J/AJ/159/57 HST spectroscopic LCs of Kepler 51b & 51d (Libby-Roberts+, 2020) ================================================================================ The featureless transmission spectra of two super-puff planets. Libby-Roberts J.E., Berta-Thompson Z.K., Desert J.-M., Masuda K., Morley C.V., Lopez E.D., Deck K.M., Fabrycky D., Fortney J.J., Line M.R., Sanchis-Ojeda R., Winn J.N. =2020AJ....159...57L ================================================================================ ADC_Keywords: Exoplanets; Spectra, infrared Keywords: Atmospheric composition ; Exoplanet atmospheres ; Exoplanet structure ; Exoplanet evolution ; Transit timing variation method ; Transits ; Hubble Space Telescope ; Exoplanets Abstract: The Kepler mission revealed a class of planets known as "super-puffs," with masses only a few times larger than Earth's but radii larger than Neptune, giving them very low mean densities. All three of the known planets orbiting the young solar-type star Kepler 51 are super-puffs. The Kepler 51 system thereby provides an opportunity for a comparative study of the structures and atmospheres of this mysterious class of planets, which may provide clues about their formation and evolution. We observed two transits each of Kepler 51b and 51d with the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope. Combining new WFC3 transit times with reanalyzed Kepler data and updated stellar parameters, we confirmed that all three planets have densities lower than 0.1g/cm^3^. We measured the WFC3 transmission spectra to be featureless between 1.15 and 1.63{mu}m, ruling out any variations greater than 0.6 scale heights (assuming a H/He-dominated atmosphere), thus showing no significant water absorption features. We interpreted the flat spectra as the result of a high-altitude aerosol layer (pressure <3mbar) on each planet. Adding this new result to the collection of flat spectra that have been observed for other sub-Neptune planets, we find support for one of the two hypotheses introduced by Crossfield & Kreidberg (2017AJ....154..261C), that planets with cooler equilibrium temperatures have more high-altitude aerosols. We strongly disfavor their other hypothesis that the H/He mass fraction drives the appearance of large-amplitude transmission features. Description: We observed two transits each of Kepler 51b and 51d with the infrared channel of Wide Field Camera 3 (WFC3) on Hubble Space Telescope (HST) (Cycle 23, GO#14218, PI Berta-Thompson). We used the G141 grism for all observations, providing slitless spectroscopy across the 1.1-1.7{mu}m wavelength range. HST successfully observed transits on 2015 September 29 and 2016 June 26 for Kepler 51b and on 2015 December 31 and 2017 January 24 for Kepler 51d. Objects: ------------------------------------------------------------------- RA (2000) DE Designation(s) (Period) ------------------------------------------------------------------- 19 45 55.142 +49 56 15.65 Kepler51b = KOI-620.01 (P=45.154) 19 45 55.14 +49 56 15.6 Kepler51c = KOI-620.03 (P=85.313) 19 45 55.14 +49 56 15.7 Kepler51d = KOI-620.02 (P=130.184) ------------------------------------------------------------------- File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table3.dat 713 774 HST Wide Field Camera 3 (WFC3) spectroscopic light curve data table9.dat 203 5100 *Markov Chain Monte Carlo (MCMC) samples from our transit timing variations (TTV) analysis -------------------------------------------------------------------------------- Note on table9.dat : Planet b,c and d reffers to Kepler 51b, Kepler 51c and Kepler 51d. -------------------------------------------------------------------------------- See also: II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) V/133 : Kepler Input Catalog (Kepler Mission Team, 2009) I/337 : Gaia DR1 (Gaia Collaboration, 2016) I/345 : Gaia DR2 (Gaia Collaboration, 2018) J/A+A/331/81 : Hyades membership (Perryman+ 1998) J/AJ/142/112 : KIC photometric calibration (Brown+, 2011) J/ApJ/736/19 : Kepler planetary candidates. II. (Borucki+, 2011) J/ApJ/747/35 : HST/WFC3 transit observation of GJ1214b (Berta+, 2012) J/ApJ/750/113 : Kepler TTVs. II. Confirmed multiplanet systems (Ford+, 2012) J/ApJ/775/L11 : Stellar rotation periods for KOIs (McQuillan+, 2013) J/ApJS/210/19 : Kepler planetary candidates. IV. 22 months (Burke+, 2014) J/ApJS/214/25 : Rosseland & Planck gaseous mean opacities (Freedman+, 2014) J/ApJ/785/15 : Transit times for Kepler-79's planets (Jontof-Hutter+, 2014) J/ApJS/217/31 : Kepler planetary candidates. VI. 4yr Q1-Q16 (Mullally+, 2015) J/AJ/154/5 : Transit timing variations of 145 Kepler planets (Hadden+, 2017) J/AJ/154/108 : California-Kepler Survey (CKS). II. Properties (Johnson+, 2017) J/AJ/153/142 : Radial velocities systems hosting sub-Saturns (Petigura+, 2017) J/AJ/156/264 : California-Kepler Survey. VII. Planet radius gap (Fulton+,2018) J/A+A/616/A10 : 46 open clusters GaiaDR2 HR diagrams (Gaia Collaboration, 2018) J/AJ/157/174 : Transiting planets Kepler-47 circumbinary system (Orosz+, 2019) Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 16 F16.8 d BJD [2457294/2457780] Barycentric Julian date at TDB of mid-exposure 18- 31 F14.12 --- F1152-1176 [0.986/1.009] Relative spectrum flux from 1.152-1.176{mu}m 33- 48 F16.14 --- e_F1152-1176 [0.002/0.003] Relative spectrum flux uncertainty from 1.152-1.176{mu}m 50- 63 F14.12 --- F1176-1200 [0.986/1.007] Relative spectrum flux from 1.176-1.200{mu}m 65- 80 F16.14 --- e_F1176-1200 [0.002/0.003] Relative spectrum flux uncertainty from 1.176-1.200{mu}m 82- 95 F14.12 --- F1200-1223 [0.985/1.008] Relative spectrum flux from 1.200-1.223{mu}m 97-112 F16.14 --- e_F1200-1223 [0.001/0.003] Relative spectrum flux uncertainty from 1.200-1.223{mu}m 114-127 F14.12 --- F1223-1247 [0.986/1.007] Relative spectrum flux from 1.223-1.247{mu}m 129-144 F16.14 --- e_F1223-1247 [0.001/0.002] Relative spectrum flux uncertainty from 1.223-1.247{mu}m 146-159 F14.12 --- F1247-1271 [0.985/1.009] Relative spectrum flux from 1.247-1.271{mu}m 161-176 F16.14 --- e_F1247-1271 [0.001/0.002] Relative spectrum flux uncertainty from 1.247-1.271{mu}m 178-191 F14.12 --- F1271-1294 [0.987/1.008] Relative spectrum flux from 1.271-1.294{mu}m 193-208 F16.14 --- e_F1271-1294 [0.001/0.002] Relative spectrum flux uncertainty from 1.271-1.294{mu}m 210-223 F14.12 --- F1294-1318 [0.985/1.008] Relative spectrum flux from 1.294-1.318{mu}m 225-240 F16.14 --- e_F1294-1318 [0.001/0.002] Relative spectrum flux uncertainty from 1.294-1.318{mu}m 242-255 F14.12 --- F1318-1342 [0.986/1.008] Relative spectrum flux from 1.318-1.342{mu}m 257-272 F16.14 --- e_F1318-1342 [0.001/0.002] Relative spectrum flux uncertainty from 1.318-1.342{mu}m 274-287 F14.12 --- F1342-1366 [0.986/1.007] Relative spectrum flux from 1.342-1.366{mu}m 289-304 F16.14 --- e_F1342-1366 [0.001/0.002] Relative spectrum flux uncertainty from 1.342-1.366{mu}m 306-319 F14.12 --- F1366-1389 [0.985/1.008] Relative spectrum flux from 1.366-1.389{u}m 321-336 F16.14 --- e_F1366-1389 [0.001/0.002] Relative spectrum flux uncertainty from 1.366-1.389{mu}m 338-351 F14.12 --- F1389-1413 [0.986/1.008] Relative spectrum flux from 1.389-1.413{mu}m 353-368 F16.14 --- e_F1389-1413 [0.001/0.002] Relative spectrum flux uncertainty from 1.389-1.413{mu}m 370-383 F14.12 --- F1413-1437 [0.986/1.008] Relative spectrum flux from 1.413-1.437{mu}m 385-400 F16.14 --- e_F1413-1437 [0.001/0.002] Relative spectrum flux uncertainty from 1.413-1.437{mu}m 402-415 F14.12 --- F1437-1460 [0.987/1.008] Relative spectrum flux from 1.437-1.460{mu}m 417-432 F16.14 --- e_F1437-1460 [0.001/0.003] Relative spectrum flux uncertainty from 1.437-1.460{mu}m 434-447 F14.12 --- F1460-1484 [0.987/1.007] Relative spectrum flux from 1.460-1.484{mu}m 449-464 F16.14 --- e_F1460-1484 [0.001/0.003] Relative spectrum flux uncertainty from 1.460-1.484{mu}m 466-479 F14.12 --- F1484-1508 [0.986/1.009] Relative spectrum flux from 1.484-1.508{mu}m 481-496 F16.14 --- e_F1484-1508 [0.001/0.003] Relative spectrum flux uncertainty from 1.484-1.508{mu}m 498-511 F14.12 --- F1508-1531 [0.984/1.01] Relative spectrum flux from 1.508-1.531{mu}m 513-528 F16.14 --- e_F1508-1531 [0.002/0.003] Relative spectrum flux uncertainty from 1.508-1.531{mu}m 530-543 F14.12 --- F1531-1555 [0.985/1.008] Relative spectrum flux from 1.531-1.555{mu}m 545-560 F16.14 --- e_F1531-1555 [0.002/0.003] Relative spectrum flux uncertainty from 1.531-1.555{mu}m 562-575 F14.12 --- F1555-1579 [0.985/1.01] Relative spectrum flux from 1.555-1.579{mu}m 577-592 F16.14 --- e_F1555-1579 [0.002/0.003] Relative spectrum flux uncertainty from 1.555-1.579{mu}m 594-607 F14.12 --- F1579-1602 [0.98/1.1] Relative spectrum flux from 1.579-1.602{mu}m 609-624 F16.14 --- e_F1579-1602 [0.002/0.003] Relative spectrum flux uncertainty from 1.579-1.602{mu}m 626-639 F14.12 --- F1602-1625 [0.986/1.009] Relative spectrum flux from 1.602-1.625{mu}m 641-656 F16.14 --- e_F1602-1625 [0.002/0.003] Relative spectrum flux uncertainty from 1.602-1.625{mu}m 658-669 F12.10 ct/pix/s Sky [0.73/1.9] Sky background, in photoelectrons/pixel/s 671-683 F13.10 pix Ypos [-0.24/0.26] Vertical centroid of the spectral trace on the detector 685-696 F12.10 --- Slope [0.007/0.01] Slope of the spectral trace on the detectors; in pixels/pixel units 698-709 F12.10 pix Width [0.72/0.78] Width of the spectral trace on the detector 711-711 A1 --- ID [bd] Planet identifier (1) 713-713 I1 --- Nvis [1/2] Visit Number -------------------------------------------------------------------------------- Note (1): Identifier as follows: b = Kepler 51b (308 occurrences) d = Kepler 51d (466 occurrences) -------------------------------------------------------------------------------- Byte-by-byte Description of file: table9.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 13 E13.8 --- Mb/M* Planet "b" to star mass ratio 15- 27 E13.8 d Perb [45.1528/45.156] Orbital period, planet "b" 29- 40 E12.7 --- ecoswb [-0.21/0.03] Sqrt(e_b_)Cos({omega}_b_), planet "b" (1) 42- 53 E12.7 --- esinwb [-0.3/0.05] Sqrt(e_b_)Sin({omega}_b_), planet "b" (1) 55- 67 E13.8 d T0b [159.1/159.2] Time, first inferior conjunction, planet "b" (2) 69- 81 E13.8 --- Mc/M* Planet "c" to star mass ratio 83- 95 E13.8 d Perc [85.3/85.321] Orbital period, planet "c" 97-108 E12.7 --- ecoswc [-0.173/0.235] Sqrt(e_c_)Cos({omega}_c_), planet "c" (1) 110-121 E12.7 --- esinwc [-0.312/0.19] Sqrt(e_c_)Sin({omega}_c_), planet "c" (1) 123-135 E13.8 d T0c [295.309/295.332] Time, first inferior conjunction, planet "c" (2) 137-149 E13.8 --- Md/M* Planet "d" to star mass ratio 151-163 E13.8 d Perd [130.1819/130.188] Orbital Period, planet "d" 165-176 E12.7 --- ecoswd [-0.17/0.21] Sqrt(e_d_)Cos({omega}_d_), planet "d" (1) 178-189 E12.7 --- esinwd [-0.282/0.17] Sqrt(e_d_)Sin({omega}_d_), planet "d" (1) 191-203 E13.8 d T0d [212.021/212.0261] Time, first inferior conjunction, planet "d" (2) -------------------------------------------------------------------------------- Note (1): With "e" the eccentricity and "{omega}" the argument of periastron of the planet. Note (2): T0 is the time of first inferior conjunction assuming a Keplerian orbit (BJD-2454833). -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Prepared by [AAS], Coralie Fix [CDS], 19-Mar-2020