Pub Date : 2014-12-10DOI: 10.5303/JKAS.2014.47.6.303
Sang-Sung Lee
We present results of our investigation of the radio intrinsic brightness temperatures of compact radio jets. The intrinsic brightness temperatures of about 100 compact radio jets at 2, 5, 8, 15, and 86 GHz are estimated based on large VLBI surveys conducted in 2001-2003 (or in 1996 for the 5 GHz sample). The multi-frequency intrinsic brightness temperatures of the sample of jets are determined by a statistical method relating the observed brightness temperatures with the maximal apparent jet speeds, assuming one representative intrinsic brightness temperature for a sample of jets at each observing frequency. By investigating the observed brightness temperatures at 15 GHz in multiple epochs, we find that the determination of the intrinsic brightness temperature for our sample is affected by the flux density variability of individual jets at time scales of a few years. This implies that it is important to use contemporaneous VLBI observations for the multi-frequency analysis of intrinsic brightness temperatures. Since our analysis is based on the VLBI observations conducted in 2001-2003, the results are not strongly affected by the flux density variability. We find that the intrinsic brightness temperature T 0 increases as T 0 ∝ ν ξ obs with ξ = 0.7 below a critical frequency ν c ? 9 GHz where the energy loss begins to dominate the emission. Above ν c , T 0 decreases with ξ = -1.2, supporting the decelerating jet model or particle cascade model. We also find that the peak value of T 0 ? 3.4 × 10 10 K is close to the equipartition temperature, implying that the VLBI cores observable at 2-86 GHz may be representing jet regions where the magnetic field energy dominates the total energy in jets.
{"title":"Intrinsic Brightness Temperatures of Compact Radio Jets as a Function of Frequency","authors":"Sang-Sung Lee","doi":"10.5303/JKAS.2014.47.6.303","DOIUrl":"https://doi.org/10.5303/JKAS.2014.47.6.303","url":null,"abstract":"We present results of our investigation of the radio intrinsic brightness temperatures of compact radio jets. The intrinsic brightness temperatures of about 100 compact radio jets at 2, 5, 8, 15, and 86 GHz are estimated based on large VLBI surveys conducted in 2001-2003 (or in 1996 for the 5 GHz sample). The multi-frequency intrinsic brightness temperatures of the sample of jets are determined by a statistical method relating the observed brightness temperatures with the maximal apparent jet speeds, assuming one representative intrinsic brightness temperature for a sample of jets at each observing frequency. By investigating the observed brightness temperatures at 15 GHz in multiple epochs, we find that the determination of the intrinsic brightness temperature for our sample is affected by the flux density variability of individual jets at time scales of a few years. This implies that it is important to use contemporaneous VLBI observations for the multi-frequency analysis of intrinsic brightness temperatures. Since our analysis is based on the VLBI observations conducted in 2001-2003, the results are not strongly affected by the flux density variability. We find that the intrinsic brightness temperature T 0 increases as T 0 ∝ ν ξ obs with ξ = 0.7 below a critical frequency ν c ? 9 GHz where the energy loss begins to dominate the emission. Above ν c , T 0 decreases with ξ = -1.2, supporting the decelerating jet model or particle cascade model. We also find that the peak value of T 0 ? 3.4 × 10 10 K is close to the equipartition temperature, implying that the VLBI cores observable at 2-86 GHz may be representing jet regions where the magnetic field energy dominates the total energy in jets.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"55 1","pages":"303-309"},"PeriodicalIF":1.0,"publicationDate":"2014-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70735906","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 : 2014-10-31DOI: 10.5303/JKAS.2014.47.5.167
J. Woo, Ji-Gang Kim, Daeseong Park, Hyun-Jin Bae, Jae-Hyuk Kim, Seung-Eun Lee, Sang Chul Kim, H. Kwon
We search for misclassified type 1 AGNs among type 2 AGNs identified with emission line flux ratios, and investigate the properties of the sample. Using 4113 local type 2 AGNs at 0.02 < z < 0.05 selected from Sloan Digital Sky Survey Data Release 7, we detected a broad component of the Hline with a Full-Width at Half-Maximum (FWHM) ranging from 1700 to 19090 km s −1 for 142 objects, based on the spectral decomposition and visual inspection. The fraction of the misclassified type 1 AGNs among type 2 AGN sample is �3.5%, implying that a large number of missing type 1 AGN population may exist. The misclassified type 1 AGNs have relatively low luminosity with a mean broad Hluminosity, log LH� = 40.50 ± 0.35 erg s −1 , while black hole mass of the sample is comparable to that of the local black hole population, with a mean black hole mass, log MBH = 6.94 ± 0.51 M⊙. The mean Eddington ratio of the sample is log Lbol/LEdd = 2.00±0.40, indicating that black hole activity is relatively weak, hence, AGN continuum is too weak to change the host galaxy color. We find that the Oiii lines show significant velocity offsets, presumably due to outflows in the narrow-line region, while the velocity offset of the narrow component of the Hline is not prominent, consistent with the ionized gas kinematics of general type 1 AGN population.
