ImageJ is a graphical user interface (GUI) driven, public domain, Java-based, software package for general image processing traditionally used mainly in life sciences fields. The image processing capabilities of ImageJ are useful and extendable to other scientific fields. Here we present AstroImageJ (AIJ), which provides an astronomy specific image display environment and tools for astronomy specific image calibration and data reduction. Although AIJ maintains the general purpose image processing capabilities of ImageJ, AIJ is streamlined for time-series differential photometry, light curve detrending and fitting, and light curve plotting, especially for applications requiring ultra-precise light curves (e.g., exoplanet transits). AIJ reads and writes standard FITS files, as well as other common image formats, provides FITS header viewing and editing, and is World Coordinate System (WCS) aware, including an automated interface to the astrometry.net web portal for plate solving images. AIJ provides research grade image calibration and analysis tools with a GUI driven approach, and easily installed cross-platform compatibility. It enables new users, even at the level of undergraduate student, high school student, or amateur astronomer, to quickly start processing, modeling, and plotting astronomical image data with one tightly integrated software package.

Planets orbiting post-common envelope binaries provide fundamental information on planet formation and evolution. We searched for such planets in NN Ser ab, an eclipsing short-period binary that shows long-term eclipse time variations. Using published, reanalysed, and new mid-eclipse times of NN Ser ab obtained between 1988 and 2010, we find excellent agreement with the light-travel-time effect produced by two additional bodies superposed on the linear ephemeris of the binary. Our multi-parameter fits accompanied by N-body simulations yield a best fit for the objects NN Ser (ab)c and d locked in the 2:1 mean motion resonance, with orbital periods P c 15.5 yrs and P d 7.7 yrs, masses M c sin i c 6.9 M Jup and M d sin i d 2.2 M Jup , and eccentricities e c 0 and e d 0.20. A secondary χ 2 minimum corresponds to an alternative solution with a period ratio of 5:2. We estimate that the progenitor binary consisted of an A star with ∼2 M and the present M dwarf secondary at an orbital separation of ∼1.5 AU. The survival of two planets through the common-envelope phase that created the present white dwarf requires fine tuning between the gravitational force and the drag force experienced by them in the expanding envelope. The alternative is a second-generation origin in a circumbinary disk created at the end of this phase. In that case, the planets would be extremely young with ages not exceeding the cooling age of the white dwarf of 10 6 yrs.

We present spectra of the optical transient of GRB 021004 obtained with the Hobby-Eberly Telescope starting 15.48, 20.31 hours, and 4.84 days after the γ-ray burst and a spectrum obtained with the H. J. Smith 2.7 m Telescope starting 14.31 hours after the γ-ray burst. GRB 021004 is the first burst afterglow for which the spectrum is dominated by absorption lines from high ionization species with multiple velocity components separated by up to 3000 km s −1. We argue that these absorption lines are likely to come from shells around a massive progenitor star. The high velocities and high ionizations arise from a combination of acceleration and flash-ionization by the burst photons and the wind velocity and steady ionization by the progenitor. We also analyze the broad-band spectrum and the light curve so as to distinguish the structure of gas within 0.3 pc of the burster. We delineate six components in the medium surrounding the γ-ray burst along the line of sight: (1) The z ∼ = 2.293 absorption lines arise from the innermost region closest to the burst, where the ionization will be highest and the 3000 km s −1 velocity comes from the intrinsic velocity of a massive star wind boosted by acceleration from the burst flux. For a mass loss rate of ∼ 6 × 10 −5 M yr −1 , this component also provides the external medium with which the jet collides over radial distances 0.004-0.3 pc to create the afterglow light. (2) A second cloud or shell produces absorption lines with a relative velocity of 560 km s −1. This component could be associated with the shell created by the fast massive star wind blowing a bubble in the preceding slow wind at a radial distance of order 10 pc or by a clump at ∼ 0.5 pc accelerated by the burst. (3) More distant clouds within the host galaxy that lie between 30-2500 pc and have been ionized by the burst will create the z ∼ = 2.33 absorption lines. (4-6) If the three bumps in the afterglow light curve at 0.14, 1.1, and 4.0 days are caused by clumps or shells in the massive star wind along the line of sight, then the radii and over-densities of these are 0.022, 0.063, and 0.12 parsecs and 50%, 10%, and 10% respectively. The immediate progenitor of the γ-ray burst could either be a WC-type Wolf-Rayet star with a high velocity wind or a highly evolved massive star the original mass of which was too small for it to become a WN-type Wolf-Rayet star. In summary, the highly ionized lines with high relative velocities most likely come from shells or clumps of material close to the progenitor and these shells were plausibly produced by a massive star soon before its collapse.

Aims. We report the discovery of a planet with a high planet-to-star mass ratio in the microlensing event MOA-2009-BLG-387, which exhibited pronounced deviations over a 12-day interval, one of the longest for any planetary event. The host is an M dwarf, with a mass in the range 0.07 M < M host < 0.49 M at 90% confidence. The planet-star mass ratio q = 0.0132 ± 0.003 has been measured extremely well, so at the best-estimated host mass, the planet mass is m p = 2.6 Jupiter masses for the median host mass, M = 0.19 M . Methods. The host mass is determined from two "higher order" microlensing parameters. One of these, the angular Einstein radius θ E = 0.31 ± 0.03 mas has been accurately measured, but the other (the microlens parallax π E , which is due to the Earth's orbital motion) is highly degenerate with the orbital motion of the planet. We statistically resolve the degeneracy between Earth and planet orbital effects by imposing priors from a Galactic model that specifies the positions and velocities of lenses and sources and a Kepler model of orbits. Results. The 90% confidence intervals for the distance, semi-major axis, and period of the planet are 3.5 kpc < D L < 7.9 kpc, 1.1 AU < a < 2.7 AU, and 3.8 yr < P < 7.6 yr, respectively.

