J/AJ/159/235 Radial Velocity jitters in ∼600 planet host stars (Luhn+, 2020)
Astrophysical insights into radial velocity jitter from an analysis of 600
planet-search stars.
Luhn J.K., Wright J.T., Howard A.W., Isaacson H.
<Astron. J., 159, 235 (2020)>
=2020AJ....159..235L 2020AJ....159..235L
ADC_Keywords: Exoplanets; Spectra, optical; Radial velocities
Keywords: Radial velocity ; Exoplanet astronomy ; Stellar astronomy ;
Stellar phenomena ; Exoplanet detection methods
Abstract:
Radial velocity (RV) detection of planets is hampered by astrophysical
processes on the surfaces of stars that induce a stochastic signal, or
"jitter," which can drown out or even mimic planetary signals. Here,
we empirically and carefully measure the RV jitter of more than 600
stars from the California Planet Search sample on a star by star
basis. As part of this process, we explore the activity-RV correlation
of stellar cycles and include appendices listing every ostensibly
companion-induced signal we removed and every activity cycle we noted.
We then use precise stellar properties from
Brewer+, 2017ApJS..230...12B 2017ApJS..230...12B to separate the sample into bins of
stellar mass and examine trends with activity and with evolutionary
state. We find that RV jitter tracks stellar evolution and that in
general, stars evolve through different stages of RV jitter: the
jitter in younger stars is driven by magnetic activity, while the
jitter in older stars is convectively driven and dominated by
granulation and oscillations. We identify the "jitter minimum"-where
activity-driven and convectively driven jitter have similar
amplitudes-for stars between 0.7 and 1.7M☉ and find that
more-massive stars reach this jitter minimum later in their lifetime,
in the subgiant or even giant phases. Finally, we comment on how these
results can inform future RV efforts, from prioritization of follow-up
targets from transit surveys like the Transiting Exoplanet Survey
Satellite (TESS) to target selection of future RV surveys.
Description:
Observations were taken at Keck Observatory using the High Resolution
Echelle Spectrometer (HIRES) with resolution R∼55000. The California
Planet Search (CPS) employs a standard observing procedure for bright
stars that ensures uniform signal-to-noise ratio and
instrumental/algorithmic velocity precision on all bright FGK targets.
Typical values for a V=8magnitude star is a signal-to-noise ratio of
190 at 5800Å for an exposure of 90s.
Table1 lists the stars for which we included additional velocities as
well as the telescopes and spectrographs where the measurements were
taken.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 89 36 Summary of additional non-Keck-HIRES (High
Resolution Echelle Spectrometer) velocities
table2.dat 97 336 Orbital parameters of Keplerian signals subtracted
from Radial Velocities (RV) time series
table3.dat 63 617 RV jitter and analysis
refs.dat 65 83 References for table1 and table2
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See also:
III/159 : Ca II H and K Measurements Made at MWO (Duncan+ 1991)
IV/38 : TESS Input Catalog - v8.0 (TIC-8) (Stassun+, 2019)
J/A+A/390/267 : The CORALIE survey for extrasolar planets VIII (Udry+, 2002)
J/A+A/415/391 : The CORALIE survey for extrasolar planets. XII (Mayor+, 2004)
J/ApJS/159/141 : Spectroscopic properties of cool stars. I. (Valenti+, 2005)
J/ApJ/646/505 : Catalog of nearby exoplanets (Butler+, 2006)
J/PASP/118/1690 : Spitzer solar-type stars list (Meyer+, 2006)
J/ApJ/654/625 : Radial velocities of 9 long-period objects (Wittenmyer+,2007)
J/ApJ/687/1264 : Age estimation for solar-type dwarfs (Mamajek+, 2008)
J/A+A/480/L33 : Radial velocities of HD 4113 and HD 156846 (Tamuz+, 2008)
J/A+A/503/601 : HD17156 transit photo. & radial velocities (Barbieri+, 2009)
J/A+A/496/527 : Radial velocity curves of HD47186 and HD181433 (Bouchy+,2009)
