Could the Galactic disk heating be due to Globular Cluster impacts? (2009)
Putte, D. Vande, Cropper, Mark, Ferreras, Ignacio
So far, six mechanisms have been proposed to account for the Galactic disk heating. Of these, the most important appear to be a combination of scattering of stars by molecular clouds and by spiral...
Detecting the effect of Globular Cluster impacts on the disk of the Milky Way (2008)
Putte, D. Vande, Cropper, Mark
The crossing of the Galactic disk by a Globular Cluster could produce star formation due to gravitational focussing or compression of disk material. We report on simulations of the effect on disk...
The focal plane instrumentation for the DUNE mission (2008)
Booth, Jeff, Cropper, Mark, Eisenhauer, Frank, Refregier, Alexandre, Collaboration, The DUNE
DUNE (Dark Universe Explorer) is a proposed mission to measure parameters of dark energy using weak gravitational lensing The particular challenges of both optical and infrared focal planes and the...
The focal plane instrumentation for the DUNE mission (2008)
Booth, Jeff, Cropper, Mark, Eisenhauer, Frank, Refregier, Alexandre, DUNE Collaboration
Detection of the optical counterpart of the proposed double degenerate polar RX J1914+24 (2007)
Gavin Ramsay, Mark Cropper, Kinwah Wu, K. O. Mason, Pasi Hakala
We have detected the optical counterpart of the proposed double degenerate polar RX J1914+24. The I band light curve is modulated on the 9.5 min period seen in Xrays. There is no evidence for any...
A comparison of white dwarf mass estimators using the Intermediate Polar XY Ari (2007)
Gavin Ramsay, Mark Cropper, Coel Hellier, Kinwah Wu
We determine the mass of the white dwarf in the eclipsing intermediate polar XY Ari following the method given in Cropper, Ramsay & Wu using a multi-temperature bremsstrahlung model. By fitting...
Accretion onto Magnetic White Dwarfs (2007)
. Recent developments in the accretion onto magnetic white dwarfs are reviewed. Accreting magnetic white dwarfs display many of the characteristics of accreting systems of a galactic scale, with the...
XMM-Newton observations of the eclipsing polar V2301 Oph (2007)
We present XMM-Newton observations of the eclipsing polar V2301 Oph which cover nearly 2.5 binary orbital cycles and 2 eclipses. This polar is believed to have the lowest magnetic field strength (7...
X-ray emissions from two-temperature accretion flows within a dipole magnetic funnel (2007)
Saxton, Curtis J., Wu, Kinwah, Canalle, Joao. B. G., Cropper, Mark, Ramsay, Gavin
We investigate the hydrodynamics of accretion channelled by a dipolar magnetic field (funnel flows). We consider situations in which the electrons and ions in the flow cannot maintain thermal...
On the Nature of Ultra-Luminous X-ray Sources from Optical/IR Measurements (2007)
Cropper, Mark, Copperwheat, Christopher, Wu, Kinwah, Soria, Roberto
We present a model for the prediction of the optical/infra-red emission from ULXs. In the model, ULXs are binary systems with accretion taking place through Roche lobe overflow. We show that...
Quasi-Periodic Variability in NGC 5408 X-1 (2007)
Strohmayer, Tod E., Mushotzky, Richard F., Winter, Lisa, Soria, Roberto, Uttley, Phil, Cropper, Mark
We report the discovery with XMM-Newton of quasiperiodic variability in the 0.2 - 10 keV X-ray flux from the ultraluminous X-ray source NGC 5408 X-1. The average power spectrum of all EPIC-pn data...
Probing the Pulsar Wind Nebula of PSR B0355+54 (2006)
McGowan, Katherine E., Vestrand, W. Tom, Kennea, Jamie A., Zane, Silvia, Cropper, Mark, Cordova, France A.
We present XMM-Newton and Chandra X-ray observations of the middle-aged radio pulsar PSR B0355+54. Our X-ray observations reveal emission not only from the pulsar itself, but also from a compact...
XMM-Newton and Chandra observations of the ultra-compact binary RX J1914+24 (2006)
Ramsay, Gavin, Cropper, Mark, Hakala, Pasi
The nature of the X-ray source RX J1914+24 has been the subject of much debate. It shows a prominent period of 569 sec in X-rays and the optical/infra-red: in most models this has been interpreted as...
McGowan, Katherine E., Zane, Silvia, Cropper, Mark, Vestrand, W. Thomas, Ho, Cheng
We report on the first XMM-Newton observation of the Vela-like pulsar PSR B2334+61. Spectral analysis reveals soft X-ray emission, with the bulk of the photons emitted at energies below ~1.5 keV. We...
