Pub Date : 2015-02-28DOI: 10.5303/JKAS.2015.48.1.57
K. Seon
Monte-Carlo radiative models of the diffuse Galactic light (DGL) in our Galaxy are calcu-lated using the dust radiative transfer code MoCafe, which is three-dimensional and takes full account of multiple scattering. The code is recently updated to use a fast voxel traversal algorithm, which has dramatically increased the computing speed. The radiative transfer models are calculated with the gen-erally accepted dust scale-height of 0.1 kpc. The stellar scale-heights are assumed to be 0.1 or 0.35 kpc, appropriate for far-ultraviolet (FUV) and optical wavelengths, respectively. The face-on optical depth, measured perpendicular to the Galactic plane, is also varied from 0.2 to 0.6, suitable to the optical to FUV wavelengths, respectively. We find that the DGL at high Galactic latitudes is mostly due to backward or large-angle scattering of starlight originating from the local stars within a radial distance of r < 0.5 kpc from the Earth. On the other hand, the DGL measured in the Galactic plane is mostly due to stars at a distance range that corresponds to an optical depth of ? 1 measured from the Earth. Therefore, the low-latitude DGL at the FUV wavelength band would be mostly caused by the stars located at a distance of r . 0.5 kpc and the optical DGL near the Galactic plane mainly originates from stars within a distance range of 1 . r . 2 kpc. We also calculate the radiative transfer models in a clumpy two-phase medium. The clumpy two-phase models provide lower intensities at high Galactic latitudes compared to the uniform density models, because of the lower effective optical depth in clumpy media. However, no significant difference in the intensity at the Galactic plane is found.
{"title":"MONTE-CARLO RADIATIVE TRANSFER MODEL OF THE DIFFUSE GALACTIC LIGHT","authors":"K. Seon","doi":"10.5303/JKAS.2015.48.1.57","DOIUrl":"https://doi.org/10.5303/JKAS.2015.48.1.57","url":null,"abstract":"Monte-Carlo radiative models of the diffuse Galactic light (DGL) in our Galaxy are calcu-lated using the dust radiative transfer code MoCafe, which is three-dimensional and takes full account of multiple scattering. The code is recently updated to use a fast voxel traversal algorithm, which has dramatically increased the computing speed. The radiative transfer models are calculated with the gen-erally accepted dust scale-height of 0.1 kpc. The stellar scale-heights are assumed to be 0.1 or 0.35 kpc, appropriate for far-ultraviolet (FUV) and optical wavelengths, respectively. The face-on optical depth, measured perpendicular to the Galactic plane, is also varied from 0.2 to 0.6, suitable to the optical to FUV wavelengths, respectively. We find that the DGL at high Galactic latitudes is mostly due to backward or large-angle scattering of starlight originating from the local stars within a radial distance of r < 0.5 kpc from the Earth. On the other hand, the DGL measured in the Galactic plane is mostly due to stars at a distance range that corresponds to an optical depth of ? 1 measured from the Earth. Therefore, the low-latitude DGL at the FUV wavelength band would be mostly caused by the stars located at a distance of r . 0.5 kpc and the optical DGL near the Galactic plane mainly originates from stars within a distance range of 1 . r . 2 kpc. We also calculate the radiative transfer models in a clumpy two-phase medium. The clumpy two-phase models provide lower intensities at high Galactic latitudes compared to the uniform density models, because of the lower effective optical depth in clumpy media. However, no significant difference in the intensity at the Galactic plane is found.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"45 1","pages":"57-66"},"PeriodicalIF":1.0,"publicationDate":"2015-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70736098","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 : 2015-02-12DOI: 10.5303/JKAS.2015.48.1.075
Changbom Park, Hyunmi Song, M. Einasto, H. Lietzen, P. Heinamaki
We use a volume-limited sample of quasars in the Sloan Digital Sky Survey (SDSS) DR7 quasar catalog to identify quasar groups and address their statistical significance. This quasar sample has a uniform selection function on the sky and nearly a maximum possible contiguous volume that can be drawn from the DR7 catalog. Quasar groups are identified by using the Friend-of-Friend algorithm with a set of fixed comoving linking lengths. We find that the richness distribution of the richest 100 quasar groups or the size distribution of the largest 100 groups are statistically equivalent with those of randomly-distributed points with the same number density and sky coverage when groups are identified with the linking length of 70 h?1Mpc. It is shown that the large-scale structures like the huge Large Quasar Group (U1.27) reported by Clowes et al. (2013) can be found with high probability even if quasars have no physical clustering, and does not challenge the initially homogeneous cosmological models. Our results are statistically more reliable than those of Nadathur (2013), where the test was made only for the largest quasar group. It is shown that the linking length should be smaller than 50 h?1Mpc in order for the quasar groups identified in the DR7 catalog not to be dominated by associations of quasars grouped by chance. We present 20 richest quasar groups identified with the linking length of 70 h?1Mpc for further analyses.
