium clouds lie along the line of sight.
Monthly Notices of the Royal Astronomical Society 08/2006; 370(4):1859 - 1866. · 4.90 Impact Factor
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M. De Pasquale,
D. Grupe,
T. S. Poole,
A. A. Breeveld,
S. Zane, S. R. Rosen,
M. J. Page,
K. O. Mason,
D. N. Burrows,
H. A. Krimm,
N. Gehrels,
J. A. Nousek,
P. W. A. Roming,
S Kobayashi,
B Zhang
[show abstract]
[hide abstract]
ABSTRACT: We present the results of X-ray and optical observations of GRB050712 performed by Swift. The X-ray lightcurve of this burst exhibits episodes of flares in the first 1000s, the same epoch at which the UVOT detected an optical counterpart. A shallow X-ray decay, with a decay slope of -0.73, followed and lasted ~70ks. This behaviour can be explained in terms of activity of GRB 'inner engine', with the possibility of that the last flare is caused by the interaction of the ejecta with the surrounding medium. We also find interesting spectral parameters for the X-ray emission. In particular, data suggest the presence of an intrinsic absorption in the first 1000s, which can be explained if circumbust medium clouds lie along the line of sight. Comment: 13 pages, 5 figures. Accepted for publication by MNRAS
05/2006;
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Massimiliano De Pasquale,
Andy P. Beardmore,
S. D. Barthelmy,
P. Boyd,
D. N. Burrows,
R. Fink,
N. Gehrels,
S. Kobayashi,
K. O. Mason,
R. McNought, [......],
J. Rich,
P. Roming, S. R. Rosen,
T. Sakamoto,
B. P. Schmidt,
J. Tueller,
A. A. Wells,
S. Zane,
B. Zhang,
H. Ziaeepour
[show abstract]
[hide abstract]
ABSTRACT: We present the results of the analysis of γ-ray and X-ray data of GRB 050401 taken with the Swift satellite, together with a series of ground-based follow-up optical observations. The Swift X-ray light curve shows a clear break at about 4900 s after the γ-ray burst (GRB). The decay indices before and after the break are consistent with a scenario of continuous injection of radiation from the ‘central engine’ of the GRB to the fireball. Alternatively, this behaviour could result if ejecta are released with a range of Lorentz factors, with the slower shells catching up the faster at the afterglow shock position. The two scenarios are observationally indistinguishable.The GRB 050401 afterglow is quite bright in the X-ray band, but weak in the optical, with an optical to X-ray flux ratio similar to those of ‘dark bursts’. We detect a significant amount of absorption in the X-ray spectrum, with NH= (1.7 ± 0.2) × 1022 cm−2 at a redshift of z= 2.9, which is typical of a dense circumburst medium. Such high column density implies an unrealistic optical extinction of 30 mag if we adopt a Galactic extinction law, which would not be consistent with the optical detection of the afterglow. This suggests that the extinction law is different from the Galactic one.
Monthly Notices of the Royal Astronomical Society 12/2005; 365(3):1031 - 1038. · 4.90 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The wide range of UV extinction properties in the Small Magellanic Cloud (SMC) probably traces the effects of star formation on interstellar dust. The Swift UVOT, with its three UV filters (centred at 1800, 2200 and 2500 A respectively) and three optical filters, is an ideal instrument to map this extinction. We present preliminary results of six-band photometry in a ~ 3.3 arcminute square field in the SMC. Fitting the resulting optical/UV spectral distributions with a dust model, we estimate the depths of extinction for 53 stars and use this to map the distribution of dust in the observed field. We briefly discuss the relevance of this study for star forming galaxies, including the hosts of Gamma-Ray Bursts.
