Author
Byeong-Gon Park
Other affiliations: Korea University of Science and Technology
Bio: Byeong-Gon Park is an academic researcher from Korea Astronomy and Space Science Institute. The author has contributed to research in topics: Gravitational microlensing & Planet. The author has an hindex of 15, co-authored 85 publications receiving 707 citations. Previous affiliations of Byeong-Gon Park include Korea University of Science and Technology.
Papers published on a yearly basis
Papers
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TL;DR: In this article, the authors present microlensing rate and time-scale predictions and spatial distributions for stellar and sub-stellar lens populations in combined disc and barred bulge models of M31.
Abstract: The Andromeda Galaxy Stellar Robotic Microlensing Project (The Angstrom Project) aims to use stellar microlensing events to trace the structure and composition of the inner regions of the Andromeda Galaxy (M31). We present microlensing rate and time-scale predictions and spatial distributions for stellar and sub-stellar lens populations in combined disc and barred bulge models of M31. We show that at least half of the stellar microlenses in and around the bulge are expected to have characteristic durations between 1 and 10 d, rising to as much as 80 per cent for brown-dwarf dominated mass functions. These short-duration events are mostly missed by current microlensing surveys that are looking for Macho candidates in the M31 dark matter halo. Our models predict that an intensive monitoring survey programme, such as Angstrom, which will be able to detect events of durations upwards of a day, could detect around 30 events per season within ∼5 arcmin of the M31 centre due to ordinary low-mass stars and remnants. This yield increases to more than 60 events for brown-dwarf dominated mass functions. The overall number of events and their average duration are sensitive diagnostics of the bulge mass, in particular the contribution of low-mass stars and brown dwarfs. The combination of an inclined disc, an offset bar-like bulge, and differences in the bulge and disc luminosity functions results in a four-way asymmetry in the number of events expected in each quadrant defined by the M31 disc axes. The asymmetry is sensitive to the bar prolongation, orientation and mass.
47 citations
TL;DR: In this paper, a similar observational setup was used for the mass determinations of free-floating planets with masses ranging from several Earth masses to several Jupiter masses, which are the populations of planets that have not been previously probed.
Abstract: Various methods have been proposed to search for extrasolar planets. Compared to the other methods, microlensing has unique applicabilities to the detections of Earth-mass and free-floating planets. However, the microlensing method is seriously flawed by the fact that the masses of the detected planets cannot be uniquely determined. Recently, Gould, Gaudi, & Han introduced an observational setup that enables one to resolve the mass degeneracy of the Earth-mass planets. The setup requires a modest adjustment to the orbit of an already proposed microlensing planet-finder satellite combined with ground-based observations. In this paper, we show that a similar observational setup can also be used for the mass determinations of free-floating planets with masses ranging from several Earth masses to several Jupiter masses. If the proposed observational setup is realized, future lensing surveys will play important roles in the studies of Earth-mass and free-floating planets, which are the populations of planets that have not been previously probed.
41 citations
TL;DR: In this paper, the authors analyzed the Kepler light curve by including a third light source and one starspot on each binary component and found that the close eclipsing pair is in a low-mass eccentric-orbit, detached configuration.
Abstract: In a recent study, Armstrong et al. presented an eclipsing binary star of about 6.2 hr period with transit-like tertiary signals occurring every 204.2 days in the Kepler public data of KIC002856960 and proposed three possible hierarchical structures: (AB)b, (AB)C, and A(BC). We analyzed the Kepler light curve by including a third light source and one starspot on each binary component. The results represent that the close eclipsing pair is in a low-mass eccentric-orbit, detached configuration. Based on 123 eclipse timings calculated from the Wilson-Devinney binary model, a period study of the close binary reveals that the orbital period has experienced a sinusoidal variation with a period and a semi-amplitude of 205 ± 2 days and 0.0021 ± 0.0002 days, respectively. The period variation would be produced by the light-travel-time effect due to a gravitationally bound third body with a minimum mass of M 3sin i 3 = 0.76 M ☉ in an eccentric orbit of e 3 = 0.61. This is consistent with the presence of third light found in our light curve solution and the tertiary signal of 204.2 day period most likely arises from the K-type star crossed by the close eclipsing binary. Then, KIC002856960 is a triply eclipsing hierarchical system, A(BC), consisting of a close binary with two M-type dwarfs and a more massive K-type component. The presence of the third star may have played an important role in the formation and evolution of the close pair, which may ultimately evolve into a contact system by angular momentum loss.