我们使用斯隆数字巡天(SDSS) DR7类星体目录中体积有限的类星体样本来识别类星体群并解决它们的统计显著性。这个类星体样本在天空中具有均匀的选择函数，并且可以从DR7星表中提取出几乎最大可能的连续体积。类星体群的识别采用一组固定的共移动连接长度的Friend-of-Friend算法。我们发现，当类星体群的连接长度为70h ?1Mpc时，最丰富的100个类星体群的丰富度分布或最大的100个类星体群的大小分布与具有相同数量密度和天空覆盖率的随机分布点的丰富度分布在统计上是相等的。研究表明，即使类星体没有物理聚类，cloes et al.(2013)报道的大型类星体群(Large Quasar Group, U1.27)这样的大尺度结构也能以高概率被发现，并且不会挑战最初的均匀宇宙学模型。我们的结果在统计上比Nadathur(2013)的结果更可靠，后者只对最大的类星体群进行了测试。结果表明，键长应小于50h ?为了使DR7星表中确定的类星体群不被偶然组合的类星体群所支配。我们提出了20个最丰富的类星体群，它们的连接长度为70 h?1Mpc以作进一步分析。
{"title":"LARGE SDSS QUASAR GROUPS AND THEIR STATISTICAL SIGNIFICANCE","authors":"Changbom Park, Hyunmi Song, M. Einasto, H. Lietzen, P. Heinamaki","doi":"10.5303/JKAS.2015.48.1.075","DOIUrl":"https://doi.org/10.5303/JKAS.2015.48.1.075","url":null,"abstract":"We use a volume-limited sample of quasars in the Sloan Digital Sky Survey (SDSS) DR7 quasar catalog to identify quasar groups and address their statistical significance. This quasar sample has a uniform selection function on the sky and nearly a maximum possible contiguous volume that can be drawn from the DR7 catalog. Quasar groups are identified by using the Friend-of-Friend algorithm with a set of fixed comoving linking lengths. We find that the richness distribution of the richest 100 quasar groups or the size distribution of the largest 100 groups are statistically equivalent with those of randomly-distributed points with the same number density and sky coverage when groups are identified with the linking length of 70 h?1Mpc. It is shown that the large-scale structures like the huge Large Quasar Group (U1.27) reported by Clowes et al. (2013) can be found with high probability even if quasars have no physical clustering, and does not challenge the initially homogeneous cosmological models. Our results are statistically more reliable than those of Nadathur (2013), where the test was made only for the largest quasar group. It is shown that the linking length should be smaller than 50 h?1Mpc in order for the quasar groups identified in the DR7 catalog not to be dominated by associations of quasars grouped by chance. We present 20 richest quasar groups identified with the linking length of 70 h?1Mpc for further analyses.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"48 1","pages":"75-82"},"PeriodicalIF":1.0,"publicationDate":"2015-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70735801","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 : 2015-02-10DOI: 10.5303/JKAS.2015.48.2.155
Hyesung Kang
In Kang (2015) we calculated the acceleration of cosmic-ray electrons at weak spherical shocks that are expected to form in the cluster outskirts, and estimated the diffuse synchrotron radiation emitted by those electrons. There we demonstrated that, at decelerating spherical shocks, the volume integrated spectra of both electrons and radiation deviate significantly from the test-particle power-laws predicted for constant planar shocks, because the shock compression ratio and the flux of inject electrons decrease in time. In this study, we consider spherical blast waves propagating through a constant density core surrounded by an isothermal halo with p ∝ r ?n in order to explore how the deceleration of the shock affects the radio emission from accelerated electrons. The surface brightness profile and the volumeintegrated radio spectrum of the model shocks are calculated by assuming a ribbon-like shock surface on a spherical shell and the associated downstream region of relativistic electrons. If the postshock magnetic field strength is about 0.7 or 7 μG, at the shock age of ∼ 50 Myr, the volume-integrated radio spectrum steepens gradually with the spectral index from α inj to α inj + 0.5 over 0.1?10 GHz, where α inj is the injection index at the shock position expected from the diffusive shock acceleration theory. Such gradual steepening could explain the curved radio spectrum of the radio relic in cluster A2266, which was interpreted as a broken power-law by Trasatti et al. (2015), if the relic shock is young enough so that the break frequency is around 1 GHz.
