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J. L. Elliot - One of the best experts on this subject based on the ideXlab platform.
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Recent Stellar Occultation Observations Using High-Speed, Portable Camera Systems
2020Co-Authors: Amanda A. S. Gulbis, J. L. Elliot, B A Babcock, M J Person, J M Pasachoff, S P Souza, C A ZuluagaAbstract:Abstract. We have recently constructed six observing systems identified as POETS (Portable Occultation Eclipse and Transit System[1]). These systems are optimized for (i) high-speed, high signal-to-noise observations at visible wavelengths and (ii) easy transport, to allow mounting on telescopes worldwide. The Andor iXon cameras have e2v CCD97 (frame transfer) sensors: a 512 ! 512 array of 16-micron pixels, back illuminated, with peak quantum efficiency > 90%. The maximum readout rate is 32 full frames per second, while binning and subframing can increase the cadence to a few hundred frames per second. Read noise in conventional modes goes below 6 electrons per pixel. Further, an electron-multiplying mode can effectively reduce the read noise to sub-electron levels, at the expense of dynamic range. The cameras are operated via a desktop computer that contains a 3 GHz Pentium 4 processor, 2 GB memory, and a 10,000 rpm hard disk. Images are triggered from a GPS receiver and have an approximately 50 nanosecond timing uncertainty. Each POETS can be transported as carry-on luggage. Here, we present instrument details, along with recent results from their use in Stellar Occultation observations by small bodies in the outer solar system. Occultations can produce data of the highest spatial resolution for any Earth-based observing method; therefore, they play a key role in determining diameters of distant solar-system bodies and probing the structure of atmospheres at the microbar level. We discuss POETS deployments in 2005-2007 to observe Stellar Occultations by Charon and Pluto (on 0.6-to 6.5-m telescopes) and future work on Occultations by Kuiper Belt objects
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an investigation of pluto s troposphere using Stellar Occultation light curves and an atmospheric radiative conductive convective model
Icarus, 2011Co-Authors: Angela M Zalucha, J. L. Elliot, Xun Zhu, A A S Gulbis, Darrell F StrobelAbstract:Abstract We use a radiative–conductive–convective model to assess the height of Pluto’s troposphere, as well as surface pressure and surface radius, from Stellar Occultation data from the years 1988, 2002, and 2006. The height of the troposphere, if it exists, is less than 1 km for all years analyzed. Pluto has at most a planetary boundary layer and not a troposphere. As in previous analyses of Pluto Occultation light curves, we find that the surface pressure is increasing with time, assuming that latitude and longitude variations in Pluto’s atmosphere are negligible. The surface pressure is found to be slightly higher ( 12.5 - 2.4 + 1.9 μbar in 1988, 18.0 - 1.7 + 11 μbar in 2002, and 18.5 ± 4.7 μbar in 2006) than in our previous analyses with the troposphere excluded. The surface radius is determined to be 1173 - 10 + 20 km . Comparison of the minimum reduced chi-squared values between the best-fit radiative–conductive–convective (i.e., troposphere-included) model and best-fit radiative–conductive (i.e., troposphere-excluded) shows that the troposphere-included model is only a slightly better fit to the data for all 3 years. Uncertainties in the small-scale physical processes of Pluto’s lower atmosphere and consequently the functional form of the model troposphere lend more confidence to the troposphere-excluded results.
