• 천문학회지
• /
• 제45권1호
• /
• pp.7-17
• /
• 2012

Y-band is a broad passband that is centered at ~1 ${\mu}m$. It is becoming a new, popular window for extragalactic study especially for observations of red objects thanks to recent CCD technology developments. In order to better understand the general characteristics of objects in Y-band, and to investigate the promise of Y-band observations with small telescopes, we carried out imaging observations of several extragalactic fields, brown dwarfs, and high redshift quasars with Y-band filter at the Mt. Lemmon Optical Astronomy Observatory and the Maidanak observatory. From our observations, we constrain the bright end of the galaxy and the stellar number counts in Y-band. We also test the usefulness of high redshift quasar (z >6) selection via i - z - Y color-color diagram, to demonstrate that the i - z - Y color-color diagram is effective for the selection of high redshift quasars even with a conventional optical CCD camera installed at a 1-m class telescope.

• 천문학회보
• /
• 제40권1호
• /
• pp.61.2-61.2
• /
• 2015

15P/Finlay is one of the Jupiter-Family Comets that has long been known since the late 19 century. The comet maintains the perihelion around 1.0 AU over a century, without showing any prominent activities (i.e. fragmentation or eruption) since the discovery. According to reports in unpublished observations, the comet exhibited an outburst in the middle of 2014 December. We conducted a imaging observation of 15P/Finlay just after the report, from 2014 December 23 to 2015 February 18 using three telescopes (the Okayama Astrophysical Observatory 50-cm telescope, the Ishigakijima Astronomical Observatory 105-cm telescope, and the Nishi-Harima Astronomical Observatory 2-m telescope), which constitute a portion of the OISTER (an inter-university observation network in the optical and infrared wavelengths). As a result of the frequent observations, we witnesses the second outburst around UT 2015 January 16. Such cometary outbursts draw the attention to researchers on ground that they could offer insight into the internal structure of comets, following a historical outburst occurred at 17P/Holmes on 2007 October 23. Although cometary outbursts have been often reported mostly in unpublished observations or unreviewed reports, it should be emphasized that there are not a sufficient number of astrophysical research which characterizes the physical properties by observing the aftermaths. This presentation provides a new observational result of 15P/Finlay outburst. Based on the morphological development of the dust cloud as well as the near-nuclear magnitude, we will derive the kinetic energy of the outburst. Finally we plan to compare the results of 15P/Finlay with those of analogical events at 17P/Holmes and P/2010 V1 (Ikeya-Murakami).

• 천문학논총
• /
• 제30권2호
• /
• pp.205-209
• /
• 2015

The Eclipsing Binaries Minima (BIMA) Monitoring Project is a CCD-based photometric observational program initiated by Bosscha Observatory - Lembang, Indonesia in June 2012. Since December 2012 the National Astronomical Research Institute of Thailand (NARIT) has joined the BIMA Project as the main partner. This project aims to build an open-database of eclipsing binary minima and to establish the orbital period of each system and its variations. The project is conducted on the basis of multisite monitoring observations of eclipsing binaries with magnitudes less than 19 mag. Differential photometry methods have been applied throughout the observations. Data reduction was performed using IRAF. The observations were carried out in BVRI bands using three different small telescopes situated in Indonesia, Thailand, and Chile. Computer programs have been developed for calculating the time of minima. To date, more than 140 eclipsing binaries have been observed. From them 71 minima have been determined. We present and discuss the O-C diagrams for some eclipsing binary systems.

• 천문학논총
• /
• 제30권2호
• /
• pp.699-701
• /
• 2015

The high plateaus in west China may provide suitable sites for astronomical observations with the institute's middle-range telescopes and possibly with larger telescopes. Under China-Japan collaborations for site survey in west China, we have been conducting searches for good sites and monitoring their characteristics over several years. As recent results of our site survey show, sites in west Tibet are revealed with a high possibility of good astronomical observations. Weather characteristics at Gar in Ali, Tibet, show its high clear-sky ratios, especially in winter, comparable to Mauna Kea, Hawaii. But it has some wind problem in winter, where stronger wind speeds, over 20m/sec, occur frequently even though the sky is clear. To find calmer sites, we have conducted numerical simulations for the Ali area using the Japan Meteorological Agency NonHydrostatic Model. We have found another site, named ZoZo Hill, near Gar. We will continue to monitor the Gar site to clarify weather characteristics over the whole year and hopefully start to negotiate for site monitoring at ZoZo Hill this year.

• 천문학회보
• /
• 제43권1호
• /
• pp.69.2-69.2
• /
• 2018

On 2018 March 27, a 1-m telescope was installed at the SNU Astronomical Observatory (SAO) which is a newly constructed building at the site where the previous Kwanak Observatory (Old observatory; 구천문대) stood. A series of test observations have been performed on this telescope, and we report the first results from the test observations in this poster. In particular, we present seeing values, limiting magnitudes and sample images taken with a $4k{\times}4k$ CCD camera ($21^{\prime}{\times}21^{\prime}$).

