| 21. |
- Horak, Jiri, et al.
(författare)
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Alpha-Viscosity Effects in Slender Tori
- 2012
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Ingår i: Publications of the Astronomical Society of Japan. - : Oxford University Press (OUP). - 0004-6264 .- 2053-051X. ; 64:4
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Tidskriftsartikel (refereegranskat)
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| 22. |
- Horák, Jíri, et al.
(författare)
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Of NBOs and kHz QPOs: a Low-Frequency Modulation in Resonant Oscillations of Relativistic Accretion Disks
- 2004
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Ingår i: Publications of the Astronomical Society of Japan. - 0004-6264. ; 56:5, s. 819-822
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Tidskriftsartikel (refereegranskat)abstract
- The origin of quasi-periodic modulations of flux in the kilohertz range (kHz QPOs), observed in low-mass X-ray binaries, is usually assumed to be physically distinct from that of the "normal branch oscillations" (NBOs) in the Z-sources. We show that a low-frequency modulation of the kHz QPOs is a natural consequence of the non-linear relativistic resonance suggested previously to explain the properties of the high-frequency twin peaks. The theoretical results discussed here are reminiscent of the 6 Hz variations of frequency and amplitude of the kHz QPOs reported by Yu, van der Klis, and Jonker (2001).
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| 23. |
- Imai, H., et al.
(författare)
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FLASHING: New high-velocity H2O masers in IRAS 18286−0959
- 2020
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Ingår i: Publication of the Astronomical Society of Japan. - : Oxford University Press (OUP). - 2053-051X .- 0004-6264. ; 72:4
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Tidskriftsartikel (refereegranskat)abstract
- We discovered new high-velocity components of H2O maser emission in one of the “water fountain” sources, IRAS 18286−0959, which has been monitored using the Nobeyama 45 m telescope in the FLASHING (Finest Legacy Acquisitions of SiO- and H2O-maser Ignitions by Nobeyama Generation) project since 2018 December. The maser spectra show new components with extremely high expansion velocities (>200 km s−1 projected in the line of sight), some of which are located symmetrically in the spectrum with respect to the systemic velocity. They were also mapped with KaVA (KVN and VERA Combined Array) in 2019 March. We located some of these maser components closer to the central stellar system than other high-velocity components (50-200 km s−1) that have been confirmed to be associated with the known bipolar outflow. The new components would have flashed in the fast collimated jet at a speed of over 300 km s−1 (soon) after 2011 when they had not been detected. The fastest of the new components seem to indicate rapid deceleration in these spectra; however, our present monitoring is still too sparse to unambiguously confirm it (up to 50 km s−1 yr−1) and too short to reveal their terminal expansion velocity, which will be equal to the expansion velocity that has been observed (vexp ∼ 120 km s−1). Future occurrences of such extreme-velocity components may provide a good opportunity to investigate possible recurrent outflow ignitions. Thus, the sculpture of the parental envelope will be traced by the dense gas that is entrained by the fast jet and exhibits spectacular distributions of the relatively stable maser features.
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| 24. |
- Imai, Hiroshi, et al.
(författare)
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FLASHING: Project overview
- 2023
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Ingår i: Publication of the Astronomical Society of Japan. - 2053-051X .- 0004-6264. ; 75:6, s. 1183-1213
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes an overview of the FLASHING (Finest Legacy Acquisitions of SiO-/H2O-maser Ignitions by the Nobeyama Generation) project promoted using the 45 m telescope of Nobeyama Radio Observatory, which aims to intensively monitor H2O (at 22 GHz) and SiO (at 43 GHz) masers associated with so-called "water fountain" sources. Here we show scientific results based on the data taken in the first five seasons of FLASHING, from 2018 December to 2023 April. We show the evolution of the H2O maser spectra, discovering new spectral components that break the record of the jet's top speed and/or systematic velocity drifts in the spectrum indicating acceleration or deceleration of the maser gas clumps. For the 43 GHz SiO maser emission, we newly detect it in one source and find that it is no longer present in another source. This implies that the jets from these water fountains can be accelerated or decelerated, and show how circumstellar envelopes are destroyed.
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| 25. |
- Izumi, Takuma, et al.
(författare)
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Submillimeter ALMA Observations of the Dense Gas in the Low-Luminosity Type-1 Active Nucleus of NGC 1097
- 2013
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Ingår i: Publications of the Astronomical society of Japan. - : Oxford University Press (OUP). - 0004-6264 .- 2053-051X. ; 65:5
-
Tidskriftsartikel (refereegranskat)abstract
- We present the first 100 pc scale view of the dense molecular gas in the central similar to 1.3 kpc of the type-1 Seyfert NGC 1097, traced by HCN (J = 4-3) and HCO+ (J = 4-3) lines afforded with ALMA band 7. This galaxy shows significant HCN enhancement with respect to HCO+ and CO in the low-J transitions, which seems to be a common characteristic in AGN environments. Using the ALMA data, we consider the characteristics of the dense gas around this AGN, and search for the mechanism of HCN enhancement. We find a high HCN (J = 4-3) to HCO+ (J = 4-3) line ratio in the nucleus. The upper limit of the brightness temperature ratio of HCN (nu(2) = 1(1f), J = 4-3) to HCN (J = 4-3) is 0.08, which indicates that IR pumping does not significantly affect the pure rotational population in this nucleus. We also find a higher HCN (J = 4-3) to CS (J = 7-6) line ratio in NGC 1097 than in starburst galaxies, which is more than 12.7 on the brightness temperature scale. Combined with similar observations from other galaxies, we tentatively suggest that this ratio appears to be higher in AGN-host galaxies than in pure starburst ones, similar to the widely used HCN to HCO+ ratio. LTE and non-LTE modeling of the observed HCN and HCO+ lines using J = 4-3 and 1-0 data from ALMA, and J = 3-2 data from SMA, reveals a high HCN to HCO+ abundance ratio (5 <= [HCN]/[HCO+] <= 20: non-LTE analysis) in the nucleus, and that the high-J lines (J = 4-3 and 3-2) are emitted from dense (10(4.5) cm(-3) <= n(H2) <= 10(6) cm(-3)), hot (70 K <= T-kin <= 550 K) regions. Finally we propose that high-temperature chemistry is more plausible to explain the observed enhanced HCN emission in NGC 1097 than pure gas-phase PDR/XDR chemistry.
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| 26. |
- Kato, Yuta, et al.
(författare)
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A high dust emissivity index beta for a CO-faint galaxy in a filamentary Ly alpha nebula at z=3.1
- 2018
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Ingår i: Publications of the Astronomical Society of Japan. - : Oxford University Press (OUP). - 0004-6264 .- 2053-051X. ; 70:5
-
Tidskriftsartikel (refereegranskat)abstract
- We present CO J = 4-3 line and 3 mm dust continuum observations of a 100 kpc-scale filamentary Ly alpha nebula (SSA22 LAB18) at z = 3.1 using the Atacama Large Millimeter/submillimeter Array (ALMA). We detected the CO J = 4-3 line at a systemic z(CO) = 3.093 +/- 0.001 at 11 sigma from one of the ALMA continuum sources associated with the Ly alpha filament. We estimated the CO J = 4-3 luminosity of L'(CO(4-3)) = (2.3 +/- 0.2) x 10(9) Kkms(-1) pc(2) for this CO source, which is one order of magnitude smaller than those of typical z > 1 dusty star-forming galaxies (DSFGs) of similar far-infrared luminosity L-IR similar to 10(12) L-circle dot. We derived a molecular gas mass of M-gas = (4.4(-0.6)(+0.9)) x 10(9) M-circle dot and a star-formation rate of SFR = 270 +/- 160M(circle dot) yr(-1). We also estimated a gas depletion time of tau(dep) = 17 +/- 10 Myr, which is shorter than those of typical DSFGs. It is suggested that this source is in the transition phase from DSFG to a gas-poor, early-type galaxy. From ALMA to Herschel multi-band dust continuum observations, we measured a dust emissivity index beta = 2.3 +/- 0.2, which is similar to those of local gas-poor, early-type galaxies. From recent laboratory experiments, the specific chemical compositions needed to reproduce such a high beta for interstellar dust at the submillimeter wavelengths. ALMA CO and multi-band dust continuum observations can constrain the evolutionary stage of high-redshift galaxies through tau(dep) and beta, and thus we can investigate the chemical composition of dust even in the early Universe.
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| 27. |
- Konishi, