Pub Date : 2017-04-30DOI: 10.5303/JKAS.2017.50.2.29
Kyungsuk Cho, K. Marubashi, R. Kim, Sung-Hong Park, E. Lim, Sujin Kim, Pankaj Kumar, V. Yurchyshyn, Y. Moon, J. Lee
{"title":"Impact of the Icme-Earth Geometry on the Strength of the Associated Geomagnetic Storm: The September 2014 and March 2015 Events","authors":"Kyungsuk Cho, K. Marubashi, R. Kim, Sung-Hong Park, E. Lim, Sujin Kim, Pankaj Kumar, V. Yurchyshyn, Y. Moon, J. Lee","doi":"10.5303/JKAS.2017.50.2.29","DOIUrl":"https://doi.org/10.5303/JKAS.2017.50.2.29","url":null,"abstract":"","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"50 1","pages":"29-39"},"PeriodicalIF":1.0,"publicationDate":"2017-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42441292","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 : 2017-02-28DOI: 10.5303/JKAS.2017.50.1.7
H. Seo, W. Jeong, S. Kim, J. Pyo, Min Gyu Kim, J. Ko, Minjin Kim, Sam Kim
{"title":"PROPERTIES OF THE SCUBA-2 850㎛ SOURCES IN THE XMM-LSS FIELD","authors":"H. Seo, W. Jeong, S. Kim, J. Pyo, Min Gyu Kim, J. Ko, Minjin Kim, Sam Kim","doi":"10.5303/JKAS.2017.50.1.7","DOIUrl":"https://doi.org/10.5303/JKAS.2017.50.1.7","url":null,"abstract":"","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"50 1","pages":"7-20"},"PeriodicalIF":1.0,"publicationDate":"2017-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49199759","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 : 2016-12-31DOI: 10.5303/JKAS.2016.49.6.295
Dong-Joo Lee, J. Koo, K. Hong, Seung-Lee Kim, Jae Woo Lee, Chung-Uk Lee, Y. Jeon, Yun-Hak Kim, B. Lim, Y. Ryu, S. Cha, Yongseok Lee, Dong Jin Kim, Byeong-Gon Park, Chun-Hwey Kim
We present the results of BV time-series photometry of the globular cluster NGC 288. Ob-servations were carried out to search for variable stars using the Korea Microlensing Telescope Network (KMTNet) 1.6-m telescopes and a 4k pre-science CCD camera during a test observation from August to December, 2014. We found a new SX Phe star and confirmed twelve previously known variable stars in NGC 288. For the semi-regular variable star V1, we newly determined a period of 37.3 days from light curves spanning 137 days. The light-curve solution of the eclipsing binary V10 indicates that the system is probably a detached system. The pulsation properties of nine SX Phe stars were examined by applying multiple frequency analysis to their light curves. We derived a new Period-Luminosity (P-L) relation, = −2.476(±0.300) logP −0.354(±0.385), from six SX Phe stars showing the fundamental mode. Additionally, the period ratios of three SX Phe stars that probably have a double-radial mode were investigated; P FO /P F = 0.779 for V5, P TO /P FO = 0.685 for V9, P SO /P FO = 0.811 for V11. This paper is the first contribution in a series assessing the detections and properties of variable stars in six southern globular clusters with the KMTNet system.
本文介绍了球状星团ngc288的BV时间序列光度测定结果。2014年8月至12月，利用韩国微透镜望远镜网络(KMTNet)的1.6 m望远镜和一台4k预科级CCD相机对变星进行了观测。我们在NGC 288中发现了一颗新的SX Phe星，并确认了12颗以前已知的变星。对于半规则变星V1，我们从137天的光曲线中新确定了37.3天的周期。食双星V10的光曲线解表明该系统可能是一个分离的系统。采用多频分析方法对9颗SX Phe星的光曲线进行了脉动特性研究。我们从六颗显示基本模态的SX Phe恒星中推导出新的周期-光度(P-L)关系=−2.476(±0.300)logP−0.354(±0.385)。此外，我们还研究了三颗可能具有双径向模式的SX Phe恒星的周期比;V5的P FO /P F = 0.779, V9的P TO /P FO = 0.685, V11的P SO /P FO = 0.811。本文是一系列利用KMTNet系统评估南方六个球状星团中变星的探测和特性的第一篇论文。
{"title":"TIME-SERIES PHOTOMETRY OF VARIABLE STARS IN THE GLOBULAR CLUSTER NGC 288","authors":"Dong-Joo Lee, J. Koo, K. Hong, Seung-Lee Kim, Jae Woo Lee, Chung-Uk Lee, Y. Jeon, Yun-Hak Kim, B. Lim, Y. Ryu, S. Cha, Yongseok Lee, Dong Jin Kim, Byeong-Gon Park, Chun-Hwey Kim","doi":"10.5303/JKAS.2016.49.6.295","DOIUrl":"https://doi.org/10.5303/JKAS.2016.49.6.295","url":null,"abstract":"We present the results of BV time-series photometry of the globular cluster NGC 288. Ob-servations were carried out to search for variable stars using the Korea Microlensing Telescope Network (KMTNet) 1.6-m telescopes and a 4k pre-science CCD camera during a test observation from August to December, 2014. We found a new SX Phe star and confirmed twelve previously known variable stars in NGC 288. For the semi-regular variable star V1, we newly determined a period of 37.3 days from light curves spanning 137 days. The light-curve solution of the eclipsing binary V10 indicates that the system is probably a detached system. The pulsation properties of nine SX Phe stars were examined by applying multiple frequency analysis to their light curves. We derived a new Period-Luminosity (P-L) relation, = −2.476(±0.300) logP −0.354(±0.385), from six SX Phe stars showing the fundamental mode. Additionally, the period ratios of three SX Phe stars that probably have a double-radial mode were investigated; P FO /P F = 0.779 for V5, P TO /P FO = 0.685 for V9, P SO /P FO = 0.811 for V11. This paper is the first contribution in a series assessing the detections and properties of variable stars in six southern globular clusters with the KMTNet system.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"49 1","pages":"295-306"},"PeriodicalIF":1.0,"publicationDate":"2016-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70738359","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 : 2016-12-31DOI: 10.5303/JKAS.2016.49.6.289
Jae-Woo Lee, R. Pogge
{"title":"Long-Term Variation of the Shutter Delay Time of Y4KCAM of the CTIO 1.0 M Telescope","authors":"Jae-Woo Lee, R. Pogge","doi":"10.5303/JKAS.2016.49.6.289","DOIUrl":"https://doi.org/10.5303/JKAS.2016.49.6.289","url":null,"abstract":"","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"49 1","pages":"289-293"},"PeriodicalIF":1.0,"publicationDate":"2016-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70738347","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 : 2016-12-31DOI: 10.5303/JKAS.2016.49.6.255
Y. Lee, Di Li, Yongdai Kim, J. H. Jung, H. Kang, C. -. Lee, I. Yim, Hyun-Chul Kim
We estimate the fractal dimension of the ρ Ophiuchus Molecular Cloud Complex, associated with star forming regions. We selected a cube (v, l, b) database, obtained with J = 1−0 transition lines of 12 CO and 13 CO at a resolution of 22′′ using a multibeam receiver system on the 14-m telescope of the Five College Radio Astronomy Observatory. Using a code developed within IRAF, we identified slice-clouds with two threshold temperatures to estimate the fractal dimension. With threshold temperatures of 2.25 K (3σ) and 3.75 K (5σ), the fractal dimension of the target cloud is estimated to be D = 1.52–1.54, where P ∝ A D/2 , which is larger than previous results. We suggest that the sampling rate (spatial resolution) of observed data must be an important parameter when estimating the fractal dimension, and that narrower or wider dispersion around an arbitrary fit line and the intercepts at NP = 100 should be checked whether they relate to rms noise level or characteristic structure of the target cloud. This issue could be investigated by analysing several high resolution databases with different quality (low or moderate sensitivity).