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first results from the mit optical rapid imaging system moris on the irtf a Stellar Occultation by pluto and a transit by exoplanet xo 2b
Publications of the Astronomical Society of the Pacific, 2011Co-Authors: A A S Gulbis, J. L. Elliot, S J Bus, E R Adams, John Rayner, W E Stahlberger, F E Rojas, R Chung, A T Tokunaga, C A ZuluagaAbstract:We present a high-speed, visible-wavelength imaging instrument: MORIS (the MIT Optical Rapid Imaging System). MORIS is mounted on the 3 m Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. Its primary component is an Andor iXon camera, a nearly 60" square field of view with high quantum efficiency, low read noise, low dark current, and full-frame readout rates ranging from as slow as desired to a maximum of between 3.5 Hz and 35 Hz (depending on the mode; read noise of 6 e- pixel-1 and 49 e- pixel-1 with electron-multiplying gain = 1, respectively). User-selectable binning and subframing can increase the cadence to a few hundred hertz. An electron-multiplying mode can be employed for photon counting, effectively reducing the read noise to subelectron levels at the expense of dynamic range. Data cubes, or individual frames, can be triggered to several-nanosecond accuracy using the Global Positioning System. MORIS is mounted on the side-facing exit window of SpeX, allowing simultaneous near-infrared and visible observations. Here, we describe the components, setup, and measured characteristics of MORIS. We also report results from the first science observations: the 2008 June 24 Stellar Occultation by Pluto and an extrasolar planetary transit by XO-2b. The Pluto Occultation of a 15.8R magnitude star has a signal-to-noise ratio of 35 per atmospheric scale height and a midtime error of 0.32 s. The XO-2b transit reaches photometric precision of 0.5 mmag in 2 minutes and has a midtime timing precision of 23 s.
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first results from the mit optical rapid imaging system moris on the irtf a Stellar Occultation by pluto and a transit by exoplanet xo 2b
arXiv: Instrumentation and Methods for Astrophysics, 2011Co-Authors: A A S Gulbis, J. L. Elliot, S J Bus, E R Adams, John Rayner, W E Stahlberger, F E Rojas, R Chung, A T Tokunaga, C A ZuluagaAbstract:We present a high-speed, visible-wavelength imaging instrument: MORIS (the MIT Optical Rapid Imaging System). MORIS is mounted on the 3-m Infrared Telescope Facility (IRTF) on Mauna Kea, HI. Its primary component is an Andor iXon camera, a nearly 60 arcsec square field of view with high quantum efficiency, low read noise, low dark current, and full-frame readout rates ranging from as slow as desired to a maximum of between 3.5 Hz and 35 Hz (depending on the mode; read noise of 6e-/pixel and 49 e-/pixel with electron-multiplying gain=1, respectively). User-selectable binning and subframing can increase the cadence to a few hundred Hz. An electron-multiplying mode can be employed for photon counting, effectively reducing the read noise to sub-electron levels at the expense of dynamic range. Data cubes, or individual frames, can be triggered to several nanosecond accuracy using the Global Positioning System. MORIS is mounted on the side-facing exit window of SpeX (Rayner et al. 2003), allowing simultaneous near-infrared and visible observations. Here we describe the components, setup, and measured characteristics of MORIS. We also report results from the first science observations: the 24 June 2008 Stellar Occultation by Pluto and an extrasolar planetary transit by XO-2b. The Pluto Occultation, of a 15.8 R magnitude star, has signal-to-noise ratio of 35 per atmospheric scale height and a midtime error of 0.32 s. The XO-2b transit reaches photometric precision of 0.5 millimagnitudes in 2 minutes and has a midtime timing precision of 23 seconds.
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size and albedo of kuiper belt object 55636 from a Stellar Occultation
Nature, 2010Co-Authors: Amanda A. S. Gulbis, J. L. Elliot, C A Zuluaga, A S Bosh, E R Adams, S E Levine, M Lockhart, A M ZangariAbstract:The Kuiper belt is a collection of small bodies (Kuiper belt objects, KBOs) that lie beyond the orbit of Neptune and which are believed to have formed contemporaneously with the planets. Their small size and great distance make them difficult to study. KBO 55636 (2002 TX300) is a member of the water-ice-rich Haumea KBO collisional family. The Haumea family are among the most highly reflective objects in the Solar System. Dynamical calculations indicate that the collision that created KBO 55636 occurred at least 1 Gyr ago. Here we report observations of a multi-chord Stellar Occultation by KBO 55636, which occurred on 9 October 2009 ut. We find that it has a mean radius of 143 ± 5 km (assuming a circular solution). Allowing for possible elliptical shapes, we find a geometric albedo of 0.88 +0.15 -0.06 in the V photometric band, which establishes that KBO 55636 is smaller than previously thought and that, like its parent body, it is highly reflective. The dynamical age implies either that KBO 55636 has an active resurfacing mechanism, or that fresh water-ice in the outer Solar System can persist for gigayear timescales.
