Physical properties, starspot activity, orbital obliquity, and transmission spectrum of the Qatar-2 planetary system from multi-colour photometry

Abstract

We present seventeen high-precision light curves of five transits of the planet Qatar-2b, obtained from four defocussed 2m-class telescopes. Three of the transits were observed simultaneously in the SDSS griz passbands using the seven-beam GROND imager on the MPG/ESO 2.2-m telescope. A fourth was observed simultaneously in Gunn grz using the CAHA 2.2-m telescope with BUSCA, and in r using the Cassini 1.52-m telescope. Every light curve shows small anomalies due to the passage of the planetary shadow over a cool spot on the surface of the host star. We fit the light curves with the prism+gemc model to obtain the photometric parameters of the system and the position, size and contrast of each spot. We use these photometric parameters and published spectroscopic measurements to obtain the physical properties of the system to high precision, finding a larger radius and lower density for both star and planet than previously thought. By tracking the change in position of one starspot between two transit observations we measure the orbital obliquity of Qatar-2 b to be 4.3 \pm 4.5 degree, strongly indicating an alignment of the stellar spin with the orbit of the planet. We calculate the rotation period and velocity of the cool host star to be 11.4 \pm 0.5 d and 3.28 \pm 0.13 km/s at a colatitude of 74 degree. We assemble the planet's transmission spectrum over the 386-976 nm wavelength range and search for variations of the measured radius of Qatar-2 b as a function of wavelength. Our analysis highlights a possible H2/He Rayleigh scattering in the blue.

arXiv comment20 pages, 14 figures, to appear in Monthly Notices of the Royal Astronomical Society

References in corpus (48)

• Planetary Radii across Five Orders of Magnitude in Mass and Stellar Insolation: Application to Transits
• On the Unique Solution of Planet and Star Parameters from an Extrasolar Planet Transit Light Curve
• A Unified Theory for the Atmospheres of the Hot and Very Hot Jupiters: Two Classes of Irradiated Atmospheres
• Hot Stars with Hot Jupiters Have High Obliquities
• Homogeneous studies of transiting extrasolar planets. IV. Thirty systems with space-based light curves
• The prevalence of dust on the exoplanet HD 189733b from Hubble and Spitzer observations
• Hubble Space Telescope Transmission Spectroscopy of the Exoplanet HD 189733b: High-altitude atmospheric haze in the optical and near-UV with STIS
• GROND - a 7-channel imager
• The Transit Light Curve Project. IX. Evidence for a Smaller Radius of the Exoplanet XO-3b
• Transmission Spectra of Three-Dimensional Hot Jupiter Model Atmospheres
• Starspots, spin-orbit misalignment, and active latitudes in the HAT-P-11 exoplanetary system
• Hubble Space Telescope times-series photometry of the planetary transit of HD189733: no moon, no rings, starspots
• High-precision photometry by telescope defocussing. I. The transiting planetary system WASP-5
• The hot-Jupiter Kepler-17b: discovery, obliquity from stroboscopic starspots, and atmospheric characterization
• An HST Optical to Near-IR Transmission Spectrum of the Hot Jupiter WASP-19b: Detection of Atmospheric Water and Likely Absence of TiO
• Starspots and spin-orbit alignment in the WASP-4 exoplanetary system
• The Detection and Characterization of a Nontransiting Planet by Transit Timing Variations
• Homogeneous studies of transiting extrasolar planets. V. New results for 38 planets
• An Improved Method for Estimating the Masses of Stars with Transiting Planets
• Transits and starspots in the WASP-19 planetary system
• High accuracy transit photometry of the planet OGLE-TR-113b with a new deconvolution-based method
• Properties of starspots on CoRoT-2
• Physical properties, transmission and emission spectra of the WASP-19 planetary system from multi-colour photometry
• Optical to near-infrared transit observations of super-Earth GJ1214b: water-world or mini-Neptune?
• HATS-1b: The First Transiting Planet Discovered by the HATSouth Survey
• Multiwavelength flux variations induced by stellar magnetic activity: effects on planetary transits
• Updated parameters for the transiting exoplanet WASP-3b using RISE, a new fast camera for the Liverpool Telescope
• A cool starspot or a second transiting planet in the TrES-1 system?
• A photometric study of the hot exoplanet WASP-19b
• Limits to the planet candidate GJ 436c
• HATS-3b: An inflated hot Jupiter transiting an F-type star
• A lower radius and mass for the transiting extrasolar planet HAT-P-8b
• Qatar-2: A K dwarf orbited by a transiting hot Jupiter and a more massive companion in an outer orbit
• High-precision photometry by telescope defocussing. IV. Confirmation of the huge radius of WASP-17b
• HATS-2b: A transiting extrasolar planet orbiting a K-type star showing starspot activity
• Physical properties and radius variations in the HAT-P-5 planetary system from simultaneous four-colour photometry
• Multi-Color Transit Photometry of GJ 1214b through BJHKs-Bands and a Long-Term Monitoring of the Stellar Variability of GJ 1214
• High-precision photometry by telescope defocussing. III. The transiting planetary system WASP-2
• Physical properties and transmission spectrum of the WASP-80 planetary system from multi-colour photometry
• Refined physical properties of the HAT-P-13 planetary system
• Optical transmission photometry of the highly inflated exoplanet WASP-17b
• Simultaneous follow-up of planetary transits: revised physical properties for the planetary systems HAT-P-16 and WASP-21
• Transmission photometry of WASP-12b: simultaneous measurement of the planetary radius in three bands
• High-precision photometry by telescope defocussing. V. WASP-15 and WASP-16
• Physical properties of the WASP-44 planetary system from simultaneous multi-colour photometry
• Refined physical properties and g',r',i',z',J,H,K transmission spectrum of WASP-23b from the ground
• A much lower density for the transiting extrasolar planet WASP-7
• First simultaneous optical/near-infrared imaging of an X-ray selected, high-redshift cluster of galaxies with GROND: the galaxy population of XMMU J0338.7+0030 at z=1.1