{"title":"RADIO EMISSION FROM WEAK SPHERICAL SHOCKS IN THE OUTSKIRTS OF GALAXY CLUSTERS","authors":"Hyesung Kang","doi":"10.5303/JKAS.2015.48.2.155","DOIUrl":"https://doi.org/10.5303/JKAS.2015.48.2.155","url":null,"abstract":"In Kang (2015) we calculated the acceleration of cosmic-ray electrons at weak spherical shocks that are expected to form in the cluster outskirts, and estimated the diffuse synchrotron radiation emitted by those electrons. There we demonstrated that, at decelerating spherical shocks, the volume integrated spectra of both electrons and radiation deviate significantly from the test-particle power-laws predicted for constant planar shocks, because the shock compression ratio and the flux of inject electrons decrease in time. In this study, we consider spherical blast waves propagating through a constant density core surrounded by an isothermal halo with p ∝ r ?n in order to explore how the deceleration of the shock affects the radio emission from accelerated electrons. The surface brightness profile and the volumeintegrated radio spectrum of the model shocks are calculated by assuming a ribbon-like shock surface on a spherical shell and the associated downstream region of relativistic electrons. If the postshock magnetic field strength is about 0.7 or 7 μG, at the shock age of ∼ 50 Myr, the volume-integrated radio spectrum steepens gradually with the spectral index from α inj to α inj + 0.5 over 0.1?10 GHz, where α inj is the injection index at the shock position expected from the diffusive shock acceleration theory. Such gradual steepening could explain the curved radio spectrum of the radio relic in cluster A2266, which was interpreted as a broken power-law by Trasatti et al. (2015), if the relic shock is young enough so that the break frequency is around 1 GHz.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"48 1","pages":"155-164"},"PeriodicalIF":1.0,"publicationDate":"2015-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70736480","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 : 2014-12-31DOI: 10.5303/JKAS.2014.47.6.259
Ji-hyun Kang, B. Koo, D. Byun
G192.8-1.1 has been known as one of the faintest supernova remnants (SNRs) in the Galaxy until the radio continuum of G192.8-1.1 is proved to be thermal by Gao et al. (2011). Yet, the nature of G192.8-1.1 has not been fully investigated. Here, we report the possible discovery of faint non-thermal radio continuum components with a spectral index α ~ 0.56 (S ν ∝ν -α ) around G192.8-1.1, while most of the radio continuum emission is thermal. Also, our Arecibo HI data reveal an HI shell, expanding with an expansion velocity of 20-60 km s -1 , that has an excellent morphological correlation with the radio continuum emission. The estimated physical parameters of the HI shell and the possible association of non-thermal radio continuum emission with it suggest G192.8-1.1 to be an ~ 0.3 Myr-old SNR. However, the presence of thermal radio continuum implies the presence of early-type stars in the same region. One possibility is that a massive star is ionizing the interior of an old SNR. If it is the case, the electron distribution assumed by the centrally-peaked surface brightness of thermal emission implies that G192.8-1.1 is a “thermal-composite” SNR, rather than a typical shell-type SNR, where the central hot gas that used to be bright in X-rays has cooled down. Therefore, we propose that G192.8-1.1 is an old evolved thermal-composite SNR showing recurring emission in the radio continuum due to a nearby massive star. The infrared image supports that the HI shell of G192.8-1.1 is currently encountering a nearby star forming region that possibly contains an early type star(s).