S W Mcdonald - One of the best experts on this subject based on the ideXlab platform.
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10199 chariklo Stellar Occultation candidates 1999 2005
The Astronomical Journal, 2000Co-Authors: R C Stone, J. L. Elliot, S W Mcdonald, E BowellAbstract:The Flagstaff Astrometric Scanning Transit Telescope was used to scan the sky in search of Occultation candidates through which the Centaur 10199 Chariklo (formerly 1997 CU26) will pass in 1999–2005. Positions for 96,397 stars (magnitudes 7.5 < V < 17.3) were determined using differential reductions to the ACT catalog of star positions and proper motions, and accuracies of ±30 mas were achieved for well-exposed images. The ephemeris for 10199 Chariklo was improved by including the new positions presented in this paper and, second, by correcting older positions taken from the literature for systematic errors. During this time period, 10199 Chariklo passes within 2'' of 117 of these stars, which are identified as Occultation candidates in this paper. Among these, 28 candidates have magnitudes V < 15.0, making them the best choices for observing programs using portable telescopes. Circumstances for each Occultation are given. Because the angular radius of 10199 Chariklo is only about 15 mas, the astrometry provided in this paper is only accurate enough for identifying possible Occultation events and is not sufficient for predicting individual shadow paths across the surface of Earth, although representative cases are given. Last-minute astrometry with a large-aperture telescope will be needed to refine each prediction.
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pluto charon Stellar Occultation candidates 2000 2009
The Astronomical Journal, 2000Co-Authors: S W Mcdonald, J. L. ElliotAbstract:We have completed a search for candidates for Occultations by Pluto and Charon over the years 2000 through 2009. Using the DE405 ephemeris and the Plu006 orbit model for Pluto and Charon, we searched for stars that lie within 10 of their respective apparent motions. The images used were CCD strip scans taken at the George R. Wallace Astrophysical Observatory, reaching a depth of 15th to 17th magnitude. As Pluto-Charon enter the Galactic plane, a dramatic increase in the number of Stellar appulses will occur. We identify 486 appulses by Pluto and 479 appulses by Charon over this period, with the frequency peaking in 2007. Further astrometry will be necessary to determine which of these appulses will have minimum separations small enough (less than 034 for Pluto or 031 for Charon) to produce an Occultation visible from Earth.
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triton Stellar Occultation candidates 2000 2009
The Astronomical Journal, 2000Co-Authors: S W Mcdonald, J. L. ElliotAbstract:As part of our ongoing program of predictions and observations of Stellar Occultations by solar system bodies, we have completed a search for candidates for Occultations by Triton over the decade 2000 to 2009. Star positions near Triton's projected orbit as determined by the DE405 ephemeris and NEP016 orbit model were measured on (unfiltered) CCD strip scans recorded with the 0.6 m telescope at the George R. Wallace Astrophysical Observatory to a depth of 16th to 18th magnitude, depending on the quality of individual strip scans. Within 10 of the predicted orbit of Triton during this period, 128 stars were found, including 12 stars brighter than 14th magnitude. Only appulses with geocentric minimum separations of less than about 037 will result in an Occultation visible from Earth, but potential errors in the ephemeris and in the positions of our candidates preclude accurate prediction of actual Occultation events without further astrometry.
