J/AJ/153/215 Photometry and spectroscopy of KELT-11 (Pepper+, 2017)
KELT-11b: A highly inflated sub-Saturn exoplanet transiting the V = 8 subgiant
HD 93396.
Pepper J., Rodriguez J.E., Collins K.A., Johnson J.A., Fulton B.J.,
Howard A.W., Beatty T.G., Stassun K.G., Isaacson H., Colon K.D., Lund M.B.,
Kuhn R.B., Siverd R.J., Gaudi B.S., Tan T.G., Curtis I., Stockdale C.,
Mawet D., Bottom M., James D., Zhou G., Bayliss D., Cargile P., Bieryla A.,
Penev K., Latham D.W., Labadie-Bartz J., Kielkopf J., Eastman J.D.,
Oberst T.E., Jensen E.L.N., Nelson P., Sliski D.H., Wittenmyer R.A.,
McCrady N., Wright J.T., Relles H.M., Stevens D.J., Joner M.D., Hintz E.
<Astron. J., 153, 215-215 (2017)>
=2017AJ....153..215P 2017AJ....153..215P (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Planets ; Photometry ;
Radial velocities
Keywords: planetary systems - planets and satellites: detection -
stars: individual: KELT-11 - techniques: photometric -
techniques: radial velocities
Abstract:
We report the discovery of a transiting exoplanet, KELT-11b, orbiting
the bright (V=8.0) subgiant HD93396. A global analysis of the system
shows that the host star is an evolved subgiant star with
Teff=5370±51K, M*=1.438-0.052+0.061M☉,
R*=2.72-0.17+0.21R☉, logg*=3.727-0.046+0.040, and
[Fe/H]=0.180±0.075. The planet is a low-mass gas giant in a
P=4.736529±0.00006 day orbit, with MP=0.195±0.018MJ,
RP=1.37-0.12+0.15RJ, ρP=0.093-0.024+0.028g/cm3,
surface gravity loggP=2.407-0.086+0.080, and equilibrium
temperature Teq=1712-46+51K. KELT-11 is the brightest known
transiting exoplanet host in the southern hemisphere by more than a
magnitude and is the sixth brightest transit host to date. The planet
is one of the most inflated planets known, with an exceptionally large
atmospheric scale height (2763km), and an associated size of the
expected atmospheric transmission signal of 5.6%. These attributes
make the KELT-11 system a valuable target for follow-up and
atmospheric characterization, and it promises to become one of the
benchmark systems for the study of inflated exoplanets.
Description:
KELT-11b is located in the Kilodegree Extremely Little Telescope
(KELT)-South field 23, which is centered at J2000
α=10h43m48s, δ=-20°00'00''. This field was
monitored from UT 2010 March 12 to UT 2014 July 9, resulting in 3910
images after post-processing and removal of bad images.
We obtained follow-up time-series photometry of KELT-11b. We obtained
nine full or partial transits in multiple bands between 2015 January
and 2016 February.
We observed an ingress of KELT-11b from the Westminster College
Observatory (WCO), PA, on UT 2015 January 1 in the I filter. The
observations employed a 0.35m f/11 Celestron C14 Schmidt-Cassegrain
telescope and SBIG STL-6303E CCD with a 3k*2k array of 9µm pixels,
yielding a 24'*16' field of view and 1.4''/pixel image scale at 3*3
pixel binning.
We observed a partial transit of KELT-11b using an 0.6m RCOS telescope
at the Moore Observatory (MORC), operated by the University of
Louisville. The telescope has an Apogee U16M 4K*4K CCD, giving a
26'*26' field of view and 0.39''/pixel. We observed the transit on UT
2015 February 08 in alternating Sloan g and i filters from before the
ingress and past the mid-transit.
We observed a transit of KELT-11b in the Sloan i-band using one of the
Miniature Exoplanet Radial Velocity Array (MINERVA) Project telescopes
(Swift et al. 2015JATIS...1b7002S 2015JATIS...1b7002S) on the night of UT 2015 February
08. MINERVA used four 0.7m PlaneWave CDK-700 telescopes that are
located on Mt. Hopkins, Arizona, at the Fred L. Whipple Observatory.
While the four telescopes are normally used to feed a single
spectrograph to discover and characterize exoplanets through radial
velocity measurements, for the KELT-11 observations, we used a single
MINERVA telescope in its photometric imaging mode. That telescope had
an Andor iKON-L 2048*2048 camera, which gave a field of view of
20.9'*20.9' and a plate scale of 0.6''/pixel. The camera has a
2048*2048 back-illuminated deep depletion sensor with fringe
suppression. Due to the brightness of KELT-11, we heavily defocused
for our observations, such that the image of KELT-11 was a "donut"
approximately 20 pixels in diameter.