Optical and Infrared Signatures of ULX's (2005)
Copperwheat, Christopher, Cropper, Mark, Soria, Roberto, Wu, Kinwah
We have constructed a model to describe the optical emission from ultra-luminous X-ray sources (ULXs). We assume a binary model with a black hole accreting matter from a Roche lobe filling companion...
XMM-Newton observations of AM CVn binaries (2005)
Ramsay, Gavin, Hakala, Pasi, Marsh, Tom, Nelemans, Gijs, Steeghs, Danny, Cropper, Mark
We present the results of XMM-Newton observations of four AM CVn systems -- AM CVn, CR Boo, HP Lib and GP Com. Their light curves show very different characteristics. The X-ray light curves show no...
Saxton, Curtis, Wu, Kinwah, Cropper, Mark, Ramsay, Gavin
We use a two-temperature hydrodynamical formulation to determine the temperature and density structures of the post-shock accretion flows in magnetic cataclysmic variables (mCVs) and calculate the...
Canalle, Joao B. G., Saxton, Curtis J., Wu, Kinwah, Cropper, Mark, Ramsay, Gavin
Field-channelled accretion flows occur in a variety of astrophysical objects, including T Tauri stars,magnetic cataclysmic variables and X-ray pulsars. We consider a curvilinear coordinate system and...
XMM-Newton observations of the ultra-compact binary RX J1914+24 (2004)
Ramsay, Gavin, Hakala, Pasi, Wu, Kinwah, Cropper, Mark, Mason, K. O., Cordova, F. A., ...
We present XMM-Newton observations of the 569 sec period system RX J1914+24 (V407 Vul). This period is believed to represent the binary orbital period making it an ultra-compact binary system. By...
The star-forming environment of a ULX in NGC 4559: an optical study (2004)
Soria, Roberto, Cropper, Mark, Pakull, Manfred, Mushotzky, Richard, Wu, Kinwah
We have studied the candidate optical counterparts and the stellar population in the star-forming complex around a bright ULX in NGC4559, using HST/WFPC2, XMM-Newton/OM, and ground-based data. We...
Classifying the zoo of ultraluminous X-ray sources (2004)
Soria, Roberto, Cropper, Mark, Motch, Christian
Ultraluminous X-ray sources (ULXs) are likely to include different physical types of objects. We discuss some possible subclasses, reviewing the properties of a sample of ULXs recently observed by...
XMM-Newton observations of the eclipsing polar EP Dra (2004)
Ramsay, Gavin, Bridge, C. M., Cropper, Mark, Mason, K. O., Cordova, F. A., Priedhorsky, W.
We present XMM-Newton observations of the eclipsing polar EP Dra which cover nearly 3 binary orbital cycles. The X-ray and UV data show evidence for a prominent dip before the eclipse which is due to...
Accretion stream mapping with genetically modified "fire-flies" (2004)
Bridge, C. M., Hakala, Pasi, Cropper, Mark, Ramsay, Gavin
We apply an eclipse mapping technique using `genetically modified fire-flies' to the eclipse light curves of HU Aqr and EP Dra. The technique makes as few assumptions as possible about the location...
Timing Analysis of the Isolated Neutron Star RX J0720.4-3125 Revisited (2004)
Cropper, Mark, Haberl, Frank, Zane, Silvia, Zavlin, Vyacheslav
We present a reanalysis of the X-ray data for RX J0720.4-3125 presented in Zane et al. (2002), using more data recently available from XMM-Newton and Chandra. This analysis also corrects the Rosat...
XMM-Newton observations of polars in low accretion states (2004)
Ramsay, Gavin, Cropper, Mark, Wu, Kinwah, Mason, Keith, Cordova, France, Priedhorsky, William
We have made a series of snap-shot observations of 37 polars using XMM-Newton. We found that 16 of these systems were in a low, or much reduced, accretion state. Of those, 6 were not detected in...
Timing analysis of the isolated neutron star RX J0720.4-3125 revisited (2004)
Cropper, Mark, Haberl, Frank, Zane, Silvia, Zavlin, Vyacheslav E.
A ULX in NGC 4559: a "mini-cartwheel" scenario? (2003)
Soria, Roberto, Cropper, Mark, Pakull, Manfred
We have studied an ultraluminous X-ray source (ULX) in NGC 4559 with XMM-Newton, and its peculiar star-forming environment with HST/WFPC2. The X-ray source is one of the brightest in its class (L_x ~...