我们估计了蛇夫座ρ分子云复合体的分形维数，它与恒星形成区域有关。我们选择了一个立方体(v, l, b)数据库，该数据库使用五校射电天文台14米望远镜上的多波束接收系统，以12 CO和13 CO的J = 1−0过渡线获得，分辨率为22 "。使用IRAF开发的代码，我们确定了具有两个阈值温度的切片云，以估计分形维数。在阈值温度为2.25 K (3σ)和3.75 K (5σ)的条件下，计算得到目标云的分形维数为D = 1.52 ~ 1.54，其中P∝A D/2，比之前的结果大。我们建议，在估计分形维数时，观测数据的采样率(空间分辨率)必须是一个重要参数，并且在任意拟合线周围更窄或更宽的色散和NP = 100处的截距应该检查它们是否与rms噪声水平或目标云的特征结构有关。这个问题可以通过分析几个不同质量(低或中等灵敏度)的高分辨率数据库来调查。
{"title":"The Fractal Dimension of the ρ Ophiucus Molecular Cloud Complex","authors":"Y. Lee, Di Li, Yongdai Kim, J. H. Jung, H. Kang, C. -. Lee, I. Yim, Hyun-Chul Kim","doi":"10.5303/JKAS.2016.49.6.255","DOIUrl":"https://doi.org/10.5303/JKAS.2016.49.6.255","url":null,"abstract":"We estimate the fractal dimension of the ρ Ophiuchus Molecular Cloud Complex, associated with star forming regions. We selected a cube (v, l, b) database, obtained with J = 1−0 transition lines of 12 CO and 13 CO at a resolution of 22′′ using a multibeam receiver system on the 14-m telescope of the Five College Radio Astronomy Observatory. Using a code developed within IRAF, we identified slice-clouds with two threshold temperatures to estimate the fractal dimension. With threshold temperatures of 2.25 K (3σ) and 3.75 K (5σ), the fractal dimension of the target cloud is estimated to be D = 1.52–1.54, where P ∝ A D/2 , which is larger than previous results. We suggest that the sampling rate (spatial resolution) of observed data must be an important parameter when estimating the fractal dimension, and that narrower or wider dispersion around an arbitrary fit line and the intercepts at NP = 100 should be checked whether they relate to rms noise level or characteristic structure of the target cloud. This issue could be investigated by analysing several high resolution databases with different quality (low or moderate sensitivity).","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"49 1","pages":"255-259"},"PeriodicalIF":1.0,"publicationDate":"2016-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70738294","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 : 2016-12-31DOI: 10.5303/JKAS.2016.49.6.261
Jaeheon Kim, Se-Hyung Cho, Dong-Hwan Yoon
We present the results of simultaneous monitoring observations of H₂O 6 1,6 –5 2,3 (22GHz) and SiO J=1–0, 2–1, 3–2 maser lines (43, 86, 129GHz) toward five post-AGB (candidate) stars, using the 21-m single-dish telescopes of the Korean VLBI Network. Depending on the target objects, 7 – 11 epochs of data were obtained. We detected both H₂O and SiO maser lines from four sources: OH16.1−0.3, OH38.10−0.13, OH65.5+1.3, and IRAS 19312+1950. We could not detect H₂O maser emission toward OH13.1+5.1 between the late OH/IR and post-AGB stage. The detected H₂O masers show typical double-peaked line profiles. The SiO masers from four sources, except IRAS 19312+1950, show the peaks around the stellar velocity as a single peak, whereas the SiO masers from IRAS 19312+1950 occur above the red peak of the H₂O maser. We analyzed the properties of detected maser lines, and investigated their evolutionary state through comparison with the full widths at zero power. The distribution of observed target sources was also investigated in the IRAS two-color diagram in relation with the evolutionary stage of post-AGB stars. From our analyses, the evolutionary sequence of observed sources is suggested as OH65.5+1.3 → OH13.1+5.1→ OH16.1−0.3 → OH38.10−0.13, except for IRAS 19312+1950. In addition, OH13.1+5.1 from which the H₂O maser has not been detected is suggested to be on the gateway toward the post-AGB stage. With respect to the enigmatic object, IRAS 19312+1950, we could not clearly figure out its nature. To properly explain the unusual phenomena of SiO and H₂O masers, it is essential to establish the relative locations and spatial distributions of two masers using VLBI technique. We also include the 1.2 – 160 μm spectral energy distribution using photometric data from the following surveys: 2MASS, WISE, MSX, IRAS, and AKARI (IRC and FIS). In addition, from the IRAS LRS spectra, we found that the depth of silicate absorption features shows significant variations depending on the evolutionary sequence, associated with the termination of AGB phase mass-loss.