我们在用发射线通量比识别的2型agn中寻找错误分类的1型agn，并研究样品的性质。利用斯隆数字巡天数据第7版(Sloan Digital Sky Survey Data Release 7)中选取的4113个0.02 < z < 0.05的局部2型agn，基于光谱分解和目视检查，我们检测到142个天体的半最大全宽(FWHM)范围为1700 ~ 19090 km s−1的Hline宽分量。2型AGN样本中1型AGN误分类比例为3.5%，说明可能存在大量缺失的1型AGN群体。错误分类的1型agn的亮度相对较低，平均亮度为40.50±0.35 erg s−1，而样本的黑洞质量与当地黑洞群相当，平均黑洞质量为log MBH = 6.94±0.51 M⊙。样本的平均Eddington比值为log Lbol/LEdd = 2.00±0.40，说明黑洞活动相对较弱，因此AGN连续体太弱，无法改变宿主星系的颜色。我们发现Oiii线显示出明显的速度偏移，可能是由于窄线区域的流出，而Hline的窄部分的速度偏移并不突出，这与一般1型AGN群体的电离气体运动学一致。
{"title":"MISCLASSIFIED TYPE 1 AGNS IN THE LOCAL UNIVERSE","authors":"J. Woo, Ji-Gang Kim, Daeseong Park, Hyun-Jin Bae, Jae-Hyuk Kim, Seung-Eun Lee, Sang Chul Kim, H. Kwon","doi":"10.5303/JKAS.2014.47.5.167","DOIUrl":"https://doi.org/10.5303/JKAS.2014.47.5.167","url":null,"abstract":"We search for misclassified type 1 AGNs among type 2 AGNs identified with emission line flux ratios, and investigate the properties of the sample. Using 4113 local type 2 AGNs at 0.02 < z < 0.05 selected from Sloan Digital Sky Survey Data Release 7, we detected a broad component of the Hline with a Full-Width at Half-Maximum (FWHM) ranging from 1700 to 19090 km s −1 for 142 objects, based on the spectral decomposition and visual inspection. The fraction of the misclassified type 1 AGNs among type 2 AGN sample is �3.5%, implying that a large number of missing type 1 AGN population may exist. The misclassified type 1 AGNs have relatively low luminosity with a mean broad Hluminosity, log LH� = 40.50 ± 0.35 erg s −1 , while black hole mass of the sample is comparable to that of the local black hole population, with a mean black hole mass, log MBH = 6.94 ± 0.51 M⊙. The mean Eddington ratio of the sample is log Lbol/LEdd = 2.00±0.40, indicating that black hole activity is relatively weak, hence, AGN continuum is too weak to change the host galaxy color. We find that the Oiii lines show significant velocity offsets, presumably due to outflows in the narrow-line region, while the velocity offset of the narrow component of the Hline is not prominent, consistent with the ionized gas kinematics of general type 1 AGN population.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"47 1","pages":"167-178"},"PeriodicalIF":1.0,"publicationDate":"2014-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70735137","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 : 2014-10-31DOI: 10.5303/JKAS.2014.47.5.163
Chulhee Kim, B. Moon, H. S. Park
In order to identify peculiar X-ray sources, we select 442 sources with no counterparts in other wavelength bands (as of the year 1999) from the ROSAT All-Sky Survey Bright Source Catalog. We cross- correlate this initial list with the NASA/IPAC Extragalactic Database, the USNO and WISE catalogs, and the HEASARC XRAY Master Catalog. Eventually, we are left with four unidentified sources with no counterparts in other wavelength bands. We present these four sources and their X-ray properties in this paper.