Twisted accretion curtains in the intermediate polar FO Aquarii (2003)
Evans, P. A., Hellier, Coel, Ramsay, Gavin, Cropper, Mark
We report on a ~37-ks XMM-Newton observation of the intermediate polar FO Aquarii, presenting X-ray and UV data from the EPIC and OM cameras. We find that the system has changed from its previously...
Probable intermediate mass black holes in NGC4559: XMM-Newton spectral and timing constraints (2003)
Cropper, Mark, Soria, Roberto, Mushotzky, Richard F., Wu, Kinwah, Markwardt, Craig B., Pakull, Manfred
We have examined X-ray and optical observations of two ultra-luminous X-ray sources, X7 and X10 in NGC4559, using XMM-Newton, Chandra and HST. The UV/X-ray luminosity of X7 exceeds 2.1e40 erg/s in...
The energy balance in polars revisited (2003)
In the EXOSAT and ROSAT eras a significant number of polars were found to show a soft/hard X-ray ratio much greater than that expected from the standard accretion shock model. This was known as the...
XMM-Newton Observations of PSR B1706-44 (2003)
McGowan, Katherine E., Zane, Silvia, Cropper, Mark, Kennea, Jamie A., Cordova, France A., Ho, Cheng, ...
We report on the XMM-Newton observations of the young, 102 ms pulsar PSR B1706-44. We have found that both a blackbody plus power-law and a magnetized atmospheric model plus power-law provide an...
XMM-Newton observations of three short period polars: V347 Pav, GG Leo and EU UMa (2003)
Ramsay, Gavin, Cropper, Mark, Mason, K. O., Cordova, F. A., Priedhorsky, W.
We present phase-resolved XMM_Newton data of three short period polars: V347 Pav, GG Leo and EU UMa. All three systems show one dominant accretion region which is seen for approximately half of the...
Spin up in RX J0806+15 - the shortest period binary (2003)
Hakala, Pasi, Ramsay, Gavin, Wu, Kinwah, Hjalmarsdotter, Linnea, Jarvinen, Silva, Jarvinen, Arto, ...
RX J0806+15 has recently been identified as the binary system with the shortest known orbital period. We present a series of observations of RX J0806+15 including new optical observations taken one...
A Concept for an STJ-based Spectrograph (2003)
Cropper, Mark, Barlow, M., Perryman, M. A. C., Horne, Keith, Bingham, R., Page, M., ...
We describe a multi-order spectrograph concept suitable for 8m-class telescopes, using the intrinsic spectral resolution of Superconducting Tunneling Junction detectors to sort the spectral orders....
Detection of Pulsed X-ray Emission from XMM-Newton Observations of PSR J0538+2817 (2003)
McGowan, Katherine E., Kennea, Jamie A., Zane, Silvia, Cordova, France A., Cropper, Mark, Ho, Cheng, ...
We report on the XMM-Newton observations of the 143 ms pulsar PSR J0538+2817. We present evidence for the first detections of pulsed X-rays from the source at a frequency which is consistent with the...
Multi-epoch spectroscopy and XMM-Newton observations of RX J2115-58 (2003)
Cropper, Mark, Ramsay, Gavin, Marsh, Tom
We present phase resolved optical spectroscopy and X-ray light curves of the asynchronous polar RX J2115-58 as they change on the beat period.
Stream eclipse mapping with 'fire-flies' (2003)
Bridge, C. M., Hakala, Pasi, Cropper, Mark, Ramsay, Gavin
We apply a new method of eclipse mapping to the light curves of eclipsing polars. The technique aims to locate the bright emission associated with the accretion stream, using a technique that makes...
Ultra-Short Period Double-Degenerate Binaries (2003)
Cropper, Mark, Ramsay, Gavin, Wu, Kinwah, Hakala, Pasi
We review the current observational status of the ROSAT sources RX J1914.4+2456 and RX J0806.3+1527, and the evidence that these are ultra-short period (
Accretion Flow Along a Dipolar Field: Application to Intermediate Polars (2003)
Canalle, J. B. G., Wu, Kinwah, Cropper, Mark, Ramsay, Gavin, Saxton, Curtis
A hydrodynamic formulation for accretion flow channeled by a dipolar magnetic field is constructed using a curvi-linear coordinate system natural to the field structure. We solve the hydrodynamic...
The XMM-Newton-MSSL survey of Polars (2003)
The XMM-Newton-MSSL survey of polars is a snapshot survey of nearly 40 polars. We present the initial results, with an emphasis on the energy balance in these systems and the number of systems which...