{"title":"MONITORING OBSERVATIONS OF H2O AND SiO MASERS TOWARD POST-AGB STARS","authors":"Jaeheon Kim, Se-Hyung Cho, Dong-Hwan Yoon","doi":"10.5303/JKAS.2016.49.6.261","DOIUrl":"https://doi.org/10.5303/JKAS.2016.49.6.261","url":null,"abstract":"We present the results of simultaneous monitoring observations of H₂O 6 1,6 –5 2,3 (22GHz) and SiO J=1–0, 2–1, 3–2 maser lines (43, 86, 129GHz) toward five post-AGB (candidate) stars, using the 21-m single-dish telescopes of the Korean VLBI Network. Depending on the target objects, 7 – 11 epochs of data were obtained. We detected both H₂O and SiO maser lines from four sources: OH16.1−0.3, OH38.10−0.13, OH65.5+1.3, and IRAS 19312+1950. We could not detect H₂O maser emission toward OH13.1+5.1 between the late OH/IR and post-AGB stage. The detected H₂O masers show typical double-peaked line profiles. The SiO masers from four sources, except IRAS 19312+1950, show the peaks around the stellar velocity as a single peak, whereas the SiO masers from IRAS 19312+1950 occur above the red peak of the H₂O maser. We analyzed the properties of detected maser lines, and investigated their evolutionary state through comparison with the full widths at zero power. The distribution of observed target sources was also investigated in the IRAS two-color diagram in relation with the evolutionary stage of post-AGB stars. From our analyses, the evolutionary sequence of observed sources is suggested as OH65.5+1.3 → OH13.1+5.1→ OH16.1−0.3 → OH38.10−0.13, except for IRAS 19312+1950. In addition, OH13.1+5.1 from which the H₂O maser has not been detected is suggested to be on the gateway toward the post-AGB stage. With respect to the enigmatic object, IRAS 19312+1950, we could not clearly figure out its nature. To properly explain the unusual phenomena of SiO and H₂O masers, it is essential to establish the relative locations and spatial distributions of two masers using VLBI technique. We also include the 1.2 – 160 μm spectral energy distribution using photometric data from the following surveys: 2MASS, WISE, MSX, IRAS, and AKARI (IRC and FIS). In addition, from the IRAS LRS spectra, we found that the depth of silicate absorption features shows significant variations depending on the evolutionary sequence, associated with the termination of AGB phase mass-loss.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"49 1","pages":"261-288"},"PeriodicalIF":1.0,"publicationDate":"2016-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70738309","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 : 2016-12-31DOI: 10.5303/JKAS.2016.49.6.239
H. Ann, H. Bae
{"title":"ENVIRONMENTAL DEPENDENCE OF WARPS IN SPIRAL GALAXIES","authors":"H. Ann, H. Bae","doi":"10.5303/JKAS.2016.49.6.239","DOIUrl":"https://doi.org/10.5303/JKAS.2016.49.6.239","url":null,"abstract":"","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"49 1","pages":"239-253"},"PeriodicalIF":1.0,"publicationDate":"2016-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70738285","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 : 2016-11-11DOI: 10.5303/JKAS.2016.49.6.233
Changbom Park, Sung-Chul Yoon, B. Koo
The missing historical record of the Cassiopeia A (Cas A) supernova (SN) event implies a large extinction to the SN, possibly greater than the interstellar extinction to the current SN remnant. Here we investigate the possibility that the guest star that appeared near Cas A in 1592{1593 in Korean history books could have been an `impostor" of the Cas A SN, i.e., a luminous transient that appeared to be a SN but did not destroy the progenitor star, with strong mass loss to have provided extra circumstellar extinction. We first review the Korean records and show that a spatial coincidence between the guest star and Cas A cannot be ruled out, as opposed to previous studies. Based on modern astrophysical findings on core-collapse SN, we argue that Cas A could have had an impostor and derive its anticipated properties. It turned out that the Cas A SN impostor must have been bright (M V = -14.7 ± 2:2 mag) and an amount of dust with visual extinction of ≥ 2.8 ± 2:2 mag should have formed in the ejected envelope and/or in a strong wind afterwards. The mass loss needs to have been spherically asymmetric in order to see the light echo from the SN event but not the one from the impostor event.