{"title":"X-RAY SOURCES WITH NO COUNTERPARTS IN OTHER WAVELENGTH BANDS","authors":"Chulhee Kim, B. Moon, H. S. Park","doi":"10.5303/JKAS.2014.47.5.163","DOIUrl":"https://doi.org/10.5303/JKAS.2014.47.5.163","url":null,"abstract":"In order to identify peculiar X-ray sources, we select 442 sources with no counterparts in other wavelength bands (as of the year 1999) from the ROSAT All-Sky Survey Bright Source Catalog. We cross- correlate this initial list with the NASA/IPAC Extragalactic Database, the USNO and WISE catalogs, and the HEASARC XRAY Master Catalog. Eventually, we are left with four unidentified sources with no counterparts in other wavelength bands. We present these four sources and their X-ray properties in this paper.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"104 1","pages":"163-166"},"PeriodicalIF":1.0,"publicationDate":"2014-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70735438","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 : 2014-10-27DOI: 10.5303/JKAS.2015.48.2.093
A. Gould, D. Huber, M. Penny, D. Stello
WFIRST microlensing observations will return high-precision parallaxes, σ(π)?0.3 μas, for the roughly 1 million stars with H vega = 14 and ∼ 0.1 mmag at H = 8), this will yield a wealth of asteroseismic data of giant stars, primarily in the Galactic bulge but including a substantial fraction of disk stars at all Galactocentric radii interior to the Sun. For brighter stars, the astrometric data will yield an external check on the radii derived from the two asteroseismic parameters, the large-frequency separation 〈?ν nl 〉 and the frequency of maximum oscillation power ν max , while for the fainter ones, it will enable a mass measurement from the single measurable asteroseismic parameter ν max . Simulations based on Kepler data indicate that WFIRST will be capable of detecting oscillations in stars from slightly less luminous than the red clump to the tip of the red giant branch, yielding roughly 1 million detections.
{"title":"WFIRST ULTRA-PRECISE ASTROMETRY II: ASTEROSEISMOLOGY","authors":"A. Gould, D. Huber, M. Penny, D. Stello","doi":"10.5303/JKAS.2015.48.2.093","DOIUrl":"https://doi.org/10.5303/JKAS.2015.48.2.093","url":null,"abstract":"WFIRST microlensing observations will return high-precision parallaxes, σ(π)?0.3 μas, for the roughly 1 million stars with H vega = 14 and ∼ 0.1 mmag at H = 8), this will yield a wealth of asteroseismic data of giant stars, primarily in the Galactic bulge but including a substantial fraction of disk stars at all Galactocentric radii interior to the Sun. For brighter stars, the astrometric data will yield an external check on the radii derived from the two asteroseismic parameters, the large-frequency separation 〈?ν nl 〉 and the frequency of maximum oscillation power ν max , while for the fainter ones, it will enable a mass measurement from the single measurable asteroseismic parameter ν max . Simulations based on Kepler data indicate that WFIRST will be capable of detecting oscillations in stars from slightly less luminous than the red clump to the tip of the red giant branch, yielding roughly 1 million detections.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"48 1","pages":"93-104"},"PeriodicalIF":1.0,"publicationDate":"2014-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70736425","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 : 2014-10-01DOI: 10.5303/JKAS.2014.47.5.179
Y. Minh, Kee-Tae Kim, Chi-Hung Yan, Yong-Sun Park, Seokho Lee, D. Lal, T. Hasegawa, X. Zhang, Y. Kuan
We study the physical and chemical properties of the molecular clump hosting a young stellar cluster, IRAS 20160+3636, which is believed to have formed via the “collect and collapse” process. Physical parameters of the UC Hii region associated with the embedded cluster are measured from the radio continuum observations. This source is found to be a typical Galactic UC Hii region, with a B0.5 type exciting star, if it is ionized by a single star. We derive a CN/HCN abundance ratio larger than 1 over this region, which may suggest that this clump is being affected by the UV radiation from the Hii region.
