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V. A. Jacobs,
R. H. Østensen,
H. Van Winckel,
S. Bloemen,
P. I. Pápics,
G. Raskin,
J. Debosscher,
S. Uttenthaler,
E. van Aarle,
C. Waelkens, E. Bauwens,
T. Verhoelst,
C. Gielen,
H. Lehmann,
R. Oreiro
[show abstract]
[hide abstract]
ABSTRACT: A close substellar companion has been claimed to orbit the bright sdB star HD
149382 with a period of 2.391d. In order to check this important discovery we
gathered 26 high resolution spectra over 55 days with the HERMES spectrograph
on the 1.2m Mercator telescope on La Palma, and analyzed the resulting radial
velocities. Our data show no sign of any significant radial-velocity
periodicities, and from the high precision of our measurements we rule out any
RV variations with amplitudes higher than 0.79 km/s on periods shorter than 50
days.
01/2011;
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S. Saesen,
A. Pigulski,
F. Carrier,
G. Michalska,
C. Aerts,
J. De Ridder,
M. Briquet,
G. Handler,
Z. Kołaczkowski,
B. Acke, [......],
V. Van Helshoecht,
E. Vanhollebeke,
H. Van Winckel,
T. Verhoelst,
M. Vučković,
C. Waelkens,
G.W. Wolf,
K. Yakut,
C. Zhang,
W. Zima
[show abstract]
[hide abstract]
ABSTRACT: As a result of the variability survey in χ Persei and NGC 6910, the number of β Cep stars that are members of these two open clusters is increased to twenty stars, nine in NGC 6910 and eleven in χ Persei. We compare pulsational properties, in particular the frequency spectra, of β Cep stars in both clusters and explain the differences in terms of the global parameters of the clusters. We also indicate that the more complicated pattern of the variability among B-type stars in χ Persei is very likely caused by higher rotational velocities of stars in this cluster. We conclude that the sample of pulsating stars in the two open clusters constitutes a very good starting point for the ensemble asteroseismology of β Cep-type stars and maybe also for other B-type pulsators (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Astronomische Nachrichten 11/2010; 331(9‐10):1080 - 1083. · 1.01 Impact Factor
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S. Saesen,
A. Pigulski,
F. Carrier,
G. Michalska,
C. Aerts,
J. De Ridder,
M. Briquet,
G. Handler,
Z. Kolaczkowski,
B. Acke, [......],
V. Van Helshoecht,
E. Vanhollebeke,
H. Van Winckel,
T. Verhoelst,
M. Vuckovic,
C. Waelkens,
G. W. Wolf,
K. Yakut,
C Zhang,
W. Zima
[show abstract]
[hide abstract]
ABSTRACT: As a result of the variability survey in Chi Persei and NGC6910, the number of Beta Cep stars that are members of these two open clusters is increased to twenty stars, nine in NGC6910 and eleven in Chi Persei. We compare pulsational properties, in particular the frequency spectra, of Beta Cep stars in both clusters and explain the differences in terms of the global parameters of the clusters. We also indicate that the more complicated pattern of the variability among B type stars in Chi Persei is very likely caused by higher rotational velocities of stars in this cluster. We conclude that the sample of pulsating stars in the two open clusters constitutes a very good starting point for the ensemble asteroseismology of Beta Cep-type stars and maybe also for other B-type pulsators. Comment: 4 pages, Astronomische Nachrichten, HELAS IV Conference, Arecife, Lanzarote, Feb 2010, submitted
04/2010;
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K. Yakut,
W. Zima,
B. Kalomeni,
H. Van Winckel,
C. Waelkens,
P. De Cat, E. Bauwens,
M. Vuckovic,
S. Saesen,
L. Le Guillou,
M. Parmaksizoglu,
K. Uluc,
I. Khamitov,
G. Raskin,
C. Aerts
[show abstract]
[hide abstract]
ABSTRACT: We present multi-colour time-series CCD photometry of the solar-age galactic open cluster M67 (NGC 2682). About 3600 frames spread over 28 nights were obtained with the 1.5 m Russian-Turkish and 1.2 m Mercator telescopes. High-precision observations of the close binary stars AH Cnc, EV Cnc, ES Cnc, the $\delta$ Scuti type systems EX Cnc and EW Cnc, and some long-period variables belonging to M67 are presented. Three full multi-colour light curves of the overcontact binary AH Cnc were obtained during three observing seasons. Likewise we gathered three light curves of EV Cnc, an EB-type binary, and two light curves of ES Cnc, a blue straggler binary. Parts of the light change of long-term variables S1024, S1040, S1045, S1063, S1242, and S1264 are obtained. Period variation analysis of AH Cnc, EV Cnc, and ES Cnc were done using all times of mid-eclipse available in the literature and those obtained in this study. In addition, we analyzed multi-colour light curves of the close binaries and also determined new frequencies for the $\delta$ Scuti systems. The physical parameters of the close binary stars were determined with simultaneous solutions of multi-colour light and radial velocity curves. Finally we determined the distance of M67 as 857(33) pc via binary star parameters, which is consistent with an independent method from earlier studies. Comment: 12 pages, 9 Figures, 13 Tables
06/2009;
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[show abstract]
[hide abstract]
