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See detailOrbital alignment and star-spot properties in the WASP-52 planetary system
Mancini, L.; Southworth, J.; Raia, G. et al

in Monthly Notices of the Royal Astronomical Society (2017), 465

We report 13 high-precision light curves of eight transits of the exoplanet WASP-52 b, obtained by using four medium-class telescopes, through different filters, and adopting the defocussing technique ... [more ▼]

We report 13 high-precision light curves of eight transits of the exoplanet WASP-52 b, obtained by using four medium-class telescopes, through different filters, and adopting the defocussing technique. One transit was recorded simultaneously from two different observatories and another one from the same site but with two different instruments, including a multiband camera. Anomalies were clearly detected in five light curves and modelled as star-spots occulted by the planet during the transit events. We fitted the clean light curves with the JKTEBOP code, and those with the anomalies with the PRISM+GEMC codes in order to simultaneously model the photometric parameters of the transits and the position, size and contrast of each star-spot. We used these new light curves and some from the literature to revise the physical properties of the WASP-52 system. Star-spots with similar characteristics were detected in four transits over a period of 43 d. In the hypothesis that we are dealing with the same star-spot, periodically occulted by the transiting planet, we estimated the projected orbital obliquity of WASP-52 b to be λ = 3.8° ± 8.4°. We also determined the true orbital obliquity, ψ = 20° ± 50°, which is, although very uncertain, the first measurement of ψ purely from star-spot crossings. We finally assembled an optical transmission spectrum of the planet and searched for variations of its radius as a function of wavelength. Our analysis suggests a flat transmission spectrum within the experimental uncertainties. [less ▲]

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See detailMiNDSTEp differential photometry of the gravitationally lensed quasars WFI 2033-4723 and HE 0047-1756: Microlensing and a new time delay
Giannini, E.; Schmidt, R. W.; Wambsganss, J. et al

in Astronomy and Astrophysics (2017), 597

Aims. We present V and R photometry of the gravitationally lensed quasars WFI 2033-4723 and HE 0047-1756. The data were taken by the MiNDSTEp collaboration with the 1.54 m Danish telescope at the ESO La ... [more ▼]

Aims. We present V and R photometry of the gravitationally lensed quasars WFI 2033-4723 and HE 0047-1756. The data were taken by the MiNDSTEp collaboration with the 1.54 m Danish telescope at the ESO La Silla observatory from 2008 to 2012. Methods. Differential photometry has been carried out using the image subtraction method as implemented in the HOTPAnTS package, additionally using GALFIT for quasar photometry. Results. The quasar WFI 2033-4723 showed brightness variations of order 0.5 mag in V and R during the campaign. The two lensed components of quasar HE 0047-1756 varied by 0.2-0.3 mag within five years. We provide, for the first time, an estimate of the time delay of component B with respect to A of Δt = (7.6 ± 1.8) days for this object. We also find evidence for a secular evolution of the magnitude difference between components A and B in both filters, which we explain as due to a long-duration microlensing event. Finally we find that both quasars WFI 2033-4723 and HE 0047-1756 become bluer when brighter, which is consistent with previous studies. © ESO, 2016. [less ▲]

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See detailFaint-source-star planetary microlensing: The discovery of the cold gas-giant planet OGLE-2014-BLG-0676Lb
Rattenbury, N. J.; Bennett, D. P.; Sumi, T. et al

in Monthly Notices of the Royal Astronomical Society (2017), 466(3), 2710-2717

We report the discovery of a planet - OGLE-2014-BLG-0676Lb- via gravitational microlensing. Observations for the lensing event were made by the following groups: Microlensing Observations in Astrophysics ... [more ▼]