{"title":"PROPERTIES OF THE MOLECULAR CLUMP AND THE ASSOCIATED ULTRACOMPACT H II REGION IN THE GAS SHELL OF THE EXPANDING H II REGION SH 2-104","authors":"Y. Minh, Kee-Tae Kim, Chi-Hung Yan, Yong-Sun Park, Seokho Lee, D. Lal, T. Hasegawa, X. Zhang, Y. Kuan","doi":"10.5303/JKAS.2014.47.5.179","DOIUrl":"https://doi.org/10.5303/JKAS.2014.47.5.179","url":null,"abstract":"We study the physical and chemical properties of the molecular clump hosting a young stellar cluster, IRAS 20160+3636, which is believed to have formed via the “collect and collapse” process. Physical parameters of the UC Hii region associated with the embedded cluster are measured from the radio continuum observations. This source is found to be a typical Galactic UC Hii region, with a B0.5 type exciting star, if it is ionized by a single star. We derive a CN/HCN abundance ratio larger than 1 over this region, which may suggest that this clump is being affected by the UV radiation from the Hii region.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"47 1","pages":"179-185"},"PeriodicalIF":1.0,"publicationDate":"2014-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70735199","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 : 2014-10-01DOI: 10.5303/JKAS.2015.48.2.113
Heeyoung Oh, T. Pyo, I. Yuk, Byeong-Gon Park
We present observational results from optical long-slit spectroscopy of parsec-scale jets of DG Tau. From HH 158 and HH 702, the optical emission lines of Hα, [O i] ??6300, 6363, [N ii] ??6548, 6584, and [S ii] ??6716, 6731 are obtained. The kinematics and physical properties (i.e., electron density, electron temperature, ionization fraction, and mass-loss rate) are investigated along the blueshifted jet up to 650′′ distance from the source. For HH 158, the radial velocity ranges from -50 to -250 km s -1 . The proper motion of the knots is 0:′′196 - 0:′′272 yr -1 . The electron density is ~10⁴ cm -3 close to the star, and decreases to ~10² cm -3 at 14′′ away from the star. Ionization fraction indicates that the gas is almost neutral in the vicinity of the source. It increases up to over 0.4 along the distance. HH 702 is located at 650′′ from the source. It shows ~ -80 km s -1 in the radial velocity. Its line ratios are similar to those at knot C of HH 158. The mass-loss rate is estimated to be about~ 10 -7 M ⊙ yr -1 , which is similar to values obtained from previous studies.
我们给出了DG Tau的秒差距尺度射流的光学长缝光谱观测结果。从HH 158和HH 702, Hα， [O i] ??6300, 6363， [N ii] ??6548, 6584，和[S ii] ??得到6716、6731。运动学和物理性质(即电子密度、电子温度、电离分数和质量损失率)沿着距离源650英寸的蓝移射流进行了研究。对于HH 158，径向速度范围为-50到-250 km s -1。结的正常运动是0:196 - 0:272 yr -1。电子密度在离恒星近的地方是~10⁴cm -3，在离恒星14英寸的地方降低到~10²cm -3。电离分数表明气体在源附近几乎是中性的。它沿着距离增加到超过0.4。HH 702位于距离源650英寸处。它显示了~ -80 km s -1的径向速度。它的线比与HH 158的C结相似。质量损失率估计约为~ 10 -7 M⊙yr -1，这与以前的研究结果相似。
{"title":"LONG-SLIT SPECTROSCOPY OF PARSEC-SCALE JETS FROM DG TAURI","authors":"Heeyoung Oh, T. Pyo, I. Yuk, Byeong-Gon Park","doi":"10.5303/JKAS.2015.48.2.113","DOIUrl":"https://doi.org/10.5303/JKAS.2015.48.2.113","url":null,"abstract":"We present observational results from optical long-slit spectroscopy of parsec-scale jets of DG Tau. From HH 158 and HH 702, the optical emission lines of Hα, [O i] ??6300, 6363, [N ii] ??6548, 6584, and [S ii] ??6716, 6731 are obtained. The kinematics and physical properties (i.e., electron density, electron temperature, ionization fraction, and mass-loss rate) are investigated along the blueshifted jet up to 650′′ distance from the source. For HH 158, the radial velocity ranges from -50 to -250 km s -1 . The proper motion of the knots is 0:′′196 - 0:′′272 yr -1 . The electron density is ~10⁴ cm -3 close to the star, and decreases to ~10² cm -3 at 14′′ away from the star. Ionization fraction indicates that the gas is almost neutral in the vicinity of the source. It increases up to over 0.4 along the distance. HH 702 is located at 650′′ from the source. It shows ~ -80 km s -1 in the radial velocity. Its line ratios are similar to those at knot C of HH 158. The mass-loss rate is estimated to be about~ 10 -7 M ⊙ yr -1 , which is similar to values obtained from previous studies.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"4 1","pages":"113-123"},"PeriodicalIF":1.0,"publicationDate":"2014-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70736467","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 : 2014-08-31DOI: 10.5303/JKAS.2014.47.4.147
J. U. Nwaffiah, R. Eze
We present measurements of the Fe Kα emission line of the intermediate polar V1223 Sagittarii observed with the Suzaku satellite. The spectrum is modeled with an absorbed thermal bremsstrahlung spectrum and three Gaussians for the three components of the Fe Kα lines. We resolve the neutral or low-ionized (6.41keV), He-like (6.70keV), and H-like (7.00keV) iron lines. We also obtain a thermal continuum temperature of 25 keV, which supports a thermal origin of the hard X-rays observed from the shock heated layers of gas between the white dwarf and the shock front. Hence, we believe that the He-like and H-like lines are from the collisional plasma. On the origin of the Fe Kα fluorescence line, we find that it could be partly from reflections of hard X-rays from the white dwarf surface and the N H absorption columns. We also discuss the Fe Kα emission line as veritable tool for the probe of some astrophysical sites.