{"title":"The Korean 1592-1593 Record of a Guest Star: An 'Impostor' of the Cassiopeia A Supernova?","authors":"Changbom Park, Sung-Chul Yoon, B. Koo","doi":"10.5303/JKAS.2016.49.6.233","DOIUrl":"https://doi.org/10.5303/JKAS.2016.49.6.233","url":null,"abstract":"The missing historical record of the Cassiopeia A (Cas A) supernova (SN) event implies a large extinction to the SN, possibly greater than the interstellar extinction to the current SN remnant. Here we investigate the possibility that the guest star that appeared near Cas A in 1592{1593 in Korean history books could have been an `impostor\" of the Cas A SN, i.e., a luminous transient that appeared to be a SN but did not destroy the progenitor star, with strong mass loss to have provided extra circumstellar extinction. We first review the Korean records and show that a spatial coincidence between the guest star and Cas A cannot be ruled out, as opposed to previous studies. Based on modern astrophysical findings on core-collapse SN, we argue that Cas A could have had an impostor and derive its anticipated properties. It turned out that the Cas A SN impostor must have been bright (M V = -14.7 ± 2:2 mag) and an amount of dust with visual extinction of ≥ 2.8 ± 2:2 mag should have formed in the ejected envelope and/or in a strong wind afterwards. The mass loss needs to have been spherically asymmetric in order to see the light echo from the SN event but not the one from the impostor event.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"49 1","pages":"233-238"},"PeriodicalIF":1.0,"publicationDate":"2016-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70738249","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 : 2016-10-31DOI: 10.5303/JKAS.2016.49.5.199
Seung-Lee Kim, S. Cha, B. Lim, Jae Woo Lee, Chung-Uk Lee, Yongseok Lee, Dong Jin Kim, Dong-Joo Lee, J. Koo, K. Hong, Y. Ryu, Byeong-Gon Park
We present photometric results of the δ Sct star V1162 Ori, which is extensively monitored for a total of 49 nights from mid-December 2014 to early-March 2015. The observations are made with three KMTNet (Korea Microlensing Telescope Network) 1.6 m telescopes installed in Chile, South Africa, and Australia. Multiple frequency analysis is applied to the data and resulted in clear detection of seven frequencies without an alias problem: five known frequencies and two new ones with small amplitudes of 1.2-1.7 mmag. The amplitudes of all but one frequency are significantly different from previous results, confirming the existence of long-term amplitude changes. We examine the variations in pulsation timings of V1162 Ori for about 30 years by using the times of maximum light obtained from our data and collected from the literatures. The O − C (Observed minus Calculated) timing diagram shows a combination of a downward parabolic variation with a period decreasing rate of (1/P)dP/dt = −4.22 × 10 −6 year −1 and a cyclic change with a period of about 2780 days. The most probable explanation for this cyclic variation is the light-travel-time effect caused by an unknown binary companion, which has a minimum mass of 0.69 M ⊙ . V1162 Ori is the first δ Sct-type pulsating star of which the observed fast period decrease can be interpreted as an evolutionary effect of a pre-main sequence star, considering its membership of the Orion OB 1c association.
{"title":"Three-Site Photometric Monitoring of the δ Sct-Type Pulsating Star V1162 Orionis: Period Change and its Implications for Pre-Main Sequence Evolution","authors":"Seung-Lee Kim, S. Cha, B. Lim, Jae Woo Lee, Chung-Uk Lee, Yongseok Lee, Dong Jin Kim, Dong-Joo Lee, J. Koo, K. Hong, Y. Ryu, Byeong-Gon Park","doi":"10.5303/JKAS.2016.49.5.199","DOIUrl":"https://doi.org/10.5303/JKAS.2016.49.5.199","url":null,"abstract":"We present photometric results of the δ Sct star V1162 Ori, which is extensively monitored for a total of 49 nights from mid-December 2014 to early-March 2015. The observations are made with three KMTNet (Korea Microlensing Telescope Network) 1.6 m telescopes installed in Chile, South Africa, and Australia. Multiple frequency analysis is applied to the data and resulted in clear detection of seven frequencies without an alias problem: five known frequencies and two new ones with small amplitudes of 1.2-1.7 mmag. The amplitudes of all but one frequency are significantly different from previous results, confirming the existence of long-term amplitude changes. We examine the variations in pulsation timings of V1162 Ori for about 30 years by using the times of maximum light obtained from our data and collected from the literatures. The O − C (Observed minus Calculated) timing diagram shows a combination of a downward parabolic variation with a period decreasing rate of (1/P)dP/dt = −4.22 × 10 −6 year −1 and a cyclic change with a period of about 2780 days. The most probable explanation for this cyclic variation is the light-travel-time effect caused by an unknown binary companion, which has a minimum mass of 0.69 M ⊙ . V1162 Ori is the first δ Sct-type pulsating star of which the observed fast period decrease can be interpreted as an evolutionary effect of a pre-main sequence star, considering its membership of the Orion OB 1c association.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"49 1","pages":"199-208"},"PeriodicalIF":1.0,"publicationDate":"2016-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70738184","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 : 2016-10-31DOI: 10.5303/JKAS.2016.49.5.209