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5145 pholus Stellar Occultation candidates 1999 2005
The Astronomical Journal, 1999Co-Authors: R C Stone, S W Mcdonald, J. L. ElliotAbstract:In search of Stellar Occultation candidates, the Flagstaff Automatic Scanning Transit Telescope (FASTT) was used to scan the sky through which the Centaur 5145 Pholus will pass during the period 1999–2005. Positions for 98,602 stars (7.0 < V < 17.7) were determined using differential reductions and the ACT catalog of star positions and proper motions, and accuracies of ±20 mas in each coordinate were achieved, except for the faintest stars observed. During the period of our search, Pholus passes within 15 of 100 of these stars, which have been identified as Occultation candidates in this paper. Circumstances for the possible Occultations are given, including finder charts for the 15 brightest stars. Since the radius of Pholus subtends approximately 10 mas, considerable astrometric effort will be required near the time of a potential event to determine whether it will result in an observable Occultation. A Stellar Occultation observed from multiple sites can be used to determine the precise radius and albedo for this object.
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triton Stellar Occultation candidates 1995 1999
The Astronomical Journal, 1995Co-Authors: S W Mcdonald, J. L. ElliotAbstract:We have completed a search for candidates for Stellar Occultations by Triton over the years 1995-1999. CCd strip scan images provided star positions in the relevant sky area to a depth of about 17.5 R magnitude. Over this time period, we find that Triton passes within 1.0 arcsec of 75 stars. Appulses with geocentric minimum separations of less than 0.35 arcsec will result in Stellar Occultations, but further astrometry and photometry is necessary to refine individual predictions for identification of actual Occultations. Finder charts are included to aid in further studies and prediction refinement. The two most promising potential Occultations, Tr176 and Tr180, occur in 1997.
M W Buie - One of the best experts on this subject based on the ideXlab platform.
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the sizes and albedos of centaurs 2014 yy _ 49 and 2013 nl _ 24 from Stellar Occultation measurements by recon
arXiv: Earth and Planetary Astrophysics, 2021Co-Authors: Ryder Strauss, M W Buie, L H Wasserman, Jj Kavelaars, Rodrigo Leiva, John Keller, Terry Bridges, R Weryk, Elizabeth Wilde, D E TrillingAbstract:In 2019, the Research and Education Collaborative Occultation Network (RECON) obtained multiple-chord Occultation measurements of two centaur objects: 2014 YY$_{49}$ on 2019 January 28 and 2013 NL$_{24}$ on 2019 September 4. RECON is a citizen-science telescope network designed to observe high-uncertainty Occultations by outer solar system objects. Adopting circular models for the object profiles, we derive a radius $r=16^{+2}_{-1}$km and a geometric albedo $p_V=0.13^{+0.015}_{-0.024}$ for 2014 YY$_{49}$, and a radius $r=66 ^{+5}_{-5}$km and geometric albedo $p_V = 0.045^{+0.006}_{-0.008}$ for 2013 NL$_{24}$. To the precision of these measurements, no atmosphere or rings are detected for either object. The two objects measured here are among the smallest distant objects measured with the Stellar Occultation technique. In addition to these geometric constraints, the Occultation measurements provide astrometric constraints for these two centaurs at a higher precision than has been feasible by direct imaging. To supplement the Occultation results, we also present an analysis of color photometry from the Pan-STARRS surveys to constrain the rotational light curve amplitudes and spectral colors of these two centaurs. We recommend that future work focus on photometry to more deliberately constrain the objects' colors and light curve amplitudes, and on follow-on Occultation efforts informed by this astrometry.
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a single chord Stellar Occultation by the extreme trans neptunian object 541132 lele a k u honua
arXiv: Earth and Planetary Astrophysics, 2020Co-Authors: M W Buie, Jj Kavelaars, B Sicardy, Rodrigo Leiva, John Keller, J Desmars, Terry Bridges, R Weryk, Dave Herald, Sean L HaleyAbstract:A Stellar Occultation by the extreme large-perihelion trans-Neptunian object (541132) Leleākūhonua (also known by the provisional designation of 2015 TG387) was predicted by the Lucky Star project and observed with the Research and Education Collaborative Occultation Network on 2018 October 20 UT. A single detection and a nearby nondetection provide constraints for the size and albedo. When a circular profile is assumed, the radius is $r={110}_{-10}^{+14}$ km, corresponding to a geometric albedo ${p}_{V}={0.21}_{-0.05}^{+0.03}$, for an adopted absolute magnitude of H V = 5.6, typical of other objects in dynamically similar orbits. The Occultation also provides a high-precision astrometric constraint.
