간행물
천문학논총 KCI 등재 Publications of the Korean Astronomical Society
- 발행기관 한국천문학회
- 자료유형 학술지
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- 수록기간 1984 ~ 2024
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Volume 30 Issue 2 (2015년 9월) 186건
21.
2015.09
구독 인증기관·개인회원 무료
James O. Chibueze, Hirofumi Sakanoue, Toshihiro Omodaka, Toshihiro Handa, Takumi Nagayama, Tatsuya Kamezaki, Ross Burns
We report results of the measurement of the trigonometric parallax of an H2O maser source in IRAS 22555+6213 with the VLBI Exploration of Radio Astrometry (VERA). The annual parallax was determined to be 0.2780.019 mas, corresponding to a distance of 3.66+0:30 -0:26 kpc. Our results con rm that IRAS 22555+6213 is located in the Perseus arm. We computed the peculiar motion of IRAS 22555+6213 to be (Usrc; Vsrc;Wsrc) = (0 ± 1,-32 ± 1, 9 ± 1) km s1, where Usrc, Vsrc, and Wsrc are directed toward the Galactic center, in the direction of Galactic rotation and toward the Galactic north pole, respectively. IRAS 22555+6213, NGC7538 and Cepheus A lie along the same line of sight, and are within 2 on the sky. Their parallax distances, with which we derived their absolute position in the Milky Way, show that IRAS 22555+6213 and NGC7538 are associated with the Perseus arm, while Cepheus A is located in the Local arm. We compared the kinematic distances of IRAS 22555+6213 derived with at and non- at rota- tion curve with its parallax distance and found the kinematic distance derived from the non- at rotation assumption (—32 km s-1 lag) to be consistent with the parallax distance.
22.
2015.09
구독 인증기관 무료, 개인회원 유료
Ross A. Burns, Takumi Nagayama, Toshihiro Handa, Toshihiro Omodaka, Akiharu Nakagawa, Hiroyuki Nakanishi, Masahiko Hayashi, Makoto Shizugami
We report our measurements of the trigonometric distance and proper motion of IRAS 20056+3350, obtained from the annual parallax of H2O masers. Our distance of D = 4:69+0:65 -0:51 kpc, which is 2.8 times larger than the near kinematic distance adopted in the literature, places IRAS 20056+3350 at the leading tip of the Local arm and proximal to the Solar circle. We estimated the proper motion of IRAS 20056+3350 to be (μα cos δ, μδ) = (—2:62 ± 0:33, —5:65 ± 0:52) mas yr-1 from the group motion of H2O masers, and use our results to estimate the angular velocity of Galactic rotation at the Galactocentric distance of the Sun, Ω0 = 29:75 ± 2:29 km s-1 kpc-1, which is consistent with the values obtained for other tangent points and Solar circle objects.
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23.
2015.09
구독 인증기관 무료, 개인회원 유료
Kitiyanee Asanok, Sandra Etoka, Malcolm D. Gray, Anita M. S. Richards, Busaba H. Kramer, Nipon Gasiprong
We present preliminary results from OH ground state phase referenced observations carried out with the Multi Element Radio Linked Interferometer Network (MERLIN) and e-MERLIN towards the massive star forming region W49A. There are three active SFRs within this complex: W49 North (W49 N), W49 South (W49 S) and W49 South West (W49 SW). The first epoch of observations was obtained in 2005 with MERLIN while the second epoch was obtained in 2013 with the e-MERLIN upgraded system. In this paper, we present 1665 and 1720 MHz maser emission towards W49 S and W49 SW. Overall, both epochs show good agreement with the previous observations of Argon et al. (2000) carried out with the Very Large Array (VLA). The better sensitivity and wider velocity coverage of the MERLIN/e-MERLIN observations allowed us to discover a new 1720 MHz OH maser site in W49 S.
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24.
