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 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 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
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
figure1.dat 77 217232 Photometry
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Byte-by-byte Description of file: figure1.dat
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Bytes Format Units Label Explanations
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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)
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Note (1): the Barycentric Julian day is given in units of Barycentric Dynamical
Time following Eastman et al. (2010PASP..122..935E 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/-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 2007Natur.449..189S).
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Acknowledgements:
Roberto Silvotti, silvotti(at)oato.inaf.it
(End) Patricia Vannier [CDS] 24-Nov-2017