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1968년 ~ 2023년까지 1,187 건의 한국천문학회지를 격월간 확인하실 수 있습니다.
- The Korean Astronomical Society (The Korean Astronomical Society)
- 계간 (Quarterly)
- ISSN : 1225-4614 (ISSN : 1225-4614)
1225-4614
- DB구축현황 : 1,187건 (DB Construction : 1,187 Articles)
총 게시글 1,187건
페이지 32/119
311
- Kim, Chul-Hee
- Journal of the Korean astronomical society = 천문학회지
- 43, n.5
- pp.153-159
- 2010
- 원문 바로보기
Color excesses of classical Cepheids in the uvby color system are estimated for the calibration stars with distances from the literature that are measured independently. Intrinsic photometric indices for these stars are calculated and a calibrated empirical relation between (b - y)<TEX>$_0$</TEX>, period, [<TEX>$c_1$</TEX>], and [<TEX>$m_1$</TEX>] is derived through a linear fit. This relation is used to determine color excesses E(b-y) for 59 Cepheids. We also examine the period-color [log P : (b - y)<TEX>$_0$</TEX>] relation, and find no signs of nonlinearity. We estimate the effective temperature and surface gravity of several Cepheids using both Kurucz and MARCS/SSG grids for [Fe=H]=0.0. We confirm that both temperature and surface gravity are higher, by about 150K and 0.4 respectively, when the MARCS/SSG atmospheric grids are used.
312
- Kook, Seung-Hwa
- Journal of the Korean astronomical society = 천문학회지
- 43, n.5
- pp.141-152
- 2010
- 원문 바로보기
UBV I CCD photometry is obtained for the open clusters NGC 4609 and Hogg 15 in Crux. For NGC 4609, CCD data are presented for the first time. From new photometry we derive the reddening, distance modulus and age of each cluster - NGC 4609 : E(B-V ) = <TEX>$0.37{\pm}0.03$</TEX>, <TEX>$V_0-M_V=10.60{\pm}0.08$</TEX>, log <TEX>$\tau$</TEX>= 7.7 <TEX>$\pm$</TEX> 0.1; Hogg 15 : E(B - V ) = 1.13 <TEX>$\pm$</TEX> 0.11, <TEX>$V_0-M_V$</TEX> = 12.50 <TEX>$\pm$</TEX> 0.15, log <TEX>$\tau$</TEX> <TEX>$\lesssim$</TEX> 6.6. The young age of Hogg 15 strongly implies that WR 47 is a member of the cluster. We also determine the mass function of these clusters and obtain a slope <TEX>$\Gamma$</TEX> = -1.2 (<TEX>$\pm$</TEX>0.3) for NGC 4609 which is normal and a somewhat shallow slope (<TEX>${\Gamma}=-0.95{\pm}0.5$</TEX>) for Hogg 15.
313
- Lee, In-Duk
- Journal of the Korean astronomical society = 천문학회지
- 43, n.3
- pp.95-104
- 2010
- 원문 바로보기
We outline our GRB afterglow observation program using the 1-m telescope at Mt. Lemmon Optical Astronomy Observatory (LOAO), and report the first observations of the GRB afterglows. During the 2007B semester, we performed follow-up imaging obsrevations of 6 GRBs, and succeeded in detecting four GRB afterglows (GRB 071010B, GRB 071018, GRB 071020, and GRB 071025) while placing useful upper limits on the light curves of the other GRBs. Among the observed events, we find that three events are special and interesting. GRB 071010B has a light curve which has an unusually long jet break time of 11.8 days. For GRB 071025, its red R-I(~2) color suggests that it is likely to be at z~5. GRB 071020 has a light curve which shows a clear brightening at 0.3-1 days after the burst, where our LOAO data play a crucial role by providing an unambiguous evidence for the brightening. These are the first successful detections of GRB afterglows by a facility owned and operated by a Korean institution, demonstrating the usefulness of the 1-m telescope for transient phenomena such as GRBs up to very high redshift.