2015.09
구독 인증기관 무료, 개인회원 유료
Koichiro Sugiyama, Yoshinori Yonekura, Kazuhito Motogi, Yu Saito, Kenta Fujisawa, Shota Ishii, Munetake Momose, Mareki Honma, Fumie Tazaki, Kei E. I. Tanaka, Takashi Hosokawa, Mizuho Uchiyama, Kohei Inayoshi
We have initiated single-dish monitoring observations of 400 methanol maser sources at 6.7 GHz using the Hitachi 32-m radio telescope from December 2012 to systematically research periodic ux variations, which are observed in some methanol maser sources associated with high-mass (proto-)stars. In our monitoring, we have made daily monitoring, so that each source has been observed every nine days with an integration time of 5 min (typical 3 detection sensitivities of 0.9 Jy). The monitoring observations help us statistically understand periodic ux variations with a period longer than 50 days. As an initial result, we present a new detection of periodic ux variations in the 6.7 GHz methanol maser source G 036.70+00.09. The period of the ux variations is ~53 days (~0.019 cycles day-1), and seems to be stable over 9 cycles, at least until the middle of August 2014.
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25.
2015.09
구독 인증기관 무료, 개인회원 유료
The Galactic center uniquely provides opportunities to resolve how star clusters form in neutral gas overdensities engulfed in a large-scale accretion flow. We have performed sensitive Green Bank 100m Telescope (GBT), Karl G. Jansky Very Large Array (JVLA), and Submillimeter Array (SMA) mapping observations of molecular gas and thermal dust emission surrounding the Galaxy's supermassive black hole (SMBH) Sgr A*. We resolved several molecular gas streams orbiting the center on ≳10 pc scales. Some of these gas streams appear connected to the well-known 2-4 pc scale molecular circumnuclear disk (CND). The CND may be the tidally trapped inner part of the large-scale accretion flow, which incorporates in ow via exterior gas filaments/arms, and ultimately feeds gas toward Sgr A*. Our high resolution GBT+JVLA NH3 images and SMA+JCMT 0.86 mm dust continuum image consistently reveal abundant dense molecular clumps in this region. These gas clumps are characterized by ≳100 times higher virial masses than the derived molecular gas masses based on 0.86 mm dust continuum emission. In addition, Class I CH3OH masers and some H2O masers are observed to be well associated with the dense clumps. We propose that the resolved gas clumps may be pressurized gas reservoirs for feeding the formation of 1-10 solar-mass stars. These sources may be the most promising candidates for ALMA to probe the process of high-mass star-formation in the Galactic center.
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26.
2015.09
구독 인증기관 무료, 개인회원 유료
H. Kuncarayakti, G. Aldering, J. P. Anderson, N. Arimoto, M. Doi, L. Galbany, M. Hamuy, Y. Hashiba, T. Kruehler, K. Maeda, T. Morokuma, T. Usuda
We describe a survey of nearby core-collapse supernova (SN) explosion sites using integral field spec- troscopy (IFS) techniques, which is an extension of the work described in Kuncarayakti et al. (2013). The project aims to constrain SN progenitor properties based on the study of the immediate environment of the SN. The stellar populations present at the SN explosion sites are studied by means of integral field spectroscopy, which enables the acquisition of both spatial and spectral information of the object simultaneously. The spectrum of the SN parent stellar population gives an estimate of its age and metal- licity. With this information, the initial mass and metallicity of the once coeval SN progenitor star are derived. While the survey is mostly done in optical, the additional utilization of near-infrared integral field spectroscopy assisted with adaptive optics (AO) enables us to examine the explosion sites in high spatial detail, down to a few parsecs. This work is being carried out using multiple 2-8 m class telescopes equipped with integral field spectrographs in Chile and Hawaii.
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27.
