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J/AJ/152/167    Radial velocities of HD 133131A and HD 133131B    (Teske+, 2016)

The Magellan PFS planet search program: radial velocity and stellar abundance analyses of the 360 au, metal-poor binary "Twins" HD 133131A & B. Teske J.K., Shectman S.A., Vogt S.S., Diaz M., Butler R.P., Crane J.D., Thompson I.B., Arriagada P. <Astron. J., 152, 167-167 (2016)> =2016AJ....152..167T (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Planets ; Radial velocities ; Equivalent widths ; Abundances Keywords: planetary systems - planets and satellites: detection - stars: individual: (HD 133131A,HD133131B) - techniques: radial velocities - techniques: spectroscopic Abstract: We present a new precision radial velocity (RV) data set that reveals multiple planets orbiting the stars in the ∼360 au, G2+G2 "twin" binary HD133131AB. Our six years of high-resolution echelle observations from MIKE and five years from the Planet Finder Spectrograph (PFS) on the Magellan telescopes indicate the presence of two eccentric planets around HD133131A with minimum masses of 1.43±0.03 and 0.63±0.15MJ at 1.44±0.005 and 4.79±0.92au, respectively. Additional PFS observations of HD133131B spanning five years indicate the presence of one eccentric planet of minimum mass 2.50±0.05MJ at 6.40±0.59au, making it one of the longest-period planets detected with RV to date. These planets are the first to be reported primarily based on data taken with the PFS on Magellan, demonstrating the instrument's precision and the advantage of long-baseline RV observations. We perform a differential analysis between the Sun and each star, and between the stars themselves, to derive stellar parameters and measure a suite of 21 abundances across a wide range of condensation temperatures. The host stars are old (likely ∼9.5Gyr) and metal-poor ([Fe/H]~-0.30), and we detect a ∼0.03dex depletion in refractory elements in HD133131A versus B (with standard errors ∼0.017). This detection and analysis adds to a small but growing sample of binary "twin" exoplanet host stars with precise abundances measured, and represents the most metal-poor and likely oldest in that sample. Overall, the planets around HD133131A and B fall in an unexpected regime in planet mass-host star metallicity space and will serve as an important benchmark for the study of long-period giant planets. Description: The radial velocity observations of HD133131A and B are part of the large Magellan Planet Search Program, which began in 2002 and is surveying a sample of ∼500 of the nearest stars (<100pc). The survey was started with observations from the Magellan Inamori Kyocera Echelle (MIKE) echelle spectrograph, mounted for a limited time on the Magellan I (Baade), but mostly on Magellan II (Clay), 6.5m telescopes at Las Campanas Observatory. In 2010, the survey switched to using the Carnegie Planet Finder Spectrograph (PFS), a temperature-controlled high-resolution echelle spectrograph built for precision radial velocity observations, on Magellan II. Only HD133131A observations from MIKE are included here. Using a 0.35*5'' slit, MIKE provides spectra with R∼70000 in the blue and ∼50000 in the red and covers 3900-6200Å. Only the red MIKE orders are used for radial velocity determination, while the blue orders provide coverage of the CaIIH and K lines for monitoring stellar activity. The MIKE observations of HD133131A span 2003 June to 2009 July, with total exposure times ranging from 150 to 600s, depending on observing conditions. Both HD133131A and B were observed with PFS, the former observations ranging from 2010 February to 2015 September, and the latter from 2010 August to 2015 September. PFS has a more limited wavelength range than MIKE (3880-6680Å), but still covers the entire iodine wavelength region, CaIIH and K, and Hα. We use a 0.5*2.5'' slit for target observations, providing R∼80000 in the iodine region. The total exposure times for the A component range from 285 to 720s, and for the B component range from 282 to 800s. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file stars.dat 24 2 Stars observed table1.dat 32 17 Magellan Inamori Kyocera Echelle (MIKE) radial velocities and S-index values for HD133131A table2.dat 32 26 Planet Finder Spectrograph (PFS) radial velocities and S-index values for HD133131A table3.dat 32 25 Planet Finder Spectrograph (PFS) radial velocities and S-index values for HD133131B table7.dat 47 413 Measured lines and equivalent widths table8.dat 65 26 Derived stellar abundances
See also: III/159 : Ca II H and K Measurements Made at MWO (Duncan+ 1991) J/ApJ/819/19 : Equivalent widths of WASP-94A and WASP-94B (Teske+, 2016) J/ApJ/801/L10 : XO-2N and XO-2S equivalent widths (Teske+, 2015) J/ApJ/734/70 : Chromospheric activity of Southern stars (Arriagada, 2011) Byte-by-byte Description of file: stars.dat
Bytes Format Units Label Explanations
1- 8 A8 --- Name Name of the system 9 A1 --- m_Name Multiplicity on the system (A or B) 11- 14 I4 d Per1 Best-fit period (1) 16- 19 I4 d Per2 ? High eccentricity best-fit period for planet c around HD133131A (2) 21- 24 I4 d Per3 ? Low eccentricity best-fit period for planet c around HD133131A (2)
Note (1): Best-fit period for planet b around HD133131A from Table4 (see the paper), and best-fit one-planet period for HD133131B from Table5 (see the paper). Note (2): From Table4 (see the paper).