G192.8-1.1一直被认为是银河系中最微弱的超新星遗迹(SNRs)之一，直到Gao等人(2011)证明G192.8-1.1的射电连续体是热的。然而，G192.8-1.1的性质尚未得到充分研究。本文报道了在G192.8-1.1附近可能发现微弱的非热射电连续谱成分，其光谱指数为α ~ 0.56 (S ν∝ν -α)，而大部分射电连续谱发射是热发射。此外，我们的阿雷西博HI数据揭示了一个HI壳，膨胀速度为20-60 km s -1，与射电连续辐射具有良好的形态相关性。估计HI壳层的物理参数以及非热射电连续辐射与其可能的关联表明，G192.8-1.1的信噪比为~ 0.3 myr。然而，热射电连续体的存在意味着在同一区域存在早期型恒星。一种可能性是，一颗大质量恒星正在电离一个老信噪比的内部。如果是这样的话，热辐射中心峰值表面亮度假设的电子分布意味着G192.8-1.1是“热复合”信噪比，而不是典型的壳型信噪比，即在x射线中曾经明亮的中心热气体已经冷却。因此，我们提出G192.8-1.1是一个古老的演化热复合信噪比，在射电连续体中显示出由附近的大质量恒星引起的反复发射。红外图像支持G192.8-1.1的HI壳层目前正在遇到附近的恒星形成区域，该区域可能包含一颗早期型恒星。
{"title":"G192.8-1.1: A CANDIDATE OF AN EVOLVED THERMAL COMPOSITE SUPERNOVA REMNANT REIGNITED BY NEARBY MASSIVE STARS","authors":"Ji-hyun Kang, B. Koo, D. Byun","doi":"10.5303/JKAS.2014.47.6.259","DOIUrl":"https://doi.org/10.5303/JKAS.2014.47.6.259","url":null,"abstract":"G192.8-1.1 has been known as one of the faintest supernova remnants (SNRs) in the Galaxy until the radio continuum of G192.8-1.1 is proved to be thermal by Gao et al. (2011). Yet, the nature of G192.8-1.1 has not been fully investigated. Here, we report the possible discovery of faint non-thermal radio continuum components with a spectral index α ~ 0.56 (S ν ∝ν -α ) around G192.8-1.1, while most of the radio continuum emission is thermal. Also, our Arecibo HI data reveal an HI shell, expanding with an expansion velocity of 20-60 km s -1 , that has an excellent morphological correlation with the radio continuum emission. The estimated physical parameters of the HI shell and the possible association of non-thermal radio continuum emission with it suggest G192.8-1.1 to be an ~ 0.3 Myr-old SNR. However, the presence of thermal radio continuum implies the presence of early-type stars in the same region. One possibility is that a massive star is ionizing the interior of an old SNR. If it is the case, the electron distribution assumed by the centrally-peaked surface brightness of thermal emission implies that G192.8-1.1 is a “thermal-composite” SNR, rather than a typical shell-type SNR, where the central hot gas that used to be bright in X-rays has cooled down. Therefore, we propose that G192.8-1.1 is an old evolved thermal-composite SNR showing recurring emission in the radio continuum due to a nearby massive star. The infrared image supports that the HI shell of G192.8-1.1 is currently encountering a nearby star forming region that possibly contains an early type star(s).","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"47 1","pages":"259-277"},"PeriodicalIF":1.0,"publicationDate":"2014-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70736022","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 : 2014-12-31DOI: 10.5303/JKAS.2014.47.6.319
Youngung Lee, Young Sik Kim, Hyung-Goo Kim, J. Jung, I. Yim, Hyun-Sil Kang, Changhoon Lee, Bong-Gyu Kim, Kwang-Tae Kim
We map two molecular clouds located in the exact anticenter region emitting in the (J = 1-0) transition of 12 CO and 13 CO using the 3-mm SIS mixer receiver on the 14-m radio telescope at Taeduk Radio Astronomy Observatory. The target clouds with anomalous velocities of V LSR ~ -20 km s -1 are distinguished from other clouds in this direction. In addition, they are located in the interarm region between the Orion Arm and the Perseus Arm. Sizes of the clouds are estimated to be about 8.6 and 10.8 pc, respectively. The total mass is estimated to be about 4 x 10³ M ⊙ using CO luminosity of the clouds. Several cores are detected, but no sign of star formation is found according to the IRAS point sources. Their larger linewidths, anomalous velocities, and their location at the interarm region make these clouds more distinguished, though their physical properties are similar to the dark clouds in the solar neighborhood in terms of mass and size.
