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ABSTRACT: The star BL Camelopardalis (GD 428, GSC 04067-00471, V=12.92, B=13.1), is a
SX Phoenicis pulsating variable showing a high amplitude variability (300-350
mmag), with a very clear period of 56.3 min, that has being recently studied by
Fauvaud et al. (2010). They show that the observed variability is due to a
clear and single pulsation, as expected for these type of pulsators. It was
discovered as a variable star on 1976 by Berg and Duthie (1977).
03/2011;
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J. H. Peña,
A. Arellano Ferro,
R. Peña Miller,
M Alvarez,
Y. Rosas,
García,
G. Muñoz,
B. Vargas, J. P. Sareyan,
C. A. Guerrero,
A. Rentería
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ABSTRACT: We present time-series uvby-beta photometry of 41 classical Cepheid stars. A brief discussion of the comparison between the presented data and previous photometric data has been done. Comment: 10 pages, 5 figures, 5 tables
07/2010;
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S. Fauvaud, J. P. Sareyan,
I. Ribas,
E. Rodríguez,
P. Lampens,
G. Klingenberg,
J. A. Farrell,
F. Fumagalli,
J. H. Simonetti,
M Wolf, [......],
A. Avdibegovic,
M. Blauzek,
J. Kliner,
P. Zasche,
S. Bartošíková,
M. Vilášek,
O. Trondal,
F. Van Den Abbeel,
R. Behrend,
H. Wücher
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ABSTRACT: Short-period high-amplitude pulsating stars of Population I ($\delta$ Sct stars) and II (SX Phe variables) exist in the lower part of the classical (Cepheid) instability strip. Most of them have very simple pulsational behaviours, only one or two radial modes being excited. Nevertheless, BL Cam is a unique object among them, being an extreme metal-deficient field high-amplitude SX Phe variable with a large number of frequencies. Based on a frequency analysis, a pulsational interpretation was previously given. aims heading (mandatory) We attempt to interpret the long-term behaviour of the residuals that were not taken into account in the previous Observed-Calculated (O-C) short-term analyses. methods heading (mandatory) An investigation of the O-C times has been carried out, using a data set based on the previous published times of light maxima, largely enriched by those obtained during an intensive multisite photometric campaign of BL Cam lasting several months. results heading (mandatory) In addition to a positive (161 $\pm$ 3) x 10$^{-9}$ yr$^{-1}$ secular relative increase in the main pulsation period of BL Cam, we detected in the O-C data short- (144.2 d) and long-term ($\sim$ 3400 d) variations, both incompatible with a scenario of stellar evolution. conclusions heading (mandatory) Interpreted as a light travel-time effect, the short-term O-C variation is indicative of a massive stellar component (0.46 to 1 M$_{\sun}$) with a short period orbit (144.2 d), within a distance of 0.7 AU from the primary. More observations are needed to confirm the long-term O-C variations: if they were also to be caused by a light travel-time effect, they could be interpreted in terms of a third component, in this case probably a brown dwarf star ($\geq$ 0.03 \ M$_{\sun}$), orbiting in $\sim$ 3400 d at a distance of 4.5 AU from the primary. Comment: 7 pages, 5 figures, accepted for publication in A&A
04/2010;
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J. H. Peña,
A. Arellano Ferro,
R. Peña Miller,
Álvarez M,
Rosas Y,
García H,
Muñoz G,
Vargas B, J. P. Sareyan,
C. A. Guerrero,
Rentería A
Revista Mexicana de Astronomía y Astrofísica : Universidad Nacional Autónoma de México. Instituto de Astronomía. 01/2010;
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ABSTRACT: Str\"omgren uvby-beta photometry is reported for the RR Lyrae stars AE, RS, ST, TV, TW, UU, and XX in Bootes. The physical parameters M/Mo, log (L/Lo), M_V, log T_eff and [Fe/H], have been estimated from the Fourier decomposition of the light curves and the empirical calibrations developed for this type of stars. Detailed behavior of the stars along the cycle of pulsation has been determined from the observed photometric indices and the synthetic indices from atmospheric models. The reddening of the zone is found to be negligible, as estimated from the reddening of several objects in the same region of the sky. Hence the distances to the individual objects are also estimated. Comment: 1 latex and 5 figures in eps
07/2009;
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P. Descamps,
F. Marchis,
T. Michalowski,
J. Berthier,
