Search

We observed occultations by Pluto during a predicted series of events in 2014 July with the 1 m telescope of the Mt. John Observatory in New Zealand. The predictions were based on updated astrometry obtained in the previous months at the USNO, CTIO, and Lowell Observatories. We successfully detected occultations by Pluto of an R = 18 mag star on July 23 (14:23:32 ± 00:00:04 UTC to 14:25:30 ± 00:00:04 UTC), with a drop of 75% of the unocculted stellar signal, and of an R = 17 star on July 24 (11:41:30 ± 00:00:08 UTC to 11:43:28 ± 00:00:08 UTC), with a drop of 80% of the unocculted stellar signal, both with 20 s exposures with our frame-transfer Portable Occultation, Eclipse, and Transit System. Since Pluto had a geocentric velocity of 22.51 km s[superscript −1] on July 23 and 22.35 km s[superscript −1] on July 24, these intervals yield limits on the chord lengths (surface and lower atmosphere) of 2700 ± 130 km and 2640 ± 250 km, respectively, indicating that the events were near central, and therefore provide astrometric constraints on the prediction method. Our coordinated observations with the 4 m AAT in Australia on July 23 and the 6.5 m Magellan/Clay on Las Campanas, the 4.1 m Southern Astrophysical Research Telescope on Cerro Pachön, the 2.5 m DuPont on Las Campanas (LCO), the 0.6 m SARA-South on Cerro Tololo of the Southeastern Association for Research in Astronomy (SARA), the MPI/ESO 2.2 m on La Silla, and the 0.45 m Cerro Calán telescope and 0.36 telescope in Constitución in Chile on July 27 and 31, which would have provided higher-cadence observations for studies of Pluto's atmosphere, were largely foiled by clouds, but led to detection with the LCO Magellan/Clay and DuPont Telescopes on July 31 of the grazing occultation of a previously unknown 15th-magnitude star, completing the trio of occultations successfully observed and reported in this paper., National Research Foundation (South Africa)

Accepted: 2014-07-21, 著者人数: 34名

Author manuscript February 21, 2013, We present the discovery of a long-term stable L5 (trailing) Neptune Trojan in data acquired to search for candidate trans-Neptunian objects for the New Horizons spacecraft to fly by during an extended post-Pluto mission. This Neptune Trojan, 2011 HM[subscript 102], has the highest inclination (29[˚ over .]4) of any known member of this population. It is intrinsically brighter than any single L5 Jupiter Trojan at H[subscript V] ~ 8.18. We have determined its gri colors (a first for any L5 Neptune Trojan), which we find to be similar to the moderately red colors of the L4 Neptune Trojans, suggesting similar surface properties for members of both Trojan clouds. We also present colors derived from archival data for two L4 Neptune Trojans (2006 RJ[subscript 103] and 2007 VL[subscript 305]), better refining the overall color distribution of the population. In this document we describe the discovery circumstances, our physical characterization of 2011 HM[subscript 102], and this object's implications for the Neptune Trojan population overall. Finally, we discuss the prospects for detecting 2011 HM[subscript 102] from the New Horizons spacecraft during its close approach in mid- to late-2013., W. M. Keck Foundation

We present photometry of four transits of the exoplanet WASP-4b, each with a precision of approximately 500 ppm and a time sampling of 40-60 s. We have used the data to refine the estimates of the system parameters and ephemerides. During two of the transits we observed a short-lived, low-amplitude anomaly that we interpret as the occultation of a starspot by the planet. We also found evidence for a pair of similar anomalies in previously published photometry. The recurrence of these anomalies suggests that the stellar rotation axis is nearly aligned with the orbital axis, or else the starspot would not have remained on the transit chord. By analyzing the timings of the anomalies we find the sky-projected stellar obliquity to be lambda = –1[superscrip +14 over subscript –12] degrees. This result is consistent with (and more constraining than) a recent observation of the Rossiter-McLaughlin effect. It suggests that the planet migration mechanism preserved the initially low obliquity, or else that tidal evolution has realigned the system. Future applications of this method using data from the CoRoT and Kepler missions will allow spin-orbit alignment to be probed for many other exoplanets., United States. National Aeronautics and Space Administration (NASA Origins program award NNX09AD36G), United States. National Aeronautics and Space Administration (NASA Origins program award NNX09AB33G), Massachusetts Institute of Technology (Class of 1942), Caja de Ahorros y Pensiones de Barcelona, Space Telescope Science Institute (Hubble Fellowship grant HF-51267.01-A)

