Pub Date : 2015-06-30DOI: 10.5303/JKAS.2015.48.3.165
K. Bach
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.
我们在标准进化理论的背景下研究了附近(~ 7.5 pc)天体测量双星μ Cas的物理性质。根据光谱测定的相对丰度([α/Fe] ?+0.4指数，[Fe/H] ~ - 0.7指数)，所有的物理输入，如不透明度和状态方程一致地产生。通过结合最近的光谱分析和HIPPARCOS视差和CHARA阵列的天文观测，构建了演化模型网格。通过对备选模型之间的χ 2最小化的统计评价，我们找到了一个可靠的进化解(M a, M B, t age) = (0.74 M⊙，0.19 M⊙，11 Gyr)，它很好地满足观测约束。特别是，我们发现μ Cas的氦丰度与原始氦含量相当(Y p ~ 0.245)。在确定主星参数的基础上，对其内部结构和p模频率进行了估计。从我们的地震计算中，μ Cas预计具有一阶间距?ν ~ 169 μ hz。本研究的最终目标是通过从光谱观测到演化计算的完整建模来描述低质量恒星内部的物理过程。
{"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":"48 1","pages":"165-175"},"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}
Pub Date : 2015-06-30DOI: 10.5303/JKAS.2015.48.3.177
Nahyun Choi, W. Park, Hye-In Lee, Tae-Geun Ji, Y. Jeon, M. Im, S. Pak
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.
{"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":"48 1","pages":"177-185"},"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}
Pub Date : 2015-06-30DOI: 10.5303/JKAS.2015.48.3.195
S. Ahn, Hee-Won Lee
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.
{"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":"48 1","pages":"195-202"},"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}
Pub Date : 2015-06-30DOI: 10.5303/JKAS.2015.48.3.187
Y. Litvinenko
Data analysis and theoretical arguments support magnetic reconnection in a chromospheric current sheet as the mechanism of the observed photospheric magnetic flux cancellation on the Sun. Flux pile-up reconnection in a Sweet{Parker current sheet can explain the observed properties of canceling magnetic features, including the speeds of canceling magnetic fragments, the magnetic uxes in the fragments, and the flux cancellation rates, inferred from the data. It is discussed how more realistic chromospheric reconnection models can be developed by relaxing the assumptions of a negligible current sheet curvature and a constant height of the reconnection site above the photosphere.
{"title":"COMMENTS ON MAGNETIC RECONNECTION MODELS OF CANCELING MAGNETIC FEATURES ON THE SUN","authors":"Y. Litvinenko","doi":"10.5303/JKAS.2015.48.3.187","DOIUrl":"https://doi.org/10.5303/JKAS.2015.48.3.187","url":null,"abstract":"Data analysis and theoretical arguments support magnetic reconnection in a chromospheric current sheet as the mechanism of the observed photospheric magnetic flux cancellation on the Sun. Flux pile-up reconnection in a Sweet{Parker current sheet can explain the observed properties of canceling magnetic features, including the speeds of canceling magnetic fragments, the magnetic uxes in the fragments, and the flux cancellation rates, inferred from the data. It is discussed how more realistic chromospheric reconnection models can be developed by relaxing the assumptions of a negligible current sheet curvature and a constant height of the reconnection site above the photosphere.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"48 1","pages":"187-190"},"PeriodicalIF":1.0,"publicationDate":"2015-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70736523","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}
Pub Date : 2015-06-02DOI: 10.5303/JKAS.2015.48.3.191
S. Trippe
Massive gravity provides a natural solution for the dark energy problem of cosmology and is also a candidate for resolving the dark matter problem. I demonstrate that, assuming reasonable scaling relations, massive gravity can provide for Milgrom's law of gravity (or "modified Newtonian dynamics") which is known to remove the need for particle dark matter from galactic dynamics. Milgrom's law comes with a characteristic acceleration, Milgrom's constant, which is observationally constrained to a0 ≈ 1.1×10 10 ms 2 . In the derivation presented here, this constant arises naturally from the cosmologically required mass of gravitons like a0 ∝ c √ � ∝ cH0 √ 3�, with �, H0, andbeing the cosmological constant, the Hubble constant, and the third cosmological parameter, respectively. My derivation suggests that massive gravity could be the mechanism behind both, dark matter and dark energy.
