• 천문학회지
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• 제42권6호
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• pp.145-153
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• 2009

We present measurements of diffuse interstellar $H_2$ absorption lines in the continuum spectra of 10 early-type stars. The data were observed with the Berkeley Extreme and Far-Ultraviolet Spectrometer (BEFS) of the ORFEUS telescope on board the ORFEUS-SPAS I and II space-shuttle missions in 1993 and 1996, respectively. The spectra extend from the interstellar cutoff at 912 $\AA$ to about 1200 $\AA$ with a resolution of ~ 3000 and statistical signal-to-noise ratios between 10 and 65. Adopting Doppler broadening velocities from high-resolution optical observations, we obtain the $H_2$ column densities of rotational levels J" = 0 through 5 for each line of sight. The kinetic temperatures derived from J" = 0 and 1 states show a small variation around the mean value of 80 K, except for the component toward HD 219188, which has a temperature of 211 K. Based on a synthetic interstellar cloud model described in our previous work, we derive the incident UV intensity IUV and the hydrogen density $n_H$ of the observed components to be -0.4 $\leq$ log $I_{UV}\leq2.2$ and $6.3{\leq}n_H2500cm^{-3}$, respectively.

• 천문학회보
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• 제37권1호
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• pp.74.1-74.1
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• 2012

It is known that the diffuse H${\alpha}$ halos around bright H II regions are more extended than the dust-scattered halos around point sources and the line ratios [S II] ${\lambda}$6716/H${\alpha}$ and [N II] ${\lambda}$6583/H${\alpha}$ observed outside of bright H II regions are generally higher than those in H II regions. These observational facts have been regarded as evidence against the dust-scattering origin of the diffuse H${\alpha}$ emission and the effect of dust-scattering has been neglected in studying the diffuse H${\alpha}$ emission. In this paper, we find, however, that dust-scattered halos of H II regions should be more extended than those of point sources and is in good agreement with the observed H${\alpha}$ profiles around H II regions. We also found that the observed line ratios [S II]/H${\alpha}$, [N II]/H${\alpha}$, and He I ${\lambda}$5876/H${\alpha}$ in the diffuse regions can be well reproduced with the dust-scattered halos around H II regions which are photoionized by late O- and/or early B-type stars in the interstellar medium with the abundances close to those of the warm neutral medium. Therefore, we conclude that the diffuse H${\alpha}$ emission may originate mostly from the dust-scattering.

• 천문학회지
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• 제49권5호
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• pp.199-208
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• 2016

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.

• 천문학회보
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• 제39권1호
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• pp.47.2-47.2
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• 2014

Several studies have reported the presence of sodium excess objects having neutral atomic absorption lines at $5895{\AA}$ (NaD) and $8190{\AA}$ that are deeper than expected based on stellar population models that match the stellar continuum. The origin of these lines is therefore hotly debated. van Dokkum & Conroy proposed that low-mass stars (0.3M) are more prevalent in massive early-type galaxies, which may lead to a strong NaI 8190 line strength. It is necessary to test this prediction, however, against other prominent optical line indices such as NaD, Mgb, and Fe5270, which can be measured with a significantly higher signal-to-noise ratio than NaI 8190. We identified a new sample of roughly one thousand NaD excess objects (NEOs; ~8% of galaxies in the sample) based on NaD line strength in the redshift range 0.00$H{\beta}$ line strengths and significant emission lines, which are indicative of the presence of young stellar populations. This result implies that the presence of the interstellar medium and/or dust contributes to the increase in NaD line strengths observed for these galaxies.

• 헤리티지:역사와 과학
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• 제46권2호
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• pp.70-95
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• 2013

건륭(乾隆) 3년(1569)에 제작된 일본 교토(京都) 고려(高麗)미술관 소장의 <치성광여래강림도(熾盛光如來降臨圖)>는 조선 전기 치성광여래강림도상으로는 현재 유일한 것이다. 보존상태가 양호하여 작품 내 거의 모든 도상과 旁題銘의 판독이 가능한 상태이며 화기 부분도 크게 손상되지 않았다. 작품은 홍색을 올린 바탕에 금니화로 $84.8{\times}66.1cm$의 비교적 작은 크기의 불화이다. 이 작품은 화면 중앙 치성광여래를 중심으로 하여 존명이 적혀 있지 않은 양대보살, 십일요(十一曜)와 천황성(天皇星), 옥황상제(玉皇上帝) 및 이십팔숙(二十八宿), 황도십이궁(黃道十二宮), 삼태육성(三台六星), 북두칠성(北斗七星) 등이 배치되어 조선시대 성수신앙의 일 단면을 살펴볼 수 있는 좋은 자료가 되고 있다. 이 작품의 도상은 고려본 치성광여래강림도와 같은 계열이기는 하지만 일부 성수에서 자미성, 천황성과 같은 도교적 성수가 등장하고 여래형 북두칠성 등 의미있는 도상변화가 나타나고 있어 조선시대 성수신앙의 전개과정을 알 수 있다. 본 <치성광여래강림도>는 주요 권속으로 십일요가 중심이 되긴 하였으나 계도성이 생략되고 월패성도 중심에서 벗어나 있어 십일요 구성에 대한 개념은 약화되고 있음을 알 수 있었다. 그리고 자미성, 옥황대제, 천황제와 같은 도교의 성수신이 포함되면서 도교와 불교 성수신의 뚜렷한 구분이 없어지는 현상도 나타나고 있다. 이 불화에 나타난 이십팔수의 별자리 그림은 중국의 치성광여래도와는 달리 우리나라 천문도의 별자리 그림을 정확히 반영하고 있어 성수신앙의 독자성도 엿볼 수 있었다. 북두칠성과 칠원성군을 동시에 그려서 칠성신앙을 강조한 사실은 칠성신앙의 중요도가 점차 높아지고 있음을 반영하는 것으로 해석할 수 있다. 또한 작품의 제작 수준으로 보아 대시주 '최씨도령(崔氏徒令)'은 유복한 계층의 어린아이일 가능성이 높아, 이 작품이 자손의 연명(延命), 소재(消災) 등을 기원하면서 제작된 호신부적 성격의 불화였을 것으로 추정해볼 수 있었다.