Cited by in corpus (45)

• Probabilistic Forecasting of the Masses and Radii of Other Worlds
• Ground-based near-UV observations of 15 transiting exoplanets: Constraints on their atmospheres and no evidence for asymmetrical transits
• The Rossiter-McLaughlin effect in Exoplanet Research
• TESS Transit Timing of Hundreds of Hot Jupiters
• The GAPS Programme with HARPS-N at TNG XVI: Measurement of the Rossiter-McLaughlin effect of the transiting planetary systems HAT-P-3, HAT-P-12, HAT-P-22, WASP-39 and WASP-60
• MuSCAT: a multicolor simultaneous camera for studying atmospheres of transiting exoplanets
• A comparison of gyrochronological and isochronal age estimates for transiting exoplanet host stars
• ExoClock Project III: 450 new exoplanet ephemerides from ground and space observations
• Transits and starspots in the WASP-6 planetary system
• Orbital alignment and starspot properties in the WASP-52 planetary system
• Bayesian mass and age estimates for transiting exoplanet host stars
• The GAPS Programme with HARPS-N at TNG. XIII. The orbital obliquity of three close-in massive planets hosted by dwarf K-type stars: WASP-43, HAT-P-20 and Qatar-2
• High-precision photometry by telescope defocussing. VII. The ultra-short period planet WASP-103
• Transmission spectroscopy of the inflated exoplanet WASP-52b, and evidence for a bright region on the stellar surface
• The GAPS Programme with HARPS-N at TNG VIII: Observations of the Rossiter-McLaughlin effect and characterisation of the transiting planetary systems HAT-P-36 and WASP-11/HAT-P-10
• ExoClock project II: A large-scale integrated study with 180 updated exoplanet ephemerides
• Starspots on WASP-85
• Homogeneously derived transit timings for 17 exoplanets and reassessed TTV trends for WASP-12 and WASP-4
• Contamination from a nearby star cannot explain the anomalous transmission spectrum of the ultra-short period giant planet WASP-103b
• A New Analysis of 8 Spitzer Phase Curves and Hot Jupiter Population Trends: Qatar-1b, Qatar-2b, WASP-52b, WASP-34b, and WASP-140b
• The stellar obliquity, planet mass, and very low albedo of Qatar-2 from K2 Photometry
• An optical transmission spectrum of the giant planet WASP-36 b
• Stellar Properties of Active G and K Stars: Exploring the Connection Between Starspots and Chromospheric Activity
• $\text{PyTranSpot}$ - A tool for multiband light curve modeling of planetary transits and stellar spots
• High-precision multi-band time-series photometry of exoplanets Qatar-1b and TrES-5b
• High-precision photometry by telescope defocussing. VIII. WASP-22, WASP-41, WASP-42 and WASP-55
• Physical properties of the HAT-P-23 and WASP-48 planetary systems from multi-colour photometry
• Recurring sets of recurring starspot occultations on exoplanet-host Qatar-2
• Forward modelling of Kepler-band variability due to faculae and spots
• Physical properties of the planetary systems WASP-45 and WASP-46 from simultaneous multi-band photometry
• Possible detection of a bimodal cloud distribution in the atmosphere of HAT-P-32\,A\,b from multi-band photometry
• Effects of refraction on transmission spectra of gas giants: decrease of the Rayleigh scattering slope and breaking of retrieval degeneracies
• HATS-13b and HATS-14b: two transiting hot Jupiters from the HATSouth survey
• Larger and faster: revised properties and a shorter orbital period for the WASP-57 planetary system from a pro-am collaboration
• Transmission spectroscopy of the hot Jupiter TrES-3 b: Disproof of an overly large Rayleigh-like feature
• The GAPS programme at TNG XLIV. Projected rotational velocities of 273 exoplanet-host stars observed with HARPS-N
• Simulations of starspot anomalies within TESS exoplanetary transit light curves -- I. The detection limits of starspot anomalies in TESS light curves
• Looking For Timing Variations in the Transits of 16 Exoplanets
• A Holistic and Probabilistic Approach to the Ground-based Data of HAT-P-19 System
• Starspot induced effects in microlensing events with rotating source star
• Physical properties and optical-infrared transmission spectrum of the giant planet XO-1b
• Simulations of starspot anomalies within TESS exoplanetary transit light curves -- II
• Simultaneous multicolour transit photometry of hot Jupiters HAT-P-19b, HAT-P-51b, HAT-P-55b, and HAT-P-65b
• Quantifying the Impact of Starspot-Crossing Events on Retrieved Parameters from Transit Lightcurves
• SIOUX project: a simultaneous multiband camera for exoplanet atmospheres studies