We report the discovery of a planet - OGLE-2014-BLG-0676Lb- via gravitational microlensing. Observations for the lensing event were made by the following groups: Microlensing Observations in Astrophysics; Optical Gravitational Lensing Experiment; Wise Observatory; RoboNET/Las Cumbres Observatory Global Telescope; Microlensing Network for the Detection of Small Terrestrial Exoplanets; and μ-FUN. All analyses of the light-curve data favour a lens system comprising a planetary mass orbiting a host star. The most-favoured binary lens model has a mass ratio between the two lens masses of (4.78 ± 0.13) × 10-3. Subject to some important assumptions, a Bayesian probability density analysis suggests the lens system comprises a 3.09-1.12+1.02 MJ planet orbiting a 0.62-0.22+0.20 M⊙ host star at a deprojected orbital separation of 4.40-1.46+2.16 au. The distance to the lens system is 2.22-0.83+0.96 kpc. Planet OGLE- 2014-BLG-0676Lb provides additional data to the growing number of cool planets discovered using gravitational microlensing against which planetary formation theories may be tested. Most of the light in the baseline of this event is expected to come from the lens and thus high-resolution imaging observations could confirm our planetary model interpretation. © 2016 The Authors. [less ▲]

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See detailFrom Dense Hot Jupiter to Low Density Neptune: The Discovery of WASP-127b, WASP-136b and WASP-138b
Lam, K. W. F.; Faedi, F.; Brown, D. J. A. et al

in Astronomy and Astrophysics (2017), 599

We report three newly discovered exoplanets from the SuperWASP survey. WASP-127b is a heavily inflated super-Neptune of mass 0.18Mj and radius 1.35Rj. This is one of the least massive planets discovered ... [more ▼]

We report three newly discovered exoplanets from the SuperWASP survey. WASP-127b is a heavily inflated super-Neptune of mass 0.18Mj and radius 1.35Rj. This is one of the least massive planets discovered by the WASP project. It orbits a bright host star (V = 10.16) of spectral type G5 with a period of 4.17 days.WASP-127b is a low density planet which has an extended atmosphere with a scale height of 2500+/-400 km, making it an ideal candidate for transmission spectroscopy. WASP-136b and WASP-138b are both hot Jupiters with mass and radii of 1.51 Mj and 1.38 Rj, and 1.22 Mj and 1.09 Rj, respectively. WASP-136b is in a 5.22-day orbit around an F9 subgiant star with a mass of 1.41 Msun and a radius of 2.21 Rsun. The discovery of WASP-136b could help constraint the characteristics of the giant planet population around evolved stars. WASP-138b orbits an F7 star with a period of 3.63 days. Its radius agrees with theoretical values from standard models, suggesting the presence of a heavy element core with a mass of 10 Mearth. The discovery of these new planets helps in exploring the diverse compositional range of short-period planets, and will aid our understanding of the physical characteristics of both gas giants and low density planets. [less ▲]

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See detailVizieR Online Data Catalog: Planet candidates discovered using K2's 1st yr (Crossfield+, 2016)
Crossfield, I. J. M.; Ciardi, D. R.; Petigura, E. A. et al

in Planet candidates discovered using K2's 1st yr (Crossfield+, 2016) (2016)

We select our FGK stellar sample from the all-sky Transiting Exoplanet Survey Satellite (TESS) Dwarf Catalog (TDC; Stassun et al. 2014, arXiv:1410.6379). We extract time-series photometry from the target ... [more ▼]