We report new mid-eclipse times of the short-period sdB/dM binary HW Virginis, which differ substantially from the times predicted by a previous model. The proposed orbits of the two planets in that model are found to be unstable. We present a new secularly stable solution, which involves two companions orbiting HW Vir with periods of 12.7 yr and 55 ± 15 yr. For orbits coplanar with the binary, the inner companion is a giant planet with mass M 3 sin i 3 14 M Jup and the outer one a brown dwarf or low-mass star with a mass of M 4 sin i 4 = 30−120 M Jup . Using the mercury6 code, we find that such a system would be stable over more than 10 7 yr, in spite of the sizeable interaction. Our model fits the observed eclipse-time variations by the light-travel time effect alone, without invoking any additional process, and provides support for the planetary hypothesis of the eclipse-time variations in close binaries. The signature of non-Keplerian orbits may be visible in the data.

Planets orbiting post-common envelope binaries provide fundamental information on planet formation and evolution, especially for the yet nearly unexplored class of circumbinary planets. We searched for such planets in DP Leo, an eclipsing short-period binary, which shows long-term eclipse-time variations. Using published, reanalysed, and new mid-eclipse times of the white dwarf in DP Leo, obtained between 1979 and 2010, we find agreement with the light-travel-time effect produced by a third body in an elliptical orbit. In particular, the measured binary period in 2009/2010 and the implied radial velocity coincide with the values predicted for the motion of the binary and the third body around the common center of mass. The orbital period, semi-major axis, and eccentricity of the third body are P c = 28.0 ± 2.0 yrs, a c = 8.2 ± 0.4 AU, and e c = 0.39 ± 0.13. Its mass of sin i c M c = 6.1 ± 0.5 M Jup qualifies it as a giant planet. It formed either as a first generation object in a protoplanetary disk around the original binary or as a second generation object in a disk formed in the common envelope shed by the progenitor of the white dwarf. Even a third generation origin in matter lost from the present accreting binary can not be entirely excluded. We searched for, but found no evidence for a fourth body.

The published version of this article presented high-precision observations of the transiting extrasolar planetary system WASP-18, which is of particular interest because accurate transit timings over a number of years may provide empirical constraints on the tidal quality factor of the host stars of gas giant planets. We have since discovered that the times recorded in the FITS headers of our observations were offset from the true values. This information was used to generate the timestamps in the photometric observations presented and analyzed in the published article, which are therefore also offset by an unknown amount.The problem has been traced back to a software "bug" (or "feature") which meant that the computer clock used in the generation of the FITS headers was only synchronized to an atomic clock when the computer was booted. WASP-18 was observed at the end of the season, when the computer had been running continuously for several months, and so was strongly affected by this problem. The timestamps in the light curve of WASP-18 are uniformly shifted to roughly 85 s later than the true values, calculated by comparison to the orbital ephemeris given by Hellier et al. (2009). A more precise value of the shift will be calculable in the future when an improved orbital ephemeris becomes available.The measured physical properties of the WASP-18 system in the published article are not affected by this problem, as they depend only on the relative values of the timestamps. However, the orbital ephemeris is significantly affected and should not be used in future analyses. For the purposes of planning further observations, we recommend that the orbital ephemeris given by Hellier et al. (2009) should be used.

We present time-resolved optical spectroscopy of the afterglows of the gamma-ray bursts GRB 990510 and GRB 990712. Through the identiÐcation of several absorption lines in the Ðrst-epoch GRB 990510 spectrum, we determine the redshift for this burst at z º 1.619. No clear emission lines are detected. The strength of the Mg I feature is indicative of a dense environment, most likely the host galaxy of GRB 990510. Although the host is extremely faint the GRB afterglow allows us to probe its inter-(V Z 28), stellar medium andÈin principleÈto measure its metallicity. The optical spectrum of GRB 990712 (whose host galaxy is the brightest of the known GRB hosts at cosmological redshifts) shows clear features both in emission and absorption, at a redshift of z \ 0.4331^0.0004. On the basis of several line emission diagnostic diagrams, we conclude that the host galaxy of GRB 990712 is most likely an H II galaxy. We derive an unreddened [O II] star formation rate of 2.7^0.8 yr~1. Correcting for the M _ measured extinction intrinsic to the host galaxy this value increases to yr~1.width, compared to that of Ðeld galaxies at z ¹ 1, also suggests that the host of GRB 990712 is vigorously forming stars. We employ the oxygen and Hb emission-line intensities to estimate the global oxygen abundance for the host of GRB 990712 : log (O/H) \ [3.7^0.4, which is slightly below the lowest metallicity one Ðnds in nearby spiral galaxies. For both GRBs we study the time evolution of the absorption lines, whose equivalent width might be expected to change with time if the burst resides in a dense compact medium. We Ðnd no evidence for a signiÐcant change in the Mg II width.