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probing the hill sphere of 486958 2014 mu69 hst fgs observations during the 2017 july 17 Stellar Occultation
The Astronomical Journal, 2018Co-Authors: Joshua A Kammer, M W Buie, John R Spencer, A S Bosh, T M Becker, K D Retherford, Alan S Stern, C B Olkin, L H WassermanAbstract:We observed the 2017 July 17 Stellar Occultation of HD 168233 by the Kuiper Belt Object (486958) 2014 MU69, the close flyby target of the extended New Horizons mission. Rather than capture a solid body Occultation by the KBO itself, our program aimed to constrain the opacity of rings, moons, or other debris in the nearby environment. We used the Hubble Space Telescope Fine Guidance Sensors (HST FGS) instrument in TRANS F583W mode to collect 40 Hz time resolution photometry of the Stellar Occultation star for two HST orbits during this observation. We present the results of reduction and calibration of the HST FGS photometry, and set upper limits on rings or other dust opacity within the Hill sphere of (486958) 2014 MU69 at distances ranging from ~20000 km to ~75000 km from the main body.
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probing the hill sphere of 486958 2014 mu _ 69 hst fgs observations during the july 17 2017 Stellar Occultation
arXiv: Earth and Planetary Astrophysics, 2018Co-Authors: J Kammer, M W Buie, A S Bosh, T M Becker, K D Retherford, C B Olkin, S A Stern, J R Spencer, L H WassermanAbstract:We observed the July 17, 2017 Stellar Occultation of HD 168233 by the Kuiper Belt Object (486958) 2014 MU$_{69}$, the close flyby target of the extended New Horizons mission. Rather than capture a solid body Occultation by the KBO itself, our program aimed to constrain the opacity of rings, moons, or other debris in the nearby environment. We used the Hubble Space Telescope Fine Guidance Sensors (HST FGS) instrument in TRANS F583W mode to collect 40 Hz time resolution photometry of the Stellar Occultation star for two HST orbits during this observation. We present the results of reduction and calibration of the HST FGS photometry, and set upper limits on rings or other dust opacity within the Hill sphere of (486958) 2014 MU$_{69}$ at distances ranging from $\sim$20,000 km to $\sim$75,000 km from the main body.
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results from the 2014 november 15th multi chord Stellar Occultation by the tno 229762 2007 uk _ 126
arXiv: Earth and Planetary Astrophysics, 2016Co-Authors: G Benedettirossi, J L Ortiz, F Bragaribas, J I B Camargo, M W Buie, M Assafin, R Vieiramartins, B Sicardy, John Keller, N MoralesAbstract:We present results derived from the first multi-chord Stellar Occultation by the trans-Neptunian object (229762) 2007 UK$_{126}$, observed on 2014 November 15. The event was observed by the Research and Education Collaborative Occultation Network (RECON) project and International Occultation Timing Association (IOTA) collaborators throughout the United States. Use of two different data analysis methods obtain a satisfactory fit to seven chords, yelding an elliptical fit to the chords with an equatorial radius of $R=338_{-10} ^{+15}$ km and equivalent radius of $R_{eq}=319_{-7} ^{+14}$ km. A circular fit also gives a radius of $R=324_{-23} ^{+30}$ km. Assuming that the object is a Maclaurin spheroid with indeterminate aspect angle, and using two published absolute magnitudes for the body, we derive possible ranges for geometric albedo between $p_{V}=0.159_{-0.013} ^{+0.007}$ and $p_{R}=0.189_{-0.015}^{+0.009}$, and for the body oblateness between $\epsilon=0.105_{-0.040} ^{+0.050}$ and $\epsilon=0.118_{-0.048} ^{+0.055}$. For a nominal rotational period of 11.05 h, an upper limit for density of $\rho=1740$ kg~m$^{-3}$ is estimated for the body.
L H Wasserman - One of the best experts on this subject based on the ideXlab platform.
