Journal of the Korean Astronomical Society最新文献_第8页

EVOLUTIONARY STATUS AND INTERNAL STRUCTURE OF μ CASSIOPEIAE 仙后座亚科的进化状况及内部结构

IF 1 4区物理与天体物理

Journal of the Korean Astronomical Society Pub Date : 2015-06-30 DOI: 10.5303/JKAS.2015.48.3.165

K. Bach

{"title":"EVOLUTIONARY STATUS AND INTERNAL STRUCTURE OF μ CASSIOPEIAE","authors":"K. Bach","doi":"10.5303/JKAS.2015.48.3.165","DOIUrl":"https://doi.org/10.5303/JKAS.2015.48.3.165","url":null,"abstract":"We investigate physical properties of the nearby (∼ 7.5 pc) astrometric binary μ Cas in the context of standard evolutionary theory. Based on the spectroscopically determined relative abundances ([α/Fe] ? +0.4 dex, [Fe/H] ∼ ?0.7 dex), all physical inputs such as opacities and equation of state are consistently generated. By combining recent spectroscopic analyses with the astrometric observations from the HIPPARCOS parallaxes and the CHARA array, the evolutionary model grids have been constructed. Through the statistical evaluation of the χ²-minimization among alternative models, we find a reliable evolutionary solution (M A , M B , t age ) = (0.74 M ⊙ , 0.19 M ⊙ , 11 Gyr) which excellently satisfies observational constraints. In particular, we find that the helium abundance of μ Cas is comparable with the primordial helium contents (Y p ∼ 0.245). On the basis of the well-defined stellar parameters of the primary star, the internal structure and the p-mode frequencies have been estimated. From our seismic computation, μ Cas is expected to have a first order spacing ?ν ∼ 169 μHz. The ultimate goal of this study is to describe physical processes inside a low-mass star through a complete modelling from the spectroscopic observation to the evolutionary computation.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2015-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70736507","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

A NEW AUTO-GUIDING SYSTEM FOR CQUEAN 一种新型的汽车自动导航系统

IF 1 4区物理与天体物理

Journal of the Korean Astronomical Society Pub Date : 2015-06-30 DOI: 10.5303/JKAS.2015.48.3.177

Nahyun Choi, W. Park, Hye-In Lee, Tae-Geun Ji, Y. Jeon, M. Im, S. Pak

{"title":"A NEW AUTO-GUIDING SYSTEM FOR CQUEAN","authors":"Nahyun Choi, W. Park, Hye-In Lee, Tae-Geun Ji, Y. Jeon, M. Im, S. Pak","doi":"10.5303/JKAS.2015.48.3.177","DOIUrl":"https://doi.org/10.5303/JKAS.2015.48.3.177","url":null,"abstract":"We develop a new auto-guiding system for the Camera for QUasars in the EArly uNiverse (CQUEAN). CQUEAN is an optical CCD camera system attached to the 2.1-m Otto-Struve Telescope (OST) at McDonald Observatory, USA. The new auto-guiding system differs from the original one in the following: instead of the cassegrain focus of the OST, it is attached to the finder scope; it has its own filter system for observation of bright targets; and it is controlled with the CQUEAN Auto-guiding Package, a newly developed auto-guiding program. Finder scope commands a very wide field of view at the expense of poorer light gathering power than that of the OST. Based on the star count data and the limiting magnitude of the system, we estimate there are more than 5.9 observable stars with a single FOV using the new auto-guiding CCD camera. An adapter is made to attach the system to the finder scope. The new auto-guiding system successfully guided the OST to obtain science data with CQUEAN during the test run in 2014 February. The FWHM and ellipticity distributions of stellar profiles on CQUEAN, images guided with the new auto-guiding system, indicate similar guiding capabilities with the original auto-guiding system but with slightly poorer guiding performance at longer exposures, as indicated by the position angle distribution. We conclude that the new auto-guiding system has overall similar guiding performance to the original system. The new auto-guiding system will be used for the second generation CQUEAN, but it can be used for other cassegrain instruments of the OST.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2015-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70736513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 6

POLARIZATION OF LYMAN α EMERGENT FROM A THICK SLAB OF NEUTRAL HYDROGEN 中性氢厚板产生的莱曼α的极化

IF 1 4区物理与天体物理

Journal of the Korean Astronomical Society Pub Date : 2015-06-30 DOI: 10.5303/JKAS.2015.48.3.195