We present six new transits of the hot Jupiter OGLE-TR-113b observed with MagIC on the Magellan Telescopes between 2007 January and 2009 May. We update the system parameters and revise the planetary radius to R[subscript p] = 1.084 ± 0.029R[subscript J] , where the error is dominated by stellar radius uncertainties. The new transit midtimes reveal no transit timing variations from a constant ephemeris of greater than 13 ± 28 s over two years, placing an upper limit of 1–2M[subscript ⊕] on the mass of any perturber in a 1:2 or 2:1 mean-motion resonance with OGLETR- 113b. Combining the new transit epochs with five epochs published between 2002 and 2006, we find hints that the orbital period of the planet may not be constant, with the best fit indicating a decrease of [dot over P] = −60±15 ms yr−1. If real, this change in period could result from either a long-period (more than eight years) timing variation due to a massive external perturber or more intriguingly from the orbital decay of the planet. The detection of a changing period is still tentative and requires additional observations, but if confirmed it would enable direct tests of tidal stability and dynamical models of close-in planets., United States. National Aeronautics and Space Administration (Origins Grant NNX07AN63G)

December 15, 2010, We report the results of the first transit timing variation analysis of the very hot Jupiter OGLE-TR-132b, using 10 transits collected over a seven-year period. Our analysis combines three previously published transit light curves with seven new transits, which were observed between 2008 February and 2009 May with the new MagIC-e2V instrument on the Magellan Telescopes in Chile. We provide a revised planetary radius of R[subscript p] = 1.23 ± 0.07R[subscript J] , which is slightly larger, but consistent within the errors, than that given by previously published results. Analysis of the planet-to-star radius ratio, orbital separation, inclination, and transit duration reveals no apparent variation in any of those parameters during the time span observed. We also find no sign of transit timing variations larger than –108 ± 49 s, with most residuals very close to zero. This allows us to place an upper limit of 5-10 M [subscript ⊕] for a coplanar, low-eccentricity perturber in either the 2:1 or 3:2 mean-motion resonance with OGLE-TR-132b. We similarly find that the data are entirely consistent with a constant orbital period and there is no evidence for orbital decay within the limits of precision of our data., United States. National Aeronautics and Space Administration (Origins Grant NNX07AN63G)

Although OGLE-TR-56b was the second transiting exoplanet discovered, only one light curve, observed in 2006, has been published besides the discovery data. We present 21 light curves of 19 different transits observed between 2003 July and 2009 July with the Magellan Telescopes and Gemini South. The combined analysis of the new light curves confirms a slightly inflated planetary radius relative to model predictions, with R[subscript p] = 1.378 ± 0.090 R[subscript J]. However, the values found for the transit duration, semimajor axis, and inclination values differ significantly from the previous result, likely due to systematic errors. The new semimajor axis and inclination, a = 0.01942 ± 0.00015 AU and i = 73fdg72 ± 0fdg18, are smaller than previously reported, while the total duration, T [subscript 14] = 7931 ± 38 s, is 18 minutes longer. The transit midtimes have errors from 23 s to several minutes, and no evidence is seen for transit midtime or duration variations. Similarly, no change is seen in the orbital period, implying a nominal stellar tidal decay factor of Q * = 10[superscript 7], with a 3omega lower limit of 10[superscript 5.7]., United States. National Aeronautics and Space Administration (NASA Origins grant NNX07AN63G), United States. National Aeronautics and Space Administration (NASA through Hubble Fellowship grant HF- 01210.01-A/HF-51233.01 awarded by the STScI, which is operated by the AURA, Inc. for NASA, under contract NAS5- 26555)

We present photometry of four transits of the exoplanet WASP-4b, each with a precision of approximately 500 ppm and a time sampling of 40-60 s. We have used the data to refine the estimates of the system parameters and ephemerides. During two of the transits we observed a short-lived, low-amplitude anomaly that we interpret as the occultation of a starspot by the planet. We also found evidence for a pair of similar anomalies in previously published photometry. The recurrence of these anomalies suggests that the stellar rotation axis is nearly aligned with the orbital axis, or else the starspot would not have remained on the transit chord. By analyzing the timings of the anomalies we find the sky-projected stellar obliquity to be lambda = –1[superscrip +14 over subscript –12] degrees. This result is consistent with (and more constraining than) a recent observation of the Rossiter-McLaughlin effect. It suggests that the planet migration mechanism preserved the initially low obliquity, or else that tidal evolution has realigned the system. Future applications of this method using data from the CoRoT and Kepler missions will allow spin-orbit alignment to be probed for many other exoplanets., United States. National Aeronautics and Space Administration (NASA Origins program award NNX09AD36G), United States. National Aeronautics and Space Administration (NASA Origins program award NNX09AB33G), Massachusetts Institute of Technology (Class of 1942), Caja de Ahorros y Pensiones de Barcelona, Space Telescope Science Institute (Hubble Fellowship grant HF-51267.01-A)

The Magellan Baade and Clay telescopes regularly produce images of ~0.5" in natural seeing. We review efforts to improve collimation, active optics response, and telescope guiding and pointing to optimize the performance of the telescopes. Procedures have been developed to monitor and analyze image quality delivered by the imaging science instruments. Improved models have been developed to correct for flexure of the telescope and primary mirror under gravity loading. Collimation has been improved using a "two-probe" Shack-Hartman technique to measure field aberrations. Field acquisition performance has been improved by implementing an open loop model for the primary mirror control. Telescope pointing has been improved by regular monitoring and adjustments to improve acquisition times.