On UT 2015 March 08, we observed a partial transit from the Perth
Exoplanet Survey Telescope (PEST) Observatory, located in Perth,
Australia. The observations were taken with a 0.3m Meade LX200
telescope working at f/5, and with a 31'*21' field of view. The camera
is an SBIG ST-8XME, with 1530*1020 pixels, yielding 1.2''/pixel. An
ingress was observed using a Cousins I filter.
On UT 2015 March 03, we observed a partial transit at the Ivan Curtis
Observatory (ICO), located in Adelaide, Australia. The observations
were taken with a 0.235m Celestron Schmidt-Cassegrain telescope with
an Antares 0.63x focal reducer, giving an overall focal ratio of
f/6.3. The camera is an Atik 320e, which uses a cooled Sony ICX274 CCD
of 1620*1220 pixels. The field of view is 16.6'*12.3', with a
resolution of 0.62''/pixel. An egress was observed using a Johnson R
filter.
We observed an ingress in the Sloan z-band at the Swarthmore College
Peter van de Kamp Observatory (PvdK) on 2015 March 18. The observatory
uses a 0.6m RCOS Telescope with an Apogee U16M 4K*4K CCD, giving a
26'*26' field of view. Using 2*2 binning, it has 0.76''/pixel.
We observed an egress of KELT-11b in the Sloan i-band during bright
time on UT 2015 May 04, using one of the 1m telescopes in the Las
Cumbres Observatory Global Telescope (LCOGT) network
(http://lcogt.net/) located at the South African Astronomical
Observatory (SAAO) in Sutherland, South Africa. The LCOGT telescopes
at SAAO have 4K*4K SBIG Science cameras and offer a 16'*16' field of
view and an unbinned pixel scale of 0.23''/pixel.
We observed one full transit of KELT-11b using the Manner-Vanderbilt
Ritchey-Chretien (MVRC) telescope located at the Mt. Lemmon summit of
the Steward Observatory, Arizona, on UT 2016 February 22 in the r'
filter. The observations employed a 0.6m f/8 RC Optical Systems
Ritchey-Chretien telescope and SBIG STX-16803 CCD with a 4k*4k array
of 9µm pixels, yielding a 26.6'*26.6' field of view and
0.39''/pixel image scale. The telescope was heavily defocused,
resulting in a typical "donut" shaped stellar PSF with a diameter of
∼25''.
We obtained spectroscopic observations of KELT-11. The observations
that provide radial velocity measurements are listed in Table6.
We obtained a spectrum with Tillinghast Reflector Echelle Spectrograph
(TRES), on the 1.5m telescope at the Fred Lawrence Whipple Observatory
(FLWO) on Mt. Hopkins, Arizona, on UT 2015 January 28. The spectrum
has a resolution of R=44000, a signal-to-noise ratio (S/N)=100.4.
Well before KELT observations of this star began, the radial velocity
of HD93396 had been monitored at the Keck Observatory using KECK High
Resolution Echelle Spectrometer (HIRES) starting in 2007 as part of
the "Retired A Stars" program (Johnson et al. 2006ApJ...652.1724J 2006ApJ...652.1724J,
2011ApJS..197...26J 2011ApJS..197...26J). Observations were conducted using the standard
setup of the California Planet Survey (Howard et al.
2010ApJ...721.1467H 2010ApJ...721.1467H; Johnson et al. 2010PASP..122..149J 2010PASP..122..149J) using the B5
decker and the iodine cell. Radial velocity measurements were made
with respect to a high S/N, iodine-free template observation (Butler
et al. 1996PASP..108..500B 1996PASP..108..500B), which we also use to measure the stellar
properties. Exposure times ranged from 50 to 120s depending on the
seeing, with an exposure meter ensuring that all exposures reached
S/N≃150 per pixel at 550nm.