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the sizes and albedos of centaurs 2014 yy _ 49 and 2013 nl _ 24 from Stellar Occultation measurements by recon
arXiv: Earth and Planetary Astrophysics, 2021Co-Authors: Ryder Strauss, M W Buie, L H Wasserman, Jj Kavelaars, Rodrigo Leiva, John Keller, Terry Bridges, R Weryk, Elizabeth Wilde, D E TrillingAbstract:In 2019, the Research and Education Collaborative Occultation Network (RECON) obtained multiple-chord Occultation measurements of two centaur objects: 2014 YY$_{49}$ on 2019 January 28 and 2013 NL$_{24}$ on 2019 September 4. RECON is a citizen-science telescope network designed to observe high-uncertainty Occultations by outer solar system objects. Adopting circular models for the object profiles, we derive a radius $r=16^{+2}_{-1}$km and a geometric albedo $p_V=0.13^{+0.015}_{-0.024}$ for 2014 YY$_{49}$, and a radius $r=66 ^{+5}_{-5}$km and geometric albedo $p_V = 0.045^{+0.006}_{-0.008}$ for 2013 NL$_{24}$. To the precision of these measurements, no atmosphere or rings are detected for either object. The two objects measured here are among the smallest distant objects measured with the Stellar Occultation technique. In addition to these geometric constraints, the Occultation measurements provide astrometric constraints for these two centaurs at a higher precision than has been feasible by direct imaging. To supplement the Occultation results, we also present an analysis of color photometry from the Pan-STARRS surveys to constrain the rotational light curve amplitudes and spectral colors of these two centaurs. We recommend that future work focus on photometry to more deliberately constrain the objects' colors and light curve amplitudes, and on follow-on Occultation efforts informed by this astrometry.
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probing the hill sphere of 486958 2014 mu69 hst fgs observations during the 2017 july 17 Stellar Occultation
The Astronomical Journal, 2018Co-Authors: Joshua A Kammer, M W Buie, John R Spencer, A S Bosh, T M Becker, K D Retherford, Alan S Stern, C B Olkin, L H WassermanAbstract:We observed the 2017 July 17 Stellar Occultation of HD 168233 by the Kuiper Belt Object (486958) 2014 MU69, the close flyby target of the extended New Horizons mission. Rather than capture a solid body Occultation by the KBO itself, our program aimed to constrain the opacity of rings, moons, or other debris in the nearby environment. We used the Hubble Space Telescope Fine Guidance Sensors (HST FGS) instrument in TRANS F583W mode to collect 40 Hz time resolution photometry of the Stellar Occultation star for two HST orbits during this observation. We present the results of reduction and calibration of the HST FGS photometry, and set upper limits on rings or other dust opacity within the Hill sphere of (486958) 2014 MU69 at distances ranging from ~20000 km to ~75000 km from the main body.
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probing the hill sphere of 486958 2014 mu _ 69 hst fgs observations during the july 17 2017 Stellar Occultation
arXiv: Earth and Planetary Astrophysics, 2018Co-Authors: J Kammer, M W Buie, A S Bosh, T M Becker, K D Retherford, C B Olkin, S A Stern, J R Spencer, L H WassermanAbstract:We observed the July 17, 2017 Stellar Occultation of HD 168233 by the Kuiper Belt Object (486958) 2014 MU$_{69}$, the close flyby target of the extended New Horizons mission. Rather than capture a solid body Occultation by the KBO itself, our program aimed to constrain the opacity of rings, moons, or other debris in the nearby environment. We used the Hubble Space Telescope Fine Guidance Sensors (HST FGS) instrument in TRANS F583W mode to collect 40 Hz time resolution photometry of the Stellar Occultation star for two HST orbits during this observation. We present the results of reduction and calibration of the HST FGS photometry, and set upper limits on rings or other dust opacity within the Hill sphere of (486958) 2014 MU$_{69}$ at distances ranging from $\sim$20,000 km to $\sim$75,000 km from the main body.
