J/AJ/152/112 Solar-type stars from SDSS-III MARVELS. VI. HD 87646 (Ma+, 2016)
Very low-mass stellar and substellar companions to solar-like stars from
MARVELS. VI. A giant planet and a brown dwarf candidate in a close binary system
HD 87646.
Ma B., Ge J., Wolszczan A., Muterspaugh M.W., Lee B., Henry G.W.,
Schneider D.P., Martin E.L., Niedzielski A., Xie J., Fleming S.W.,
Thomas N., Williamson M., Zhu Z., Agol E., Bizyaev D., da Costa L.N.,
Jiang P., Fiorenzano A.F.M., Hernandez J.I.G., Guo P., Grieves N., Li R.,
Liu J., Mahadevan S., Mazeh T., Nguyen D.C., Paegert M., Sithajan S.,
Stassun K., Thirupathi S., van Eyken J.C., Wan X., Wang J.,
Wisniewski J.P., Zhao B., Zucker S.
<Astron. J., 152, 112-112 (2016)>
=2016AJ....152..112M 2016AJ....152..112M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Radial velocities
Keywords: binaries: close - brown dwarfs - planetary systems
Abstract:
We report the detections of a giant planet (MARVELS-7b) and a brown
dwarf (BD) candidate (MARVELS-7c) around the primary star in the close
binary system, HD87646. To the best of our knowledge, it is the first
close binary system with more than one substellar circumprimary
companion that has been discovered. The detection of this giant planet
was accomplished using the first multi-object Doppler instrument
(KeckET) at the Sloan Digital Sky Survey (SDSS) telescope. Subsequent
radial velocity observations using the Exoplanet Tracker at the Kitt
Peak National Observatory, the High Resolution Spectrograph at the
Hobby Eberley telescope, the "Classic" spectrograph at the Automatic
Spectroscopic Telescope at the Fairborn Observatory, and MARVELS from
SDSS-III confirmed this giant planet discovery and revealed the
existence of a long-period BD in this binary. HD87646 is a close
binary with a separation of ∼22 au between the two stars,
estimated using the Hipparcos catalog and our newly acquired AO image
from PALAO on the 200inch Hale Telescope at Palomar. The primary star
in the binary, HD87646A, has Teff=5770±80K, logg=4.1±0.1, and
[Fe/H]=-0.17±0.08. The derived minimum masses of the two substellar
companions of HD87646A are 12.4±0.7MJup and 57.0±3.7MJup. The
periods are 13.481±0.001days and 674±4 days and the measured
eccentricities are 0.05±0.02 and 0.50±0.02 respectively. Our
dynamical simulations show that the system is stable if the binary
orbit has a large semimajor axis and a low eccentricity, which can be
verified with future astrometry observations.
Description:
We have obtained a total of 16 observations of HD87646 using the W.M.
Keck Exoplanet Tracker (KeckET) from 2006 December to 2007 June. The
radial velocities obtained are listed in Table1. The KeckET instrument
was constructed in 2005 August-2006 February with support from the
Keck Foundation. It was coupled with a wide field Sloan Digital Sky
Survey telescope (SDSS) and used for the pilot Multi-Object APO RV
Exoplanet Large-Area Survey (MARVELS). This is the sixth paper in this
series, examining the low-mass companions around solar-type stars from
the SDSS-III MARVELS survey (Wisniewski et al. 2012, Cat.
J/AJ/143/107; Fleming et al. 2012AJ....144...72F 2012AJ....144...72F; Ma et al.
2013AJ....145...20M 2013AJ....145...20M; Jiang et al. 2013AJ....146...65J 2013AJ....146...65J; De Lee et al.
2013AJ....145..155D 2013AJ....145..155D). The KeckET instrument consists of eight
subsystems-a multi-object fiber feed, an iodine cell, a fixed-delay
interferometer system, a slit, a collimator, a grating, a camera, and
a 4k*4k CCD detector. In addition, it contains four auxiliary
subsystems: the interferometer control, an instrument calibration
system, a photon flux monitoring system, and a thermal probe and
control system. The instrument is fed with 60 fibers with 200µm
core diameters, which are coupled to 180µm core diameter short
fibers from the SDSS telescope, corresponding to 3arcsec on the sky at
f/5. The resolving power for the spectrograph is R=5100, and the
wavelength coverage is ∼900Å, centered at 5400Å. KeckET has one
spectrograph and one 4k*4k CCD camera that captures one of the two
interferometer outputs, and has a 5.5% detection efficiency from the
telescope to the detector without the iodine cell under the typical
APO seeing conditions (∼1.5arcsec seeing). The CCD camera records
fringing spectra from 59 objects in a single exposure.
Subsequent observations were performed using the Exoplanet Tracker
(ET) instrument at Kitt Peak National Observatory (KPNO). Initial
follow-up was performed in 2007 November. Additional data points were
obtained at KPNO in 2008 January, February, and May. The integration
time was 35-40 minutes in 2007 November and 20 minutes in 2008
January, February, and May. A total of 40 data points were obtained
from 2007 November to 2008 May and are also listed in Table1.
Follow-up observations of HD87646 were conducted with the fiber-fed
High Resolution Spectrograph (HRS) of the Hobby Eberley telescope
(HET). The observations were executed in queue scheduled mode and used
a 2 arcsec fiber, with the HRS slit set, to yield a spectral
resolution of R∼60000. A total of 29 data points were obtained between
2007 December and 2008 March. The HRS spectra consisted of 46 echelle
orders recorded on the blue CCD (407-592nm) and 24 orders on the red
one (602-784nm). The spectral data used for RV measurements were
extracted from the 17 orders (505-592nm) in which the I2 cell
superimposed strong absorption lines. The radial velocities obtained
are also provided in Table1.
HD87646 was selected as an radial velocity survey target by the
Multi-object APO RV Exoplanet Large-area Survey (MARVELS) preselection
criterion. The star has been monitored at 23 epochs using the MARVELS
instrument mounted on the SDSS 2.5m Telescope at APO between 2009 May
and 2011 December. The MARVELS instrument is a fiber-fed dispersed
fixed-delay interferometer instrument capable of observing 60 objects
simultaneously and covers a wavelength range of 5000-5700Å with a
resolution of R∼12000. The final differential radial velocity products
are included in the SDSS Data Release 12 (Alam et al.
2015ApJS..219...12A 2015ApJS..219...12A) and are presented in Table1.
We have obtained additional observations of HD87646 with a fiber-fed
echelle spectrograph situated at the 2m Automatic Spectroscopic
Telescope (AST) in the Fairborn Observatory. Through 2011 June, the
detector was a 2048*4096 SITe ST-002A CCD with 15µm pixels. The AST
echelle spectrograph has 21 orders that cover the wavelength range of
4920-7100Å, and has an average resolution of 0.17Å. In the
summer of 2011, the SITe CCD detector and dewar were replaced with a
Fairchild 486 CCD having 4K*4K 15µm pixels, which required a new
readout electronics package, and a new dewar with a Cryotiger
refrigeration system. The echelle spectrograms that were obtained with
this new detector have 48 orders, covering the wavelength range of
3800-8260Å. A total of 135 data points were obtained from 2009
March through 2013 October and are listed in Table1.
Objects:
------------------------------------------------------------
RA (ICRS) DE Designation(s) (Period)
-------------------------------------------------------------
10 06 40.77 +17 53 42.4 HD 87646 = HIP 49522 (P=13.481)
-------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 42 246 Radial velocities for HD 87646
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See also:
V/130 : Geneva-Copenhagen Survey of Solar neighbourhood III (Holmberg+, 2009)
J/AJ/143/107 : Radial velocities of TYC 4110-01037-1 (Wisniewski+, 2012)
J/A+A/479/271 : HD 196885 radial velocities (Correia+, 2008)
J/ApJ/637/1102 : Lick indices for metal-rich stars (Robinson+, 2006)
J/A+A/426/695 : Radial velocities of HD 41004A/B (Zucker+, 2004)
J/A+A/404/775 : Radial velocities of HD 41004A/B (Zucker+, 2003)
J/A+A/392/215 : The CORALIE survey for extrasolar planets. IX. (Santos+ 2002)
J/ApJS/137/117 : Las Campanas Distant Cluster Survey (LCDCS) (Gonzales+, 2001)
J/A+AS/129/237 : G and K dwarfs abundances (Feltzing+ 1998)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Tel Telescope that obtained the data (1)
10- 30 F21.13 d JD Julian Date (UTC) of the observation
32- 38 F7.1 m/s RV [-1785/23320] Radial velocity
40- 42 I3 m/s e_RV [10/522] Error in RV
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Note (1): The number of observations is given after the description in ()s:
KeckET = The multi-object W.M. Keck Exoplanet Tracker (KeckET) pilot
survey (16);
KPNO = The Exoplanet Tracker (ET) instrument at KPNO (40);
HET = The fiber-fed High Resolution Spectrograph of
the Hobby Eberley telescope (29);
MARVELS = The MARVELS instrument mounted on the SDSS 2.5m Telescope
at APO (23);
Fairborn = The fiber-fed echelle spectrograph situated at the 2m Automatic
Spectroscopic Telescope in Fairborn Observatory (135).
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History:
From electronic version of the journal
References:
Wisniewski et al., Paper I 2012AJ....143..107W 2012AJ....143..107W, Cat. J/AJ/143/107
Fleming et al., Paper II 2012AJ....144...72F 2012AJ....144...72F
Ma et al., Paper III 2013AJ....145...20M 2013AJ....145...20M
Jiang et al., Paper IV 2013AJ....146...65J 2013AJ....146...65J
De Lee et al., Paper V 2013AJ....145..155D 2013AJ....145..155D
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 05-Dec-2016