我们利用台德射电天文台14米射电望远镜上的3毫米SIS混频器接收器，绘制了位于12 CO和13 CO (J = 1-0)跃迁的精确反中心区域的两个分子云。在该方向上，具有V LSR ~ -20 km s -1异常速度的目标云与其他云有所区别。此外，它们位于猎户座臂和英仙座臂之间的臂间区域。云的大小估计分别为8.6%和10.8%。根据云的CO光度估计其总质量约为4 × 10³M⊙。探测到几个核心，但根据IRAS点源没有发现恒星形成的迹象。它们更大的线宽，异常的速度，以及它们在臂间区的位置使这些云更加明显，尽管它们的物理性质在质量和大小方面与太阳附近的黑云相似。
{"title":"TWO MOLECULAR CLOUDS WITH ANOMALOUS VELOCITIES IN THE GALACTIC ANTICENTER","authors":"Youngung Lee, Young Sik Kim, Hyung-Goo Kim, J. Jung, I. Yim, Hyun-Sil Kang, Changhoon Lee, Bong-Gyu Kim, Kwang-Tae Kim","doi":"10.5303/JKAS.2014.47.6.319","DOIUrl":"https://doi.org/10.5303/JKAS.2014.47.6.319","url":null,"abstract":"We map two molecular clouds located in the exact anticenter region emitting in the (J = 1-0) transition of 12 CO and 13 CO using the 3-mm SIS mixer receiver on the 14-m radio telescope at Taeduk Radio Astronomy Observatory. The target clouds with anomalous velocities of V LSR ~ -20 km s -1 are distinguished from other clouds in this direction. In addition, they are located in the interarm region between the Orion Arm and the Perseus Arm. Sizes of the clouds are estimated to be about 8.6 and 10.8 pc, respectively. The total mass is estimated to be about 4 x 10³ M ⊙ using CO luminosity of the clouds. Several cores are detected, but no sign of star formation is found according to the IRAS point sources. Their larger linewidths, anomalous velocities, and their location at the interarm region make these clouds more distinguished, though their physical properties are similar to the dark clouds in the solar neighborhood in terms of mass and size.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"47 1","pages":"319-325"},"PeriodicalIF":1.0,"publicationDate":"2014-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70735991","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 : 2014-12-31DOI: 10.5303/JKAS.2014.47.6.255
I. Cho, S. Bong, Kyungsuk Cho, Jaejin Lee, R. Kim, Young-deuk Park, Yeon-Han Kim
Using sunspot number data from 270 historical stations for the period 1981-2013, we investigate their personal reduction coefficients (k) statistically. Chang & Oh (2012) perform a simulation showing that the k varies with the solar cycle. We try to verify their results using observational data. For this, a weighted mean and weighted standard deviation of monthly sunspot number are used to estimate the error from observed data. We find that the observed error (noise) is much smaller than that used in the simulation. Thus no distinct k-variation with the solar cycle is observed contrary to the simulation. In addition, the probability distribution of k is determined to be non-Gaussian with a fat-tail on the right side. This result implies that the relative sunspot number after 1981 might be overestimated since the mean value of k is less than that of the Gaussian distribution.
