J/AJ/163/171 The EXPRES Stellar Signals Project. II. RVel (Zhao+, 2022)
The EXPRES Stellar Signals Project.
II. State of the Field in Disentangling Photospheric Velocities.
Zhao L.L., Fischer D.A., Ford E.B., Wise A., Cretignier M., Aigrain S.,
Barragan O., Bedell M., Buchhave L.A., Camacho J.D., Cegla H.M.,
Cisewski-Kehe J., Collier Cameron A., de Beurs Z.L., Dodson-Robinson S.,
Dumusque X., Faria J.P., Gilbertson C., Haley C., Harrell J., Hogg D.W.,
Holzer P., John A.A., Klein B., Lafarga M., Lienhard F., Maguire-Rajpaul V.,
Mortier A., Nicholson B., Palumbo M.L., Ramirez Delgado V., Shallue C.J.,
Vanderburg A., Viana P.T.P., Zhao J., Zicher N., Cabot S.H.C., Henry G.W.,
Roettenbacher R.M., Brewer J.M., Llama J., Petersburg R.R., Szymkowiak A.E.
<Astron. J., 163, 171 (2022)>
=2022AJ....163..171Z 2022AJ....163..171Z
ADC_Keywords: Exoplanets; Spectra, optical; Radial velocities
Keywords: Radial velocity ; Exoplanet detection methods ; Planet hosting
stars ; Stellar activity ; Spectrometers
Abstract:
Measured spectral shifts due to intrinsic stellar variability (e.g.,
pulsations, granulation) and activity (e.g., spots, plages) are the
largest source of error for extreme-precision radial-velocity (EPRV)
exoplanet detection. Several methods are designed to disentangle
stellar signals from true center-of-mass shifts due to planets. The
Extreme-precision Spectrograph (EXPRES) Stellar Signals Project (ESSP)
presents a self-consistent comparison of 22 different methods tested
on the same extreme-precision spectroscopic data from EXPRES. Methods
derived new activity indicators, constructed models for mapping an
indicator to the needed radial-velocity (RV) correction, or separated
out shape- and shift-driven RV components. Since no ground truth is
known when using real data, relative method performance is assessed
using the total and nightly scatter of returned RVs and agreement
between the results of different methods. Nearly all submitted methods
return a lower RV rms than classic linear decorrelation, but no method
is yet consistently reducing the RV rms to sub-meter-per-second
levels. There is a concerning lack of agreement between the RVs
returned by different methods. These results suggest that continued
progress in this field necessitates increased interpretability of
methods, high-cadence data to capture stellar signals at all
timescales, and continued tests like the ESSP using consistent data
sets with more advanced metrics for method performance. Future
comparisons should make use of various well-characterized data
sets-such as solar data or data with known injected planetary and/or
stellar signals-to better understand method performance and whether
planetary signals are preserved.
Description:
EXPRES is an optical (390-780nm), fiber-fed spectrograph with a median
resolution of R∼137000. The instrument was fully commissioned at the
4.3m Lowell Discovery Telescope (LDT) near Flagstaff, AZ in 2019
January and is being used for an RVel planet survey on about 125
(partial) nights per year.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 161 4 Stellar parameters
table3.dat 164 521 Chunk-by-chunk radial velocities
table5.dat 40 6604 Photometry and long-term trend
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See also:
J/ApJ/457/L99 : 25yr CaII-HK observations F-K nearby stars (Baliunas+, 1996)
J/ApJS/141/503 : Radial Velocities for 889 late-type stars (Nidever+, 2002)
J/A+A/495/959 : Radial velocity curve of HD 189733 (Boisse+, 2009)
J/A+A/506/303 : CoRoT-7 radial velocities (Queloz+, 2009)
J/ApJ/725/875 : Chromospheric activity for CPS stars (Isaacson+, 2010)
J/A+A/535/A55 : 4 stars with long-period planets (Dumusque+, 2011)
J/ApJ/746/101 : Diameters and temperatures of AFG stars (Boyajian+, 2012)
J/A+A/560/A61 : A frequency Comb calibrated solar atlas (Molaro+, 2013)
J/A+A/551/A79 : Radial velocity period variations in τCeti (Tuomi+, 2013)
J/A+A/566/A35 : Radial velocities of HD 41248 (Santos+, 2014)
J/ApJS/225/32 : Extended abundance analysis of cool stars (Brewer+, 2016)
J/A+A/593/A5 : Radial velocity fitting challenge dataset (Dumusque, 2016)
J/MNRAS/472/1618 : Kepler study of starspot lifetimes (Giles+, 2017)
J/A+A/607/A124 : K-G-F dwarfs stellar granulation variability (Meunier+, 2017)
J/MNRAS/474/2094 : Inferring probabilistic stellar rot periods (Angus+, 2018)
J/AJ/155/126 : Radial velocities & photometry of Kdwarf HD26965 (Diaz+, 2018)
J/A+A/636/A36 : Absolute radial velocities CARMENES M dwarfs (Lafarga+, 2020)