J/A+A/498/L5 : Photometry and spectroscopy of HD 80606b (Moutou+, 2009)
J/ApJS/182/97 : Radial velocities of multi-planet systems (Wittenmyer+, 2009)
J/ApJ/693/1084 : Ten new and updated multiplanet systems (Wright+, 2009)
J/A+A/513/A69 : HD9446 radial velocity curve (Hebrard+, 2010)
J/ApJ/725/875 : Chromospheric activity for CPS stars (Isaacson+, 2010)
J/A+A/512/A48 : HARPS RV of HD125612, HD215497, HIP5158 (Lo Curto+, 2010)
J/ApJ/708/1366 : Radial velocities for 61 Vir (Vogt+, 2010)
J/ApJ/727/117 : Radial velocities of 4 exoplanet candidates (Meschiari+,2011)
J/A+A/526/A111 : Radial velocity of HD85390, 90156 & 103197 (Mordasini+, 2011)
J/A+A/534/A58 : HD20794, HD85512, HD192310 HARPS RVs (Pepe+, 2011)
J/A+A/545/A55 : Extrasolar planets. Radial velocities 5 stars (Boisse+, 2012)
J/A+A/538/A113 : Extrasolar planets. Radial velocities of 8 stars (Diaz+,2012)
J/ApJ/761/46 : HD 37605 radial velocities and photometry (Wang+, 2012)
J/ApJ/767/127 : Asteroseismic solutions for 77 Kepler stars (Huber+, 2013)
J/ApJ/776/67 : Rotational tracks (van Saders+, 2013)
J/ApJ/788/L9 : Stellar parameters of KIC planet-host stars (Bastien+, 2014)
J/ApJ/786/2 : Spitzer photometric time series HD97658 (Van Grootel+, 2014)
J/ApJ/800/135 : HARPS-N radial velocities of KOI-69 (Dressing+, 2015)
J/ApJS/225/32 : Extended abundance analysis of cool stars (Brewer+, 2016)
J/ApJ/821/89 : 12yrs of radial velocity obs. exoplanet systems (Bryan+,2016)
J/A+A/585/A134 : HD1461, HD40307, and HD204313 radial velocities (Diaz+, 2016)
J/ApJ/830/46 : RVs of 3 Neptune-mass planet hosts (Fulton+, 2016)
J/A+A/588/A145 : Radial velocities 8 stars with giant planets (Hebrard+, 2016)
J/ApJ/817/104 : Keck/HIRES radial velocity obs. of HD32963 (Rowan+, 2016)
J/AJ/153/208 : LCES HIRES/Keck RVs Exoplanet Survey (Butler+, 2017)
J/ApJ/835/25 : Calibrated solar S-index time series (Egeland+, 2017)
J/AJ/153/215 : Photometry and spectroscopy of KELT-11 (Pepper+, 2017)
J/AJ/155/126 : Radial velocities & photom. of K dwarf HD26965 (Diaz+, 2018)
J/ApJ/860/109 : Keck HIRES obs. of 245 subgiants (Ghezzi+, 2018)
J/AJ/157/149 : Transit parameters for planets around subgiants (Luhn+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Stellar identifier
11- 50 A40 --- Tel Telescope used
52- 79 A28 --- Inst Instrument used
81- 83 I3 --- Nobs [5/229] Number of observations
85- 89 A5 --- Ref Reference used
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Stellar identifier
11- 11 A1 --- f_Name [a]? Flag on Name (1)
13- 13 A1 --- Com Companion identifier
15- 22 F8.3 MJup msini [0.002/5266] Companion mass
24- 24 A1 --- l_P Limit flag on P (2)
25- 33 F9.3 d P [0.67/73000] Orbital period (3)
35- 39 F5.2 AU a [0.01/36] Semi-major axis
41- 50 F10.2 d Tp [2217697/5202518] Julian Date of periastron (3)
52- 56 F5.3 --- e [0/0.99] Eccentricity (3)
58- 62 F5.1 deg omega [0.9/360] Argument of periastron (ω) (3)
64- 71 F8.2 m/s K [0.2/81376] Velocity amplitude (3)
73- 80 F8.2 m/s gamma [-7394/8668] Constant offset (γ) (3)
82- 89 F8.5 m/s dvdt [-0.036/0.648] Linear trend (3)
91- 95 A5 --- Ref Orbit reference and bibcode
97 A1 --- f_Ref [*]? Flag on Ref; * = unconfirmed
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Note (1): Flag as follows:
a = HD 45350 is host to a known planet with a published period of 963
days (Endl+, 2006AJ....131.3131E 2006AJ....131.3131E). When using the best-fit parameters
from (ndl+, 2006AJ....131.3131E 2006AJ....131.3131E), we obtain a rather poor fit. In
fact, our resulting best fit is worse than when using a simple blind
fit for this star (reduced χ2 improves from 63 to 10, and the jitter
decreases from 8 to 4m/s). Given the large number of observations
after the publication of the most recent best fit, we are inclined to
believe that we have much better constraints on the orbital parameters
now, which we report in this table.
