J/A+A/619/A2 Velocity curves of 3 open cluster stars (Delgado Mena+, 2018)
Planets around evolved intermediate-mass stars in open clusters.
II: Are there really planets around IC4651 No 9122, NGC2423 No 3
and NGC4349 No 127?
Delgado Mena E., Lovis C., Santos N.C., Gomes da Silva J., Mortier A.,
Tsantaki M., Sousa S.G., Figueira P., Cunha M.S., Campante T.L.,
Adibekyan V.Zh., Faria J.P., Montalto M.
<Astron. Astrophys. 619, A2 (2018)>
=2018A&A...619A...2D 2018A&A...619A...2D (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, double and multiple ; Radial velocities
Keywords: stars: individual: IC4651 No. 9122 -
stars: individual: NGC2423 No. 3 -
stars: individual: NGC4349 No. 127 - planetary systems -
planets and satellites: detection -
open clusters and associations: general
Abstract:
The aim of this work is to search for planets around intermediate-mass
stars in open clusters by using data from an extensive survey with
more than 15 years of observations.
We obtain high-precision radial velocities (RV) with the HARPS
spectrograph for a sample of 142 giant stars in 17 open clusters. We
fit Keplerian orbits when a significant periodic signal is detected.
We also study the variation of stellar activity indicators and
line-profile variations to discard stellar-induced signals.
We present the discovery of a periodic RV signal compatible with the
presence of a planet candidate in the 1.15Gyr open cluster IC4651
orbiting the 2.06M☉ star No. 9122. If confirmed, the planet
candidate would have a minimum mass of 7.2MJ and a period of 747
days. However, we also find that the FWHM of the CCF varies with a
period close to the RV, casting doubts on the planetary nature of the
signal. We also provide refined parameters for the previously
discovered planet around NGC2423 No. 3 but show evidence that the BIS
of the CCF is correlated with the RV during some of the observing
periods. This fact advises us that this might not be a real planet and
that the RV variations could be caused by stellar activity and/or
pulsations. Finally, we show that the previously reported signal by a
brown dwarf around NGC4349 No. 127 is presumably produced by stellar
activity modulation.
The long-term monitoring of several red giants in open clusters has
allowed us to find periodic RV variations in several stars. However,
we also show that the follow-up of this kind of stars should last more
than one orbital period to detect long-term signals of stellar origin.
This work warns that although it is possible to detect planets around
red giants, large-amplitude, long-period RV modulations do exist in
such stars that can mimic the presence of an orbiting planetary body.
Therefore, we need to better understand how such RV modulations behave
as stars evolve along the Red Giant Branch and perform a detailed
study of all the possible stellar-induced signals (e.g. spots,
pulsations, granulation) to comprehend the origin of RV variations.
Description:
The RV sample used in this work is fully described in Paper I, Lovis &
Mayor (2007A&A...472..657L 2007A&A...472..657L). The objects analyzed here have been
followed for nearly 5 years (from March 2005 to October 2009) with
HARPS (ESO-3.6m, La Silla) and some of them were also observed with
CORALIE (1.2 m-Swiss Telescope, La Silla) in previous years.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 72 3 List of studied stars
tableb1.dat 34 57 Radial velocities for IC 4651 No. 9122
tableb2.dat 34 45 Radial velocities for NGC 2423 No. 3
tableb3.dat 34 25 Radial velocities for NGC 4349 No. 127
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Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Name Star name
17- 18 I2 h RAh Right ascension (J2000)
20- 21 I2 min RAm Right ascension (J2000)
23- 27 F5.2 s RAs Right ascension (J2000)
29 A1 --- DE- Declination sign (J2000)
30- 31 I2 deg DEd Declination (J2000)
33- 34 I2 arcmin DEm Declination (J2000)
36- 39 F4.1 arcsec DEs Declination (J2000)
41- 51 A11 --- FileName Name of the table with radial velocity data
53- 72 A20 --- SName Simbad name
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Byte-by-byte Description of file: tableb1.dat tableb2.dat tableb3.dat
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Bytes Format Units Label Explanations
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1- 12 F12.6 d BJD Date of observation (BJD-2400000)
16- 24 F9.5 km/s RV Radial Velocity
28- 34 F7.5 km/s e_RV Error in Radial Velocity
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Acknowledgements:
Elisa Delgado Mena, elisa.delgado(at)astro.up.pt
References:
Lovis & Mayor, Paper I 2007A&A...472..657L 2007A&A...472..657L
(End) Elisa Delgado Mena [IA, Portugal], Patricia Vannier [CDS] 02-Aug-2018