Directly detecting thermal emission from young extrasolar planets allows measurement of their atmospheric compositions and luminosities, which are influenced by their formation mechanisms. Using the Gemini Planet Imager, we discovered a planet orbiting the ~20-million-year-old star 51 Eridani at a projected separation of 13 astronomical units. Near-infrared observations show a spectrum with strong methane and water-vapor absorption. Modeling of the spectra and photometry yields a luminosity (normalized by the luminosity of the Sun) of 1.6 to 4.0 × 10(-6) and an effective temperature of 600 to 750 kelvin. For this age and luminosity, "hot-start" formation models indicate a mass twice that of Jupiter. This planet also has a sufficiently low luminosity to be consistent with the "cold-start" core-accretion process that may have formed Jupiter.

One of the most intriguing results from the γ-ray instruments currently in orbit has been the detection of powerful flares from the Crab Nebula. Such events, with a cadence of about one per year, can be so dramatic as to make the system the brightest source in the γ-ray sky as occurred in 2011 April. These flares challenge our understanding of pulsar wind nebulae and models for particle acceleration. To pinpoint the production site(s) within the Nebula, a multiwavelength campaign has been carried out using Keck, Hubble Space Telescope (HST), and Chandra X-ray Observatory. As the short time scales of the flares ( 1 day) suggest a small emitting region, the Crab's inner knot, located within a fraction of an arcsecond from the pulsar, has been proposed to be just such a site. In this paper, we focus on IR, optical, and X-ray observations of this feature to see if it might be related to the γ-ray flares and to try to understand its nature. We find that the knot's radial size, tangential size, peak flux, and the ratio of the knot flux to that of the pulsar as measured with HST are all correlated with the projected distance of the knot from the pulsar. A new approach, using singular value decomposition for analyzing time series of images, was introduced yielding results consistent with the more traditional methods while some uncertainties were substantially reduced.We exploit the new characterization of the Crab's inner knot to discuss constraints on standard shock-model parameters that may be inferred from our observations assuming the inner knot lies near to the shocked surface. These include inferences as to wind magnetization σ, shock shape parameters such as incident angle δ 1 and poloidal radius of curvature R c , as well as the IR/optical emitting particle enthalpy fraction. We find that while the standard shock model gives good agreement with observation in many respects, there remain two puzzles: (a) the observed angular size of the knot relative to the pulsar-knot separation is measured to be much smaller than expected; (b) the variable, yet high degree of polarization reported is difficult to reconcile with a highly relativistic downstream flow. In contrast, the IR/optical flux of the inner knot is marginally consistent with the scenario that the shock accelerates most of the optical emitting particles in the nebula.Subject headings: neutron stars: general -pulsars: individual -Crab nebula and pulsar (PSR B0531+21) -inner knot γ-ray flares.

In this contribution we review the recent progress in the modeling of Pulsar Wind Nebulae (PWN). We start with a brief overview of the relevant physical processes in the magnetosphere, the wind-zone and the inflated nebula bubble. Radiative signatures and particle transport processes obtained from 3D simulations of PWN are discussed in the context of optical and X-ray observations. We then proceed to consider particle acceleration in PWN and elaborate on what can be learned about the particle acceleration from the dynamical structures called "wisps" observed in the Crab nebula. We also discuss recent observational and theoretical results of gamma-ray flares and the inner knot of the Crab nebula, which had been proposed as the emission site of the flares. We extend the discussion to GeV flares from binary systems in which the pulsar wind interacts with the stellar wind from a companion star. The chapter concludes with a discussion of solved and unsolved problems posed by PWN.Comment: To appear in "Jets and Winds in Pulsar Wind Nebulae, Gamma-ray Bursts and Blazars: Physics of Extreme Energy Release" of the Space Science Reviews series. The final publication is available at Springer via http://dx.doi.org/10.1007/s11214-017-0344-

We present ground-based optical observations of the September 2009 and January 2010 transits of HD 80606b. Based on 3 partial light curves of the September 2009 event, we derive a midtransit time of T c [HJD] = 2455099.196 ± 0.026, which is about 1σ away from the previously predicted time. We observed the January 2010 event from 9 different locations, with most phases of the transit being observed by at least 3 different teams. We determine a midtransit time of T c [HJD] = 2455210.6502 ± 0.0064, which is within 1.3σ of the time derived from a Spitzer observation of the same event.