Variability of the Accretion Stream in the Eclipsing Polar EP Dra (2003)
Bridge, C. M., Cropper, Mark, Ramsay, Gavin, Reynolds, A. P., Perryman, M. A. C.
We present the first high time resolution light curves for six eclipses of the magnetic cataclysmic variable EP Dra, taken using the superconducting tunnel junction imager S-Cam2. The system shows a...
XMM-Newton observations of the polars EV UMa, RX J1002-19 and RX J1007-20 (2002)
We present XMM-Newton data of three strongly magnetic cataclysmic variables (polars) EV UMa, RX J1002-19 and RX J1007-20. These include the polar with the shortest orbital period (EV UMa) and the...
STJ Observations of the Eclipsing Polar HU Aqr (2002)
Bridge, C. M., Cropper, Mark, Ramsay, Gavin, Perryman, M. A. C., Favata, F., ...
We apply an eclipse mapping technique to observations of the eclipsing magnetic cataclysmic variable HU Aqr. The observations were made with the S-Cam2 Superconducting Tunnel Junction detector at the...
First X-ray observations of the polar CE Gru (2002)
We report the detection of the polar CE Gru in X-rays for the first time. We find evidence for a dip seen in the hard X-ray light curve which we attribute to the accretion stream obscuring the...
XMM-Newton observations of the asynchronous polar BY Cam (2002)
We report observations of the asynchronous polar BY Cam made using XMM-Newton. We find evidence for two accretion regions which have significantly different spectra. In both regions we find evidence...
Timing analysis of the isolated neutron star RX J0720.4-3125 (2002)
Zane, Silvia, Haberl, Frank, Cropper, Mark, Zavlin, Vyacheslav E., Lumb, David, Sembay, Steve, ...
We present a combined analysis of XMM-Newton, Chandra and Rosat observations of the isolated neutron star RXJ0720.4-3125, spanning a total period of \sim 7 years. We develop a maximum likelihood...
Timing study of the isolated neutron star RX J0720.4-3125 (2002)
Zane, Silvia, Haberl, Frank, Cropper, Mark, Zavlin, Vyacheslav E., Lumb, David, Sembay, Steve, ...
We present a combined analysis of XMM-Newton, Chandra and Rosat observations of the isolated neutron star RX J0720.4-3125, spanning a total period of \sim 7 years. We develop a maximum likelihood...
Timing analysis of the isolated neutron star RX J0720.4-3125 (2002)
Zane, Silvia, Haberl, Frank, Cropper, Mark, Zavlin, Vyacheslav E., Lumb, David, Sembay, Steve, ...
We present a combined analysis of XMM-Newton, Chandra and ROSAT observations of the isolated neutron star RX J0720.4-3125, spanning a total period of similar to7 yr. We develop a maximum likelihood...
Pandel, Dirk, Cordova, France A., Shirey, Robert E., Ramsay, Gavin, Cropper, Mark, Mason, Keith O., ...
XMM-Newton was used to observe two eclipsing, magnetic cataclysmic variables, DP Leo and WW Hor, continuously for three orbital cycles each. Both systems were in an intermediate state of accretion....
Indirect imaging of the accretion stream in eclipsing polars IV: V895 Cen (2001)
Salvi, Nikita, Ramsay, Gavin, Cropper, Mark, Buckley, D. A. H., Stobie, R. S.
We present spectroscopic and high speed photometric data of the eclipsing polar V895 Cen. We find that the eclipsed component is consistent with it being the accretion regions on the white dwarf....
An electrically powered binary star? (2001)
Wu, Kinwah, Cropper, Mark, Ramsay, Gavin, Sekiguchi, Kazuhiro
We propose a model for stellar binary systems consisting of a magnetic and a non-magnetic white-dwarf pair which is powered principally by electrical energy. In our model the luminosity is caused by...
Ionisation Structure in Accretion Shocks with a Composite Cooling Function (2001)
Wu, Kinwah, Cropper, Mark, Ramsay, Gavin
We have investigated the ionisation structure of the post-shock regions of magnetic cataclysmic variables using an analytic density and temperature structure model in which effects due to...
The lower boundary of the accretion column in magnetic cataclysmic variables (2001)
Using a parameterised function for the mass loss at the base of the post-shock region, we have constructed a formulation for magnetically confined accretion flows which avoids singularities, such as...
First XMM-Newton observations of an isolated neutron star: RXJ0720.4-3125 (2000)
Paerels, Frits, Motch, Christian, Haberl, Frank, Zavlin, Vyacheslav E., Zane, Silvia, Ramsay, Gavin, ...
