HIGH-CADENCE, HIGH-CONTRAST IMAGING FOR EXOPLANET MAPPING: OBSERVATIONS OF THE HR 8799 PLANETS WITH VLT/SPHERE SATELLITE-SPOT-CORRECTED RELATIVE PHOTOMETRY

Time-resolved photometry is an important new probe of the physics of condensate clouds in extrasolar planets and brown dwarfs. Extreme adaptive optics systems can directly image planets, but precise brightness measurements are challenging. We present VLT/SPHERE high-contrast, time-resolved broad H-band near-infrared photometry for four exoplanets in the HR 8799 system, sampling changes from night to night over five nights with relatively short integrations. The photospheres of these four planets are often modeled by patchy clouds and may show large-amplitude rotational brightness modulations. Our observations provide high-quality images of the system. We present a detailed performance analysis of different data analysis approaches to accurately measure the relative brightnesses of the four exoplanets. We explore the information in satellite spots and demonstrate their use as a proxy for image quality. While the brightness variations of the satellite spots are strongly correlated, we also identify a second-order anti-correlation pattern between the different spots. Our study finds that PCA-based KLIP reduction with satellite spot-modulated artificial planet-injection based photometry (SMAP) leads to a significant (~3x) gain in photometric accuracy over standard aperture-based photometry and reaches 0.1 mag per point accuracy for our dataset, the signal-to-noise of which is limited by small field rotation. Relative planet-to-planet photometry can be compared be- tween nights, enabling observations spanning multiple nights to probe variability. Recent high-quality relative H-band photometry of the b-c planet pair agree to about 1%.

[1]  Andrew Serio,et al.  THE FIRST H-BAND SPECTRUM OF THE GIANT PLANET β PICTORIS b , 2014, 1407.4469.

[2]  Discovery of Rotational Modulations in the Planetary-Mass Companion 2M1207b: Intermediate Rotation Period and Heterogeneous Clouds in a Low Gravity Atmosphere , 2015, 1512.02706.

[3]  Daniel Apai,et al.  HST SPECTRAL MAPPING OF L/T TRANSITION BROWN DWARFS REVEALS CLOUD THICKNESS VARIATIONS , 2013, 1303.4151.

[4]  David Le Mignant,et al.  High contrast polarimetry in the infrared with SPHERE on the VLT , 2014, Astronomical Telescopes and Instrumentation.

[5]  A. Heinze,et al.  WEATHER ON OTHER WORLDS. III. A SURVEY FOR T DWARFS WITH HIGH-AMPLITUDE OPTICAL VARIABILITY , 2014, 1412.6733.

[6]  Michael C. Liu,et al.  VARIABILITY IN A YOUNG, L/T TRANSITION PLANETARY-MASS OBJECT , 2015, 1510.07625.

[7]  B. Macintosh,et al.  Angular Differential Imaging: A Powerful High-Contrast Imaging Technique , 2005, astro-ph/0512335.

[8]  Tae-Soo Pyo,et al.  A COMBINED SUBARU/VLT/MMT 1–5 μm STUDY OF PLANETS ORBITING HR 8799: IMPLICATIONS FOR ATMOSPHERIC PROPERTIES, MASSES, AND FORMATION , 2011, 1101.1973.

[9]  R. Soummer,et al.  DETECTION AND CHARACTERIZATION OF EXOPLANETS AND DISKS USING PROJECTIONS ON KARHUNEN–LOÈVE EIGENIMAGES , 2012, 1207.4197.

[10]  C. Baranec,et al.  RECONNAISSANCE OF THE HR 8799 EXOSOLAR SYSTEM. II. ASTROMETRY AND ORBITAL MOTION , 2014, 1409.6388.

[11]  David Lafreniere,et al.  PHOTOMETRIC VARIABILITY OF THE T2.5 BROWN DWARF SIMP J013656.5+093347: EVIDENCE FOR EVOLVING WEATHER PATTERNS , 2009, 0906.3514.

[12]  I. Reid,et al.  CLOUD STRUCTURE OF THE NEAREST BROWN DWARFS: SPECTROSCOPIC VARIABILITY OF LUHMAN 16AB FROM THE HUBBLE SPACE TELESCOPE , 2014, 1411.0003.

[13]  Etienne Artigau,et al.  LARGE-AMPLITUDE VARIATIONS OF AN L/T TRANSITION BROWN DWARF: MULTI-WAVELENGTH OBSERVATIONS OF PATCHY, HIGH-CONTRAST CLOUD FEATURES , 2012, 1201.3403.

[14]  I. Reid,et al.  BROWN DWARF PHOTOSPHERES ARE PATCHY: A HUBBLE SPACE TELESCOPE NEAR-INFRARED SPECTROSCOPIC SURVEY FINDS FREQUENT LOW-LEVEL VARIABILITY , 2013, 1312.5294.

[15]  Bernd Freytag,et al.  WEATHER ON THE NEAREST BROWN DWARFS: RESOLVED SIMULTANEOUS MULTI-WAVELENGTH VARIABILITY MONITORING OF WISE J104915.57−531906.1AB , 2013, 1310.5144.

[16]  T. Fusco,et al.  First light of the VLT planet finder SPHERE II. The physical properties and the architecture of the young systems PZ Telescopii and HD 1160 revisited , 2015, 1511.04072.

[17]  D. Fantinel,et al.  First light of the VLT planet finder SPHERE IV : Physical and chemical properties of the planets around HR8799 , 2015, 1511.04082.

[18]  R. Street,et al.  A MONITORING CAMPAIGN FOR LUHMAN 16AB. I. DETECTION OF RESOLVED NEAR-INFRARED SPECTROSCOPIC VARIABILITY , 2014, 1402.2342.