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Stellar Occultation by 2060 chiron
Icarus, 1996Co-Authors: S J Bus, M W Buie, David G Schleicher, W B Hubbard, R L Marcialis, R E Hill, L H Wasserman, John R Spencer, R L MillisAbstract:Abstract A 14th magnitude double star was occulted by 2060 Chiron on 1993 November 7. Observations of this event were obtained from five locations in California. An Occultation by Chiron's nucleus was recorded at one of these sites, while a possible graze by the nucleus was seen at the next closest location. If this possible graze represents a true detection of the nucleus, Chiron's radius is determined to be 89.6 ± 6.8 km, assuming a circular outline for the shape. If the nucleus was not seen at the second location, Chiron's radius is only constrained as being greater than 90.2 ± 6.5 km. The presence of dust in Chiron's inner coma was also detected in four of the five Occultation datasets. Lightcurve features were identified that may be explained by narrow, collimated jets of material, and by a much larger region of dust distributed asymmetrically about Chiron's nucleus. Periodic fluctuations in the dust may have been detected in one of the lightcurves. If this periodicity is real, and is induced as a result of Chiron's rotation, then a minimum expansion velocity for the dust is found to be ∼40 m sec−1.
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chiron Stellar Occultation candidates 1993 1996
DPS, 1993Co-Authors: S J Bus, L H Wasserman, J. L. ElliotAbstract:A photographic search was conducted for stars that may be occulted by the unusual solar system object (2060) Chiron during the period from fall 1993 through summer 1996. 44 candidates were identified to a limiting V magnitude of 16, and for which the minimum appulse separation with Chiron is predicted to be less than 2.5 arcsec. The successful observation of a Stellar Occultation by Chiron would give a direct measure of its diameter (currently estimated to be between 60 and 300 km), and would help considerably in constraining Chiron's surface properties and volatile makeup. If at the time of the Occultation, Chiron exhibits a significant coma, there is also the potential for measuring the optical-depth profile of the dust in its inner coma.
C B Olkin - One of the best experts on this subject based on the ideXlab platform.
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probing the hill sphere of 486958 2014 mu69 hst fgs observations during the 2017 july 17 Stellar Occultation
The Astronomical Journal, 2018Co-Authors: Joshua A Kammer, M W Buie, John R Spencer, A S Bosh, T M Becker, K D Retherford, Alan S Stern, C B Olkin, L H WassermanAbstract:We observed the 2017 July 17 Stellar Occultation of HD 168233 by the Kuiper Belt Object (486958) 2014 MU69, the close flyby target of the extended New Horizons mission. Rather than capture a solid body Occultation by the KBO itself, our program aimed to constrain the opacity of rings, moons, or other debris in the nearby environment. We used the Hubble Space Telescope Fine Guidance Sensors (HST FGS) instrument in TRANS F583W mode to collect 40 Hz time resolution photometry of the Stellar Occultation star for two HST orbits during this observation. We present the results of reduction and calibration of the HST FGS photometry, and set upper limits on rings or other dust opacity within the Hill sphere of (486958) 2014 MU69 at distances ranging from ~20000 km to ~75000 km from the main body.
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probing the hill sphere of 486958 2014 mu _ 69 hst fgs observations during the july 17 2017 Stellar Occultation
arXiv: Earth and Planetary Astrophysics, 2018Co-Authors: J Kammer, M W Buie, A S Bosh, T M Becker, K D Retherford, C B Olkin, S A Stern, J R Spencer, L H WassermanAbstract:We observed the July 17, 2017 Stellar Occultation of HD 168233 by the Kuiper Belt Object (486958) 2014 MU$_{69}$, the close flyby target of the extended New Horizons mission. Rather than capture a solid body Occultation by the KBO itself, our program aimed to constrain the opacity of rings, moons, or other debris in the nearby environment. We used the Hubble Space Telescope Fine Guidance Sensors (HST FGS) instrument in TRANS F583W mode to collect 40 Hz time resolution photometry of the Stellar Occultation star for two HST orbits during this observation. We present the results of reduction and calibration of the HST FGS photometry, and set upper limits on rings or other dust opacity within the Hill sphere of (486958) 2014 MU$_{69}$ at distances ranging from $\sim$20,000 km to $\sim$75,000 km from the main body.