S. Ahn, Hee-Won Lee

{"title":"POLARIZATION OF LYMAN α EMERGENT FROM A THICK SLAB OF NEUTRAL HYDROGEN","authors":"S. Ahn, Hee-Won Lee","doi":"10.5303/JKAS.2015.48.3.195","DOIUrl":"https://doi.org/10.5303/JKAS.2015.48.3.195","url":null,"abstract":"Star forming galaxies found in the early universe exhibit asymmetric Lyα emission line that results from multiple scattering in a neutral thick medium surrounding the Lyα emission source. It is expected that emergent Lyα will be significantly polarized through a large number of resonance scattering events followed by a number of successive wing scatterings. In this study we adopt a Monte Carlo method to calculate the polarization of Lyα transferred in a very thick static slab of Hi. Resonantly scattered radiation associated with transitions between 1S½? 2P½ ,3/2 is only weakly polarized and therefore linear polarization of the emergent Lyα is mainly dependent on the number of off-resonant wing scattering events. The number of wing scattering events just before escape from the slab is determined by the product of the Doppler parameter a and the line center optical depth τ0, which, in turn, determines the behavior of the linear polarization of Lyα. This result is analogous to the study of polarized radiative transfer of Thomson scattered photons in an electron slab, where the emergent photons are polarized in the direction perpendicular to the slab when the scattering optical depth is small and polarized in the parallel direction when the slab is optically thick. Our simulated spectropolarimetry of Lyα shows that the line center is negligibly polarized, the near wing parts polarized in the direction parallel to the slab and the far wing parts are polarized in the direction perpendicular to the slab. We emphasize that the flip of polarization direction in the wing parts of Lyα naturally reflects the diffusive nature of the Lyα transfer process in thick neutral media.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2015-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70736285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 7

COMMENTS ON MAGNETIC RECONNECTION MODELS OF CANCELING MAGNETIC FEATURES ON THE SUN 太阳磁场特征相消的磁重联模型评述

IF 1 4区物理与天体物理

Journal of the Korean Astronomical Society Pub Date : 2015-06-30 DOI: 10.5303/JKAS.2015.48.3.187

Y. Litvinenko

引用次数: 4

MILGROM’S LAW AND Λ’S SHADOW: HOW MASSIVE GRAVITY CONNECTS GALACTIC AND COSMIC DYNAMICS 米尔格罗姆定律和Λ的阴影:大质量引力如何连接银河和宇宙动力学

IF 1 4区物理与天体物理

Journal of the Korean Astronomical Society Pub Date : 2015-06-02 DOI: 10.5303/JKAS.2015.48.3.191

S. Trippe

引用次数: 1

ACCRETION FLOW AND DISPARATE PROFILES OF RAMAN SCATTERED O VI λλ 1032, 1038 IN THE SYMBIOTIC STAR V1016 CYGNI 共生恒星v1016 cygni中vi λ 1032, 1038散射的吸积流和不同的拉曼谱线

IF 1 4区物理与天体物理

Journal of the Korean Astronomical Society Pub Date : 2015-04-30 DOI: 10.5303/JKAS.2015.48.2.105

Jeong-Eun Heo, Hee-Won Lee

{"title":"ACCRETION FLOW AND DISPARATE PROFILES OF RAMAN SCATTERED O VI λλ 1032, 1038 IN THE SYMBIOTIC STAR V1016 CYGNI","authors":"Jeong-Eun Heo, Hee-Won Lee","doi":"10.5303/JKAS.2015.48.2.105","DOIUrl":"https://doi.org/10.5303/JKAS.2015.48.2.105","url":null,"abstract":"The symbiotic star V1016 Cygni, a detached binary system consisting of a hot white dwarf and a mass-losing Mira variable, shows very broad emission features at around 6825 A and 7082 A, which are Raman scattered Ovi ?? 1032, 1038 by atomic hydrogen. In the high resolution spectrum of V1016 Cyg obtained with the Bohyunsan Optical Echelle Spectrograph these broad features exhibit double peak profiles with the red peak stronger than the blue counterpart. However, their profiles differ in such a way that the blue peak of the 7082 feature is relatively weaker than the 6825 counterpart when the two Raman features are normalized to exhibit an equal red peak strength in the Doppler factor space. Assuming that an accretion flow around the white dwarf is responsible for the double peak profiles, we attribute this disparity in the profiles to the local variation of the flux ratio of Ovi ?? 1032, 1038 in the accretion flow. A Monte Carlo technique is adopted to provide emissivity maps showing the local emissivity of Ovi ?1032 and Ovi ?1038 in the vicinity of the white dwarf. We also present a map indicating the differing flux ratios of Ovi ?? 1032 and 1038. Our result shows that the flux ratio reaches its maximum of 2 in the emission region responsible for the central trough of the Raman feature and that the flux ratio in the inner red emission region is almost 1. The blue emission region and the outer red emission region exhibit an intermediate ratio around 1.5. We conclude that the disparity in the profiles of the two Raman Ovi features strongly implies accretion flow around the white dwarf, which is azimuthally asymmetric.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2015-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70736463","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 12