大质量引力为宇宙学的暗能量问题提供了一个自然的解决方案，也是解决暗物质问题的一个候选方案。我证明，假设合理的比例关系，大质量引力可以提供米尔格罗姆引力定律(或“修正牛顿动力学”)，该定律被认为从星系动力学中消除了对粒子暗物质的需要。米尔格罗姆定律有一个特征加速度，米尔格罗姆常数，观测约束为a0≈1.1×10 10 ms 2。在这里给出的推导中，这个常数是由宇宙学要求的引力子质量自然产生的，比如a0∝c√∝cH0√3，其中，和分别是宇宙学常数、哈勃常数和第三个宇宙学参数。我的推导表明，巨大的引力可能是暗物质和暗能量背后的机制。
{"title":"MILGROM’S LAW AND Λ’S SHADOW: HOW MASSIVE GRAVITY CONNECTS GALACTIC AND COSMIC DYNAMICS","authors":"S. Trippe","doi":"10.5303/JKAS.2015.48.3.191","DOIUrl":"https://doi.org/10.5303/JKAS.2015.48.3.191","url":null,"abstract":"Massive gravity provides a natural solution for the dark energy problem of cosmology and is also a candidate for resolving the dark matter problem. I demonstrate that, assuming reasonable scaling relations, massive gravity can provide for Milgrom's law of gravity (or \"modified Newtonian dynamics\") which is known to remove the need for particle dark matter from galactic dynamics. Milgrom's law comes with a characteristic acceleration, Milgrom's constant, which is observationally constrained to a0 ≈ 1.1×10 10 ms 2 . In the derivation presented here, this constant arises naturally from the cosmologically required mass of gravitons like a0 ∝ c √ � ∝ cH0 √ 3�, with �, H0, andbeing the cosmological constant, the Hubble constant, and the third cosmological parameter, respectively. My derivation suggests that massive gravity could be the mechanism behind both, dark matter and dark energy.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"48 1","pages":"191-194"},"PeriodicalIF":1.0,"publicationDate":"2015-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70736149","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}
Pub Date : 2015-04-30DOI: 10.5303/JKAS.2015.48.2.105
Jeong-Eun Heo, Hee-Won Lee
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.
{"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":"48 1","pages":"105-112"},"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}
Pub Date : 2015-03-27DOI: 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.
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.
{"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":"48 1","pages":"125-137"},"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}
Pub Date : 2015-02-28DOI: 10.5303/JKAS.2015.48.1.1
S. M. Amin
The orbital period changes of theWUMa eclipsing binary AU Ser are studied using the (O?C) method. We conclude that the period variation is due to mass transfer from the primary star to the secondary one at a very low and decreasing rate dP/dt = ?8.872× 10 ?8 , superimposed on the sinusoidal variation due to a third body orbiting the binary with period 42.87 ± 3.16 years, orbital eccentricity e = 0.52±0.12 and a longitude of periastron passage ! = 133°.7±15. On studying the magnetic activity, we have concluded that the Applegate mechanism failed to describe the cycling variation of the (O ? C) diagram of AU Ser.
{"title":"MASS TRANSFER AND LIGHT TIME EFFECT STUDIES FOR AU SERPENTIS","authors":"S. M. Amin","doi":"10.5303/JKAS.2015.48.1.1","DOIUrl":"https://doi.org/10.5303/JKAS.2015.48.1.1","url":null,"abstract":"The orbital period changes of theWUMa eclipsing binary AU Ser are studied using the (O?C) method. We conclude that the period variation is due to mass transfer from the primary star to the secondary one at a very low and decreasing rate dP/dt = ?8.872× 10 ?8 , superimposed on the sinusoidal variation due to a third body orbiting the binary with period 42.87 ± 3.16 years, orbital eccentricity e = 0.52±0.12 and a longitude of periastron passage ! = 133°.7±15. On studying the magnetic activity, we have concluded that the Applegate mechanism failed to describe the cycling variation of the (O ? C) diagram of AU Ser.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"48 1","pages":"1-7"},"PeriodicalIF":1.0,"publicationDate":"2015-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70735917","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}
Pub Date : 2015-02-28DOI: 10.5303/JKAS.2015.48.1.021
E. Kang, M. Im
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.
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Pub Date : 2015-02-28DOI: 10.5303/JKAS.2015.48.1.83
D. Han, Myeong-Gu Park
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.
最近的大规模调查，如斯隆数字巡天，已经产生了具有明确选择效应的多图像引力透镜类星体的均匀样本。对这些进行统计分析可以得出对宇宙学参数的独立约束。本文利用斯隆数字巡天类星体透镜搜索(SQLS)中透镜类星体的图像分离统计来推导宇宙学参数的约束条件。我们的分析不需要知道放大偏差，这只能从类星体在所有红移时的光度函数的详细知识中估计出来，并且在后续观测中考虑到对暗透镜星系的选择对小像分离类星体的偏差进行确认。我们首先利用透镜类星体的平均像差作为红移的函数，发现具有极端曲率的宇宙学模型与观测到的透镜类星体不一致。然后，我们将最大似然检验应用于16个透镜类星体的统计样本，这些类星体都测量了透镜星系的红移和星等。似然包含了在给定透镜星系光度的情况下，以与Im et al.(1997)相同的方式实现观测到的图像分离的概率。我们发现宇宙常数(即真空能量密度)的95%置信范围为0.72≤Ω Λ≤1.0。我们还发现，只要物质密度为m，状态参数方程就可以与?1一致。0.4(95%置信范围)。我们得出结论，包含透镜星系亮度的图像分离统计可以为宇宙学参数提供强大的约束。
{"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":"48 1","pages":"83-92"},"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}
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