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size and shape from Stellar Occultation observations of the double jupiter trojan patroclus and menoetius
The Astronomical Journal, 2015Co-Authors: M W Buie, C B Olkin, Dave Herald, W J Merline, K J Walsh, H F Levison, Brad Timerson, W M Owen, Harry B Abramson, Katherine J AbramsonAbstract:We present results of a Stellar Occultation by the Jupiter Trojan asteroid Patroclus and its nearly equal size moon, Menoetius. The geocentric mid-time of the event was 2013 October 21 06:43:02 UT. Eleven sites out of 36 successfully recorded an Occultation. Seven chords across Patroclus yielded an elliptical limb fit of 124.6 by 98.2 km. There were six chords across Menoetius that yielded an elliptical limb fit of 117.2 by 93.0 km. There were three sites that got chords on both objects. At the time of the Occultation we measured a separation of 664.6 km (0.247 arcsec) and a position angle for Menoetius of 2657 measured eastward from J2000 north. Combining this Occultation data with previous light curve data, the axial ratios of both objects are 1.3 : 1.21 : 1, indicative of a mostly oblate ellipsoid with a slight asymmetry in its equatorial projection. The oblate shape is not an equilibrium shape for the current rotation period, but would be if it were rotating with an ~8 h period. This faster period is consistent with a pre-evolved state of the system with an orbital separation that is 50% smaller. Our best estimate of the system density is 0.88 g cm−3.
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evidence that pluto s atmosphere does not collapse from Occultations including the 2013 may 04 event
Icarus, 2015Co-Authors: C B Olkin, M W Buie, Leslie A Young, M Assafin, B Sicardy, D Borncamp, A Pickles, F B Bianco, Dias A De Oliveira, Michael GillonAbstract:Combining Stellar Occultation observations probing Pluto’s atmosphere from 1988 to 2013, and models of energy balance between Pluto’s surface and atmosphere, we find the preferred models are consistent with Pluto retaining a collisional atmosphere throughout its 248-year orbit. The Occultation results show an increasing atmospheric pressure with time in the current epoch, a trend present only in models with a high thermal inertia and a permanent N2 ice cap at Pluto’s north rotational pole.
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pluto s atmospheric structure from the july 2007 Stellar Occultation
Icarus, 2014Co-Authors: C B Olkin, M W Buie, R G French, L A Young, E F Young, R R Howell, J Regester, C Ruhland, T Natusch, D J RammAbstract:Abstract In July 2007, we observed a Stellar Occultation by Pluto from three sites in New Zealand and Australia. From these Occultation observations, we find that Pluto’s atmospheric pressure is still at the increased level measured in 2002 and 2006 with a pressure at a radius of 1275 km of 2.09 ± 0.09 μbar. One of the sites, Mt. John Observatory, was ∼70 km from the shadow center and we recorded the first central-flash Occultation by Pluto. We carried out a dual-wavelength observation from this site with two different cameras using filtered high-time resolution observations in the visible from the one-meter telescope at Mt. John Observatory. From our central-flash observations, we find the elliptical shape that best matches the data corresponds to a nearly prolate atmosphere with an ellipticity of 0.09. The flux observed in the central-flash data can be fit equally well with either a haze layer or a thermal gradient in the altitudes probed by the Occultation. However, the star light contributing to the central-flash Occultation for the haze layer model would pass through a radius of 1130 km from Pluto’s center. Given our current best estimate of Pluto’s surface radius is greater than 1151 km (Tholen, D.J., Buie, M.W. [1997]. Bulk properties of Pluto and Charon. In: Stern, S.A., Tholen, D.J. (Eds.), Pluto and Charon. The University of Arizona Press), we prefer the thermal gradient solution or a combination of haze and thermal gradient to explain the Occultation light curves.
