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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 (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) 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 ( 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, 2011ApJS..197...26J). Observations were conducted using the standard setup of the California Planet Survey (Howard et al. 2010ApJ...721.1467H; Johnson et al. 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), 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). 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). 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)
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.
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)
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.
History: From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 21-Aug-2017
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