11/2005;
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P. W. A. Roming,
P. Schady,
D. B. Fox,
B Zhang,
E. Liang,
K. O. Mason,
E. Rol,
D. N. Burrows,
A. J. Blustin,
P. T. Boyd, [......],
V. Mangano,
P. Meszaros,
A. N. Morgan,
J. A. Nousek,
J. P. Osborne,
D. M. Palmer,
T. Poole,
M. D. Still,
G. Tagliaferri,
S. Zane
[show abstract]
[hide abstract]
ABSTRACT: Very early observations with the Swift satellite of gamma-ray burst (GRB) afterglows reveal that the optical component is not detected in a large number of cases. This is in contrast to the bright optical flashes previously discovered in some GRBs (e.g. GRB 990123 and GRB 021211). Comparisons of the X-ray afterglow flux to the optical afterglow flux and prompt gamma-ray fluence is used to quantify the seemingly deficient optical, and in some cases X-ray, light at these early epochs. This comparison reveals that some of these bursts appear to have higher than normal gamma-ray efficiencies. We discuss possible mechanisms and their feasibility for explaining the apparent lack of early optical emission. The mechanisms considered include: foreground extinction, circumburst absorption, Ly-alpha blanketing and absorption due to high redshift, low density environments, rapid temporal decay, and intrinsic weakness of the reverse shock. Of these, foreground extinction, circumburst absorption, and high redshift provide the best explanations for most of the non-detections in our sample. There is tentative evidence of suppression of the strong reverse shock emission. This could be because of a Poynting-flux-dominated flow or a pure non-relativistic hydrodynamical reverse shock. Comment: 22 pages, 5 figures. Accepted for publication in ApJ
09/2005;
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[show abstract]
[hide abstract]
ABSTRACT: We present highly time-resolved HST FOS UV spectroscopy of the nova-like binary V795 Her. Several key results emerge. For the first time we find a strong 2.6-h signature in the variability of the UV lines. The HST data reveal no evidence of a 4.8-h ‘period’, in contrast to our previous IUE observations. This, and differences in the spectral line characteristics, suggests that HST found the system in a different state from earlier IUE observations. The C IV line alone contains a fairly stable, asymmetric, extended blueward absorption trough which we associate with a wind outflow. The 2.6-h variations of the line profiles are largely confined to an interval of about 0.4 in phase and to the velocity regime −1500 < v < 0 km s−1, the changes being dominated by the apparent decline and re-emergence of a blueshifted emission peak. The complex profiles permit many empirical interpretations, but the simplest attributes the variability to a narrow (FWHM∼1000 km s−1) emission component which is always blueshifted with a mean velocity of around –600 km s−1. This interpretation, however, is not readily related to any obvious source within the binary. An alternative picture, which attempts to relate the UV and (simultaneously observed) optical line behaviour, invokes a more stable, broad (FWHM∼2000 km s−1) emission feature, the intrinsic morphology of which is disguised by superposed constant and variable absorption components. One tentative physical explanation of such a decomposition involves an accretion stream that overflows the accretion disc. However, several problems with this model remain to be resolved. We also draw attention to similarities between the velocity-restricted behaviour in the UV lines of V795 Her and that in the optical lines of T Tauri stars. This might indicate a connection between V795 Her and the magnetically influenced inflow/outflow characteristics associated with the central star in T Tauri systems. If such a connection were eventually demonstrated, it would reopen the question of whether the 2.6-h period in V795 Her is really the binary period and whether the system is in fact related to the intermediate polars.
Monthly Notices of the Royal Astronomical Society 04/2002; 299(2):305 - 318. · 4.90 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Results of the first low-resolution (6 Angstroms), time-resolved Hubble
Space Telescope (HST) Faint Object Spectrograph (FOS) observation of the
prototypical strong-field intermediate polar system, PQ Gem, are
presented. The lambdalambda1150-2600 continuum light curve is dominated
by the 13.9-min rotational signature of the white dwarf at all UV
wavelengths covered, with a broadly constant fractional modulation
depth. The rotational profile contains a dip which is deepest in the
far-UV and which we believe, like its X-ray counterpart, is caused by
stream occultation of the white dwarf. The continuum and emission-line
fluxes are also modulated on the 14.5-min beat period but, remarkably,
vary in antiphase. This complex behaviour facilitates the identification
and partial isolation of two spin-modulated spectral components and a
beat component. One spin component has a blue spectral distribution
whose temperature is <~50000K if no allowance is made for the
absorbing effects of the stream, but may be much hotter (consistent with
earlier X-ray estimates) if, as seems likely, the absorber is not
completely optically thick. The other spin-modulated component has a red
spectral distribution whose temperature (<~10000K) and luminosity
probably associate it with the magnetospheric accretion flow itself. The
beat continuum component has a temperature in the region of 17000K and
appears to be radiated by a region whose size is comparable to that of
the white dwarf. The beat pulsation in the emission lines may also
originate from a region of similar dimensions. We consider one- and
two-site hypotheses to explain the antiphased line and continuum beat
modulations, but are unable to arrive at a convincing solution.
Monthly Notices of the Royal Astronomical Society 06/1997; 288:891-902. · 4.90 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Pointed EUVE and ROSAT observations of the AM Her type binary QS Tel (RE
1938-461) are reported, together with complementary contemporaneous
optical measurements. The EUVE data reveal a double-peaked orbital light
curve, dramatically different from the `bright-faint' morphology seen
during the ROSAT WFC survey discovery observations, indicating that two
accretion sites were active. A deep dip is present during one of the
EUVE flux maxima and probably arises from occultation of the emission
site by the accretion flow rather than via an eclipse by the companion
star. This dip, which does not appear to be accompanied by significant
spectral hardening, possesses a slow (~300s) ingress but much more rapid
(~40s) egress. Both ingress and a restricted phase interval near mid-dip
are affected by strong flare-like activity. Blackbody representation of
the EUVE spectra yields a low emission temperature ~15 eV. The inferred
estimates of the soft component flux point to a large soft/hard
component flux ratio (>~15). However, we also find tentative evidence
of an ionization edge at 85A and absorption lines at 98 and 116A,
possibly due to NeVI, NeVIII and NeVII respectively. Contemporaneous
optical photometry shows the light curve to vary substantially over 3d
but, where we have simultaneity, there is no significant correlation
between the optical and EUV fluxes. During the earlier ROSAT pointed
observation, the source was in a single-pole mode but the intensity of
the bright interval had declined by a factor ~5 relative to the survey
observation. A counterpart to the EUVE dip was seen in both the WFC and
PSPC bands during the bright interval, the WFC event being similar in
morphology to the EUVE dip and more protracted than the PSPC dip.