We select our FGK stellar sample from the all-sky Transiting Exoplanet Survey Satellite (TESS) Dwarf Catalog (TDC; Stassun et al. 2014, arXiv:1410.6379). We extract time-series photometry from the target pixel files provided by the K2 project using circular, stationary, soft-edged apertures. See section 2 for further explanations. We obtained high-resolution optical spectra of 83 planet candidate hosts using the HIRES echelle spectrometer on the 10m Keck I telescope (R=55000). We obtained spectra of 27 candidate host stars using the Levy high-resolution optical spectrograph mounted at the Automated Planet Finder (APF; R~80000 or 100000). We obtained spectra of a small number of candidate stellar hosts using the FEROS fiber-fed echelle spectrograph at the 2.2m MPG telescope (R~48000). See section 3.1 for further details. We obtained high-resolution imaging (HRI) for 164 of our candidate systems. Our primary instrument for this work was NIRC2 at the 10m Keck II telescope, with which we observed 110 systems. As part of multi-semester program GN-2015B-LP-5 (PI Crossfield) at Gemini Observatory, we observed 40 systems with the NIRI camera in the K-band. We also observed 33 stars with PHARO/PALM-3000 at the 5m Hale Telescope and 14 systems with LMIRCam at LBT, all at the K-band. We observed 39 stars at visible wavelengths using the automated Robo-AO laser adaptive optics system at the Palomar 1.5m telescope. Through our Long-Term Gemini program we also acquired high-resolution speckle imaging of 32 systems in narrowband filters centered at 692 and 880nm using the DSSI camera at the Gemini North telescope. See section 3.3 for further explanations. (7 data files). [less ▲]

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See detailWASP-86b and WASP-102b: super-dense versus bloated planets
Faedi, F.; Gómez Maqueo Chew, Y.; Pollacco, D. et al

E-print/Working paper (2016)

We report the discovery of two transiting planetary systems: a super dense, sub-Jupiter mass planet WASP-86b (\mpl\ = 0.82 $\pm$ 0.06 \mj, \rpl\ = 0.63 $\pm$ 0.01 \rj), and a bloated, Saturn-like planet ... [more ▼]

We report the discovery of two transiting planetary systems: a super dense, sub-Jupiter mass planet WASP-86b (\mpl\ = 0.82 $\pm$ 0.06 \mj, \rpl\ = 0.63 $\pm$ 0.01 \rj), and a bloated, Saturn-like planet WASP-102b (\mpl\ = 0.62 $\pm$ 0.04 \mj, \rpl\=1.27 $\pm$ 0.03 \rj). They orbit their host star every $\sim$5.03, and $\sim$2.71 days, respectively. The planet hosting WASP-86 is a F7 star (\teff\ = 6330$\pm$110 K, \feh\ = $+$0.23 $\pm$ 0.14 dex, and age $\sim$0.8--1~Gyr), WASP-102 is a G0 star (\teff\ = 5940$\pm$140 K, \feh\ = $-$0.09$\pm$ 0.19 dex, and age $\sim$1~Gyr). These two systems highlight the diversity of planetary radii over similar masses for giant planets with masses between Saturn and Jupiter. WASP-102b shows a larger than model-predicted radius, indicating that the planet is receiving a strong incident flux which contributes to the inflation of its radius. On the other hand, with a density of $\rho_{pl}$ = 3.24$\pm$~0.3~$\rho_{jup}$, WASP-86b is the densest gas giant planet among planets with masses in the range 0.05 $<M$_{pl}$<$ 2.0 \mj. With a stellar mass of 1.34 M$_{\odot}$ and \feh = $+$0.23 dex, WASP-86 could host additional massive and dense planets given that its protoplanetary disc is expected to also have been enriched with heavy elements. In order to match WASP-86b's density, an extrapolation of theoretical models predicts a planet composition of more than 80\% in heavy elements (whether confined in a core or mixed in the envelope). This fraction corresponds to a core mass of approximately 210\me\ for WASP-86b's mass of \mpl$\sim$260\,\me. Only planets with masses larger than about 2\mj\ have larger densities than that of WASP-86b, making it exceptional in its mass range. [less ▲]

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See detailHigh-precision photometry by telescope defocussing - VIII.WASP-22, WASP-41,WASP-42 andWASP-55
Southworth, J.; Tregloan-Reed, J.; Andersen, M. I. et al

in Monthly Notices of the Royal Astronomical Society (2016), 457(4), 4205-4217

We present 13 high-precision and four additional light curves of four bright southernhemisphere transiting planetary systems: WASP-22, WASP-41, WASP-42 and WASP-55. In the cases of WASP-42 and WASP-55 ... [more ▼]

