The field high-amplitude SX Phoenicis variable BL Camelopardalis: results from a multisite photometric campaign. I. Pulsation
E. Rodríguez
(1)
,
S. Fauvaud
(2, 3)
,
J. A. Farrell
(4)
,
A.-Y. Zhou
(5)
,
Jean-Pierre Sareyan
(6)
,
M. J. López-González
(1)
,
Marc-Antoine Dupret
(7, 8)
,
A. Grigahcène
(9)
,
Joris de Ridder
(10)
,
G. Klingenberg
(11)
,
M. Wolf
(12)
,
P. van Cauteren
(13)
,
P. Lampens
(14)
,
D. Martínez
(1)
,
V. M. Casanova
(1)
,
F. J. Aceituno
(1)
,
M. Helvaci
(15)
,
E. G. Hintz
(16)
,
L. Král
(17)
,
F. Fumagalli
(3)
,
J. H. Simonetti
(18)
,
B. H. Granslo
(11)
,
L. Kotková
(19)
,
G. Santacana
(2)
,
J. Michelet
(20)
,
M. Fauvaud
(2)
,
J.-M. Vugnon
(21)
,
H. Sadsaoud
(9)
,
S. Aliouane
(9)
,
Z. C. Grigahcéne
(9)
,
Susana Martin-Ruiz
(1)
,
Pedro J. Amado
(1)
,
Juan Carlos Suárez
(1)
,
Andrés Moya
(1)
,
H. Kucáková
(17)
,
R. Kocián
(17)
,
K. Truparová
(17)
,
A. Avdibegovic
(12)
,
M. Blazek
(12)
,
J. Kliner
(12)
,
P. Zasche
(12)
,
M. Vilásek
(17)
,
S. Bartosíková
(17)
,
B. Yasarsoy
(22)
,
C. Ulusoy
(22)
,
K. A. Graham
(23)
,
M. P. Nicholson
(23)
,
O. Trondal
(11)
,
C. Yesilyaprak
(24)
,
D. Coker
(15)
