Publications (22)
Anomalous Orbital Characteristics of the AQ Col (EC 05217-3914) System
T. Otani, A. E. Lynas-Gray, D. Kilkenny +6
AQ Col (EC 05217-3914) is one of the first detected pulsating subdwarf B (sdB) stars and has been considered to be a single star. Photometric monitoring of AQ Col reveals a pulsati…
The DA+dMe eclipsing binary EC13471-1258: its cup runneth over...just
D. O'Donoghue, C. Koen, D. Kilkenny +5
EC13471-1258 is a detached eclipsing binary with Porb = 3h37m, comprising a DA white dwarf and a dMe dwarf. Total eclipses of the white dwarf lasting 14 min, and a large amplitude…
Structure of Herbig AeBe disks at the milliarcsecond scale A statistical survey in the H band using PIONIER-VLTI
B. Lazareff, J. -P. Berger, J. Kluska +26
Context. It is now generally accepted that the near-infrared excess of Herbig AeBe stars originates in the dust of a circumstellar disk. Aims. The aims of this article are to infer…
Photometry of the Magnetic White Dwarf SDSS 121209.31+013627.7
C. Koen, P. F. L. Maxted
The results of 27 hours of time series photometry of SDSS 121209.31+013627.7 are presented. The binary period established from spectroscopy is confirmed and refined to 0.061412 d (…
The Gamma Doradus variables, a new class of pulsating stars. The case of HD 224945
E. Poretti, C. Akan, M. Bossi +3
A multisite campaign involving five observatories allowed us to solve the light curve of the Gamma Doradus star HD 224945. The multiperiodic content, the high frequency term at 3.0…
Asteroseismology and forced oscillations of HD 209295, the first member of two classes of pulsating star
G. Handler, L. A. Balona, R. R. Shobbrook +9
We report the discovery of both intermediate-order gravity mode and low-order pressure mode pulsation in the same star, HD 209295. It is therefore both a gamma Doradus and a delta…
Metallicity estimates for A-, F-, and G-type stars from the Edinburgh-Cape blue object survey
T. C. Beers, S. Rossi, D. O'Donoghue +4
The Edinburgh-Cape Blue Object Survey is an ongoing project to identify and analyse a large sample of hot stars selected initially on the basis of photographic colours (down to a m…
UBV(RI)_C photometry of transiting planet host stars
P. F. L. Maxted, C. Koen, B. Smalley
We present new UBV(RI)_C photometry of 22 stars that host transiting planets, 19 of which were discovered by the WASP survey. We use these data together with 2MASS JHK_S photometry…
A detection threshold in the amplitude spectra calculated from Kepler data obtained during K2 mission
A. S. Baran, C. Koen, B. Pokrzywka
We present our analysis of simulated data in order to derive a detection threshold which can be used in the pre-whitening process of amplitude spectra. In case of ground-based data…
Multi-wavelength Observations of the Binary System PSR B1259-63/LS~2883 around the 2014 Periastron Passage
M. Chernyakova, A. Neronov, B. van Soelen +16
We report on the results of the extensive multi-wavelength campaign from optical to GeV gamma-rays of the 2014 periastron passage of PSR B1259-63, which is a unique high-mass gamma…
Two candidate brown dwarf companions around core helium-burning stars
V. Schaffenroth, L. Classen, K. Nagel +4
Hot subdwarf stars of spectral type B (sdBs) are evolved, core helium-burning objects. The formation of those objects is puzzling, because the progenitor star has to lose almost it…
The multiperiodicity of the Doradus stars HD 224945 and HD 224638 as detected from a multisite campaign
E. Poretti, C. Koen, M. Bossi +8
We discuss new photometric data collected on the gamma Dor variables HD 224945 and HD 224638. Multiperiodicity was detected in both stars, thanks to the clear spectral window of a…
The Detailed Forms of the LMC Cepheid PL and PLC Relations
C. Koen, S. Kanbur, C. Ngeow
Possible deviations from linearity of the LMC Cepheid PL and PLC relations are investigated. Two datasets are studied, respectively from the OGLE and MACHO projects. A nonparametri…
Discovery and analysis of Gamma Doradus type pulsations in the Cloud and the effect of metallicity on pulsation
E. Poretti, C. Koen, P. Martinez +3
We present multi-site photometric observations of the F0 IV star HR 2740=QW Pup which reveal it to be a Gamma Dor type variable pulsating with four frequencies: 1.0434, 0.9951, 1.1…
Sporadic Long-term Variability in Radio Activity from a Brown Dwarf
A. Antonova, J. G. Doyle, G. Hallinan +2
Radio activity has been observed in a large variety of stellar objects, including in the last few years, ultra-cool dwarfs. To explore the extent of long-term radio activity in ult…
Discovery and analysis of p-mode and g-mode oscillations in the A-type primary of the eccentric binary HD 209295
G. Handler, L. A. Balona, R. R. Shobbrook +8
We have discovered both intermediate-order gravity mode and low-order pressure mode pulsation in the same star, HD 209295. It is therefore both a Gamma Doradus and a Delta Scuti st…
The rapidly pulsating sdO star, SDSS J160043.6+074802.9
C. RodrÃguez-López, A. E. Lynas-Gray, D. Kilkenny +7
A spectroscopic analysis of SDSS J160043.6+074802.9, a binary system containing a pulsating subdwarf-O (sdO) star with a late-type companion, yields Teff = 70 000 +/- 5000 K and lo…
New Periodic Variables from the Hipparcos Epoch Photometry
C. Koen, L. Eyer
Two selection statistics are used to extract new candidate periodic variables from the epoch photometry of the Hipparcos catalogue. The primary selection criterion is a signal to n…
A Detection Threshold in the Amplitude Spectra Calculated from TESS Time-Series Data
A. S. Baran, C. Koen
We present results of time-series data simulation. We aimed at estimating the threshold used for detecting signals in amplitude spectra, calculated from simulating TESS photometry…
KPD 0422+5421: A New Short Period Subdwarf B/White Dwarf Binary
C. Koen, Jerome A. Orosz, Richard A. Wade
The sdB star KPD 0422+5421 was discovered to be a single-lined spectroscopic binary with a period of P=0.0901795 +/- (3\times 10^{-7}) days (2 hours, 10 minutes). The U and B light…
Low-mass stellar and substellar companions to sdB stars
S. Geier, L. Classen, P. Bruenner +9
It has been suggested that besides stellar companions, substellar objects in close orbits may be able to trigger mass loss in a common envelope phase and form hot subdwarfs. In an…
Optical Spectra of Ultracool Dwarfs with the Southern African Large Telescope
C. Koen, B. Miszalski, P. Väisänen +1
New spectra of 81 ultracool dwarfs (spectral types M7 and later) are discussed. Spectral classifications of 49 objects are available in the literature, while 32 objects are newly c…