J/AJ/146/102 Multi-frequency fit of periodic B stars in NGC 884 (Saesen+, 2013)
Pulsating B-type stars in the open cluster NGC 884: frequencies, mode
identification, and asteroseismology.
Saesen S., Briquet M., Aerts C., Miglio A., Carrier F.
<Astron. J., 146, 102 (2013)>
=2013AJ....146..102S 2013AJ....146..102S
ADC_Keywords: Clusters, open ; Stars, B-type
Keywords: open clusters and associations: individual: NGC 884 -
stars: early-type - stars: oscillations - techniques: photometric
Abstract:
Recent progress in the seismic interpretation of field β Cep
stars has resulted in improvements of the physical description in the
stellar structure and evolution model computations of massive stars.
Further asteroseismic constraints can be obtained from studying
ensembles of stars in a young open cluster, which all have similar
age, distance, and chemical composition. We present an observational
asteroseismology study based on the discovery of numerous
multi-periodic and mono-periodic B stars in the open cluster NGC 884.
We describe a thorough investigation of the pulsational properties of
all B-type stars in the cluster. Overall, our detailed frequency
analysis resulted in 115 detected frequencies in 65 stars. We found 36
mono-periodic, 16 bi-periodic, 10 tri-periodic, and 2 quadru-periodic
stars and one star with nine independent frequencies. We also derived
the amplitudes and phases of all detected frequencies in the U, B, V,
and I filter, if available. We achieved unambiguous identifications of
the mode degree for 12 of the detected frequencies in nine of the
pulsators. Imposing the identified degrees and measured frequencies of
the radial, dipole, and quadrupole modes of five pulsators led to a
seismic cluster age estimate of log(age/yr)=7.12-7.28 from a
comparison with stellar models. Our study is a proof-of-concept for
and illustrates the current status of ensemble asteroseismology of a
young open cluster.
Description:
The extensive overall 12-site campaign resulted in almost 77500 images
and 92hr of photoelectric data in UBVI, spread over three observing
seasons (details in Saesen et al., 2010, cat. J/A+A/515/A16).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 150 131 Results of the multi-frequency fit to the U, B, V,
and I light curves of all B stars
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See also:
J/AJ/144/158 : Properties of B and Be stars in h and X Persei (Marsh+, 2012)
J/A+A/515/A16 : UBVI light curves of NGC 884 variables (Saesen+, 2010)
J/PASP/114/233 : h and χ Per memberships (Uribe+, 2002)
J/ApJ/576/880 : CCD UBV photometry of h and χ Per (Slesnick+, 2002)
J/A+A/325/987 : UBV magnitude of NGC 884 B-type pulsators (Krzesinski+ 1997)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- --- [Oo]
4- 7 I4 --- Oo [1898/2753] Star Oosterhoff number,
in Simbad
9- 10 A2 --- --- [f_]
11 I1 --- i [1/9]? Frequency identifier (1)
12 A1 --- --- [_]
14- 22 F9.6 d-1 f(i) ? Frequency fi of the observed mode (1)
24- 27 I4 Md-1 e_f(i) ? Uncertainty in f(i)
29 A1 --- f_f(i) [abc] Combined frequency (2)
31- 35 F5.2 mmag Uamp ? U band amplitude
37- 40 I4 10umag e_Uamp ? Uncertainty in Uamp
42- 45 F4.2 --- Uphi [0/1]? U band phase (1)
47- 50 I4 10-3 e_Uphi ? Uncertainty in Uphi
52- 54 F3.1 --- S/NU ? U band signal-to-noise (3)
56- 60 F5.2 mmag Bamp ? B band amplitude
62- 65 I4 10umag e_Bamp ? Uncertainty in B-A
67- 71 F5.3 --- Bphi [0/1]? B band phase (1)
73- 76 I4 10-3 e_Bphi ? Uncertainty in B-phi
78- 81 F4.1 --- S/NB ? B band signal-to-noise (3)
83- 87 F5.2 mmag Vamp ? V band amplitude
90- 92 I3 10umag e_Vamp ? Uncertainty in V-A
94- 98 F5.3 --- Vphi [0/1]? V band phase (1)
100-103 I4 10-3 e_Vphi ? Uncertainty in V-phi
105-108 F4.1 --- S/NV ? V band signal-to-noise (3)
110-114 F5.2 mmag Iamp ? I band amplitude
117-119 I3 10umag e_Iamp ? Uncertainty in I-A
121-125 F5.3 --- Iphi [0/1]? I band phase (1)
128-130 I3 10-3 e_Iphi ? Uncertainty in I-phi
132-134 F3.1 --- S/NI ? I band signal-to-noise (3)
136-150 A15 --- l Mode identification of the degree ℓ (4)
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Note (1): The signal is written as
C+Σi(Aisin(2πfi(t-t0)+2πφi)) with t0=HJD2453000,
and where Ai stands for amplitude, and +2πφi is the phase.
Note (2): Indicates combination frequencies, defined as follows:
a = 2*f1;
b = f3-f1;
c = f1-f2.
Note (3): S/N values are only provided when larger than 3.
Note (4): Based on elimination of degrees from 0 to 4. When specific degrees
were preferred on the basis of their χ2-values, the number is
followed by a "b". When none of the degree possibilities remained, we note
this by a "/". A blank line means we had insufficient information for
mode identification.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 16-Jul-2014