Note (2): Stars listed with periods>36500 have hit the maximum period
limit in RVLIN (Wright+, 2009ApJS..182..205W 2009ApJS..182..205W). In these cases we
believe the fit contains curvature but is a companion with period more
than 100years. We include the fit because we believe it to be
subtracting center of mass motions, despite a poorly-fit and
poorly-constrained period.
Note (3): These are the 7 orbital parameters output from RVLIN
(Wright+, 2009ApJS..182..205W 2009ApJS..182..205W). Mass and semi-major axis are
calculated from these parameters using the stellar mass. Orbit
reference lists the reference where the initial guesses to the fitting
procedure were obtained.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Stellar identifier
12- 20 F9.3 m/s jit [1.89/11390] Calculated radial velocity jitter
22- 29 F8.3 m/s e_jit [0.065/2748] Uncertainty in Jitter (1)
31- 33 I3 --- o_jit [5/911] Number of observations in Jitter (2)
35- 38 F4.2 [cm2/s] logg [2.81/4.69] log surface gravity
40- 43 F4.2 --- Sindex [0.03/0.88] Mount Wilson activity S-index
45 A1 --- BFF Blind fit flag; blind fit attempted (4)
47 I1 --- PF [1]? Planet Flag; Keplerian signal subtracted
49 I1 --- Np-p [0/4]? Number of published planets
51 I1 --- Np-u [0/3]? Number of unpublished planets
53 A1 --- LTF Linear trend flag; linear trend subtracted (3)
55 A1 --- Out Outlier(s) removed (3)
57 A1 --- RMSpu RMS uses only post-upgread Keck observations (3)
59 A1 --- Remove Pre-upgrade observations are discarded (3)
61 A1 --- Off Pre- and post-upgrade Keck offset (5)
63- 63 A1 --- No No alterations made to RVs (6)
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Note (1): In the calculation as given in Equation A5, Appendix A of the article.
Note (2): Note that while our criterion is that stars have more than 10
observations, we do not apply this criterion to the actual jitter
calculation, where we occasionally remove the observations before
the Keck upgrades in 2004 from the jitter calculation. This applies
to a total of 6 stars.
Note (3): A "x" means the flag is checked.
Note (4): The blind fit flag is used to show the stars for which no initial
inputs (i.e. published planets) were used in the fit. This flag does
not mean that the blind fit was accepted, merely that a blind fit
was attempted. Acceptance or rejection of a blind fit is further
indicated with the planet flag PF.
Note (5): The pre- and post-upgrade Keck velocities were treated as separate
telescopes with an offset between them.
Note (6): Flag that indicates stars for which no alterations were made to the
RVs. Note that because we first try a blind fit to every star without
published a published planet, this flag is equivalent to having
BFF=1 with no other flags checked. We include this column to
explicitly indicate stars for which the raw RVs were used to
calculate the RV RMS (no subtractions or removals).
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Ref Reference code
7- 25 A19 --- Author Main author of the reference
27- 45 A19 --- BIB Bibcode of the reference
47- 65 A19 --- Note Associated catalog or comment
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 15-Jun-2020