We present 13 high-precision and four additional light curves of four bright southernhemisphere transiting planetary systems: WASP-22, WASP-41, WASP-42 and WASP-55. In the cases of WASP-42 and WASP-55, these are the first follow-up observations since their discovery papers. We present refined measurements of the physical properties and orbital ephemerides of all four systems. No indications of transit timing variations were seen. All four planets have radii inflated above those expected from theoretical models of gas-giant planets; WASP-55 b is the most discrepant with a mass of 0.63MJup and a radius of 1.34 RJup. WASP-41 shows brightness anomalies during transit due to the planet occulting spots on the stellar surface. Two anomalies observed 3.1 d apart are very likely due to the same spot. We measure its change in position and determine a rotation period for the host star of 18.6 ± 1.5 d, in good agreement with a published measurement from spot-induced brightness modulation, and a sky-projected orbital obliquity of λ = 6 ± 11°. We conclude with a compilation of obliquity measurements from spot-tracking analyses and a discussion of this technique in the study of the orbital configurations of hot Jupiters. © 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. [less ▲]

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See detailSPITZER PARALLAX of OGLE-2015-BLG-0966: A COLD NEPTUNE in the GALACTIC DISK
Street, R. A.; Udalski, A.; Novati, S. C. et al

in Astrophysical Journal (2016), 819(2),

We report the detection of a cold Neptune mplanet = 21 ± 2 M⊕ orbiting a 0.38 Mo M dwarf lying 2.5-3.3 kpc toward the Galactic center as part of a campaign combining ground-based and Spitzer observations ... [more ▼]

We report the detection of a cold Neptune mplanet = 21 ± 2 M⊕ orbiting a 0.38 Mo M dwarf lying 2.5-3.3 kpc toward the Galactic center as part of a campaign combining ground-based and Spitzer observations to measure the Galactic distribution of planets. This is the first time that the complex real-time protocols described by Yee et al., which aim to maximize planet sensitivity while maintaining sample integrity, have been carried out in practice. Multiple survey and follow up teams successfully combined their efforts within the framework of these protocols to detect this planet. This is the second planet in the Spitzer Galactic distribution sample. Both are in the near to mid-disk and are clearly not in the Galactic bulge. © 2016. The American Astronomical Society. All rights reserved. [less ▲]

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See detailSPITZER OBSERVATIONS of OGLE-2015-BLG-1212 REVEAL A NEW PATH TOWARD BREAKING STRONG MICROLENS DEGENERACIES
Bozza, V.; Shvartzvald, Y.; Udalski, A. et al

in Astrophysical Journal (2016), 820(1),

Spitzer microlensing parallax observations of OGLE-2015-BLG-1212 decisively break a degeneracy between planetary and binary solutions that is somewhat ambiguous when only ground-based data are considered ... [more ▼]

Spitzer microlensing parallax observations of OGLE-2015-BLG-1212 decisively break a degeneracy between planetary and binary solutions that is somewhat ambiguous when only ground-based data are considered. Only eight viable models survive out of an initial set of 32 local minima in the parameter space. These models clearly indicate that the lens is a stellar binary system possibly located within the bulge of our Galaxy, ruling out the planetary alternative. We argue that several types of discrete degeneracies can be broken via such space-based parallax observations. © 2016. The American Astronomical Society. All rights reserved.. [less ▲]

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See detailErratum to A detailed census of variable stars in the globular cluster NGC 6333 (M9) from CCD differential photometry
Arellano Ferro, A.; Bramich, D. M.; Figuera Jaimes, R. et al

in Monthly Notices of the Royal Astronomical Society (2016), 458(2), 1188-1189

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See detailErratum: Estimating the parameters of globular cluster M 30 (NGC 7099) from time-series photometry (Astronomy and Astrophysics (2013) 555 (A36))
Kains, N.; Bramich, D. M.; Arellano Ferro, A. et al

in Astronomy and Astrophysics (2016), 588

[No abstract available]