本文介绍了用Suzaku卫星观测到的中极人马座V1223的Fe - k - α发射谱线。光谱用吸收热轫致辐射谱和Fe - k - α谱的三个分量的三个高斯谱来建模。我们解析了中性或低电离(6.41keV)，类he (6.70keV)和类h (7.00keV)铁谱线。我们还获得了25 keV的热连续温度，这支持了从白矮星和激波锋面之间的激波加热气体层观察到的硬x射线的热起源。因此，我们认为类he线和类h线来自于碰撞等离子体。在Fe - k - α荧光谱线的起源上，我们发现它可能部分来自白矮星表面的硬x射线反射和N - H吸收柱。我们还讨论了Fe - k - α发射线作为探测某些天体物理点的可靠工具。
{"title":"THE FE Kα EMISSION LINE OF INTERMEDIATE POLAR V1223 SAGITTARII","authors":"J. U. Nwaffiah, R. Eze","doi":"10.5303/JKAS.2014.47.4.147","DOIUrl":"https://doi.org/10.5303/JKAS.2014.47.4.147","url":null,"abstract":"We present measurements of the Fe Kα emission line of the intermediate polar V1223 Sagittarii observed with the Suzaku satellite. The spectrum is modeled with an absorbed thermal bremsstrahlung spectrum and three Gaussians for the three components of the Fe Kα lines. We resolve the neutral or low-ionized (6.41keV), He-like (6.70keV), and H-like (7.00keV) iron lines. We also obtain a thermal continuum temperature of 25 keV, which supports a thermal origin of the hard X-rays observed from the shock heated layers of gas between the white dwarf and the shock front. Hence, we believe that the He-like and H-like lines are from the collisional plasma. On the origin of the Fe Kα fluorescence line, we find that it could be partly from reflections of hard X-rays from the white dwarf surface and the N H absorption columns. We also discuss the Fe Kα emission line as veritable tool for the probe of some astrophysical sites.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"47 1","pages":"147-152"},"PeriodicalIF":1.0,"publicationDate":"2014-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70734823","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 : 2014-08-31DOI: 10.5303/JKAS.2014.47.4.123
Young-Joo Kwon, K. Suh
A silicate carbon star is a carbon star which shows circumstellar silicate dust features. We col-lect a sample of 44 silicate carbon stars from the literature and investigate the validity of the classification. For some objects, it is uncertain whether the central star is a carbon star. We confirm that 29 objects are verified silicate carbon stars. We classify the confirmed objects into three subclasses based on the evolution phase of the central star. To investigate the effect of the chemical transition phase from O to C, we use the radiative transfer models for the detached silicate dust shells. The spectral energy distributions and the infrared two-color diagrams of the silicate carbon stars are compared with the theoretical model results. For the chemical transition model without considering the effect of a disk, we find that the life time of the silicate feature is about 50 to 400 years depending on the initial dust optical depth.