J/AJ/159/187 : 1st RVs with EXPRES spectrograph: 51Peg (Petersburg+, 2020)
J/A+A/639/A77 : Proxima Cen RV, FWHM and fluxes (Suarez Mascareno+, 2020)
J/AJ/161/26 : EXPRES II HD101501 photometry & radial velocity (Cabot+, 2021)
J/AJ/161/80 : Excalibur calib. method HD34411 RVs with EXPRESS (Zhao+, 2021)
J/AJ/163/19 : EXPRES III. Photo. & RVel of epsEridani (Roettenbacher+, 2022)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- HD Stellar identifier
11- 13 A3 --- SpT Spectral type
15- 18 F4.2 mag Vmag [3.5/5.34] V-band magnitude from
Ducati, 2002, II/237
20- 23 F4.2 mag B-V [0.62/0.82] B-V color from from
Ducati, 2002, II/237
25- 30 F6.3 [-] logRHK [-5.09/-4.48] Median log R'HK index from
Isaacson+, J/ApJ/725/875
32- 37 F6.3 [-] e_logRHK [-0.002] Error on logRHK
39- 44 F6.3 pc Dist [3.65/12.5] Distance
46- 50 F5.3 pc e_Dist [0.002/0.04] Error on Dist
52 A1 --- r_Dist References used for Dist (1)
54- 60 F7.3 km/s RVel [-42.3/66.6] Radial velocity
62- 67 F6.4 km/s e_RVel [0.0002/0.08] Error on radial velocity
69 A1 --- r_RVel References used for RVel (1)
71- 75 F5.3 Lsun Lum [0.45/1.74] Luminosity
77- 81 F5.3 Lsun e_Lum [0.002/0.03] Error on Lum
83 A1 --- r_Lum References used for Lum (1)
85- 88 F4.2 Rsun Rad [0.82/1.28] Radius from
Brewer+, 2016, J/ApJS/225/32
90- 93 F4.2 Rsun e_Rad [0.02/0.04] Error on Rad
95- 98 F4.2 Msun Mass [0.8/1.08] Mass from Brewer+, 2016, J/ApJS/225/32
100-103 F4.2 Msun e_Mass [0.1/0.2] Error on Mass
105-108 I4 K Teff [5092/5873] Effective temperature from
Brewer+, 2016, J/ApJS/225/32
110-111 I2 K e_Teff [25] Error on Teff
113-116 F4.2 [-] logg [4.26/4.6] Surface gravity from
Brewer+, 2016, J/ApJS/225/32
118-122 F5.3 [-] e_logg [0.028] Error on logg
124-128 F5.2 [-] Fe/H [-0.53/0.1] Log metallicity from
Brewer+, 2016, J/ApJS/225/32
130-133 F4.2 [-] e_Fe/H [0.01] Error on Fe/H
135-138 F4.1 Gyr Age [3.5/12.8] Age from Brewer+, 2016, J/ApJS/225/32
140-143 F4.1 Gyr e_Age [-3.1/-0.8] Negative error on Age
145-148 F4.1 Gyr E_Age [1/2.8] Positive error on Age
150-152 F3.1 km/s vsini [0.1/2.2] Rotational velocity from
Brewer+, 2016, J/ApJS/225/32
154-156 F3.1 km/s e_vsini [0.7] Error on vsini
158-161 F4.1 d Prot [17.1/40]? Rotation period from
Baliunas+, 1996, J/ApJ/457/L99
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Note (1): References as follows:
a = Gaia DR2, 2018, I/345
b = Hypparcos, 2007, I/311
c = Nidever+, 2002, J/ApJS/141/503
d = Boyajian+, 2012, J/ApJ/746/101
e = Pijpers, 2003A&A...400..241P 2003A&A...400..241P
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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- 9 A9 --- HD Target HD catalog number
11- 33 A23 --- Fits Spectrum FITS file name
35- 45 F11.5 d MJD [58524/59181] Modified Julian Date, JD-2400000.5
47- 47 I1 --- Epoch [4/5] Instrument Epoch (1)
49- 51 I3 --- SNR [147/318] Spectrum median signal-to-noise
53- 58 F6.3 m/s RVel1 [-9.33/8.56] CBC Radial velocity
60- 64 F5.3 m/s e_RVel1 [0.2/0.6] Uncertainty in RVel1
66- 75 F10.3 m/s RVel2 [-42348/66492] CCF Radial velocity
77- 81 F5.3 m/s e_RVel2 [0.1/0.5] Uncertainty in RVel2
83- 87 F5.3 --- SHK [0.09/0.31]? SHK Continuum normalized emission
in the CaH&K lines
89- 93 F5.3 --- Ha [0.16/0.24] Normalized Hα emission (2)
95- 99 F5.3 0.1nm EWHa [1.56/2.38] Hα Equivalent Width, Angstroms
101-108 F8.3 m/s FWHM [6510/7644] CCF FWHM
110-115 F6.3 m/s e_FWHM [19.3/35.6] Uncertainty in FWHM
117-124 F8.3 m/s BIS [-101/-36.8] Bisector span
126-132 F7.3 m/s Vspan [-79.1/76.2] Velocity span (3)
134-138 F5.3 m/s BIG [0.05/3.63] Bi-Gaussian skew parameter (4)
140-145 F6.3 --- Skew [-1.07/0.45] Skew Normal (5)
147-155 F9.6 mag gmag [-0.005/0.006] Photometric measurement at time
of RVel (6)
157-164 F8.6 mag e_gmag [0.0002/0.004] Uncertainty in gmag
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Note (1): As described in Petersburg+, 2020, J/AJ/159/187
Note (2): Normalized Hα
Note (3): Section 2.1.3, Boisse+, 2011A&A...528A...4B 2011A&A...528A...4B
Note (4): Section 2.1.3, Figueira+, 2013A&A...557A..93F 2013A&A...557A..93F
Note (5): Section 2.1.3, Simola+, 2019A&A...622A.131S 2019A&A...622A.131S
Note (6): Photometric measurement inter-/extra-polated to time stamp of the
RV using a GP model described in Section 2.2
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- HD Target HD catalog number
11- 19 F9.3 d MJD [49095/59023] Modified Julian Date, JD-2400000.5
21- 28 F8.5 mag by2 [-2.64/-0.61] (b+y)/2
30- 40 F11.8 mag Trend [-2.64/-0.62] Trend
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 28-Apr-2022