{"title":"STATISTICAL STUDY ON PERSONAL REDUCTION COEFFICIENTS OF SUNSPOT NUMBERS SINCE 1981","authors":"I. Cho, S. Bong, Kyungsuk Cho, Jaejin Lee, R. Kim, Young-deuk Park, Yeon-Han Kim","doi":"10.5303/JKAS.2014.47.6.255","DOIUrl":"https://doi.org/10.5303/JKAS.2014.47.6.255","url":null,"abstract":"Using sunspot number data from 270 historical stations for the period 1981-2013, we investigate their personal reduction coefficients (k) statistically. Chang & Oh (2012) perform a simulation showing that the k varies with the solar cycle. We try to verify their results using observational data. For this, a weighted mean and weighted standard deviation of monthly sunspot number are used to estimate the error from observed data. We find that the observed error (noise) is much smaller than that used in the simulation. Thus no distinct k-variation with the solar cycle is observed contrary to the simulation. In addition, the probability distribution of k is determined to be non-Gaussian with a fat-tail on the right side. This result implies that the relative sunspot number after 1981 might be overestimated since the mean value of k is less than that of the Gaussian distribution.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"47 1","pages":"255-258"},"PeriodicalIF":1.0,"publicationDate":"2014-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70735950","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 : 2014-12-31DOI: 10.5303/JKAS.2014.47.6.201
Y. Yun, Yong-Sun Park, Chang-Hee Kim, Bangwon Lee, Jung-Hoon Kim, Saeho Yoo, Chul-Hwan Lee, Jinwook Han, Young Yun Kim
We report the development of solar flux receivers operating at 2.8 GHz to monitor solar radio activity. Radio waves from the sun are amplified, filtered, and then transmitted to a power meter sensor without frequency down-conversion. To measure solar flux, a calibration scheme is designed with a noise source, an ambient load, and a hot load at 100 ℃. The receiver is attached to a 1.8 m parabolic antenna in Icheon, owned by National Radio Research Agency, and observation is being conducted during day time on a daily basis. We compare the solar fluxes measured for last seven months with solar fluxes obtained by DRAO in Penticton, Canada, and by the Hiraiso solar observatory in Japan, and finally establish equations to convert observed flux to the so-called Penticton flux with an accuracy better than 3.2 sfu.
