• Journal of Astronomy and Space Sciences
• /
• 제34권3호
• /
• pp.199-205
• /
• 2017

A high resolution spectroscopic observation of the red supergiant star RM_1-390 in the Large Magellanic Cloud was made from a 3.6 m telescope at the European Southern Observatory. Spectral resolving power was R=20,000, with a signal-to-noise ratio S/N > 100. We found the atmospheric parameters of RM_1-390 to be as follows: the effective temperature $T_{eff}=4,250{\pm}50K$, the surface gravity ${\log}\;g=0.16{\pm}0.1$, the microturbulent velocity $v_{micro}=2.5km/s$, the macroturbulence velocity $v_{macro}=9km/s$ and the iron abundance $[Fe/H]=-0.73{\pm}0.11$. The abundances of 18 chemical elements from silicon to thorium in the atmosphere of RM_1-390 were found using the spectrum synthesis method. The relative deficiencies of all elements are close to that of iron. The fit of abundance pattern by the solar system distribution of r- and s-element isotopes shows the importance of the s-process. The plot of relative abundances as a function of second ionization potentials of corresponding chemical elements allows us to find a possibility of convective energy transport in the photosphere of RM_1-390.

• Journal of Astronomy and Space Sciences
• /
• 제26권3호
• /
• pp.295-304
• /
• 2009

대마젤란은하 중심부에 위치한 식쌍성 EROS 1010에 대한 CCD 측광관측을 2006년과 2007년에 수행하여 BV 광도곡선을 완성하였다. BV 광도곡선은 EROS팀과 OGLE팀이 각각 관측한 BR과 I 광도곡선과 함께 Wilson & Devinney 차등보정법으로 분석하여 측광학적인 해를 제시하였다. 한편 대마젤란은하의 거리지수를 $m-M=18.^m3{\sim}18.^m5$ 사이로 가정하고, EROS 1010에 대한 절대량을 구하였다.

• 천문학회보
• /
• 제41권2호
• /
• pp.30.1-30.1
• /
• 2016

We have estimated a metallicity map of the Large Magellanic Cloud (LMC) using the Magellanic Cloud Photometric Survey (MCPS) and Optical Gravitational Lensing Experiment (OGLE III) photometric data. This is a first of its kind, high-spatial resolution map of metallicity up to a radius of $4^{\circ}-5^{\circ}$, derived using large area photometric data and calibrated using spectroscopic data of Red Giant Branch (RGB) stars. The RGB is identified in the V, (V - I) colour- magnitude diagrams of small subregions of varying sizes in both data sets. The slope of the RGB is used as an indicator of the mean metallicity of a subregion, and it is calibrated to metallicity using spectroscopic data for field and cluster red giants in selected subregions. The mean metallicity of the LMC is found to be [Fe/H] = -0.37 dex (${\sigma}[Fe/H]=0.12$) from MCPS data, and [Fe/H] = -0.39 dex (${\sigma}[Fe/H]=0.10$) from OGLE III data. The bar is found to have an uniform and higher metallicity compared to the disk, and is indicative of an active bar in the past. Both the data sets suggest a shallow radial metallicity gradient up to a radius of 4 kpc ($-0.049{\pm}0.002$ dex kpc-1 to $-0.066{\pm}0.006$ dex kpc-1). This metallicity gradient of the LMC disk, though shallow, resembles the gradient seen in spiral galaxies, and similar to that found in our Galaxy.

• 천문학논총
• /
• 제27권4호
• /
• pp.231-234
• /
• 2012

We present preliminary results of supernova remnants (SNRs) in the Large Magellanic Cloud (LMC) seen by AKARI as well as Spitzer. By examining the AKARI LMC survey and the Spitzer data, we have searched for IR counterparts to 45 known SNRs in the LMC and could identify 28 SNRs with associated IR emission. 13 SNRs among them are newly detected in IR bands. For the entire IR SNRs, we make a catalog containing general information and the AKARI and/or Spitzer fluxes. Using the catalog, their IR colors and the possible correlation of the IR fluxes with the X-ray fluxes are examined. For some interesting SNRs, we have performed NIR spectroscopy with AKARI. An aromatic feature at $3.3{\mu}m$ can be identified in LMC SNR N49. We investigate the characteristics of the IR features and discuss the PAH mission mechanism in SNRs.

• 천문학회보
• /
• 제38권1호
• /
• pp.52.2-52.2
• /
• 2013

We compile a near-infrared photometric and polarimetric catalog for the $5{\times}9$ fields (${\sim}39^{\prime}{\times}69^{\prime}$) in the eastern side of the Large Magellanic Cloud (LMC). The photometric and the polarimetric data were obtained in J, H, and Ks bands using JHKs-simultaneous imaging polarimeter SIRPOL of the InfraRed Survey Facility (IRSF) in 2008 December and 2011 December. We estimate quality of the data using the method and the result from the IRSF Magellanic Clouds point source catalog which was published on 2007 June. In this poster, we present configuration of the catalog and the results of the verification.

• 천문학회보
• /
• 제42권2호
• /
• pp.42.2-42.2
• /
• 2017

The Large Magellanic Cloud (LMC) is a unique target to study the detail structures of molecular clouds and star-forming regions, due to its proximity and face-on orientation from us. Most part of the astrophysical subjects for the LMC have been investigated, but the magnetic field is still veiling despite its role in the evolution of the interstellar medium (ISM) and in the main force to influence the star formation process. Measuring polarization of the background stars behind interstellar medium allows us to describe the existence of magnetic fields through the polarization vector map. In this presentation, I introduce the near-infrared polarimetric results for the $39^{\prime}{\times}69^{\prime}$ field of the northeastern region of the LMC and the N159/N160 star-forming complex therein. The polarimetric observations were conducted at IRSF/SIRPOL 1.4 m telescope. These results allow us to examine both the global geometry of the large-scale magnetic field in the northeastern region and the close structure of the magnetic field in the complex. Prominent patterns of polarization vectors mainly follow dust emission features in the mid-infrared bands, which imply that the large-scale magnetic fields are highly involved in the structure of the dust cloud in the LMC. In addition, local magnetic field structures in the N159/N160 star-forming complex are investigated with the comparison between polarization vectors and molecular cloud emissions, suggesting that the magnetic fields are resulted from the sequential formation history of this complex. I propose that ionizing radiation from massive stellar clusters and the expanding bubble of the ionized gas and dust in this complex probably affect the nascent magnetic field structure.

• 천문학회보
• /
• 제34권2호
• /
• pp.77.2-77.2
• /
• 2009

• 천문학회보
• /
• 제34권1호
• /
• pp.53.2-53.2
• /
• 2009

• 한국우주과학회:학술대회논문집(한국우주과학회보)
• /
• 한국우주과학회 2009년도 한국우주과학회보 제18권1호
• /
• pp.31.1-31.1
• /
• 2009

• 천문학회보
• /
• 제37권1호
• /
• pp.78.1-78.1
• /
• 2012

We present near-IR imaging polarimetry of the 5${\times}$9 fields (-39'${\times}$69') centered at 30 Doradus in the Large Magellanic Cloud (LMC), using the InfraRed Survey Facility (IRSF). We obtained polarimetry data in J, H, and Ks bands using the JHKs-simultaneous imaging polarimeter SIRPOL in 2008 December and 2011 December. We measured Stokes parameters of point-like sources to derive the degree of polarization and the polarization position angle. Since our results are suffered from non-photometric weather, we compare the polarization results from 2008 and those from 2011, and examine the photometric reliabilities between the two runs. Our survey data will be compared with molecular and dust maps to reveal the large-scale magnetic field properties in the star-forming clouds.