[19]  Anthony Boccaletti,et al.  Near-Infrared Detection and Characterization of the Exoplanet HD 95086 b with the Gemini Planet Imager , 2014, 1404.4635.

[20]  B. Macintosh,et al.  Images of a fourth planet orbiting HR 8799 , 2010, Nature.

[21]  C. Marois,et al.  Accurate Astrometry and Photometry of Saturated and Coronagraphic Point Spread Functions , 2006, astro-ph/0604256.

[22]  D. Fantinel,et al.  First light of the VLT planet finder SPHERE - III. New spectrophotometry and astrometry of the HR 8799 exoplanetary system , 2015, 1511.04083.

[23]  A. Lagrange,et al.  THE INNER DISK STRUCTURE, DISK–PLANET INTERACTIONS, AND TEMPORAL EVOLUTION IN THE β PICTORIS SYSTEM: A TWO-EPOCH HST/STIS CORONAGRAPHIC STUDY , 2015, 1501.03181.

[24]  C. Fabron,et al.  SPHERE: a planet finder instrument for the VLT , 2006, Astronomical Telescopes + Instrumentation.

[25]  Bruce Macintosh,et al.  SIMULTANEOUS DETECTION OF WATER, METHANE, AND CARBON MONOXIDE IN THE ATMOSPHERE OF EXOPLANET HR 8799 b , 2015, 1503.03539.

[26]  B. Macintosh,et al.  Direct Imaging of Multiple Planets Orbiting the Star HR 8799 , 2008, Science.

[27]  Jr.,et al.  RECONNAISSANCE OF THE HR 8799 EXOSOLAR SYSTEM. I. NEAR-INFRARED SPECTROSCOPY , 2013, 1303.2627.

[28]  R. Soummer Apodized Pupil Lyot Coronagraphs for Arbitrary Telescope Apertures , 2004, astro-ph/0412221.

[29]  Julien H. Girard,et al.  The near-infrared spectral energy distribution of β Pictoris b , 2013, 1302.1160.

[30]  Peter Plavchan,et al.  WEATHER ON OTHER WORLDS. II. SURVEY RESULTS: SPOTS ARE UBIQUITOUS ON L AND T DWARFS , 2014, 1411.3051.

[31]  B. Macintosh,et al.  CLOUDS AND CHEMISTRY IN THE ATMOSPHERE OF EXTRASOLAR PLANET HR8799b , 2011, 1103.3895.

[32]  D. Apai,et al.  AEOLUS: A MARKOV CHAIN MONTE CARLO CODE FOR MAPPING ULTRACOOL ATMOSPHERES. AN APPLICATION ON JUPITER AND BROWN DWARF HST LIGHT CURVES , 2015, 1510.04251.

[33]  Jean-Pierre Véran,et al.  Exoplanet imaging with LOCI processing: photometry and astrometry with the new SOSIE pipeline , 2010, Astronomical Telescopes + Instrumentation.

[34]  D. Apai,et al.  Clouds in Brown Dwarfs and Giant Planets , 2013 .

[35]  Julien H. Girard,et al.  High angular resolution detection of β Pictoris b at 2.18 μm , 2011 .

[36]  Terry Jones,et al.  FIRST LIGHT LBT AO IMAGES OF HR 8799 bcde AT 1.6 AND 3.3 μm: NEW DISCREPANCIES BETWEEN YOUNG PLANETS AND OLD BROWN DWARFS , 2012, 1203.2615.

[37]  David Mouillet,et al.  Photometric characterization of exoplanets using angular and spectral differential imaging , 2010, 1004.4825.

[38]  D. Apai,et al.  MAPPING DIRECTLY IMAGED GIANT EXOPLANETS , 2012, 1210.6915.

[39]  S. Esposito,et al.  The LEECH Exoplanet Imaging Survey. Further constraints on the planet architecture of the HR 8799 system (Corrigendum) , 2014, 1412.6989.

[40]  Kjetil Dohlen,et al.  The infra-red dual imaging and spectrograph for SPHERE: design and performance , 2008, Astronomical Telescopes + Instrumentation.

[41]  B. Oppenheimer,et al.  Astrometry and Photometry with Coronagraphs , 2006, astro-ph/0606136.

[42]  I. Reid,et al.  VERTICAL ATMOSPHERIC STRUCTURE IN A VARIABLE BROWN DWARF: PRESSURE-DEPENDENT PHASE SHIFTS IN SIMULTANEOUS HUBBLE SPACE TELESCOPE–SPITZER LIGHT CURVES , 2012, 1210.6654.

[43]  C. Marois,et al.  A NEW ALGORITHM FOR POINT SPREAD FUNCTION SUBTRACTION IN HIGH-CONTRAST IMAGING: A DEMONSTRATION WITH ANGULAR DIFFERENTIAL IMAGING , 2007 .

[44]  USA,et al.  Fast-evolving weather for the coolest of our two new substellar neighbours , 2013, 1304.0481.

[45]  Kjetil Dohlen,et al.  Exoplanet characterization with long slit spectroscopy , 2008 .

[46]  A. Boccaletti,et al.  A Giant Planet Imaged in the Disk of the Young Star β Pictoris , 2010, Science.

[47]  Michael C. Liu,et al.  Substructure in the Circumstellar Disk Around the Young Star AU Microscopii , 2004, Science.

[48]  Adam Amara,et al.  PYNPOINT: An image processing package for finding exoplanets , 2012, 1207.6637.

[49]  R. Galicher,et al.  Physical and orbital properties of β Pictoris b , 2014, 1407.4001.