32 citations
University of Warsaw1, Korea Astronomy and Space Science Institute2, Isfahan University of Technology3, Ohio State University4, Max Planck Society5, University of Canterbury6, Chungbuk National University7, Harvard University8, California Institute of Technology9, Zhejiang University10, Tsinghua University11, University of Toronto12, Kyung Hee University13, University of Salerno14, University of St Andrews15, Heidelberg University16, University of Copenhagen17, University of Antofagasta18, University of Kent19, University of Hamburg20, Stockholm University21, Keele University22, Nagoya University23, University of Atacama24, University of Rome Tor Vergata25, University of Coimbra26, Sharif University of Technology27, Pontifical Catholic University of Chile28, Open University29, Aarhus University30
TL;DR: The OGLE-2017-BLG-1434Lb is the only known super-Earth with a mass ratio q ≥ 1×10-4 as mentioned in this paper, which is the smallest mass ratio known.
Abstract: We report the discovery of a cold Super-Earth planet (mp=4.4±0.5 M⊕) orbiting a low-mass (M=0.23±0.03) M⊙ dwarf at projected separation a⊥=1.18±0.10 a.u., i.e., about 1.9 times the distance the snow line. The system is quite nearby for a microlensing planet, DL=0.86±0.09 kpc. Indeed, it was the large lens-source relative parallax πrel=1.0 mas (combined with the low mass M) that gave rise to the large, and thus well-measured, "microlens parallax" πE∝(πrel/M)1/2 that enabled these precise measurements. OGLE-2017-BLG-1434Lb is the eighth microlensing planet with planet-host mass ratio q<1×10-4.
We apply a new planet-detection sensitivity method, which is a variant of "V/Vmax", to seven of these eight planets to derive the mass-ratio function in this regime. We find dN/d lnq ∝ qp, with p=1.05+0.78-0.68, which confirms the "turnover" in the mass function found by Suzuki et al. relative to the power law of opposite sign n=-0.93±0.13 at higher mass ratios q≳2×10-4. We combine our result with that of Suzuki et al. to obtain p=0.73+0.42-0.34.
30 citations
TL;DR: The BOAO photometric survey of open clusters as discussed by the authors was initiated to enlarge the understanding of Galactic structure using UBVI CCD photometry of open cluster, which have been little studied before.
Abstract: We have initiated a long-term project, the BOAO photometric survey of open clusters, to enlarge our understanding of Galactic structure using UBVI CCD photometry of open clusters, which have been little studied before. This is the second paper of the project, in which we present the photometry of 12 open clusters. We have determined the cluster parameters by fitting the Padua isochrones to the color-magnitude diagrams of the clusters. All the clusters except for Be 60 and NGC 1348 are found to be intermediate-age to old (0.2–4.0 Gyrs) open clusters with a mean metallicity of [Fe/H] ≈ 0.0.
30 citations
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15 Mar 1979
TL;DR: In this article, the experimental estimation of parameters for models can be solved through use of the likelihood ratio test, with particular attention to photon counting experiments, and procedures presented solve a greater range of problems than those currently in use, yet are no more difficult to apply.
Abstract: Many problems in the experimental estimation of parameters for models can be solved through use of the likelihood ratio test. Applications of the likelihood ratio, with particular attention to photon counting experiments, are discussed. The procedures presented solve a greater range of problems than those currently in use, yet are no more difficult to apply. The procedures are proved analytically, and examples from current problems in astronomy are discussed.
1,748 citations
1,288 citations
03 Jun 2001
Abstract: We present the largest galaxies as seen in the near-infrared (1–2 μm), imaged with the Two Micron All Sky Survey (2MASS), ranging in angular size from 1' to 15. We highlight the 100 largest in the sample. The galaxies span all Hubble morphological types, including elliptical galaxies, normal and barred spirals, and dwarf and peculiar classes. The 2MASS Large Galaxy Atlas provides the necessary sensitivity and angular resolution to examine in detail morphologies in the near-infrared, which may be radically different from those in the optical. Internal structures such as spirals, bulges, warps, rings, bars, and star formation regions are resolved by 2MASS. In addition to large mosaic images, the atlas includes astrometric, photometric, and shape global measurements for each galaxy. A comparison of fundamental measures (e.g., surface brightness, Hubble type) is carried out for the sample and compared with the Third Reference Catalogue. We further showcase NGC 253 and M51 (NGC 5194/5195) to demonstrate the quality and depth of the data. The atlas represents the first uniform, all-sky, dust-penetrated view of galaxies of every type, as seen in the near-infrared wavelength window that is most sensitive to the dominant mass component of galaxies. The images and catalogs are available through the NASA/IPAC Extragalactic Database and Infrared Science Archive and are part of the 2MASS Extended Source Catalog.