2015.09
구독 인증기관 무료, 개인회원 유료
Young Galactic supernova remnants (SNRs) are where we can observe closely supernova (SN) ejecta and their interaction with the circumstellar/interstellar medium. They also provide an opportunity to explore the explosion and the final stage of the evolution of massive stars. Near-infrared (NIR) emission lines in SNRs mostly originate from shocked dense material. In shocked SN ejecta, forbidden lines from heavy ions are prominent, while in shocked circumstellar/interstellar medium, [Fe II] and H2 lines are prominent. [Fe II] lines are strong in both media, and therefore [Fe II] line images provide a good starting point for the NIR study of SNRs. There are about twenty SNRs detected in [Fe II] lines, some of which have been studied in NIR spectroscopy. We will review the NIR [Fe II] observations of SNRs and introduce our recent NIR spectroscopic study of the young core-collapse SNR Cas A where we detected strong [P II] lines.
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28.
2015.09
구독 인증기관 무료, 개인회원 유료
Luke M. Bozzetto, Miroslav D. Filipovic, Frank Haberl, Manami Sasaki, Patrick Kavanagh, Pierre Maggi, Dejan Urosevic, Richard Sturm
We present an ongoing study of the complete sample of supernova remnants (SNRs) and candidates in the Magellanic Clouds. 108 objects in both Clouds are considered to be either SNR or reliable candidates. This represents the most complete sample of all known SNRs in any galaxy. It therefore allows us to study SNR population properties such as the age-diameter (Age-D) relation. Here, we show that this Age-D relation is strongly dependant on the local environment in which SNRs are residing.
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29.
2015.09
구독 인증기관 무료, 개인회원 유료
The traditional view of dust in the interstellar medium is that it is made of graphite and silicates. In this paper, we discuss the evidence for complex organics being a major component of interstellar dust. Comparison between astronomical infrared spectra and laboratory spectra of amorphous carbonaceous materials suggests that organics of mixed aromatic-aliphatic structures are widely present in circumstellar, interstellar, and galactic environments. Scenarios for the synthesis of these compounds in the late stages of stellar evolution are presented.
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30.
2015.09
구독 인증기관 무료, 개인회원 유료
We have carried out optical spectroscopic measurements of emission lines for a sample of Galactic plan- etary nebulae with Wolf-Rayet (WR) stars and weak emission-line stars (wels). The plasma diagnostics and elemental abundance analysis have been done using both collisionally excited lines (CELs) and optical recombination lines (ORLs). It was found that the abundance discrepancy factors (ADF = ORL/CEL) are closely correlated with the difference between temperatures derived from forbidden lines and those from He i recombination lines, implying the existence of H-deficient materials embedded in the nebula. The Hβ surface brightness correlations suggest that they might be also related to the nebular evolution.
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31.
2015.09
구독 인증기관 무료, 개인회원 유료
We have carried out integral field unit (IFU) spectroscopy of Hα, [N ii] and [Oiii] emission lines for a sample of Galactic planetary nebulae (PNe) with Wolf-Rayet (WR) stars and weak emission-line stars (wels). Comparing their spatially-resolved kinematic observations with morpho-kinematic models allowed us to disentangle their three-dimensional gaseous structures. Our results indicate that these PNe have axisymmetric morphologies, either bipolar or elliptical. In many cases the associated kinematic maps for the PNe around hot central stars also reveal the presence of so-called fast low-ionization emission regions.
4,000원
32.
2015.09
구독 인증기관 무료, 개인회원 유료
NGC147 and NGC185, paired satellites of the Andromeda galaxy, possess the same order of mass and analogous structures, but they show di erent star formation and different amounts of interstellar gas and dust. Therefore, we present the first reconstruction of the star formation history of NGC147 and NGC185. Asymptotic Giant Branch stars are highly evolved stars that are brightest in K-band. This maximum K-band magnitude is related to the birth mass of stars. As a result, we have found a 9.9 Gyrold single star formation epoch for NGC185 followed by relatively continuous star formation. NGC147, however, has passed through two star formation episodes; one is as old as ~6 Gyr and the other is as recent as 850 Myr. Asymptotic Giant Branch stars are also important dust factories; by fitting Spectral Energy Distributions to observed near and mid infrared data for each star, we were able to measure the dust production rates of individual stars; on order of 10-5M⊙yr-1. Hence, we estimate the total mass entering the interstellar medium to be 1.06 X 10-4M⊙ yr-1 and 2.89 X 10-4M⊙ yr-1 for NGC147 and NGC185.