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See detailPhysical properties of the planetary systems WASP-45 and WASP-46 from simultaneous multiband photometry
Ciceri, S.; Mancini, L.; Southworth, J. et al

in Monthly Notices of the Royal Astronomical Society (2016), 456(1), 990-1002

Accurate measurements of the physical characteristics of a large number of exoplanets are useful to strongly constrain theoretical models of planet formation and evolution, which lead to the large variety ... [more ▼]

Accurate measurements of the physical characteristics of a large number of exoplanets are useful to strongly constrain theoretical models of planet formation and evolution, which lead to the large variety of exoplanets and planetary-system configurations that have been observed. We present a study of the planetary systemsWASP-45 andWASP-46, both composed of a mainsequence star and a close-in hot Jupiter, based on 29 new high-quality light curves of transits events. In particular, one transit of WASP-45 b and four of WASP-46 b were simultaneously observed in four optical filters, while one transit of WASP-46 b was observed with the NTT obtaining a precision of 0.30 mmag with a cadence of roughly 3 min. We also obtained five new spectra of WASP-45 with the FEROS spectrograph. We improved by a factor of 4 the measurement of the radius of the planet WASP-45 b, and found that WASP-46 b is slightly less massive and smaller than previously reported. Both planets now have a more accurate measurement of the density (0.959 ± 0.077 ρJup instead of 0.64 ± 0.30 ρJup for WASP-45 b, and 1.103 ± 0.052 ρJup instead of 0.94 ± 0.11 ρJup for WASP-46 b). We tentatively detected radius variations with wavelength for both planets, in particular in the case of WASP-45 b we found a slightly larger absorption in the redder bands than in the bluer ones. No hints for the presence of an additional planetary companion in the two systems were found either from the photometric or radial velocity measurements. © 2015 The Authors. [less ▲]

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See detailExploring the crowded central region of ten Galactic globular clusters using EMCCDs: Variable star searches and new discoveries
Figuera Jaimes, R.; Bramich, D. M.; Skottfelt, J. et al

in Astronomy and Astrophysics (2016), 588

Aims. We aim to obtain time-series photometry of the very crowded central regions of Galactic globular clusters; to obtain better angular resolution thanhas been previously achieved with conventional CCDs ... [more ▼]

Aims. We aim to obtain time-series photometry of the very crowded central regions of Galactic globular clusters; to obtain better angular resolution thanhas been previously achieved with conventional CCDs on ground-based telescopes; and to complete, or improve, the census of the variable star population in those stellar systems. Methods. Images were taken using the Danish 1.54-m Telescope at the ESO observatory at La Silla in Chile. The telescope was equipped with an electron-multiplying CCD, and the short-exposure-time images obtained (ten images per second) were stacked using the shift-and-add technique to produce the normal-exposure-time images (minutes). Photometry was performed via difference image analysis. Automatic detection of variable stars in the field was attempted. Results. The light curves of 12 541 stars in the cores of ten globular clusters were statistically analysed to automatically extract the variable stars. We obtained light curves for 31 previously known variable stars (3 long-period irregular, 2 semi-regular, 20 RR Lyrae, 1 SX Phoenicis, 3 cataclysmic variables, 1 W Ursae Majoris-type and 1 unclassified) and we discovered 30 new variables (16 long-period irregular, 7 semi-regular, 4 RR Lyrae, 1 SX Phoenicis and 2 unclassified). Fluxes and photometric measurements for these stars are available in electronic form through the Strasbourg astronomical Data Center. © ESO, 2016. [less ▲]