ABSTRACT: Context: Among late-type red giants, an interesting change occurs in the structure of the outer atmospheric layers as one moves to later spectral types in the Hertzsprung-Russell diagram: a chromosphere is always present, but the coronal emission diminishes and a cool massive wind steps in. Aims: Where most studies have focussed on short-wavelength observations, this article explores the influence of the chromosphere and the wind on long-wavelength photometric measurements. Methods: The observational spectral energy distributions are compared with the theoretical predictions of the MARCS atmosphere models for a sample of 9 K- and M-giants. The discrepancies found are explained using basic models for flux emission originating from a chromosphere or an ionized wind. Results: For 7 out of 9 sample stars, a clear flux excess is detected at (sub)millimeter and/or centimeter wavelengths. The precise start of the excess depends upon the star under consideration. The flux at wavelengths shorter than about 1 mm is most likely dominated by an optically thick chromosphere, where an optically thick ionized wind is the main flux contributor at longer wavelengths. Conclusions: Although the optical to mid-infrared spectrum of the studied K- and M-giants is well represented by a radiative equilibrium atmospheric model, the presence of a chromosphere and/or ionized stellar wind at higher altitudes dominates the spectrum in the (sub)millimeter and centimeter wavelength ranges. The presence of a flux excess also has implications on the role of these stars as fiducial spectrophotometric calibrators in the (sub)millimeter and centimeter wavelength range. Comment: 13 pages, 6 figures, 7 pages of online material, submitted to A&A
05/2009;
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[show abstract]
[hide abstract]
ABSTRACT: For the spectro-photometric calibration of space based instruments, like the Medium Resolution Spectrometer (MRS) of the Mid
InfraRed Instrument (MIRI) on board the James Webb Space Telescope (JWST), the accuracy is limited to our knowledge of the
spectra of the sources used as calibrators. As the sensitivity of this instrument is much higher than previous ones, there
is a need for stars with a more accurately modeled spectrum which can be used as a calibrator. In the selection of such sources
we include objects with different spectral types and make sure we cover the whole flux range of the instrument.
Here we will describe a list of candidate sources for this purpose, as well as the preparatory observations needed to further
increase the accuracy of the modeled spectra.
05/2008: pages 145-148;
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A Pigulski,
G Handler,
G Michalska,
Z Kolaczkowski,
G Kopacki,
A Narwid,
E Vanhollebeke,
M Ste'slicki,
K Lefever,
K Gazeas, [......],
B Steininger,
G Davignon,
P ~G Beck,
K Yakut,
R Drummond,
J -N Fu,
X -J Jiang,
C Zhang,
J Provencal,
L Decin
Communications in Asteroseismology 06/2007; 150:191.
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A. Pigulski,
G. Handler,
G. Michalska,
Z. Kołaczkowski,
G. Kopacki,
A. Narwid,
E. Vanhollebeke,
M. Steślicki,
K. Lefever,
K. Gazeas, [......],
B. Steininger,
G. Davignon,
P. G. Beck,
K. Yakut,
R. Drummond,
J.-N. Fu,
X.-J. Jiang,
C. Zhang,
J. Provencal,
L. Decin
Communications in Asteroseismology 05/2007; 150:191.
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[show abstract]
[hide abstract]
ABSTRACT: One of the main ingredients in establishing the relation between input
signal and output flux from a spectrometer, is the accurate
determination of the {spectrophotometric calibration}. In case of
spectrometers onboard satellites, the accuracy of this part of the
calibration pedigree is ultimately linked to the reliability of the
candidate calibrators as being fiducial. In this contribution, we deal
with the spectrophotometric calibration of {infrared}
spectrometers in the 2-200 μm wavelength range. We outline a general
selection procedure to arrive at a set of fiducial IR calibrators, and
apply the method to the Medium Resolution Spectrometer of MIRI which
will be onboard the James Webb Space Telescope.
03/2007; 364:443.
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K. Yakut,
W. Zima,
B. Kalomeni,
H. Van Winckel,
C. Waelkens,
P. De Cat, E. Bauwens,
M. Vučković,
S. Saesen,
L. Le Guillou,
M. Parmaksızoğlu,
K. Uluç,
I. Khamitov,
G. Raskin,
C. Aerts
[show abstract]
[hide abstract]
ABSTRACT: We present multi-colour time-series CCD photometry of the solar-age galactic open cluster M 67 (NGC 2682). About 3600 frames spread over 28 nights were obtained with the 1.5 m Russian-Turkish and 1.2 m Mercator telescopes. High-precision observations of the close binary stars AH Cnc, EV Cnc, ES Cnc, the $\delta$ Scuti type systems EX Cnc and EW Cnc, and some long-period variables belonging to M 67 are presented. Three full multi-colour light curves of the overcontact binary AH Cnc were obtained during three observing seasons. Likewise we gathered three light curves of EV Cnc, an EB-type binary, and two light curves of ES Cnc, a blue straggler binary. Parts of the light change of long-term variables S1024, S1040, S1045, S1063, S1242, and S1264 are obtained. Period variation analysis of AH Cnc, EV Cnc, and ES Cnc were done using all times of mid-eclipse available in the literature and those obtained in this study. In addition, we analyzed multi-colour light curves of the close binaries and also determined new frequencies for the $\delta$ Scuti systems. The physical parameters of the close binary stars were determined with simultaneous solutions of multi-colour light and radial velocity curves. Finally we determined the distance of M 67 as 857(33) pc via binary star parameters, which is consistent with an independent method from earlier studies.
http://dx.doi.org/10.1051/0004-6361/200911918.