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33.
2015.09
구독 인증기관 무료, 개인회원 유료
S. -B. Qian, Z. -T. Han, L. -Y. Zhu, W. -P. Liao, E. Fernandez Lajus, M. Zejda, L. Liu, B. Soonthornthum, X. Zhou
Due to the lack of an accretion disk in a polar (magnetic cataclysmic variable, MCV), the material transferred from the secondary is directly accreted onto the white dwarf, forming an accretion stream and a hot spot on the white-dwarf component. During the eclipses, different light components can be isolated. Therefore, the monitoring of eclipsing polars could provide valuable information on several modern astrophysical problems, e.g., CVs as planetary hosting stars, mass transfer and mass accretion in CVs, and the magnetic activity of the most rapidly rotating cool dwarfs. In the past five years, we have monitored about 10 eclipsing polars (e.g., DP Leo and HU Aqr) using several 2-m class telescopes and about 100 eclipse profiles were obtained. In this paper, we will introduce the progress of our research group at YNOs. The first direct evidence of variable mass transfer in a CV is obtained and we show that it is the dark-spot activity that causes the mass transfer in CVs. Magnetic activity cycles of the cool secondary were detected and we show that the variable mass transfer is not caused by magnetic activity cycles. These results will shed light on the structure and evolution of close binary stars (e.g., CVs and Algols).
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34.
2015.09
구독 인증기관 무료, 개인회원 유료
Dust has recently been found to be prevalent in compact binaries such as non-magnetic Cataclysmic Variable systems. As a possible source of this dust is from solid bodies, we explore impacts to non-magnetic Cataclysmic Variable disks. We use three-dimensional Smoothed Particle Hydrodynamic simulations to search for impact signatures. From injections of whole bodies to these disks, we find pulse shapes in simulated bolometric light curves that resemble impact ashes in the light curves of the Shoemaker-Levy 9 event. As a result, we tentatively identify these light curve shapes as signatures of impacts.
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35.
2015.09
구독 인증기관 무료, 개인회원 유료
Andrei K. Dambis, L. N. Berdnikov, A. Yu. Kniazev, V. V. Kravtsov, A. S. Rastorguev, R. Sefako, O. V. Vozyakova, M. V. Zabolotskikh
We use ALLWISE data release W1- and W2-band epoch photometry collected by the Wide-Field Infrared Survey Explorer (WISE) to determine slopes of the period-luminosity relations for RR Lyrae stars in 15 globular clusters in the corresponding bands. We further combine these results with V- and K-band photometry of Galactic field RR Lyrae stars to determine the metallicity slopes of the log PF - [Fe/H]-MK, log PF - [Fe/H]-MW1, and log PF - [Fe/H]- MW2 period-metallicity-luminosity relations. We infer the zero points of these relations and determine the kinematical parameters of thick-disk and halo RR Lyraes via statistical parallax, and estimate the RR Lyrae-based distances to 18 Local-Group galaxies including the center of the Milky Way.
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36.
2015.09
구독 인증기관 무료, 개인회원 유료
The calibration of the period luminosity relation (PLR) for Galactic Mira variables is one of the principle aims of the VERA project. We observe H2O maser emission at 22 GHz associated with Mira variables in order to determine their distances based on annual parallaxes. We conduct multi-epoch VLBI observations over 1{2 years with a typical interval of one month using VERA in order to obtain annual parallaxes with an accuracy of better than than 10%. Recently, the annnual parallax of T Lep was determined to be 3.060.04 mas corresponding to a distance of 3274 pc (Nakagawa et al., 2014). The circumstellar distribution and kinematics of H2O masers was also revealed. With accurate distances to the sources, calibrations of K-band absolute magnitudes (MK) can be improved compared to conventional studies. By compiling Mira variables whose distances were determined with astrometric VLBI, we obtained a PLR of MK = 3.51 logP + 1.37 ± 0.07.