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See detailHigh-resolution Imaging of Transiting Extrasolar Planetary systems (HITEP): I. Lucky imaging observations of 101 systems in the southern hemisphere
Evans, D. F.; Southworth, J.; Maxted, P. F. L. et al

in Astronomy and Astrophysics (2016), 589

Context. Wide binaries are a potential pathway for the formation of hot Jupiters. The binary fraction among host stars is an important discriminator between competing formation theories, but has not been ... [more ▼]

Context. Wide binaries are a potential pathway for the formation of hot Jupiters. The binary fraction among host stars is an important discriminator between competing formation theories, but has not been well characterised. Additionally, contaminating light from unresolved stars can significantly affect the accuracy of photometric and spectroscopic measurements in studies of transiting exoplanets. Aims. We observed 101 transiting exoplanet host systems in the Southern hemisphere in order to create a homogeneous catalogue of both bound companion stars and contaminating background stars, in an area of the sky where transiting exoplanetary systems have not been systematically searched for stellar companions. We investigate the binary fraction among the host stars in order to test theories for the formation of hot Jupiters. Methods. Lucky imaging observations from the Two Colour Instrument on the Danish 1.54 m telescope at La Silla were used to search for previously unresolved stars at small angular separations. The separations and relative magnitudes of all detected stars were measured. For 12 candidate companions to 10 host stars, previous astrometric measurements were used to evaluate how likely the companions are to be physically associated. Results. We provide measurements of 499 candidate companions within 20 arcsec of our sample of 101 planet host stars. 51 candidates are located within 5 arcsec of a host star, and we provide the first published measurements for 27 of these. Calibrations for the plate scale and colour performance of the Two Colour Instrument are presented. Conclusions. We find that the overall multiplicity rate of the host stars is 38-13 +17%, consistent with the rate among solar-type stars in our sensitivity range, suggesting that planet formation does not preferentially occur in long period binaries compared to a random sample of field stars. Long period stellar companions (P > 10 yr) appear to occur independently of short period companions, and so the population of close-in stellar companions is unconstrained by our study. © ESO, 2016. [less ▲]

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See detailTHE SPITZER MICROLENSING PROGRAM AS A PROBE for GLOBULAR CLUSTER PLANETS: ANALYSIS of OGLE-2015-BLG-0448
Poleski, R.; Zhu, W.; Christie, G. W. et al

in Astrophysical Journal (2016), 823(1),

The microlensing event OGLE-2015-BLG-0448 was observed by Spitzer and lay within the tidal radius of the globular cluster NGC 6558. The event had moderate magnification and was intensively observed, hence ... [more ▼]

The microlensing event OGLE-2015-BLG-0448 was observed by Spitzer and lay within the tidal radius of the globular cluster NGC 6558. The event had moderate magnification and was intensively observed, hence it had the potential to probe the distribution of planets in globular clusters. We measure the proper motion of NGC 6558 ((μcl (N, E) = +0.36 ± 0.10, +1.42 ± 0.10 mas yr-1) as well as the source and show that the lens is not a cluster member. Even though this particular event does not probe the distribution of planets in globular clusters, other potential cluster lens events can be verified using our methodology. Additionally, we find that microlens parallax measured using Optical Gravitational Lens Experiment (OGLE) photometry is consistent with the value found based on the light curve displacement between the Earth and Spitzer. © 2016. The American Astronomical Society. All rights reserved. [less ▲]

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See detailMASS MEASUREMENTS of ISOLATED OBJECTS from SPACE-BASED MICROLENSING
Zhu, W.; Calchi Novati, S.; Gould, A. et al

in Astrophysical Journal (2016), 825(1),

We report on the mass and distance measurements of two single-lens events from the 2015 Spitzer microlensing campaign. With both finite-source effect and microlens parallax measurements, we find that the ... [more ▼]