{"title":"Development of 2.8-GHz Solar Flux Receivers","authors":"Y. Yun, Yong-Sun Park, Chang-Hee Kim, Bangwon Lee, Jung-Hoon Kim, Saeho Yoo, Chul-Hwan Lee, Jinwook Han, Young Yun Kim","doi":"10.5303/JKAS.2014.47.6.201","DOIUrl":"https://doi.org/10.5303/JKAS.2014.47.6.201","url":null,"abstract":"We report the development of solar flux receivers operating at 2.8 GHz to monitor solar radio activity. Radio waves from the sun are amplified, filtered, and then transmitted to a power meter sensor without frequency down-conversion. To measure solar flux, a calibration scheme is designed with a noise source, an ambient load, and a hot load at 100 ℃. The receiver is attached to a 1.8 m parabolic antenna in Icheon, owned by National Radio Research Agency, and observation is being conducted during day time on a daily basis. We compare the solar fluxes measured for last seven months with solar fluxes obtained by DRAO in Penticton, Canada, and by the Hiraiso solar observatory in Japan, and finally establish equations to convert observed flux to the so-called Penticton flux with an accuracy better than 3.2 sfu.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"47 1","pages":"201-207"},"PeriodicalIF":1.0,"publicationDate":"2014-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70735254","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 : 2014-12-31DOI: 10.5303/JKAS.2014.47.6.219
K. Suh
The main site of dust formation is believed to be the cool envelopes around AGB stars. Nearly all AGB stars can be identified as long-period variables (LPVs) with large amplitude pulsation. Shock waves produce by the strong pulsation and radiation pressure on newly formed dust grains drive dusty stellar winds with high mass-loss rates. IR observations of AGB stars identify various dust species in different physical conditions. Radio observations of gas phase materials are helpful to understand the overall properties of the stellar winds. In this paper, we review (i) classification of AGB stars; (ii) IR two-color diagrams of AGB stars; (iii) pulsation of AGB stars; (iv) dust around AGB stars including dusty stellar winds; (v) dust envelopes around AGB stars; (vi) mass-loss and evolution of AGB stars; and (vii) contribution of AGB dust to galactic environments. We discuss various observational evidences and their theoretical interpretations.
{"title":"ASTROPHYSICS OF DUSTY STELLAR WINDS FROM AGB STARS","authors":"K. Suh","doi":"10.5303/JKAS.2014.47.6.219","DOIUrl":"https://doi.org/10.5303/JKAS.2014.47.6.219","url":null,"abstract":"The main site of dust formation is believed to be the cool envelopes around AGB stars. Nearly all AGB stars can be identified as long-period variables (LPVs) with large amplitude pulsation. Shock waves produce by the strong pulsation and radiation pressure on newly formed dust grains drive dusty stellar winds with high mass-loss rates. IR observations of AGB stars identify various dust species in different physical conditions. Radio observations of gas phase materials are helpful to understand the overall properties of the stellar winds. In this paper, we review (i) classification of AGB stars; (ii) IR two-color diagrams of AGB stars; (iii) pulsation of AGB stars; (iv) dust around AGB stars including dusty stellar winds; (v) dust envelopes around AGB stars; (vi) mass-loss and evolution of AGB stars; and (vii) contribution of AGB dust to galactic environments. We discuss various observational evidences and their theoretical interpretations.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"47 1","pages":"219-233"},"PeriodicalIF":1.0,"publicationDate":"2014-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70735477","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 : 2014-12-31DOI: 10.5303/JKAS.2014.47.6.209
E. Jeong, Jin-Yi Lee, Y. Moon, Jong-Yeop Park
In this study we develop a set of solar proton event (SPE) forecast models with NOAA scales by Multi Layer Perceptron (MLP), one of neural network methods, using GOES solar X-ray flare data from 1976 to 2011. Our MLP models are the first attempt to forecast the SPE scales by the neural network method. The combinations of X-ray flare class, impulsive time, and location are used for input data. For this study we make a number of trials by changing the number of layers and nodes as well as combinations of the input data. To find the best model, we use the summation of F-scores weighted by SPE scales, where F-score is the harmonic mean of PODy (recall) and precision (positive predictive value), in order to minimize both misses and false alarms. We find that the MLP models are much better than the multiple linear regression model and one layer MLP model gives the best result.
