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J/A+A/611/A85       Time-series photometry of V391 Peg         (Silvotti+, 2018)

The sdB pulsating star V391 Peg and its putative giant planet revisited after 13 years of time-series photometric data. Silvotti R., Schuh S., Kim S.-L., Lutz R., Reed M., Benatti S., Janulis R., Lanteri L., Ostensen R., Marsh T.R., Dhillon V.S., 10 , Paparo M., Molnar L. <Astron. Astrophys. 611, A85 (2018)> =2018A&A...611A..85S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, horizontal branch ; Stars, subdwarf ; Photometry Keywords: stars: horizontal-branch - stars: oscillations - asteroseismology - stars: individual: V391 Peg - planets and satellites: detection - planets and satellites: individual: V391 Peg b Abstract: V391 Peg (alias HS 2201+2610) is a subdwarf B (sdB) pulsating star that shows both p- and g-modes. By studying the arrival times of the p-mode maxima and minima through the O-C method, the presence of a planet was inferred with an orbital period of 3.2yr and a minimum mass of 3.2MJup (Silvotti et al., 2007Natur.449..189S). In this article we present an updated O-C analysis using a larger data set of 1066 hours of photometric time series (∼2.5x larger in terms of the number of data points), which covers the period between 1999 and 2012 (compared with 1999-2006 of the previous analysis). Up to the end of 2008, the new O-C diagram of the main pulsation frequency (f1) is compatible with (and improves) the previous two-component solution representing the long-term variation of the pulsation period (parabolic component) and the giant planet (sine wave component). Since 2009, the O-C trend of f1 changes, and the time derivative of the pulsation period (dP/dt) passes from positive to negative; the reason of this change of regime is not clear and could be related to nonlinear interactions between different pulsation modes. With the new data, the O-C diagram of the secondary pulsation frequency (f2) continues to show two components (parabola and sine wave), like in the previous analysis. Various solutions are proposed to fit the O-C diagrams of f1 and f2 , but in all of them, the sinusoidal components of f1 and f2 differ or at least agree less well than before. The nice agreement found previously was a coincidence due to various small effects that are carefully analysed. Now, with a larger dataset, the presence of a planet is more uncertain and would require confirmation with an independent method. The new data allow us to improve the measurement of dP/dt for f1 and f2: using only the data up to the end of 2008, we obtain dP/dt1=(1.34±0.04)x10-12 and dP/dt2=(1.62±0.22)x10-12. The long-term variation of the two main pulsation periods (and the change of sign of dP/dt1) is visible also in direct measurements made over several years. The absence of peaks near f1 in the Fourier transform and the secondary peak close to f2 confirm a previous identification as l=0 and l=1, respectively, and suggest a stellar rotation period of about 40 days. The new data allow constraining the main g-mode pulsation periods of the star. Description: The table contains 217232 photometric measurements of V391 Peg b in relative flux. The mean value was set to zero in each single run. Most of them were taken with a Johnson B filter (more details in the paper). Some outlayers were removed. In many observations low-frequency variations were also removed using cubic spline interpolation or Fourier filtering. Objects: ---------------------------------------------------- RA (2000) DE Designation(s) ---------------------------------------------------- 22 04 12.11 +26 25 07.8 V391 Peg = HS 2201+2610 ---------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file figure1.dat 77 217232 Photometry
Byte-by-byte Description of file: figure1.dat
Bytes Format Units Label Explanations
1- 15 F15.10 d BJD Barycentric Julian Day (BJD-2450000) TDB (1) 18- 26 F9.6 --- RFlux Relative flux (2) 28- 77 A50 --- Comments Beginning of each observing run (3)
Note (1): the Barycentric Julian day is given in units of Barycentric Dynamical Time following Eastman et al. (2010PASP..122..935E). Note (2): relative flux is obtained by dividing the ADUs by the mean value of each observing run and subtracting 1 (F/<F>-1). Note (3): a symbol "#" in column 28 marks the beginning of each observing run. More information on telescopes/instruments/filters used is in the paper and in Silvotti et al. (2007Natur.449..189S).
Acknowledgements: Roberto Silvotti, silvotti(at)oato.inaf.it
(End) Patricia Vannier [CDS] 24-Nov-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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