• 천문학회보
• /
• 제38권1호
• /
• pp.26-26
• /
• 2013

The high Antarctic plateau is the driest and coldest environment on the surface of the Earth and offers superlative conditions for the conduct of a wide range of astronomical observations, from optical to millimetre wavebands. This includes, especially, the infrared - where the sky background is greatly reduced from temperate sites - and the sub-millimetre / THz bands - where new or cleaner atmospheric windows can be viewed through. Astronomical observations have now been conducted from five locations on the Antarctic plateau - the South Pole, Domes A, C and F, and Ridge A. Ambitious plans for the construction of observatories there have been announced. An IAU Symposium on "Astrophysics from Antarctica" featured as part of last year's IAU General Assembly in Beijing. This talk will provide an overview of astronomy in Antarctica, describing the special conditions that make some forms of observation particularly favourable there, and discuss the development of observatories on the Antarctic plateau and the plans for their future development.

• 천문학회보
• /
• 제39권1호
• /
• pp.64-64
• /
• 2014

FU Orionis type object is a category of low mass pre-main sequence star which displays optical outburst caused by accreting material at rapid rates from their surrounding disks in a few months. V1057 Cyg was about 16 mag. In late 1969, however, it rapidly brightened more than 5 mag and classified as a FU Orionis type object. After the outburst the brightness began to weaken monotonously and in 1990's magnitude decreased 13.0 mag. We carried out photometric observations of V1057 Cyg in V R I bands from 2013 November 7 to 20 with the 76 cm Ritchey-Chretien telescope at Kyung Hee Astronomical Observatory (KHAO). These result can display the recent brightness change of V1057Cyg during observation period. We also discuss possibilities of using an on-campus telescope for astronomical research works.

• 천문학회지
• /
• 제37권5호
• /
• pp.307-313
• /
• 2004

Clusters of galaxies are believed to constitute a population of astrophysical objects potentially able to emit electromagnetic radiation up to gamma-ray energies. Evidence of the existence of non-thermal radiation processes in galaxy clusters is indicated from observations of diffuse radio halos, hard X-ray and EUV excess emission. The presence of cosmic ray acceleration processes and its confinement on cosmological timescales nearly inevitably yields in predicting energetic gamma-ray emission, either directly deduceably from a cluster's multifreqency emission characteristics or indirectly during large-scale cosmological structure formation processes. This theoretical reasoning suggests several scenarios to actually detect galaxy clusters at gamma-ray wavelengths: Either resolved as individual sources of point-like or extended gamma-ray emission, by investigating spatial-statistical correlations with unidentified gamma-ray sources or, if unresolved, through their contribution to the extragalactic diffuse gamma-ray background. In the following I review the situation concerning the proposed relation between galaxy clusters and high-energy gamma-ray observations from an observational point-of-view.

• 천문학회보
• /
• 제39권2호
• /
• pp.79.2-79.2
• /
• 2014

Galactic radio pulsar population is diverse. So far about 2300 radio pulsars are known in the Milky Way, in addition to Large and Small Magellanic Clouds. Radio pulsar observations at a few hundreds MHz up to ~10 GHz have been active and they are proved to be fruitful. Low frequencies are preferred mainly because of the steep ratio spectrum of pulsars. However, developments in pulsar backends (e.g. a wide-band spectrometer) and improved system sensitivities make it possible to observe pulsars at higher frequencies using large, single-dish telescopes up to ~18 GHz. Going forward, mm-wavelength observations is expected to open a new window in pulsar astronomy. In particular, frequencies well above ~15 GHz are pre-requisite to detect pulsars in the Galactic Center where radio pulsed signals are severely scattered by interactions with the interstellar medium. Recent discoveries strongly imply that there are subsets of pulsars with an apparently flat spectrum, such as magnetars. In April 2014, the first pulsar (magnetar) was discovered only 3 arcmin from Sgr A*, PSR J1745-2900. We will present a brief overview on pulsar populations focusing on those observable at high frequencies. We will also discuss prospects of pulsar observations in mm-wavelengths and how we can utilize the Korean VLBI network.

• 천문학회보
• /
• 제39권2호
• /
• pp.112.2-112.2
• /
• 2014

We propose simultaneous monitoring observations of 22 GHz $H_2O$ and 43/86/129 GHz SiO masers toward ~15 evolved stars in order to investigate spatial structure and dynamical effect from SiO to $H_2O$ maser regions including mass-loss process and development of asymmetry in circumstellar envelopes. We also aim at investigating mutual association and difference between SiO and $H_2O$ masers for establishing SiO and $H_2O$ maser models coupled to hydrodynamical model of circumstellar envelope. In addition, the correlation and difference of SiO maser properties among J=1-0, J=2-1, and J=3-2 transition masers are traced according to different type of stars for constraining SiO pumping models. These scientific goals and target sources were determined based on KVN single dish and VLBI feasibility test observations at 4 bands. As a total observing time of every 2 month monitoring, about 90 and 360 hours (in average per year) are required for single dish and VLBI observations, respectively. From the 2014B observing season, these monitoring observations will be derived as one of KVN key science programs.