J. Pollock,
P. Wiggins,
M. Birlan,
F. Colas,
F. Vachier,
S. Fauvaud,
M. Fauvaud, J.-P. Sareyan,
F. Pilcher,
D.A. Klinglesmith
[show abstract]
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ABSTRACT: Mutual event observations between the two components of 90 Antiope were carried out in 2007–2008. The pole position was refined to λ0 = 199.5 ± 0.5° and β0 = 39.8 ± 5° in J2000 ecliptic coordinates, leaving intact the physical solution for the components, assimilated to two perfect Roche ellipsoids, and derived after the 2005 mutual event season (Descamps, P., Marchis, F., Michalowski, T., Vachier, F., Colas, F., Berthier, J., Assafin, M., Dunckel, P.B., Polinska, M., Pych, W., Hestroffer, D., Miller, K., Vieira-Martins, R., Birlan, M., Teng-Chuen-Yu, J.-P., Peyrot, A., Payet, B., Dorseuil, J., Léonie, Y., Dijoux, T., 2007. Figure of the double Asteroid 90 Antiope from AO and lightcurves observations. Icarus 187, 482–499). Furthermore, a large-scale geological depression, located on one of the components, was introduced to better match the observed lightcurves. This vast geological feature of about 68 km in diameter, which could be postulated as a bowl-shaped impact crater, is indeed responsible of the photometric asymmetries seen on the “shoulders” of the lightcurves. The bulk density was then recomputed to 1.28 ± 0.04 g cm−3 to take into account this large-scale non-convexity. This giant crater could be the aftermath of a tremendous collision of a 100-km sized proto-Antiope with another Themis family member. This statement is supported by the fact that Antiope is sufficiently porous (∼50%) to survive such an impact without being wholly destroyed. This violent shock would have then imparted enough angular momentum for fissioning of proto-Antiope into two equisized bodies. We calculated that the impactor must have a diameter greater than ∼17 km, for an impact velocity ranging between 1 and 4 km/s. With such a projectile, this event has a substantial 50% probability to have occurred over the age of the Themis family.
Icarus. 05/2009;
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ABSTRACT: Strömgren uvby -B fi photometry is reported for the RR Lyrae stars AE, RS, ST, TV, TW, UU, and XX in Bootes. The physical parameters M=Mfi, log(L=Lfi), MV , log Tef and [Fe/H], have been estimated from the Fourier decomposition of the light curves and the empirical calibrations developed for this type of stars. The obtained [Fe/H] values are compared with those calculated from the AS index for some sample stars. It was found that reddening in the zone is negligible compared to that shown by several objects in the same sky zone. From that, distance to the stars was calculated. The variation of the unreddened indexes (b-y)0 and c1 along the pulsational cycle allows the direct comparison with the theoretical grids and, hence, an independent determination of Tef and log g.
Revista Mexicana de Astronomía y Astrofísica : Universidad Nacional Autónoma de México. Instituto de Astronomía. 01/2009;
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S Martín-Ruiz,
E Rodríguez,
A Grigahcène,
J C Suárez,
A Moya,
V Costa,
A Rolland,
P J Amado,
E G Hintz,
S L Kim,
S Oh,
A V Kusakin,
A Y Zhou,
A Arellano,
R Peniche,
J H Peña, J P Sareyan
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ABSTRACT: The variability of the two γ Doradus star belong to Pleiades cluster, HD 22702 and HD 23585, have been confirmed by using new photometric measurements collected during a multisite campaign in 1998. Respect to previous observing runs, the frequency analysis shows new peaks close the 3 cd-1 for both stars. With the aim of performing a modal identification, the method based on amplitudes ratios and phase shifts with non-adiabatic time dependent convection (TDC) has been applied. The physical parameters obtained from the photometry put the star HD 23585 out the blue observational edge of the γ Dor region in the HR diagram. This behaviour together with the high value of vsini have not allowed us to perform an identification of the excited modes. Respect to the the star HD 22702, a preliminary study of stability provides results consistent with a l = 2 identification for the found oscillation frequencies except for f3, where a l = 1 mode is also probable. Also for this star, the TDC treatment has not been able to discrimante the found modes. Therefore, in addition to new vsini measurements, it is fundamental to carry out an exhaustive modelling by considering the pertinent corrections in the rotation.