We present the high resolution spectrum of the isolated neutron star RXJ0720.4-3125, obtained with the Reflection Grating Spectrometer on XMM-Newton, complemented with the broad band spectrum...
Cropper, Mark, Zane, Silvia, Ramsay, Gavin, Haberl, Frank, Motch, Christian
We model the spin pulse intensity and hardness ratio profiles of the isolated neutron star RXJ0720.4--3125 using XMM-Newton data. The observed variation is approximately sinusoidal with a...
Simultaneous optical polarimetry and X-ray data of the near synchronous polar RX J2115-5840 (2000)
Ramsay, Gavin, Potter, Stephen, Cropper, Mark, Buckley, David A. H., Harrop-Allin, M. K.
We present simultaneous optical polarimetry and X-ray data of the near synchronous polar RX J2115-5840. We model the polarisation data using the Stokes imaging technique of Potter et al. We find that...
Stokes imaging of the accretion region in Magnetic Cataclysmic Variables - II. V347 Pav. (2000)
S.B. Potter, Mark Cropper, P.J. Hakala
In this paper we present an objective map of the cyclotron emission region in a magnetic Cataclysmic Variable from polarimetric observations of the AM Her system V347 Pav. As the system parameters of...
Detection of the optical counterpart of the proposed double degenerate polar RX J1914+24 (1999)
Ramsay, Gavin, Cropper, Mark, Wu, Kinwah, Mason, Keith, Hakala, Pasi
We have detected the optical counterpart of the proposed double degenerate polar RX J1914+24. The I band light curve is modulated on the 9.5 min period seen in X-rays. There is no evidence for any...
The Emission from Post-Shock Flows in mCVs (1999)
Cropper, Mark, Wu, Kinwah, Ramsay, Gavin
We re-examine the vertical structure of the post-shock flow in the accretion region of mCVs, and the X-ray emission as a function of height. We then predict X-ray light curves and phase-resolved...
Cropper, Mark, Wu, Kinwah, Ramsay, Gavin, Kocabiyik, Aysegul
We have calculated the temperature and density structure of the hot postshock plasma in magnetically confined accretion flows, including the gravitational potential. This avoids the inconsistency of...
RX J2115--5840: confirmation of a new near-synchronous polar (1998)
Ramsay, Gavin, Buckley, David A. H., Cropper, Mark, Harrop-Allin, M. K.
Following the suggestion of Schwope et al that the magnetic cataclysmic variable RX J2115-5840 maybe a near-synchronous polar, we obtained optical polarimetry of this system over a 2 week period....
Indirect imaging of the accretion stream in HU Aquarii (1998)
Harrop-Allin, M K, Cropper, Mark, Hakala, P, Hellier, C, Ramseyer, T
We apply our technique for indirect imaging of the accretion stream to UBVR eclipse profiles of HU Aqr obtained when the system was in a high state. We perform model fits to the eclipses using two...
The optical counterpart of the double degenerate polar RX J1914+24 (1998)
Ramsay, Gavin, Cropper, Mark, Mason, Keith, Hakala, Pasi
Cropper et al 1998 presented X-ray observations of RX J1914+24 and claimed that the most likely interpretation of their data was that of a double degenerate Polar. Here we show the preliminary...
Continuum and line emission from post-shockc flows (1998)
Cropper, Mark, Wu, Kinwah, Ramsay, Gavin
The post-shock flow in the accretion region of MCVs is considered to be a magnetically confined cooling flow. The X-ray spectrum from this hot plasma is emitted from a range of temperatures and...
RX J2115-5840: confirmation of a new near-synchronous polar (1998)
Ramsay, Gavin, Buckley, David, Cropper, Mark, Harrop-Allin, M Kate
Schwope et al (1997) suggested that the newly discovered Polar RX J2115-5840 is a near-synchronous system. We have obtained circular polarisation observations of RX J2115-5840 which show that the...
Projected XMM Vision for MCVs (1998)
James, Cynthia H., Branduardi-Raymont, Graziella, Cropper, Mark
The XMM satellite has a scientific payload of 3 EPIC and 2 RGS instruments which provide for both imaging and non-dispersive spectroscopy as well as medium-to-high resolution dispersive spectroscopy,...
The GOSSIP on the MCV V347 Pav (1998)
Potter, S. B., Cropper, Mark, Hakala, Pasi
Modelling of the polarized cyclotron emission from magnetic cataclysmic variables (MCVs) has been a powerful technique for determining the structure of the accretion zones on the white dwarf. Until...