Bibcode
Molnar, L.; Paparo, M.; Dhillon, V. S.; Marsh, T. R.; Østensen, R.; Lanteri, L.; Janulis, R.; Benatti, S.; Reed, M.; Lutz, R.; Kim, S.-L.; Schuh, S.; Silvotti, R.
Bibliographical reference
Astronomy and Astrophysics, Volume 611, id.A85, 13 pp.
Advertised on:
4
2018
Journal
Citations
18
Refereed citations
14
Description
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, in a previous article the
presence of a planet was inferred with an orbital period of 3.2 years
and a minimum mass of 3.2 MJup. Here we present an updated
O-C analysis using a larger data set of 1066 h of photometric time
series ( 2.5× 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 (p.)
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 analyzed. 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 p. for f1 and
f2: using only the data up to the end of 2008, we obtain
p.1 = (1.34 ± 0.04) ×
10-12 and p.2 = (1.62 ± 0.22)
× 10-12. The long-term variation of the two main
pulsation periods (and the change of sign of p.1)
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.
The complete set of data shown in Fig. 1 is only available at the CDS
via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/611/A85Based
on observations obtained at the following observatories: WHT 4.2m, TNG
3.6m, Calar Alto 2.2m, NOT 2.5m, Loiano 1.5m, LOAO 1.0m, MDM 1.3m,
Moletai 1.6m, MONET-North 1.2m, Piszkéstető 1.0m, Mercator
1.2m, Wise 1.0m, Lulin 1.0m, Baker 0.6m.
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