1
IAA -
Instituto de Astrofísica de Andalucía
2 Association AstroQueyras
3 GEOS - Groupe européen d’observation stellaire
4 Sulphur Flats Observatory
5 National Astronomical Observatoires-CAS
6 Observatoire de la Côte d'Azur
7 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
8 Pôle Astronomie du LESIA
9 CRAAG - Centre de Recherche en Astronomie Astrophysique et Géophysique - Observatoire d'Alger
10 Instituut voor Sterrenkunde, Katholieke Universiteit Leuven
11 Variable Star Section, Norwegian Astronomical Society
12 UK - Univerzita Karlova [Praha, Česká republika] = Charles University [Prague, Czech Republic]
13 Beersel Hills Observatory
14 Koninklijke Sterrenwacht van België
15 Department of Astronomy and Space Sciences, Ankara University
16 Department of Physics and Astronomy, Brigham Young University
17 Observatory and Planetarium of Johann Palisa, VSB - Technical University
18 Martin Observatory, Physics Dep., Virginia Polytechnic Institute & State University, Blacksburg
19 Astronomical Institute, Academy of Sciences
20 CALA - Club d'Astronomie Lyon Ampéré [Vaulx-en-Velin]
21 Club Eclipse : Club d'Etudes du Ciel, de la Lune, des Instruments, des Planètes, du Soleil et des Etoiles...
22 Ege University Observatory
23 AAVSO - American Association of Variable Star Observers
24 Department of Physics, Akdeniz University
2 Association AstroQueyras
3 GEOS - Groupe européen d’observation stellaire
4 Sulphur Flats Observatory
5 National Astronomical Observatoires-CAS
6 Observatoire de la Côte d'Azur
7 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
8 Pôle Astronomie du LESIA
9 CRAAG - Centre de Recherche en Astronomie Astrophysique et Géophysique - Observatoire d'Alger
10 Instituut voor Sterrenkunde, Katholieke Universiteit Leuven
11 Variable Star Section, Norwegian Astronomical Society
12 UK - Univerzita Karlova [Praha, Česká republika] = Charles University [Prague, Czech Republic]
13 Beersel Hills Observatory
14 Koninklijke Sterrenwacht van België
15 Department of Astronomy and Space Sciences, Ankara University
16 Department of Physics and Astronomy, Brigham Young University
17 Observatory and Planetarium of Johann Palisa, VSB - Technical University
18 Martin Observatory, Physics Dep., Virginia Polytechnic Institute & State University, Blacksburg
19 Astronomical Institute, Academy of Sciences
20 CALA - Club d'Astronomie Lyon Ampéré [Vaulx-en-Velin]
21 Club Eclipse : Club d'Etudes du Ciel, de la Lune, des Instruments, des Planètes, du Soleil et des Etoiles...
22 Ege University Observatory
23 AAVSO - American Association of Variable Star Observers
24 Department of Physics, Akdeniz University
Résumé
Context: BL Cam is an extreme metal-deficient field high-amplitude SX Phe-type variable where a very complex frequency spectrum is detected, with a number of independent nonradial modes excited, unusual among the high-amplitude pulsators in the Lower Classical Instability Strip.
Aims: An extensive and detailed study has been carried out to investigate the pulsational content and properties of this object.
Methods: The analysis is based on 283 h of CCD observations obtained in the Johnson V filter, during a long multisite photometric campaign carried out along the Northern autumn-winter of 2005-2006. Additionally, multicolour BI photometry was also collected to study the phase shifts and amplitude ratios, between light curves obtained in different filters, for modal discrimination of the main excited modes.
Results: The detailed frequency analysis revealed a very rich and dense pulsational content consisting of 25 significant peaks, 22 of them corresponding to independent modes: one is the already known main periodicity f0 = 25.5765 cd-1 (Delta V = 153 mmag) and the other 21 are excited modes showing very small amplitudes. Some additional periodicities are probably still remaining in the residuals. This represents the most complex spectrum ever detected in a high-amplitude pulsator of this type. The majority of the secondary modes suspected from earlier works are confirmed here and, additionally, a large number of new peaks are detected. The amplitude of the main periodicity f0 seems to be stable during decades, but the majority of the secondary modes show strong amplitude changes from one epoch to another. The suspected fundamental radial nature of the main periodicity of BL Cam is confirmed, while the secondary peak f1 = 25.2523 cd-1 is identified as a nonradial mixed mode g4 with l = 1. The radial double-mode nature, claimed by some authors for the main two frequencies of BL Cam, is not confirmed. Nevertheless, the frequency f6 = 32.6464 cd-1 could correspond to the first radial overtone.
Aims: An extensive and detailed study has been carried out to investigate the pulsational content and properties of this object.
Methods: The analysis is based on 283 h of CCD observations obtained in the Johnson V filter, during a long multisite photometric campaign carried out along the Northern autumn-winter of 2005-2006. Additionally, multicolour BI photometry was also collected to study the phase shifts and amplitude ratios, between light curves obtained in different filters, for modal discrimination of the main excited modes.
Results: The detailed frequency analysis revealed a very rich and dense pulsational content consisting of 25 significant peaks, 22 of them corresponding to independent modes: one is the already known main periodicity f0 = 25.5765 cd-1 (Delta V = 153 mmag) and the other 21 are excited modes showing very small amplitudes. Some additional periodicities are probably still remaining in the residuals. This represents the most complex spectrum ever detected in a high-amplitude pulsator of this type. The majority of the secondary modes suspected from earlier works are confirmed here and, additionally, a large number of new peaks are detected. The amplitude of the main periodicity f0 seems to be stable during decades, but the majority of the secondary modes show strong amplitude changes from one epoch to another. The suspected fundamental radial nature of the main periodicity of BL Cam is confirmed, while the secondary peak f1 = 25.2523 cd-1 is identified as a nonradial mixed mode g4 with l = 1. The radial double-mode nature, claimed by some authors for the main two frequencies of BL Cam, is not confirmed. Nevertheless, the frequency f6 = 32.6464 cd-1 could correspond to the first radial overtone.
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