269 citations · 728 across the 18 of their papers we have counts for
19 papers
CoBiToM project. III. Physical characterisation of the potential merger candidates AL Lep, ASAS J082243+1927.0, and ZZ PsA
Sofia Palafouta, Kosmas D. Gazeas, Pasi Hakala +3
Contact binaries (CBs) are key systems for investigating the late evolutionary stages that may lead to stellar coalescence. Systems with an extremely low mass ratio and high fill-o…
Circular polarimetry of suspect wind-accreting pre-polars II
Pasi Hakala, Steven Parsons, Gavin Ramsay +2
The origin of white dwarf magnetic fields is an open question. Furthermore, such fields play a vital role in the evolution of interacting binary stars. Here we present a study of w…
ASASSN-14dx: A cataclysmic variable harbouring a massive pulsating white dwarf
Pasi Hakala, Ingrid Pelisoli, Boris T. Gaensicke +5
We present the results of our study of ASASSN-14dx, a previously known but poorly characterised cataclysmic variable (CV). The source was observed as part of an ongoing high-time-r…
Discovery of two new polars evolved past the period bounce
Tim Cunningham, Ilaria Caiazzo, Gracjan Sienkiewicz +13
We report the discovery of two new magnetic cataclysmic variables with brown dwarf companions and long orbital periods ( and min). This discovery incr…
Characterising high and low accretion states in VY Scl CVs using ZTF and TESS data
C. Duffy, Kinwah Wu, G. Ramsay +4
VY Scl binaries are a sub-class of cataclysmic variable (CV) which show extended low states, but do not show outbursts which are seen in other classes of CV. To better determine ho…
Searching for stellar cycles on low mass stars using TESS data
Gavin Ramsay, Pasi Hakala, J. Gerry Doyle
We have searched for stellar activity cycles in late low mass M dwarfs (M0--M6) located in the TESS north and south continuous viewing zones using data from sectors 1--61 (Cycle 1…
Discovery, observations and modelling of a new eclipsing polar: MASTER OT J061451.70-272535.5
H. Breytenbach, D. A. H. Buckley, P. Hakala +9
We report the discovery of a new eclipsing polar, MASTER OT J061451.70-272535.5, detected as an optical transient by MASTER auto-detection software at the recently commissioned MAS…
High-resolution optical spectroscopy of RS Ophiuchi during 2008 -- 2009
A. Somero, P. Hakala, G. A. Wynn
RS Ophiuchi is a symbiotic variable and a recurrent nova. We have monitored it with the Nordic Optical Telescope and obtained 30 high resolution (R=46 000) optical spectra over one…
An AO-assisted variability study of four globular clusters
R. Salinas, R. Contreras Ramos, J. Strader +4
The image subtraction technique applied to study variable stars in globular clusters represented a leap in the number of new detections, with the drawback that many of these new li…
SDSS unveils a population of intrinsically faint cataclysmic variables at the minimum orbital period
B. T. Gaensicke, M. Dillon, J. Southworth +15
We discuss the properties of 137 cataclysmic variables (CVs) which are included in the Sloan Digital Sky Survey (SDSS) spectroscopic data base, and for which accurate orbital perio…
Optical spectroscopy and photometry of SAX J1808.4-3658 in outburst
P. Elebert, M. T. Reynolds, P. J. Callanan +8
We present phase resolved optical spectroscopy and photometry of V4580 Sagittarii, the optical counterpart to the accretion powered millisecond pulsar SAX J1808.4-3658, obtained du…
RXTE determination of the intermediate polar status of XSS J00564+4548, IGR J17195-4100, and XSS J12270-4859
O. W. Butters, A. J. Norton, P. Hakala +2
Aims: We determine the nature of the intermediate polar candidates XSS J00564+4548, IGR J17195-4100, and XSS J12270-4859. Methods: Pointed RXTE observations searched for intermedia…
Orbital periods of cataclysmic variables identified by the SDSS. II. Measurements for six objects, including two eclipsing systems
John Southworth, T. R. Marsh, B. T. Gaensicke +4
Continuing our work from Paper I (Southworth et al., 2006) we present medium-resolution spectroscopy and broad-band photometry of seven cataclysmic variables (CVs) discovered by th…
3D eclipse mapping in AM Herculis systems - `Genetically modified fireflies'
Pasi J. Hakala Mark Cropper Gavin Ramsay
In order to map the 3-dimensional location and shape of the emission originating within the accretion stream in AM Her systems, we have investigated the possibilities of relaxing t…
RX J0806+15: the shortest period binary?
G. Ramsay, P. Hakala, M. Cropper
The X-ray source RX J0806+15 was discovered using ROSAT, and shows an X-ray light curve with a prominent modulation on a period of 321.5 sec. We present optical observations in whi…
On the multi-periodicities in the X-ray dipper XB 1916-053
L. Homer, P. A. Charles, P. Hakala +4
Using the Rossi X-ray Timing Explorer and the Nordic Optical Telescope we have obtained the highest ever quality X-ray/white-light high-speed photometry of XB 1916-053. We refine t…
Detection of the optical counterpart of the proposed double degenerate polar RX J1914+24
Gavin Ramsay, Mark Cropper, Kinwah Wu +2
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…
UV Spectroscopy of AB Doradus with the Hubble Space Telescope. Impulsive flares and bimodal profiles of the CIV 1549 line in a young star
O. Vilhu, P. Muhli, J. Huovelin +3
We observed AB Doradus, a young and active late type star (K0 - K2 IV-V, P= 0.514 d) with the Goddard High Resolution Spectrograph of the post-COSTAR Hubble Space Telescope with th…
Automated Source Classification using a Kohonen Network
Petri Mahonen, Pasi Hakala
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 ne…