A NEW HARDWARE CORRELATOR IN KOREA: PERFORMANCE EVALUATION USING KVN OBSERVATIONS 韩国一种新的硬件相关器:使用KVN观察进行性能评估

IF 1 4区物理与天体物理

Journal of the Korean Astronomical Society Pub Date : 2015-03-27 DOI: 10.5303/JKAS.2015.48.2.125

Sang-Sung Lee, C. Oh, D. Roh, Se-jin Oh, Jongsoo Kim, J. Yeom, H. Kim, Dong-Gyu Jung, D. Byun, T. Jung, N. Kawaguchi, K. Shibata, Kiyoaki Wajima Kasi, J Korea, Ust, Shao, China., Naoj, Japan.

{"title":"A NEW HARDWARE CORRELATOR IN KOREA: PERFORMANCE EVALUATION USING KVN OBSERVATIONS","authors":"Sang-Sung Lee, C. Oh, D. Roh, Se-jin Oh, Jongsoo Kim, J. Yeom, H. Kim, Dong-Gyu Jung, D. Byun, T. Jung, N. Kawaguchi, K. Shibata, Kiyoaki Wajima Kasi, J Korea, Ust, Shao, China., Naoj, Japan.","doi":"10.5303/JKAS.2015.48.2.125","DOIUrl":"https://doi.org/10.5303/JKAS.2015.48.2.125","url":null,"abstract":"We report results of the performance evaluation of a new hardware correlator in Korea, the Daejeon correlator, developed by the Korea Astronomy and Space Science Institute (KASI) and the National Astronomical Observatory of Japan (NAOJ). We conduct Very Long Baseline Interferometry (VLBI) observations at 22 GHz with the Korean VLBI Network (KVN) in Korea and the VLBI Exploration of Radio Astrometry (VERA) in Japan, and correlated the aquired data with the Daejeon correlator. For evaluating the performance of the new hardware correlator, we compare the correlation outputs from the Daejeon correlator for KVN observations with those from a software correlator, the Distributed FX (DiFX). We investigate the correlated flux densities and brightness distributions of extragalactic compact radio sources. The comparison of the two correlator outputs shows that they are consistent with each other within < 8%, which is comparable with the amplitude calibration uncertainties of KVN observations at 22 GHz. We also find that the 8% difference in flux density is caused mainly by (a) the difference in the way of fringe phase tracking between the DiFX software correlator and the Daejeon hardware correlator, and (b) an unusual pattern (a double-layer pattern) of the amplitude correlation output from the Daejeon correlator. The visibility amplitude loss by the double-layer pattern is as small as 3%. We conclude that the new hardware correlator produces reasonable correlation outputs for continuum observations, which are consistent with the outputs from the DiFX software correlator.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2015-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70736472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 26

MASS TRANSFER AND LIGHT TIME EFFECT STUDIES FOR AU SERPENTIS 蛇的传质和光时效应研究

IF 1 4区物理与天体物理

Journal of the Korean Astronomical Society Pub Date : 2015-02-28 DOI: 10.5303/JKAS.2015.48.1.1

S. M. Amin

引用次数: 2

Massive Structures of Galaxies at High Redshifts in the Great Observatories Origins Deep Survey Fields 大天文台起源深巡天域中高红移星系的大质量结构

IF 1 4区物理与天体物理

Journal of the Korean Astronomical Society Pub Date : 2015-02-28 DOI: 10.5303/JKAS.2015.48.1.021