{"title":"FORECAST OF SOLAR PROTON EVENTS WITH NOAA SCALES BASED ON SOLAR X-RAY FLARE DATA USING NEURAL NETWORK","authors":"E. Jeong, Jin-Yi Lee, Y. Moon, Jong-Yeop Park","doi":"10.5303/JKAS.2014.47.6.209","DOIUrl":"https://doi.org/10.5303/JKAS.2014.47.6.209","url":null,"abstract":"In this study we develop a set of solar proton event (SPE) forecast models with NOAA scales by Multi Layer Perceptron (MLP), one of neural network methods, using GOES solar X-ray flare data from 1976 to 2011. Our MLP models are the first attempt to forecast the SPE scales by the neural network method. The combinations of X-ray flare class, impulsive time, and location are used for input data. For this study we make a number of trials by changing the number of layers and nodes as well as combinations of the input data. To find the best model, we use the summation of F-scores weighted by SPE scales, where F-score is the harmonic mean of PODy (recall) and precision (positive predictive value), in order to minimize both misses and false alarms. We find that the MLP models are much better than the multiple linear regression model and one layer MLP model gives the best result.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"47 1","pages":"209-214"},"PeriodicalIF":1.0,"publicationDate":"2014-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70735351","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 : 2014-12-29DOI: 10.5303/JKAS.2014.47.6.293
Se-Hyung Cho, Jaeheon Kim, Y. Yun
Simultaneous time monitoring observations of H₂O 6 16 -5 23 , SiO J = 1-0, 2-1, 3-2, and 29 SiO v = 0, J = 1-0 lines are carried out in the direction of the Mira variable star TX Cam with the Korean VLBI Network single dish radio telescopes. For the first time, the H₂O maser emission from TX Cam is detected near the stellar velocity at five epochs from April 10, 2013 (o = 3.13) to June 4, 2014 (o = 3.89) including minimum optical phases. The intensities of H₂O masers are very weak compared to SiO masers. The variation of peak antenna temperature ratios among SiO v = 1, J = 1-0, J = 2-1, and J = 3-2 masers is investigated according to their phases. The shift of peak velocities of H₂O and SiO masers with respect to the stellar velocity is also investigated according to observed optical phases. The H₂O maser emission occurs around the stellar velocity during our monitoring interval. On the other hand, the peak velocities of SiO masers show a spread compared to the stellar velocity. The peak velocities of SiO J = 2-1, and J = 3-2 masers show a smaller spread with respect to the stellar velocity than those of SiO J = 1-0 masers. These simultaneous observations of multi-frequencies will provide a good constraint for maser pumping models and a good probe for investigating the stellar atmosphere and envelope according to their different excitation conditions.
{"title":"First Detection of 22 GHz H2O Masers in TX Camelopardalis","authors":"Se-Hyung Cho, Jaeheon Kim, Y. Yun","doi":"10.5303/JKAS.2014.47.6.293","DOIUrl":"https://doi.org/10.5303/JKAS.2014.47.6.293","url":null,"abstract":"Simultaneous time monitoring observations of H₂O 6 16 -5 23 , SiO J = 1-0, 2-1, 3-2, and 29 SiO v = 0, J = 1-0 lines are carried out in the direction of the Mira variable star TX Cam with the Korean VLBI Network single dish radio telescopes. For the first time, the H₂O maser emission from TX Cam is detected near the stellar velocity at five epochs from April 10, 2013 (o = 3.13) to June 4, 2014 (o = 3.89) including minimum optical phases. The intensities of H₂O masers are very weak compared to SiO masers. The variation of peak antenna temperature ratios among SiO v = 1, J = 1-0, J = 2-1, and J = 3-2 masers is investigated according to their phases. The shift of peak velocities of H₂O and SiO masers with respect to the stellar velocity is also investigated according to observed optical phases. The H₂O maser emission occurs around the stellar velocity during our monitoring interval. On the other hand, the peak velocities of SiO masers show a spread compared to the stellar velocity. The peak velocities of SiO J = 2-1, and J = 3-2 masers show a smaller spread with respect to the stellar velocity than those of SiO J = 1-0 masers. These simultaneous observations of multi-frequencies will provide a good constraint for maser pumping models and a good probe for investigating the stellar atmosphere and envelope according to their different excitation conditions.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"47 1","pages":"293-302"},"PeriodicalIF":1.0,"publicationDate":"2014-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70735787","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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