J/ApJ/805/175 Keck and APF radial velocities of HD7924 (Fulton+, 2015)
Three super-earths orbiting HD 7924.
Fulton B.J., Weiss L.M., Sinukoff E., Isaacson H., Howard A.W., Marcy G.W.,
Henry G.W., Holden B.P., Kibrick R.I.
<Astrophys. J., 805, 175 (2015)>
=2015ApJ...805..175F 2015ApJ...805..175F (SIMBAD/NED BibCode)
ADC_Keywords: Radial velocities ; Stars, double and multiple ; Planets
Keywords: planetary systems; stars: individual: HD 7924
Abstract:
We report the discovery of two super-Earth-mass planets orbiting the
nearby K0.5 dwarf HD 7924, which was previously known to host one
small planet. The new companions have masses of 7.9 and 6.4M⊕,
and orbital periods of 15.3 and 24.5 days. We perform a joint analysis
of high-precision radial velocity data from Keck/HIRES and the new
Automated Planet Finder Telescope (APF) to robustly detect three total
planets in the system. We refine the ephemeris of the previously known
planet using 5yr of new Keck data and high-cadence observations over
the last 1.3yr with the APF. With this new ephemeris, we show that a
previous transit search for the inner-most planet would have covered
70% of the predicted ingress or egress times. Photometric data
collected over the last eight years using the Automated Photometric
Telescope shows no evidence for transits of any of the planets, which
would be detectable if the planets transit and their compositions are
hydrogen-dominated. We detect a long-period signal that we interpret
as the stellar magnetic activity cycle since it is strongly correlated
with the CaII H and K activity index. We also detect two additional
short-period signals that we attribute to rotationally modulated
starspots and a one-month alias. The high-cadence APF data help to
distinguish between the true orbital periods and aliases caused by the
window function of the Keck data. The planets orbiting HD 7924 are a
local example of the compact, multi-planet systems that the Kepler
Mission found in great abundance.
Description:
We collected 599 new RV measurements for HD 7924 over the last five
years since the discovery of HD 7924b (H09; Howard+,
2009ApJ...696...75H 2009ApJ...696...75H) using the HIRES spectrograph on the Keck I
telescope. When this new data is combined with the data from H09 and
APF we have over 10yr of observational baseline (see Figure 1(a)).
The APF is a 2.4m f/15 Cassegrain telescope built by Electro-optical
Systems Technologies housed in an IceStorm-2 dome located at Lick
Observatory atop Mount Hamilton, 20 miles east of San Jose, CA.
We collected 1855 differential photometry measurements of HD 7924
using the T8 0.8m automated photometric telescope (APT) at Fairborn
observatory in Arizona. The measurements were collected between 2006
December 31 and 2014 December 1.
Objects:
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RA (ICRS) DE Designation(s) (Period)
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01 21 59.11 +76 42 37.0 HD 7924 = HIP 6379 (Pb=5.3979 Pc=15.299 Pd=24.451)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 33 906 Radial velocities of HD 7924
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See also:
J/ApJ/784/45 : Kepler's multiple planet candidates. III. (Rowe+, 2014)
J/ApJS/210/20 : Small Kepler planets radial velocities (Marcy+, 2014)
J/ApJ/772/80 : Radial velocities of HAT-P-17 (Fulton+, 2013)
J/A+A/556/A150 : SWEETCat I. Stellar parameters for host stars (Santos+, 2013)
J/ApJ/768/155 : RVs and photometry of HD 38529 system (Henry+, 2013)
J/ApJS/204/24 : Kepler planetary candidates. III. (Batalha+, 2013)
J/ApJ/757/112 : Stellar diameters. II. K and M-stars (Boyajian+, 2012)
J/A+A/546/A61 : Radial velocities for XHIP catalogue (de Bruijne+, 2012)
J/ApJS/197/8 : Kepler's candidate mult. transiting planets (Lissauer+, 2011)
J/AJ/142/176 : Exoplanet host stars II. Speckle interferometry (Mason+, 2011)
J/AJ/142/84 : 10 new transit light curves of HAT-P-13b (Fulton+, 2011)
J/ApJ/733/68 : Exoplanet masses derived from RVs (Brown+, 2011)
J/PASP/123/412 : Exoplanet Orbit Database (Wright+, 2011)
J/ApJ/725/875 : Chromospheric activity for CPS stars (Isaacson+, 2010)
J/other/Sci/330.653 : Detected planets in the Eta-Earth Survey (Howard+, 2010)
J/other/A+ARV/18.67 : Accurate masses and radii of normal stars (Torres+, 2010)
J/A+A/507/487 : GJ 581 radial velocity curve (Mayor+, 2009)
J/ApJS/168/297 : Stellar parameters of nearby cool stars (Takeda+, 2007)
J/ApJS/159/141 : Spectroscopic properties of cool stars. I. (Valenti+, 2005)
http://exoplanets.org/ : Exoplanet Orbit database home page
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 13 F13.5 d BJDTDB Julian Date in Barycentric Dynamical Time
15- 20 F6.2 m/s RV [-12.2/14.3] Radial Velocity
22- 25 F4.2 m/s e_RV [0.7/3.1] Uncertainty in RV
27 A1 --- Inst Instrument (1)
29- 33 F5.3 --- SHK [0.1/0.3]? CaII H&K stellar activity index
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Note (1): Instrument as follows:
k = Keck/HIRES (pre-upgrade)
j = Keck/HIRES (post-upgrade)
a = Automated Planet Finder (APF) Telescope
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 17-Sep-2015