To supplement the HIRES radial velocity spectra, we also observed
KELT-11 with the Levy spectrograph on the Automated Planet Finder
(APF) telescope at Lick Observatory. We collected 16 radial velocity
measurements between 2015 January 12 and 2015 November 4. The
observational setup was similar to the setup used for the APF
observations described in Fulton et al. (2015ApJ...810...30F 2015ApJ...810...30F). We
observed the star through a cell of gaseous iodine using the standard
1''*3'' slit for a spectral resolution of R≃100000, and
collected an iodine-free template spectrum using the 0.75''*8'' slit
(R≃120000, Vogt et al. 2014PASP..126..359V 2014PASP..126..359V). Exposure times
ranged from 18 to 30 minutes depending on seeing and transparency to
obtain S/N≃100pixel-1 at 550nm.
Objects:
-------------------------------------------------------------
RA (ICRS) DE Designation(s) (Period)
-------------------------------------------------------------
10 46 49.741 -09 23 56.48 KELT-11 = HD 93396 (P=4.7360001)
-------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
star.dat 43 1 Star observed
table3.dat 29 3910 Discovery light curve from Kilodegree Extremely
Little Telescope (KELT)
figure2.dat 44 4634 The individual follow-up observations of
KELT-11b from the Kilodegree Extremely Little
Telescope (KELT) follow-up network
table6.dat 40 32 KELT-11 radial velocity observations with High
Resolution Echelle Spectrometer (HIRES) and
Automated Planet Finder (APF)
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See also:
I/259 : The Tycho-2 Catalogue (Hog+ 2000)
J/ApJ/805/175 : Keck and APF radial velocities of HD7924 (Fulton+, 2015)
J/ApJ/761/123 : KELT-1 photometry and spectroscopy follow-up (Siverd+, 2012)
Byte-by-byte Description of file: star.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Name Star name
9- 10 I2 h RAh Hour of Right Ascension (J2000) (1)
12- 13 I2 min RAm Minute of Right Ascension (J2000) (1)
15- 20 F6.3 s RAs Second of Right Ascension (J2000) (1)
22 A1 --- DE- Sign of the Declination (J2000) (1)
23- 24 I2 deg DEd Degree of Declination (J2000) (1)
26- 27 I2 arcmin DEm Arcminute of Declination (J2000) (1)
29- 33 F5.2 arcsec DEs Arcsecond of Declination (J2000) (1)
35- 43 F9.7 d Per Period
--------------------------------------------------------------------------------
Note (1): From the Tycho-2 catalog (Hog et al. 2000, Cat. I/259).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 F14.6 d JD Julian Date (JDTT)
16- 22 F7.4 mag mag [-0.025/0.027] Relative Kilodegree Extremely
Little Telescope (KELT) magnitude
24- 29 F6.4 mag e_mag [0.001/0.0052] Uncertainty in mag
--------------------------------------------------------------------------------
Byte-by-byte Description of file: figure2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Obs Observatory code: either ICO, LCOGT-CPT, MINERVA,
MORC, MVRC, PEST, PvdK, or WCO (the full
observational details are provided in Table4 of
the paper) (1)
11 A1 --- Flt Filter used (Johnson R, Cousins I, I, Sloan g,
r', Sloan i, or Sloan z)
13- 26 F14.6 d BJD Barycentric Julian Date (BJDTDB)
28- 35 F8.6 --- Flux [0.96/1.023] Relative flux in Flt
37- 44 F8.6 --- e_Flux [0.000149/0.00182] Uncertainty in Flux
--------------------------------------------------------------------------------
Note (1): Observatory codes are defined as follows:
LCOGT-CPT = Las Cumbres Observatory Global Telescope-CPT;
MINERVA = Miniature Exoplanet Radial Velocity Array;
MORC = Moore Observatory RCOS telescope;
MVRC = Manner-Vanderbilt Ritchey-Chretien;
PEST = Perth Exoplanet Survey Telescope;
PvdK = Peter van de Kamp Observatory;
WCO = Westminster College Observatory;
ICO = Ivan Curtis Observatory.
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Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 F14.6 d BJD Barycentric Julian Date (BJDTDB)
16- 20 F5.1 m/s RV [-24/35.6] Radial velocity
22- 24 F3.1 m/s e_RV [1.3/3.7] Uncertainty in RV
26- 30 F5.1 m/s BS [-20.7/13.4]? Bisector span
32- 34 F3.1 m/s e_BS [1.7/8.8]? Uncertainty in BS
36- 40 A5 --- Inst Instrument used (HIRES or APF) (1)
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Note (1): The instruments used are defined as follows:
HIRES = Keck Observatory/High Resolution Echelle Spectrometer;
APF = Levy spectrograph on the Automated Planet Finder (APF) telescope at
Lick Observatory.
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History:
From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 21-Aug-2017