{"title":"A NEW CATALOG OF SILICATE CARBON STARS","authors":"Young-Joo Kwon, K. Suh","doi":"10.5303/JKAS.2014.47.4.123","DOIUrl":"https://doi.org/10.5303/JKAS.2014.47.4.123","url":null,"abstract":"A silicate carbon star is a carbon star which shows circumstellar silicate dust features. We col-lect a sample of 44 silicate carbon stars from the literature and investigate the validity of the classification. For some objects, it is uncertain whether the central star is a carbon star. We confirm that 29 objects are verified silicate carbon stars. We classify the confirmed objects into three subclasses based on the evolution phase of the central star. To investigate the effect of the chemical transition phase from O to C, we use the radiative transfer models for the detached silicate dust shells. The spectral energy distributions and the infrared two-color diagrams of the silicate carbon stars are compared with the theoretical model results. For the chemical transition model without considering the effect of a disk, we find that the life time of the silicate feature is about 50 to 400 years depending on the initial dust optical depth.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"47 1","pages":"123-135"},"PeriodicalIF":1.0,"publicationDate":"2014-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70734709","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 : 2014-07-22DOI: 10.5303/JKAS.2014.47.4.153
A. Gould
I show that the standard microlensing technique to measure the angular radius of a star using color/surface-brightness relations can be inverted, via late-time proper motion measurements, to calibrate these relations. The method is especially useful for very metal-rich stars because such stars are in short supply in the solar neighborhood where other methods are most effective, but very abundant in Galactic bulge microlensing fields. I provide a list of eight spectroscopically identified high-metallicity bulge stars with the requisite finite-source effects, seven of which will be suitable calibrators when the Giant Magellan Telescope comes on line. Many more such sources can be extracted from current and future microlensing surveys.
{"title":"A NEW METHOD TO CALIBRATE THE STELLAR COLOR/SURFACE-BRIGHTNESS RELATION","authors":"A. Gould","doi":"10.5303/JKAS.2014.47.4.153","DOIUrl":"https://doi.org/10.5303/JKAS.2014.47.4.153","url":null,"abstract":"I show that the standard microlensing technique to measure the angular radius of a star using color/surface-brightness relations can be inverted, via late-time proper motion measurements, to calibrate these relations. The method is especially useful for very metal-rich stars because such stars are in short supply in the solar neighborhood where other methods are most effective, but very abundant in Galactic bulge microlensing fields. I provide a list of eight spectroscopically identified high-metallicity bulge stars with the requisite finite-source effects, seven of which will be suitable calibrators when the Giant Magellan Telescope comes on line. Many more such sources can be extracted from current and future microlensing surveys.","PeriodicalId":49994,"journal":{"name":"Journal of the Korean Astronomical Society","volume":"47 1","pages":"153-158"},"PeriodicalIF":1.0,"publicationDate":"2014-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70734935","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 : 2014-06-30DOI: 10.5303/JKAS.2014.47.3.115
Yingbo Liu, Feng Wang, Kaifan Ji, H. Deng, W. Dai, Bo Liang
The New Vacuum Solar Telescope (NVST) is a 1-meter vacuum solar telescope that aims to observe the fine structures of active regions on the Sun. The main tasks of the NVST are high resolution imaging and spectral observations, including the measurements of the solar magnetic field. The NVST has been collecting more than 20 million FITS files since it began routine observations in 2012 and produces a maximum observational records of 120 thousand files in a day. Given the large amount of files, the effective archiving and retrieval of files becomes a critical and urgent problem. In this study, we implement a new data archiving system for the NVST based on the Fastbit Not Only Structured Query Language (NoSQL) database. Comparing to the relational database (i.e., MySQL; My Structured Query Language), the Fastbit database manifests distinctive advantages on indexing and querying performance. In a large scale database of 40 million records, the multi-field combined query response time of Fastbit database is about 15 times faster and fully meets the requirements of the NVST. Our study brings a new idea for massive astronomical data archiving and would contribute to the design of data management systems for other astronomical telescopes.
新型真空太阳望远镜(NVST)是一个1米长的真空太阳望远镜，旨在观察太阳活跃区域的精细结构。NVST的主要任务是高分辨率成像和光谱观测，包括太阳磁场的测量。自2012年开始常规观测以来，NVST已经收集了超过2000万个FITS文件，每天产生的最大观测记录为12万个文件。面对海量的文件，如何对文件进行有效的归档和检索就成为一个关键而迫切的问题。在本研究中，我们基于Fastbit Not Only Structured Query Language (NoSQL)数据库实现了一个新的NVST数据归档系统。与关系型数据库(即MySQL;我的结构化查询语言)，Fastbit数据库在索引和查询性能上表现出独特的优势。在4000万条记录的大型数据库中，Fastbit数据库的多字段组合查询响应时间要快15倍左右，完全满足NVST的要求。本研究为海量天文数据的归档提供了新的思路，对其他天文望远镜数据管理系统的设计也有一定的借鉴意义。
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