Quasi-simultaneous V- and I-band photometry shows a broad dip centred on
the X-ray event, with greater depth at red wavelengths. A hard spectral
component is detected in the ROSAT spectrum. This collection of
observations highlights the variable behaviour of QS Tel but also
provides a rather clean, simple example of a change of accretion mode in
an AM Her system. We consider the implications of this result and also
discuss the nature of the accretion flow.
Monthly Notices of the Royal Astronomical Society 05/1996; 280:1121-1142. · 4.90 Impact Factor
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åp. 08/1995; 300:392.
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Monthly Notices of the Royal Astronomical Society 10/1994; 271:372-384. · 4.90 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: ROSA T observations of three cataclysmic variables with disputed
intermediate polar (DQ Her star) designations are presented. Pronounced
variability, with possible time- scales of 12.5, 2.5 or 4.5 h, is seen
in the X-ray light curve of V426 Oph; these variations may be
accompanied by spectral changes. This system may have been caught in the
decline from a dwarf nova outburst, being significantly brighter and
softer during the early part of the observation. The previously reported
orbital and rotational X-ray/optical periodicities in SW UMa were not
detected in the ROSA T observations of this star: we place an upper
limit of 20 per cent on the pulse fraction of any rotational modulation.
Spectral analysis indicates that a two-temperature origin for the X-ray
emission is probably appropriate. An X-ray imaging detection of the
HEAO-1 source, 1H0709 -360, is also presented. The weak signal precludes
a detailed spectral analysis, but we are able to place limits on the
column to the source. When extrapolated to the 2-10 keV band, the
constraints imposed by the ROSAT data yield a flux that is about two
orders of magnitude fainter than that implied by the HEAO-1 detection.
The intermediate polar classification of each of the three sources
remains unconfirmed. Key words: stars: individual: V426 Oph - stars:
individual: SW UMa - stars: individual: 1H0709 -360 - novae, cataclysmic
variables - X-rays: stars.
Monthly Notices of the Royal Astronomical Society 07/1994; 269:913. · 4.90 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We present the results of spin phase-resolved optical spectroscopy of
the intermediate polar GK Persei. Our data show that, in common with
other such systems, the spectrum is modulated at the spin period of the
white dwarf, but the characteristics of the modulation in GK Per are not
typical of the class. The V/R ratio spin modulation shows a `glitch' in
phase in the space of one day, whilst an equivalent width modulation
shows no such phenomenon. This suggests either that the accretion
geometry in GK Per is unstable, or that the modulation pattern is
produced by the interplay of multiple spinmodulated components. The fact
that H is single-peaked whereas the other Balmer lines are not indicates
the presence of an additional emission region producing optically thin
Balmer lines via radiative recombination. Key words: binaries:
spectroscopic - stars: individual: GK Per - stars: magnetic fields -
novae, cataclysmic variables - stars: variables: other - X-rays: stars.
Monthly Notices of the Royal Astronomical Society 06/1994; 269:517. · 4.90 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We present the results of ROSAT X-ray and EUV observations of the
eclipsing AM Her star UZ For. Data have been obtained during faint and
bright phases and, most interestingly, during the rise interval when the
emission region appears over the limb of the white dwarf. The source is
seen weakly in the X-ray telescope during the faint phase. We find that
the rise to the bright phase is resolved, which is direct evidence of a
spatially extended soft X-ray emission region and which places
constraints on the size of the emission region. We show evidence that
the blackbody temperature in the rise interval is about 10 percent lower
than in the bright phase. The soft X-ray excess is at least a factor of
7.
Monthly Notices of the Royal Astronomical Society 05/1993; 262:993-999. · 4.90 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The discovery of a probable new AM Her star, RE1149 + 28, in
observations made with the Rosat Wide-Field Camera is reported. The
light curve measured from the all-sky EUV survey data is highly variable
and exhibits a 1-d periodicity which probably reflects an underlying
binary period of either 90 or 103 min. The morphology of the modulation
indicates that there is a single EUV-emitting pole in RE1149 + 28 and
that this pole is rotated out of view, behind the white dwarf, for
approximately half the binary orbital period. Optical spectroscopy shows
clear evidence of systematic radial velocity motion in the emission
lines at a period consistent with the 90- or 103-min photometric
variation. The EUV data constrain the blackbody emission temperature to
be between 10 and 40 eV. RE1149 + 28 exhibits an unusually large
EUV-to-optical flux ratio compared to previously known AM Her stars
detected in the Rosat survey.
Monthly Notices of the Royal Astronomical Society 08/1992; 258:277-284. · 4.90 Impact Factor
