J/AJ/155/24 Radial velocity and planet detectability in alpha Cen (Zhao+, 2018)
Planet detectability in the α Centauri system.
Zhao L., Fischer D.A., Brewer J., Giguere M., Rojas-Ayala B.
<Astron. J., 155, 24 (2018)>
=2018AJ....155...24Z 2018AJ....155...24Z (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Radial velocities
Keywords: planetary systems - planets and satellites: detection -
stars: fundamental parameters - stars: individual (Alpha Centauri) -
techniques: radial velocities
Abstract:
We use more than a decade of radial-velocity measurements for
α Cen A, B, and Proxima Centauri from the High Accuracy Radial
Velocity Planet Searcher, CTIO High Resolution Spectrograph, and the
Ultraviolet and Visual Echelle Spectrograph to identify the Msin(i),
and orbital periods of planets that could have been detected if they
existed. At each point in a mass-period grid, we sample a simulated,
Keplerian signal with the precision and cadence of existing data and
assess the probability that the signal could have been produced by
noise alone. Existing data places detection thresholds in the classically
defined habitable zones at about Msin(i) of 53 M⊕, for
α Cen A, 8.4 M⊕, for α Cen B, and 0.47 M⊕,
for Proxima Centauri. Additionally, we examine the impact of systematic
errors, or "red noise" in the data. A comparison of white- and red-noise
simulations highlights quasi-periodic variability in the radial
velocities that may be caused by systematic errors, photospheric
velocity signals, or planetary signals. For example, the red-noise
simulations show a peak above white-noise simulations at the period of
Proxima Centauri b. We also carry out a spectroscopic analysis of the
chemical composition of the α Centauri stars. The stars have
super-solar metallicity with ratios of C/O and Mg/Si that are similar
to the Sun, suggesting that any small planets in the α Cen system
may be compositionally similar to our terrestrial planets. Although
the small projected separation of α Cen A and B currently hampers
extreme-precision radial-velocity measurements, the angular separation
is now increasing. By 2019, α Cen A and B will be ideal targets
for renewed Doppler planet surveys.
Description:
In this work, we publish radial-velocity observations of α Cen A
and B, obtained at the Cerro Tololo Interamerican Observatory (CTIO)
with the Echelle Spectrograph (ES) from 2008-2010 and the CTIO High
Resolution (CHIRON) spectrograph. These data, together with archived data
from the High Accuracy Radial Velocity Planet Searcher (HARPS) and the
Ultraviolet and Visual Echelle Spectrograph (UVES) of α Cen B
and Proxima Centauri are used to test planet detectability and place
constraints on the mass and orbital periods of putative planets that
may remain undetected around these three stars.
Objects:
------------------------------------------------------------
RA (ICRS) DE Designation(s)
------------------------------------------------------------
14 39 36.20 -60 50 08.2 α Centauri = * alf Cen
14 39 36.49 -60 50 02.4 α Cen A = * alf Cen A
14 39 35.06 -60 50 15.1 α Cen B = * alf Cen B
------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 32 467 Relative, Binned RV Data from the Telescope
--------------------------------------------------------------------------------
See also:
J/A+A/328/261 : Spectroscopy of Alpha Cen (Neuforge-Verheecke+ 1997)
J/A+A/415/331 : HST/STIS spectra of alpha Cen A (Pagano+, 2004)
J/A+A/459/669 : JHKs photometry around α Cen (Kervella+, 2006)
J/A+A/464/373 : VRIZJHK photometry around Alpha Cen (Kervella+, 2007)
J/AJ/138/1037 : Star formation in Centaurus A Group dwarfs (Cote+ 2009)
J/A+A/615/A172 : alpha Cen A and B chemical composition (Morel, 2018)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 1 A1 --- Comp [AB] α Centauri component
3- 12 F10.4 d JD Observation date (JD-2440000)
14- 20 F7.2 m/s RV [-729.09/393.27] Radial velocity
22- 25 F4.2 m/s e_RV [0.86/8.91] Uncertainty in RV
27- 32 A6 --- Inst Instrument used, Echelle Spectrograph (ES) or
CHIRON
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 14-Sep-2018