Murat Kaplan

A time-symmetric block time-step algorithm for N-body simulations

Abstract The method of choice for integrating the equations of motion of the general N -body problem has been to use an individual time step scheme. For the sake of efficiency, block time steps have been the most popular, where all time step sizes are smaller than a maximum time step size by an integer power of two. We present the first successful attempt to construct a time-symmetric integration scheme, based on block time steps. We demonstrate how our scheme shows a vastly better long-time behavior of energy errors, in the form of a random walk rather than a linear drift. Increasing the number of particles makes the improvement even more pronounced.

Optical observations of NEA 162173 (1999 JU3) during the 2011-2012 apparition

Context. Near-Earth asteroid 162173 (1999 JU3) is a potential target of two asteroid sample return missions, not only because of its accessibility but also because of the first C-type asteroid for exploration missions. The lightcurve-related physical properties of this object were investigated during the 2011–2012 apparition. Aims. We aim to confirm the physical parameters useful for JAXA’s Hayabusa 2 mission, such as rotational period, absolute magnitude, and phase function. Our data complement previous studies that did not cover low phase angles. Methods. With optical imagers and 1−2 m class telescopes, we acquired the photometric data at different phase angles. We independently derived the rotational lightcurve and the phase curve of the asteroid. Results. We have analyzed the lightcurve of 162173 (1999 JU3), and derived a synodic rotational period of 7.625 ± 0.003 h, the axis ratio a/b = 1.12. The absolute magnitude HR = 18.69 ± 0.07 mag and the phase slope of G = −0.09 ± 0.03 were also obtained based on the observations made during the 2011 − 2012 apparition. These physical properties are in good agreement with the previous results obtained during the 2007−2008 apparition.

Shape and spin determination of Barbarian asteroids

Context. The so-called Barbarian asteroids share peculiar, but common polarimetric properties, probably related to both their shape and composition. They are named after (234) Barbara, the first on which such properties were identified. As has been suggested, large scale topographic features could play a role in the polarimetric response, if the shapes of Barbarians are particularly irregular and present a variety of scattering/incidence angles. This idea is supported by the shape of (234) Barbara, that appears to be deeply excavated by wide concave areas revealed by photometry and stellar occultations. Aims. With these motivations, we started an observation campaign to characterise the shape and rotation properties of Small Main-Belt Asteroid Spectroscopic Survey (SMASS) type L and Ld asteroids. As many of them show long rotation periods, we activated a worldwide network of observers to obtain a dense temporal coverage. Methods. We used light-curve inversion technique in order to determine the sidereal rotation periods of 15 asteroids and the convergence to a stable shape and pole coordinates for 8 of them. By using available data from occultations, we are able to scale some shapes to an absolute size. We also study the rotation periods of our sample looking for confirmation of the suspected abundance of asteroids with long rotation periods. Results. Our results show that the shape models of our sample do not seem to have peculiar properties with respect to asteroids with similar size, while an excess of slow rotators is most probably confirmed.

A-Track: A new approach for detection of moving objects in FITS images

Abstract We have developed a fast, open-source, cross-platform pipeline, called A-Track, for detecting the moving objects (asteroids and comets) in sequential telescope images in FITS format. The pipeline is coded in Python 3. The moving objects are detected using a modified line detection algorithm, called MILD. We tested the pipeline on astronomical data acquired by an SI-1100 CCD with a 1-meter telescope. We found that A-Track performs very well in terms of detection efficiency, stability, and processing time. The code is hosted on GitHub under the GNU GPL v3 license. Program summary Program title: A-TRACK Catalogue identifier: AFBC_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AFBC_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: GNU General Public Licence Version 3 No. of lines in distributed program, including test data, etc.: 313100 No. of bytes in distributed program, including test data, etc.: 89443558 Distribution format: tar.gz Programming language: Python 3. Computer: Personal Computer. Operating system: Any OS where Python 3 and subprograms are installed. Classification: 14. External routines: Numpy, Pandas, SExtractor, PyFITS, Alipy, f2n, docopt, Imagemagick, git-all, scipy, matplatlib, astroasciidata. Nature of problem: Asteroid and comet detection. Solution method: A multiple image line detection algorithm for sequential FITS images. Running time: ∼1 min

A Dynamic Era-Based Time-Symmetric Block Time-Step Algorithm with Parallel Implementations

The time-symmetric block time--step (TSBTS) algorithm is a newly developed efficient scheme for

A recursive algorithm for finding HDMR terms for sensitivity analysis

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Rotational Properties of the Maria Asteroid Family

--body integrations. It is constructed on an era-based iteration. In this work, we re-designed the TSBTS integration scheme with dynamically changing era size. A number of numerical tests were performed to show the importance of choosing the size of the era, especially for long time integrations. Our second aim was to show that the TSBTS scheme is as suitable as previously known schemes for developing parallel

Interactions between brown-dwarf binaries and Sun-like stars

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Astrometry with A-Track Using Gaia DR1 Catalogue

--body codes. In this work, we relied on a parallel scheme using the copy algorithm for the time-symmetric scheme. We implemented a hybrid of data and task parallelization for force calculation to handle load balancing problems that can appear in practice. Using the Plummer model initial conditions for different numbers of particles, we obtained the expected efficiency and speedup for a small number of particles. Although parallelization of the direct

Dynamical analyses on the transitivity from JFC and Centaur regions to NEAs with Tisserand parameters from 2 to 3

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