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37.
2015.09
구독 인증기관 무료, 개인회원 유료
Michael Ting-Chang Yang, Yi Chou, Chin-Ping Hu, Yi-Hao Su, Hung-En Hsieh, Ching-Ping Lin, Po-Sheng Chuang, Nai-Hui Liao
The Palomar Transient Factory is a project making use of a Schmidt 48 inch telescope located on the Palomar Mountain, which is surveying the sky with dynamical cadences. It was deployed in 2009 and the observed sky region is over 1200 square degrees. We have studied the long-term periodic variabilities of the known galactic cataclysmic variables (CVs). More than 20 of the sources had been found to have long term periodic signals, ranging from several tens of days to several hundreds of days. Some possible scenarios are proposed to explain the results, such as a magnetic field change of the companion star, precession of the accretion disk, triple systems and superoutburst cycles. Some preliminary discussion will be presented in this article.
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38.
2015.09
구독 인증기관 무료, 개인회원 유료
Several contact binary systems in four stellar clusters or their fields are reported here; NGC7789-V12, EP Cep and ES Cep in NGC188, NGC104-V95 and V710 Mon. Their multiple light curves were analyzed by the 2010 version of the W-D code, and their physical parameters were obtained.
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39.
2015.09
구독 인증기관 무료, 개인회원 유료
The common-envelope process is a complicated phase in binary evolution. A lot of effort has been dedicated to study the common-envelope stage, but many questions related to this process are yet to be answered. If one member of the binary survives the common-envelope phase, the binary will emerge as a white dwarf accompanied by a low-mass main sequence star in close orbit, often referred as a post common-envelope binary (PCEB). SDSS J0745+2631 is among the list of newly found PCEBs from the Sloan Digital Sky Survey (SDSS). This star is proposed to be a strong eclipsing system candidate due to the ellipsoidal modulation in its light curve. In this work, we aim to con rm the eclipsing nature of SDSS J0745+2631 and to determine the stellar and orbital parameters using the software Binary Maker 3.0 (BM3.0). We detected the primary eclipse in the light curve of SDSS J0745+2631 in our follow-up observation from January 2014 using the ULTRASPEC instrument at the Thai National Observatory. The data obtained on 7th and 8th January 2014 in g filter show an evident drop in brightness during the eclipse of the white dwarf, but this eclipse is less prominent in the data taken on the next night using a clear filter. According to our preliminary model, we find that SDSS J0745+2631 hosts a rather hot white dwarf with an e ective temperature of 11500K. The companion star is a red dwarf star with a temperature of 3800K and radius of 0.3100 R⊙. The red dwarf star almost fills its Roche lobe, causing a large ellipsoidal modulation. The mass ratio of the binary given by the Binary Maker 3.0 (BM3.0) model is M2/M1 = 0.33.
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40.
2015.09
구독 인증기관 무료, 개인회원 유료
G. K. Haans, D. G. Ramadhan, S. Akhyar, R. Azaliah, J. Suherli, P. Irawati, T. Sarotsakulchai, Z. M. Arifin, A. Richichi, H. L. Malasan, B. Soonthornthum
The Eclipsing Binaries Minima (BIMA) Monitoring Project is a CCD-based photometric observational program initiated by Bosscha Observatory - Lembang, Indonesia in June 2012. Since December 2012 the National Astronomical Research Institute of Thailand (NARIT) has joined the BIMA Project as the main partner. This project aims to build an open-database of eclipsing binary minima and to establish the orbital period of each system and its variations. The project is conducted on the basis of multisite monitoring observations of eclipsing binaries with magnitudes less than 19 mag. Di erential photometry methods have been applied throughout the observations. Data reduction was performed using IRAF. The observations were carried out in BVRI bands using three di erent small telescopes situated in Indonesia, Thailand, and Chile. Computer programs have been developed for calculating the time of minima. To date, more than 140 eclipsing binaries have been observed. From them 71 minima have been determined. We present and discuss the O-C diagrams for some eclipsing binary systems.
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