314
- Ha, Ji-Sung
- Journal of the Korean astronomical society = 천문학회지
- 43, n.6
- pp.213-223
- 2010
- 원문 바로보기
Young Stellar Objects (YSOs) in the early evolutionary stages are very embedded, and thus they emit most of their energy at long wavelengths such as far-infrared (FIR) and submillimeter (Submm). Therefore, the FIR observational data are very important to classify the accurate evolutionary stages of these embedded YSOs, and to better constrain their physical parameters in the dust continuum modeling. We selected 28 YSOs, which were detected in the AKARI Far-Infrared Surveyor (FIS), from the Spitzer c2d legacy YSO catalogs to test the effect of FIR fluxes on the classification of their evolutionary stages and on the constraining of envelope properties, internal luminosity, and UV strength of the Interstellar Radiation Field (ISRF). According to our test, one can mis-classify the evolutionary stages of YSOs, especially the very embedded ones if the FIR fluxes are not included. In addition, the total amount of heating of YSOs can be underestimated without the FIR observational data.
315
- Kim, Sang-Hyuk
- Journal of the Korean astronomical society = 천문학회지
- 43, n.5
- pp.169-181
- 2010
- 원문 바로보기
We develop a proto-model of an off-axis reflective telescope for infrared wide-field observations based on the design of Schwarzschild-Chang type telescope. With only two mirrors, this design achieves an entrance pupil diameter of 50 mm and an effective focal length of 100 mm. We can apply this design to a mid-infrared telescope with a field of view of <TEX>$8^{\circ}{\times}8^{\circ}$</TEX>. In spite of the substantial advantages of off-axis telescopes in the infrared compared to refractive or on-axis reflective telescopes, it is known to be difficult to align the mirrors in off-axis systems because of their asymmetric structures. Off-axis mirrors of our telescope are manufactured at the Korea Basic Science Institute (KBSI). We analyze the fabricated mirror surfaces by fitting polynomial functions to the measured data. We accomplish alignment of this two-mirror off-axis system using a ray tracing method. A simple imaging test is performed to compare a pinhole image with a simulated prediction.
316
- Cho, Jae-Sang
- Journal of the Korean astronomical society = 천문학회지
- 43, n.2
- pp.41-54
- 2010
- 원문 바로보기
We report relative proper motion measurements of <TEX>$H_{2}O$</TEX> masers in massive star-forming region W51 Main, based on data sets of VLBI observations for <TEX>$H_{2}O$</TEX> masers at 22 GHz with Japanese VERA telescopes from 2003 to 2006. Data reductions and single-beam imaging analysis are to measure internal kinematics of maser spots and eventually to estimate the three-dimensional kinematics of <TEX>$H_{2}O$</TEX> masers in W51 Main. Average space motions and proper motion measurements of <TEX>$H_{2}O$</TEX> masers are given both graphical and in table formats. We find in this study that W51 Main appears to be associated with hyper-compact H II region with multiple massive proto-stars whose spectral types are of late O.
317
- Doh, Seong-Jae
- Journal of the Korean astronomical society = 천문학회지
- 43, n.6
- pp.183-190
- 2010
- 원문 바로보기
According to the historical documents and paintings in many civilizations, rocks that fell from the sky fascinated humans as the message from the God or supernaturals. Scientific progress allows humans to recognize these exciting extraterrestrial objects as meteorites. Meteorites contain a wealth of pivotal information regarding formation of the early Solar System. Meteorites also provide broader scientific insights on, for example, the origin of life, interplanetary transfer of life forms, massive depletion of biosphere on Earth, and evolution of lithosphere on Earth-like planetary bodies.