Journal of Physics Conference Series 10/2008; 118(1):012049.
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M Alvarez, J. P. Sareyan,
L. Parrao,
J. H. Pena,
L. Fox Machado,
E. Poretti,
S. Martin-Ruiz,
P. Amado,
R. Garrido,
C. Aerts,
Z. Csurby,
M. Paparo
[show abstract]
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ABSTRACT: We present the analysis of the variability of HD 170699, a COROT star showing the characteristics of a non evolutionary Delta Scuti star with high rotational velocity. There is a clear period of 10.45 c/d with 5.29 mmag amplitude in the y filter. From the data, it can be seen that the star shows multi-periodicity and it is necessary to add more frequencies to adjust the observations
10/2008;
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[show abstract]
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ABSTRACT: Observing Delta Scuti stars is most important as their multi-frequency spectrum of radial pulsations provide strong constraints on the physics of the stars interior; so any new detection and observation of these stars is a valuable contribution to asteroseismology. While performing uvby-beta photoelectric photometry of some RR Lyrae stars acquired in 2005 at the Observatorio Astronomico Nacional, Mexico, we also observed several standard stars, HD115520 among them. After the reduction this star showed indications of variability. In view of this, a new observing run was carried out in 2006 during which we were able to demonstrate its variability and its nature as a Delta Scuti star. New observations in 2007 permitted us to determine its periodic content with more accuracy. This, along with the uvby-beta photoelectric photometry allowed us to deduce its physical characteristics and pulsational modes. Comment: 6 pages. To be published in Journal of Physics: Conference Series. Proc. of the workshop Helioseismology, Asteroseismology and MHD Connections held in Gottingen, Germany, 20-24 August 2007
09/2008;
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Revista Mexicana de Astronomía y Astrofísica. 01/2007;
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[show abstract]
[hide abstract]
ABSTRACT: Se han obtenido nuevas observaciones de estrellas en la dirección del cúmulo abierto Per. Estas observaciones se han combinado con las de la literatura en el sistema uvby- de Strömgren. A partir de ellas se ha determinado una membresía fotométrica que se ha comparado con la derivada de los estudios de movimientos propios y de Hipparcos. Se han determinado características físicas para las estrellas y para el cúmulo.
