RAT J1953+1859: a dwarf nova discovered through high amplitude QPOs in quiescence (2009)
Ramsay, Gavin, Hakala, Pasi, Barclay, Thomas, Wheatley, Peter, Marshall, George, Lehto, Harry, ...
We report the discovery of an accreting binary, RAT J1953+1859, made during the RApid Temporal Survey (RATS) on the Isaac Newton Telescope. It showed high amplitude (0.3 mag) quasi-periodic...
2XMMi J225036.9+573154 - a new eclipsing AM Her binary discovered using XMM-Newton (2009)
Ramsay, Gavin, Rosen, Simon, Hakala, Pasi, Barclay, Thomas
We report the discovery of an eclipsing polar, 2XMMi J225036.9+573154, using XMM-Newton. It was discovered by searching the light curves in the 2XMMi catalogue for objects showing X-ray variability....
Light Curve Morphology Study of UW CrB -- Evidence for a 5 d Superorbital Period (2008)
Hakala, Pasi, Hjalmarsdotter, Linnea, Hannikainen, Diana C., Muhli, Panu
Since its discovery in 1990, UW CrB (also known as MS1603+2600) has remained a peculiar source without firm classification. Our current understanding is that it is an Accretion Disc Corona (ADC) low...
The defining characteristics of Intermediate Polars - the case of three candidate systems (2008)
Ramsay, Gavin, Wheatley, Peter J., Norton, A. J., Hakala, Pasi, Baskill, Darren
Intermediate Polars (IPs) are a group of cataclysmic variables (CVs) which are thought to contain white dwarfs which have a magnetic field strength in the range ~0.1-10MG. A significant fraction of...
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...
Modeling of orbital modulation of Cygnus X-3 by particle simulations (2007)
Vilhu, Osmi, Hakala, Pasi, Hjalmarsdotter, Linnea, Hannikainen, Diana, Paizis, Ada, McCollough, Michael
The formation of the circumbinary envelope of Cygnus X-3 was studied by particle simulations of the WR (Wolf Rayet) companion wind. Light curves resulting from electron scattering absorption in this...
XMM-Newton observations of AM CVn binaries: V396 Hya & SDSS J1240-01 (2006)
Ramsay, Gavin, Groot, Paul J., Marsh, Tom, Nelemans, Gijs, Steeghs, Danny, Hakala, Pasi
We present the results of XMM-Newton observations of two AM CVn systems - V396 Hya and SDSS J1240-01. Both systems are detected in X-rays and in the UV: neither shows coherent variability in their...
Ramsay, Gavin, Napiwotzki, Ralf, Hakala, Pasi, Lehto, Harry
The RApid Temporal Survey (RATS) is a survey to detect objects whose optical intensity varies on timescales of less than ~70 min. In our pilot dataset taken with the INT and the Wide Field Camera in...
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...
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...
RApid Temporal Survey - RATS I: Overview and first results (2005)
We present the aim and first results of the RApid Temporal Survey (RATS) made using the Wide Field Camera on the Isaac Newton Telescope. Our initial survey covers 3 square degrees, reaches a depth of...
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...
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...
XMM-Newton observations of the dwarf nova YZ Cnc in quiescence (2004)
Hakala, Pasi, Ramsay, Gavin, Wheatley, Peter, Harlaftis, Emilios, Papadimitriou, C.
We present results from the XMM observations of the dwarf nova YZ Cnc in a quiescent state. We have performed a detailed time series analysis of the resulting light curves. Unusually, we do not...
We revisit the XMM-Newton observations of the dwarf nova OY Car taken in July 2000 which occured shortly after an outburst. Ramsay et al (2001a) found a prominent energy dependent modulation at a...
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...
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 (
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...
Evidence for evolving accretion disk structure in 4U 1957+115 (1998)
Hakala, Pasi, Muhli, Panu, Dubus, Guillaume
We present results of the first multicolour photometric study of 4U1957+115, one of the optically less studied low mass X-ray binaries (LMXB). Our quasi-simultaneous UBVRI observations reveal that...
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...
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...
Automated Source Classification using a Kohonen Network (1995)
We report progress in the development of automatic star/galaxy classifier for processing images generated by large galaxy surveys like APM. Our classification method is based on neural networks using...