J/MNRAS/446/4008 RT Aur and SZ tau UBV light curves (Evans+, 2015)
Observations of Cepheids with the MOST satellite: contrast between pulsation
modes.
Evans N.R., Szabo R., Derekas A., Szabados L., Cameron C., Matthews J.M.,
Sasselov D., Kuschnig R., Rowe J.F., Guenther D.B., Moffat A.F.J.,
Rucinski S.M., Weiss W.W.
<Mon. Not. R. Astron. Soc., 446, 4008-4018 (2015)>
=2015MNRAS.446.4008E 2015MNRAS.446.4008E (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Photometry, UBV
Keywords: techniques: photometric - stars: individual: RT Aur -
stars: individual: SZ Tau - stars: variables: Cepheids
Abstract:
The quantity and quality of satellite photometric data strings is
revealing details in Cepheid variation at very low levels.
Specifically, we observed a Cepheid pulsating in the fundamental mode
and one pulsating in the first overtone with the Canadian MOST
(Microvariability and Oscillations of Stars) satellite. The 3.7-d
period fundamental mode pulsator (RT Aur) has a light curve that
repeats precisely, and can be modelled by a Fourier series very
accurately. The overtone pulsator (SZ Tau, 3.1d period) on the other
hand shows light-curve variation from cycle to cycle which we
characterize by the variations in the Fourier parameters. We present
arguments that we are seeing instability in the pulsation cycle of the
overtone pulsator, and that this is also a characteristic of the O-C
curves of overtone pulsators. On the other hand, deviations from cycle
to cycle as a function of pulsation phase follow a similar pattern in
both stars, increasing after minimum radius. In summary, pulsation in
the overtone pulsator is less stable than that of the fundamental mode
pulsator at both long and short time-scales.
Description:
The MOST satellite is a photometric satellite fully described in
Walker et al. (2003PASP..115.1023W 2003PASP..115.1023W), with the first science presented
in Matthews et al. (2004Natur.430...51M 2004Natur.430...51M).
For SZ Tau, observations were obtained in 2012 November
(JD 2456238 - JD 2456257) resulting in a continuous data set covering
19d with a cadence of 1-min. For RT Aur, the observations were carried
out in 2012 December 2012 (JD 2456278 - JD 2456300). For this
target, the 22d-long observations were interleaved with another
target, resulting in gaps in the light curve.
Objects:
-----------------------------------------------
RA (2000) DE Designation(s)
-----------------------------------------------
06 28 34.09 +30 29 34.9 RT Aur = HD 45412
04 37 14.78 +18 32 34.9 SZ Tau = HD 29260
-----------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 29 89 O-C values of RT Aurigae
table5.dat 29 38 O-C values of SZ Tauri
table6.dat 28 36 New UBV photometric data of SZ Tau
refs.dat 96 21 References
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 F10.4 d HJD Heliocentric Julian date (HJD-2400000)
12- 16 I5 --- E Epoch of the determination in cycles
18- 24 F7.4 d O-C Observed minus computed time
26 I1 --- W Weigth
28- 29 I2 --- Ref Reference for the data
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 F10.4 d HJD Heliocentric Julian date (HJD-2400000)
12- 16 F5.3 mag Vmag V magnitude
18- 22 F5.3 mag B-V B-V colour index
24- 28 F5.3 mag U-B ?=- U-B colour index
--------------------------------------------------------------------------------
Byte-by-byte Description of file: refs.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Ref Reference number
4- 22 A19 --- BibCode BibCode
24- 44 A21 --- Aut Author's name
46- 96 A51 --- Com Comments
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 23-Jul-2015