Revista Mexicana de Astronomía y Astrofísica. 01/2006;
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G. Handler,
M. Jerzykiewicz,
E. Rodríguez,
K. Uytterhoeven,
P. J. Amado,
T. N. Dorokhova,
N. I. Dorokhov,
E. Poretti, J.-P. Sareyan,
L. Parrao, [......],
T. Sahin,
V. Antoci,
S. N. Udovichenko,
K. Csorba,
R. Crowe,
B. Berkey,
S. Stewart,
D. Terry,
D. E. Mkrtichian,
C. Aerts
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ABSTRACT: We report a multisite photometric campaign for the β Cephei star 12 Lacertae. 750 h of high-quality differential photoelectric Strömgren, Johnson and Geneva time-series photometry were obtained with nine telescopes during 190 nights. Our frequency analysis results in the detection of 23 sinusoidal signals in the light curves. Ten of those correspond to independent pulsation modes, and the remainder are combination frequencies. We find some slow aperiodic variability such as that seemingly present in several β Cephei stars. We perform mode identification from our colour photometry, derive the spherical degree ℓ for the five strongest modes unambiguously and provide constraints on ℓ for the weaker modes. We find a mixture of modes of 0 ≤ℓ≤ 4. In particular, we prove that the previously suspected rotationally split triplet within the modes of 12 Lac consists of modes of different ℓ; their equal frequency splitting must thus be accidental.One of the periodic signals we detected in the light curves is argued to be a linearly stable mode excited to visible amplitude by non-linear mode coupling via a 2:1 resonance. We also find a low-frequency signal in the light variations whose physical nature is unclear; it could be a parent or daughter mode resonantly coupled. The remaining combination frequencies are consistent with simple light-curve distortions.The range of excited pulsation frequencies of 12 Lac may be sufficiently large that it cannot be reproduced by standard models. We suspect that the star has a larger metal abundance in the pulsational driving zone, a hypothesis also capable of explaining the presence of β Cephei stars in the Large Magellanic Cloud.
Monthly Notices of the Royal Astronomical Society 12/2005; 365(1):327 - 338. · 4.90 Impact Factor
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G. Handler,
M. Jerzykiewicz,
E Rodriguez,
K. Uytterhoeven,
P. J. Amado,
T. N. Dorokhova,
N. I. Dorokhov,
E. Poretti, J. P. Sareyan,
L. Parrao, [......],
T. Sahin,
V. Antoci,
S. N. Udovichenko,
K. Csorba,
R. Crowe,
B. Berkey,
S. Stewart,
D. Terry,
D. E. Mkrtichian,
C. Aerts
[show abstract]
[hide abstract]
ABSTRACT: We report a multisite photometric campaign for the Beta Cephei star 12 Lacertae. 750 hours of high-quality differential photoelectric Stromgren, Johnson and Geneva time-series photometry were obtained with 9 telescopes during 190 nights. Our frequency analysis results in the detection of 23 sinusoidal signals in the light curves. Eleven of those correspond to independent pulsation modes, and the remainder are combination frequencies. We find some slow aperiodic variability such as that seemingly present in several Beta Cephei stars. We perform mode identification from our colour photometry, derive the spherical degree l for the five strongest modes unambiguously and provide constraints on l for the weaker modes. We find a mixture of modes of 0 <= l <= 4. In particular, we prove that the previously suspected rotationally split triplet within the modes of 12 Lac consists of modes of different l; their equal frequency splitting must thus be accidental. One of the periodic signals we detected in the light curves is argued to be a linearly stable mode excited to visible amplitude by nonlinear mode coupling via a 2:1 resonance. We also find a low-frequency signal in the light variations whose physical nature is unclear; it could be a parent or daughter mode resonantly coupled. The remaining combination frequencies are consistent with simple light-curve distortions. The range of excited pulsation frequencies of 12 Lac may be sufficiently large that it cannot be reproduced by standard models. We suspect that the star has a larger metal abundance in the pulsational driving zone, a hypothesis also capable of explaining the presence of Beta Cephei stars in the LMC. Comment: 12 pages, 7 figures, MNRAS, in press
10/2005;
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M. Breger,
F. Rodler,
M. L. Pretorius,
S. Martin-Ruiz,
P. J. Amado,
V. Costa,
R. Garrido,
P. Lopez de Coca,
I. Olivares,
E Rodriguez,
A. Rolland,
T. Tshenye,
G. Handler,
E. Poretti, J. P. Sareyan,
M Alvarez,