Byte-by-byte Description of file: table[123].dat
Bytes Format Units Label Explanations
1- 13 F13.5 d JD Julian Date 15- 20 F6.2 m/s RV [-45.8/63.2] Radial velocity 22- 25 F4.2 m/s e_RV [1/10] Uncertainty in RV 27- 32 F6.4 --- S [0.131/0.3851]? S-index (1)
Note (1): To evaluate the stellar activity levels of HD133131A and B, we measure Mt. Wilson S-index values in every radial velocity observation spectrum. The S-index compares the flux in triangle-weighted bins with Full-Widths at Half-Maximum (FWHMs) of 1.09Å centered on the CaII H&K lines (at 3968.47 and 3933.66Å) to the flux in two rectangular 20Å wide continuum regions centered on 3901 and 4001Å (Duncan et al. 1991, Cat. III/159). This index is known to be correlated with spot activity on the stellar surface, and serves as a proxy for chromospheric activity that could cause radial velocity shifts that mimic those induced by planets. Please refer to Section 4 in the paper for additional details about the S-index. Missing Magellan Inamori Kyocera Echelle (MIKE) HD133131A S-index values are due to the absence of a thorium argon (ThAr) calibration frame, which is necessary to derive a wavelength solution and an accurate S-index value.
Byte-by-byte Description of file: table7.dat
Bytes Format Units Label Explanations
1- 5 F5.1 --- Ion [6/106] Ion 7- 14 F8.3 0.1nm lambda [4218.72/6607] Wavelength λ (in Å) 16- 21 F6.4 eV EP [0/8.537] Excitation potential Χ 23- 29 F7.4 [-] loggf [-5/0.6] Log of the oscillator strength 31- 35 F5.1 0.1pm EWS [3.3/137.9] Equivalent width of the solar spectrum (EW) (in mÅ) 37- 41 F5.1 0.1pm EWA [1.8/117.8]? Equivalent width of the HD133131A spectrum (in mÅ) 43- 47 F5.1 0.1pm EWB [1.8/118.5]? Equivalent width of the HD133131B spectrum (in mÅ)
Byte-by-byte Description of file: table8.dat
Bytes Format Units Label Explanations
1- 5 A5 --- Species Species 7 A1 --- f_Species [ab] Flag on Species (a or b) (1) 9- 12 I4 K Tc [40/1741] Condensation temperature 14- 19 F6.3 [Sun] A-Vesta [-0.476/-0.242] Δ[X/H] abundance for the A-Vesta set of parameters (2) 21- 26 F6.3 [Sun] e_A-Vesta [-0.034/0.091] Total error in A-Vesta (3) 28- 33 F6.3 [Sun] B-Vesta [-0.449/-0.236] Δ[X/H] abundance for the B-Vesta set of parameters (4) 35- 39 F5.3 [Sun] e_B-Vesta [0.008/0.087] Total error in B-Vesta (3) 41- 46 F6.3 [Sun] B-A [-0.005/0.057] Δ[X/H] abundance for the B-A set of parameters (5) 48- 52 F5.3 [Sun] e_B-A [0.006/0.057] Total error in B-A (3) 54- 59 F6.3 [Sun] A-B [-0.05/0.007] Δ[X/H] abundance for the A-B set of parameters (5) 61- 65 F5.3 [Sun] e_A-B [0.007/0.058] Total error in A-B (3)
Note (1): The flag codes are defined as follows: a = These elements have only one line measured, so the line-to-line to scatter value adopted in their error calculation is the greatest line-to-line scatter from the rest of the elements with >3 lines measured; b = The errors on the oxygen abundances were conservatively estimated as the average of all the other elemental abundance errors, within each parameter set. Note (2): Comparing star HD133131A to the Sun. Our solar spectrum comes from Planet Finder Spectrograph (PFS) observations on 2016 January 7 UT of reflected sunlight from the asteroid Vesta. Note (3): Including line-to-line scatter and the errors propogated from each parameter uncertainty. Note (4): Comparing star HD133131B to the Sun. Our solar spectrum comes from Planet Finder Spectrograph (PFS) observations on 2016 January 7 UT of reflected sunlight from the asteroid Vesta. Note (5): Comparing the two stars (HD133131A and HD133131B) to each other.
History: From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 03-May-2017
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