We report on the mass and distance measurements of two single-lens events from the 2015 Spitzer microlensing campaign. With both finite-source effect and microlens parallax measurements, we find that the lens of OGLE-2015-BLG-1268 is very likely a brown dwarf (BD). Assuming that the source star lies behind the same amount of dust as the Bulge red clump, we find the lens is a 45 ±7 BD at 5.9 ±1.0 kpc. The lens of of the second event, OGLE-2015-BLG-0763, is a 0.50 ±0.04 star at 6.9 ±1.0 kpc. We show that the probability to definitively measure the mass of isolated microlenses is dramatically increased once simultaneous ground- and space-based observations are conducted. © 2016. The American Astronomical Society. All rights reserved. [less ▲]

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See detailMany new variable stars discovered in the core of the globular cluster NGC 6715 (M 54) with EMCCD observations
Figuera Jaimes, R.; Bramich, D. M.; Kains, N. et al

in Astronomy and Astrophysics (2016), 592

Context. We show the benefits of using electron-multiplying CCDs and the shift-and-add technique as a tool to minimise the effects of atmospheric turbulence, such as blending between stars in crowded ... [more ▼]

Context. We show the benefits of using electron-multiplying CCDs and the shift-and-add technique as a tool to minimise the effects of atmospheric turbulence, such as blending between stars in crowded fields, and to avoid saturated stars in the fields observed. We intend to complete, or improve on, the census of the variable star population in globular cluster NGC 6715. Aims. Our aim is to obtain high-precision time-series photometry of the very crowded central region of this stellar system via the collection of better angular resolution images than has been previously achieved with conventional CCDs on ground-based telescopes. Methods. Observations were carried out using the Danish 1.54-m telescope at the ESO La Silla observatory in Chile. The telescope is equipped with an electron-multiplying CCD that enables short-exposure-time images to be obtained (ten images per second) that were stacked using the shift-and-add technique to produce the normal-exposure-time images (minutes). The high precision photometry was performed via difference image analysis employing the DanDIA pipeline. We attempted automatic detection of variable stars in the field. Results. We statistically analysed the light curves of 1405 stars in the crowded central region of NGC 6715 to automatically identify the variable stars present in this cluster. We found light curves for 17 previously known variable stars near the edges of our reference image (16 RR Lyrae and 1 semi-regular) and we discovered 67 new variables (30 RR Lyrae, 21 irregular (long-period type), 3 semi-regular, 1 W Virginis, 1 eclipsing binary, and 11 unclassified). Photometric measurements for these stars are available in electronic form through the Strasbourg Astronomical Data Centre. © 2016 ESO. [less ▲]

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See detailOGLE-2015-BLG-0479LA,B: BINARY GRAVITATIONAL MICROLENS CHARACTERIZED by SIMULTANEOUS GROUND-BASED and SPACE-BASED OBSERVATIONS
Han, C.; Udalski, A.; Gould, A. et al

in Astrophysical Journal (2016), 828(1),

We present a combined analysis of the observations of the gravitational microlensing event OGLE-2015-BLG-0479 taken both from the ground and by the Spitzer Space Telescope. The light curves seen from the ... [more ▼]

We present a combined analysis of the observations of the gravitational microlensing event OGLE-2015-BLG-0479 taken both from the ground and by the Spitzer Space Telescope. The light curves seen from the ground and from space exhibit a time offset of ∼13 days between the caustic spikes, indicating that the relative lens-source positions seen from the two places are displaced by parallax effects. From modeling the light curves, we measure the space-based microlens parallax. Combined with the angular Einstein radius measured by analyzing the caustic crossings, we determine the mass and distance of the lens. We find that the lens is a binary composed of two G-type stars with masses of ∼1.0 M⊙ and ∼0.9 M⊙ located at a distance of ∼3 kpc. In addition, we are able to constrain the complete orbital parameters of the lens thanks to the precise measurement of the microlens parallax derived from the joint analysis. In contrast to the binary event OGLE-2014-BLG-1050, which was also observed by Spitzer, we find that the interpretation of OGLE-2015-BLG-0479 does not suffer from the degeneracy between (±, ±) and (±, ∓) solutions, confirming that the four-fold parallax degeneracy in single-lens events collapses into the two-fold degeneracy for the general case of binary-lens events. The location of the blend in the color-magnitude diagram is consistent with the lens properties, suggesting that the blend is the lens itself. The blend is bright enough for spectroscopy and thus this possibility can be checked from future follow-up observations. © 2016. The American Astronomical Society. All rights reserved. [less ▲]