P. M. Kilmartin,
W. Zima
[show abstract]
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ABSTRACT: A high-accuracy multisite campaign was carried out from 2002 January to May with a photometric coverage of 398 hours at five observatories. The concentration on a few selected sites gives better consistency and accuracy than collecting smaller amounts from a larger number of sites. 23 frequencies were detected with a high statistical significance. 6 of these are new. The 17 frequencies found in common with the 1992-1995 data are the modes with highest amplitudes. This indicates that the pulsation spectrum of FG Vir is relatively stable over the ten-year period. Two frequencies have variable amplitudes and phases from year to year as well as during 2002. These were both found to be double modes with close frequencies. For the mode at 12.15 c/d this leads to an apparent modulation with a time scale of about 129d. The close frequencies at 12.15 c/d are composed of a radial and a nonradial mode, suggesting a similarity with the Blazhko Effect seen in RR Lyrae stars. Comment: 8 pages, 4 figures, 2 tables
04/2004;
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P. Mathias,
J.-M. Le Contel,
E. Chapellier,
S. Jankov, J. P. Sareyan,
E. Poretti,
R. Garrido,
E Rodriguez,
A. Arellano Ferro,
M Alvarez,
L. Parrao,
J. Pena,
L. Eyer,
C. Aerts,
P. De Cat,
W. W. Weiss,
A. Zhou
[show abstract]
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ABSTRACT: We present the first results of a 2-year high-resolution spectroscopy campaign of 59 candidate Gamma Doradus stars which were mainly discovered from the HIPPARCOS astrometric mission. More than 60 % of the stars present line profile variations which can be interpreted as due to pulsation related to Gamma Doradus stars. For all stars we also derived the projected rotation velocity (up to more than 200 km\s). The amplitude ratios 2K/Delta m for the main HIPPARCOS frequency are in the range 35 - 96 (km\s)\mag. Less than 50 % of the candidates are possible members of binary systems, with 20 stars being confirmed Gamma Doradus. At least 6 stars present composite spectra, and in all but one case (for which only one spectrum could be obtained), the narrow component shows line profile variations, pointing towards an uncomfortable situation if this narrow component originates from a shell surrounding the star. This paper is the first of a series concerning mode identification using both photometric and spectroscopic methods for the confirmed Gamma Doradus stars of the present sample. Comment: 11 pages, 8 figures, Accepted for Astronomy & Astrophysics
02/2004;
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P. Mathias,
E. Chapellier,
J.-M. Le Contel,
S. Jankov, J.-P. Sareyan,
R. Garrido,
E. Rodriguez,
E. Poretti,
M. Alvarez,
A. Arellano Ferro,
L. Parrao,
J. Peña,
L. Eyer,
C. Aerts,
P. De Cat,
W. W. Weiss,
A. Zhou
[show abstract]
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ABSTRACT: We present here preliminary results of a large spectroscopic survey
(more than 50 stars) of γ Doradus candidates. The aim of this
study is first to confirm bona fide members of this class of g-pulsators
which are still poorly known and second to select candidates for future
space mission such as COROt, but also Eddington. We show in particular
some unexpected results that cannot be derived from photometry alone,
such as ellipsoidal variations and activity.
12/2003; 538:355-358.
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P. Mathias,
M. Chadid,
E. Chapellier,
J.-M. Le Contel, J.-P. Sareyan,
R. Garrido,
E. Rodriguez,
E. Poretti,
M. Alvarez,
L. Parrao,
A. Arellano Ferro,
L. Eyer,
C. Aerts,
P. De Cat,
W. W. Weiss,
A. Zhou
04/2003; -1:359-362.
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ABSTRACT: V2109 Cyg is a pulsating star discovered by the Hipparcos satellite (ESA
1997) with a period of 0.1860d and full amplitude Delta V=0.16. However,
the type of variability as RRLyr or delta Sct-type pulsator is subject
of controversy. From this study, the star is classified as belonging to
the delta Sct group as an evolved member with solar abundances. In
fact, the m1 index curve is slightly reversed over the pulsation cycle,
in very good agreement with that expected from the photometric
calibrations. Concerning the frequency content, besides the main
frequency f1=5.3745c/d, a secondary peak is found at f2=5.8332c/d
(f1/f2=0.92) f1 being identified as a radial mode and f2 as a non-radial
one.
02/2003; 292:125.
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Minor Planet Bulletin. 08/2001; 28:44-45.