659 citations
Book•
01 May 2011TL;DR: In this paper, the authors present an overview of the solar system and its evolution, including the formation and evolution of stars, asteroids, and free-floating planets, as well as their internal and external structures.
Abstract: 1. Introduction 2. Radial velocities 3. Astrometry 4. Timing 5. Microlensing 6. Transits 7. Imaging 8. Host stars 9. Brown dwarfs and free-floating planets 10. Formation and evolution 11. Interiors and atmospheres 12. The Solar System Appendixes References Index.
527 citations
Pontifical Catholic University of Chile1, Princeton University2, University of Hertfordshire3, European Southern Observatory4, Atacama Large Millimeter Submillimeter Array5, University of Cambridge6, University of Edinburgh7, University of Manchester8, Queen Mary University of London9, University of La Serena10, University of Lisbon11, Instituto de Astronomía Teórica y Experimental12, INAF13, University of Warsaw14, University of Concepción15, Valparaiso University16, National University of Cordoba17, University of Florida18, National Scientific and Technical Research Council19, University of São Paulo20, National University of La Plata21, University of Padua22, University of Wisconsin–Whitewater23, Universidade Federal do Rio Grande do Sul24, University of Chile25, Peking University26, Kyung Hee University27, Max Planck Society28, University of Alicante29, University College London30, University of Cincinnati31, University of Leeds32, Ames Research Center33, UK Astronomy Technology Centre34, University of La Laguna35, Spanish National Research Council36, University of Southampton37, Saint Mary's University38, Macquarie University39, Australian Astronomical Observatory40, Andrés Bello National University41, Hartebeesthoek Radio Astronomy Observatory42, Aryabhatta Research Institute of Observational Sciences43, University of Kent44
TL;DR: The ESO VISTA public survey VISTA variables in the V�a L�ctea (VVV) started in 2010 and is expected to run for about five years.
Abstract: Context The ESO public survey VISTA variables in the V�a L�ctea (VVV) started in 2010 VVV targets 562 sq deg in the Galactic bulge and an adjacent plane region and is expected to run for about five years Aims: We describe the progress of the survey observations in the first observing season, the observing strategy, and quality of the data obtained Methods: The observations are carried out on the 4-m VISTA telescope in the ZYJHK s filters In addition to the multi-band imaging the variability monitoring campaign in the K s filter has started Data reduction is carried out using the pipeline at the Cambridge Astronomical Survey Unit The photometric and astrometric calibration is performed via the numerous 2MASS sources observed in each pointing Results: The first data release contains the aperture photometry and astrometric catalogues for 348 individual pointings in the ZYJHK s filters taken in the 2010 observing season The typical image quality is 09 arcsec {-10 arcsec} The stringent photometric and image quality requirements of the survey are satisfied in 100% of the JHK s images in the disk area and 90% of the JHK s images in the bulge area The completeness in the Z and Y images is 84% in the disk, and 40% in the bulge The first season catalogues contain 128 � 10 8 stellar sources in the bulge and 168 � 10 8 in the disk area detected in at least one of the photometric bands The combined, multi-band catalogues contain more than 163 � 10 8 stellar sources About 10% of these are double detections because of overlapping adjacent pointings These overlapping multiple detections are used to characterise the quality of the data The images in the JHK s bands extend typically 4 mag deeper than 2MASS The magnitude limit and photometric quality depend strongly on crowding in the inner Galactic regions The astrometry for K s = 15-18 mag has rms 35-175 mas Conclusions: The VVV Survey data products offer a unique dataset to map the stellar populations in the Galactic bulge and the adjacent plane and provide an exciting new tool for the study of the structure, content, and star-formation history of our Galaxy, as well as for investigations of the newly discovered star clusters, star-forming regions in the disk, high proper motion stars, asteroids, planetary nebulae, and other interesting objects Based on observations taken within the ESO VISTA Public Survey VVV, Programme ID 179B-2002
418 citations