318
- Choi, Yun-Young
- Journal of the Korean astronomical society = 천문학회지
- 43, n.6
- pp.191-200
- 2010
- 원문 바로보기
We present the Korea Institute for Advanced Study Value-Added Galaxy Catalog (KIAS VAGC), a catalog of galaxies based on the Large Scale Structure (LSS) sample of New York University Value-Added Galaxy Catalog (NYU VAGC) Data Release 7. Our catalog supplements redshifts of 10,497 galaxies with 10 < <TEX>$r_P\;{\leq}\;17.6$</TEX> (1455 with 10 < <TEX>$r_P\;{\leq}\;14.5$</TEX>) to the NYU VAGC LSS sample. Redshifts from various existing catalogs such as the Updated Zwicky Catalog, the IRAS Point Source Catalog Redshift Survey, the Third Reference Catalogue of Bright Galaxies, and the Two Degree Field Galaxy Redshift Survey have been put into the NYU VAGC photometric catalog. Our supplementation significantly improves spectroscopic completeness: the area covered by the spectroscopic sample with completeness higher than 95% increases from 2.119 to 1.737 sr. Our catalog also provides morphological types of all galaxies that are determined by the automated morphology classification scheme of Park & Choi (2005), and related parameters, together with fundamental photometry parameters supplied by the NYU VAGC. Our catalog contains matches to objects in the Max Planck for Astronomy (MPA) & Johns Hopkins University (JHU) spectrum measurements (Data Release 7). This new catalog, the KIAS VAGC, is complementary to the NYU VAGC and MPA-JHU catalog.
319
- Kim, Sung-Soo
- Journal of the Korean astronomical society = 천문학회지
- 43, n.4
- pp.105-113
- 2010
- 원문 바로보기
We study the dynamical evolution of the M87 globular cluster (GC) system using the most advanced and realistic Fokker-Planck (FP) model.By comparing our FP models with both mass function (MF) and radial distribution (RD) of the observed GC system, we find the best-fit initial (at M87's age of 2-3 Gyr) MF and RD for three GC groups: all GCs, blue GCs, and red GCs. We estimate the initial total mass in GCs to be <TEX>$1.8^{+0.3}_{-0.2}{\times}10^{10}M_{\bigodot}$</TEX>, which is about 100 times larger than that of the Milky Way GC system. We also find that the fraction of the total mass currently in GCs is 34\%. When blue and red GCs are fitted separately, blue GCs initially have a larger total mass and a shallower radial distribution than red GCs. If one assumes that most of the significant major merger events of M87 have ended by the age of 2-3 Gyr, our finding that blue (metal-poor) GCs initially had a shallower radial distribution supports the major merger scenario for the origin of metallicity bimodality.
320
- Kim, Gwan-Jeong
- Journal of the Korean astronomical society = 천문학회지
- 43, n.1
- pp.9-23
- 2010
- 원문 바로보기
In this paper we examined the association of Infrared Dark Cloud (IRDC) cores with YSOs and the geometric properties of the IRDC cores. For this study a total of 13,650 IRDC cores were collected mainly from the catalogs of the IRDC cores published from other studies and partially from our catalog of IRDC cores containing new 789 IRDC core candidates. The YSO candidates were searched for using the GLIMPSE, MSX, and IRAS point sources by the shape of their SED or using activity of water or methanol maser. The association of the IRDC cores with these YSOs was checked by their line-of-sight coincidence within the dimension of the IRDC core. This work found that a total of 4,110 IRDC cores have YSO candidates while 9,540 IRDC cores have no indication of the existence of YSOs. Considering the 12,200 IRDC cores within the GLIMPSE survey region for which the YSO candidates were determined with better sensitivity, we found that 4,098 IRDC cores (34%) have at least one YSO candidate and 1,072 cores among them seem to have embedded YSOs, while the rest 8,102 (66%) have no YSO candidate. Therefore, the ratio of [N(IRDC core with protostars)]/[N(IRDC core without YSO)] for 12,200 IRDC cores is about 0.13. Taking into account this ratio and typical lifetime of high-mass embedded YSOs, we suggest that the IRDC cores would spend about <TEX>$10^4\sim10^5$</TEX> years to form high-mass stars. However, we should note that the GLIMPSE point sources have a minimum detectable luminosity of about <TEX>$1.2 L_{\odot}$</TEX> at a typical IRDC core's distance of ~4 kpc. Therefore, the ratio given here should be a 100ver limit and the estimated lifetime of starless IRDC cores can be an upper limit. The physical parameters of the IRDC cores somewhat vary depending on how many YSO candidates the IRDC cores contain. The IRDC cores with more YSOs tend to be larger, more elongated, and have better darkness contrast than the IRDC cores with fewer or no YSOs.