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See detail197 Candidates and 104 Validated Planets in K2' First Five Fields
Crossfield, I. J. M.; Ciardi, D. R.; Petigura, E. A. et al

in Astrophysical Journal Supplement Series (2016), 226

We present 197 planet candidates discovered using data from the first year of the NASA K2 mission (Campaigns 0-4), along with the results of an intensive program of photometric analyses, stellar ... [more ▼]

We present 197 planet candidates discovered using data from the first year of the NASA K2 mission (Campaigns 0-4), along with the results of an intensive program of photometric analyses, stellar spectroscopy, high-resolution imaging, and statistical validation. We distill these candidates into sets of 104 validated planets (57 in multi-planet systems), 30 false positives, and 63 remaining candidates. Our validated systems span a range of properties, with median values of R P = 2.3 {R}\oplus , P = 8.6 days, {T}{eff} = 5300 K, and Kp = 12.7 mag. Stellar spectroscopy provides precise stellar and planetary parameters for most of these systems. We show that K2 has increased by 30% the number of small planets known to orbit moderately bright stars (1-4 R ⊕, Kp = 9-13 mag). Of particular interest are 76 planets smaller than 2 R ⊕, 15 orbiting stars brighter than Kp = 11.5 mag, 5 receiving Earth-like irradiation levels, and several multi-planet systems—including 4 planets orbiting the M dwarf K2-72 near mean-motion resonances. By quantifying the likelihood that each candidate is a planet we demonstrate that our candidate sample has an overall false positive rate of 15%-30%, with rates substantially lower for small candidates (\lt 2{R}\oplus ) and larger for candidates with radii \gt 8{R}\oplus and/or with P\lt 3 {{days}}. Extrapolation of the current planetary yield suggests that K2 will discover between 500 and 1000 planets in its planned four-year mission, assuming sufficient follow-up resources are available. Efficient observing and analysis, together with an organized and coherent follow-up strategy, are essential for maximizing the efficacy of planet-validation efforts for K2, TESS, and future large-scale surveys. [less ▲]

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See detailLarger and faster: revised properties and a shorter orbital period for the WASP-57 planetary system from a pro-am collaboration
Southworth, John; Mancini, L.; Tregloan-Reed, J. et al

in Monthly Notices of the Royal Astronomical Society (2015), 454

Transits in the WASP-57 planetary system have been found to occur half an hour earlier than expected. We present 10 transit light curves from amateur telescopes, on which this discovery was based, 13 ... [more ▼]

Transits in the WASP-57 planetary system have been found to occur half an hour earlier than expected. We present 10 transit light curves from amateur telescopes, on which this discovery was based, 13 transit light curves from professional facilities which confirm and refine this finding, and high-resolution imaging which show no evidence for nearby companions. We use these data to determine a new and precise orbital ephemeris, and measure the physical properties of the system. Our revised orbital period is 4.5 s shorter than found from the discovery data alone, which explains the early occurrence of the transits. We also find both the star and planet to be larger and less massive than previously thought. The measured mass and radius of the planet are now consistent with theoretical models of gas giants containing no heavy-element core, as expected for the subsolar metallicity of the host star. Two transits were observed simultaneously in four passbands. We use the resulting light curves to measure the planet's radius as a function of wavelength, finding that our data are sufficient in principle but not in practise to constrain its atmospheric properties. We conclude with a discussion of the current and future status of transmission photometry studies for probing the atmospheres of gas-giant transiting planets. [less ▲]

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