M. He, D. moon, H. Neilson, Jaejoon Lee, Sang Chul Kim, M. Pak, H. S. Park, Dong Jin Kim, Yongseok Lee, Seung-Lee Kim, Chung-Uk Lee
We present analyses of ~1250 variable sources identified in a 20 square degree field toward NGC 2784 by the KMTNet Supernova Program. We categorize the variable sources into three groups based on their B-band variability. The first group consists of 31 high variability sources with their B-band RMS variability greater than 0.3 magnitudes. The second group of medium variability contains 265 sources with RMS variability between 0.05 and 0.3 magnitudes. The remaining 951 sources belong to the third group of low variability with an RMS variability smaller than 0.05 magnitudes. Of the entire ~1250 sources, 4 clearly show periods of variability greater than 100 days, while the rest have periods shorter than ~51 days or no reliable periods. The majority of the sources show either rather irregular variability or short periods faster than 2 days. Most of the sources with reliable period determination between 2 and 51 days belong to the low-variability group, although a few belong to the medium-variability group. All the variable sources with periods longer than 35 days appear to be very red with B-V > 1.5 and V-I > 2.1 magnitudes. We classify candidates of 51 Cepheids, 17 semi-regular variables, 3 Mira types, 2 RV(B) Tauri stars, 26 eclipsing binary systems and 1 active galactic nucleus. The majority of long-term variables in our sample belong to either Mira or semi-regular types, indicating that long-term variability may be more prominent in post-main sequence phases of late-type stars. The depth of the eclipsing dips of the 26 candidates for eclipsing binaries is equivalent to ~0.61 as the average relative size of the two stars in the binary system. Our results illustrate the power of the KMTNet Supernova Program for future studies of variable objects.
{"title":"KMTNET SUPERNOVA PROGRAM VARIABLE OBJECTS I. NGC 2784 FIELD","authors":"M. He, D. moon, H. Neilson, Jaejoon Lee, Sang Chul Kim, M. Pak, H. S. Park, Dong Jin Kim, Yongseok Lee, Seung-Lee Kim, Chung-Uk Lee","doi":"10.5303/JKAS.2016.49.5.209","DOIUrl":"https://doi.org/10.5303/JKAS.2016.49.5.209","url":null,"abstract":"We present analyses of ~1250 variable sources identified in a 20 square degree field toward NGC 2784 by the KMTNet Supernova Program. We categorize the variable sources into three groups based on their B-band variability. The first group consists of 31 high variability sources with their B-band RMS variability greater than 0.3 magnitudes. The second group of medium variability contains 265 sources with RMS variability between 0.05 and 0.3 magnitudes. The remaining 951 sources belong to the third group of low variability with an RMS variability smaller than 0.05 magnitudes. Of the entire ~1250 sources, 4 clearly show periods of variability greater than 100 days, while the rest have periods shorter than ~51 days or no reliable periods. The majority of the sources show either rather irregular variability or short periods faster than 2 days. Most of the sources with reliable period determination between 2 and 51 days belong to the low-variability group, although a few belong to the medium-variability group. All the variable sources with periods longer than 35 days appear to be very red with B-V > 1.5 and V-I > 2.1 magnitudes. We classify candidates of 51 Cepheids, 17 semi-regular variables, 3 Mira types, 2 RV(B) Tauri stars, 26 eclipsing binary systems and 1 active galactic nucleus. The majority of long-term variables in our sample belong to either Mira or semi-regular types, indicating that long-term variability may be more prominent in post-main sequence phases of late-type stars. The depth of the eclipsing dips of the 26 candidates for eclipsing binaries is equivalent to ~0.61 as the average relative size of the two stars in the binary system. Our results illustrate the power of the KMTNet Supernova Program for future studies of variable objects.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"60 1","pages":"209-223"},"PeriodicalIF":1.0,"publicationDate":"2016-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70738201","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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