E. Kang, M. Im

{"title":"Massive Structures of Galaxies at High Redshifts in the Great Observatories Origins Deep Survey Fields","authors":"E. Kang, M. Im","doi":"10.5303/JKAS.2015.48.1.021","DOIUrl":"https://doi.org/10.5303/JKAS.2015.48.1.021","url":null,"abstract":"If the Universe is dominated by cold dark matter and dark energy as in the currently popular ΛCDM cosmology, it is expected that large scale structures form gradually, with galaxy clusters of mass M ? 10 14 M ⊙ appearing at around 6 Gyrs after the Big Bang (z ∼ 1). Here, we report the discovery of 59 massive structures of galaxies with masses greater than a few times 10 13 M ⊙ at redshifts between z = 0.6 and 4.5 in the Great Observatories Origins Deep Survey fields. The massive structures are identified by running top-hat filters on the two dimensional spatial distribution of magnitude-limited samples of galaxies using a combination of spectroscopic and photometric redshifts. We analyze the Millennium simulation data in a similar way to the analysis of the observational data in order to test the _CDM cosmology. We find that there are too many massive structures (M > 7×1013M ⊙ ) observed at z > 2 in comparison with the simulation predictions by a factor of a few, giving a probability of < 1/2500 of the observed data being consistent with the simulation. Our result suggests that massive structures have emerged early, but the reason for the discrepancy with the simulation is unclear. It could be due to the limitation of the simulation such as the lack of key, unrecognized ingredients (strong non-Gaussianity or other baryonic physics), or simply a difficulty in the halo mass estimation from observation, or a fundamental problem of the ΛCDM cosmology. On the other hand, the over-abundance of massive structures at high redshifts does not favor heavy neutrino mass of ∼ 0.3 eV or larger, as heavy neutrinos make the discrepancy between the observation and the simulation more pronounced by a factor of 3 or more.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2015-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70736058","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 9

CONSTRAINING COSMOLOGICAL PARAMETERS WITH IMAGE SEPARATION STATISTICS OF GRAVITATIONALLY LENSED SDSS QUASARS: MEAN IMAGE SEPARATION AND LIKELIHOOD INCORPORATING LENS GALAXY BRIGHTNESS 用引力透镜SDSS类星体的图像分离统计约束宇宙学参数:考虑透镜星系亮度的平均图像分离和似然

IF 1 4区物理与天体物理

Journal of the Korean Astronomical Society Pub Date : 2015-02-28 DOI: 10.5303/JKAS.2015.48.1.83

D. Han, Myeong-Gu Park

{"title":"CONSTRAINING COSMOLOGICAL PARAMETERS WITH IMAGE SEPARATION STATISTICS OF GRAVITATIONALLY LENSED SDSS QUASARS: MEAN IMAGE SEPARATION AND LIKELIHOOD INCORPORATING LENS GALAXY BRIGHTNESS","authors":"D. Han, Myeong-Gu Park","doi":"10.5303/JKAS.2015.48.1.83","DOIUrl":"https://doi.org/10.5303/JKAS.2015.48.1.83","url":null,"abstract":"Recent large scale surveys such as Sloan Digital Sky Survey have produced homogeneous samples of multiple-image gravitationally lensed quasars with well-defined selection effects. Statistical analysis on these can yield independent constraints on cosmological parameters. Here we use the image separation statistics of lensed quasars from Sloan Digital Sky Survey Quasar Lens Search (SQLS) to derive constraints on cosmological parameters. Our analysis does not require knowledge of the magnification bias, which can only be estimated from the detailed knowledge on the quasar luminosity function at all redshifts, and includes the consideration for the bias against small image separation quasars due to selection against faint lens galaxy in the follow-up observations for confirmation. We first use the mean image separation of the lensed quasars as a function of redshift to find that cosmological models with extreme curvature are inconsistent with observed lensed quasars. We then apply the maximum likelihood test to the statistical sample of 16 lensed quasars that have both measured redshift and magnitude of lens galaxy. The likelihood incorporates the probability that the observed image separation is realized given the luminosity of the lens galaxy in the same manner as Im et al. (1997). We find that the 95% confidence range for the cosmological constant (i.e., the vacuum energy density) is 0.72 ≤ Ω Λ ≤ 1.0 for a flat universe. We also find that the equation of state parameter can be consistent with ?1 as long as the matter density m . 0.4 (95% confidence range). We conclude that the image separation statistics incorporating the brightness of lens galaxies can provide robust constraints on the cosmological parameters.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2015-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70736306","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4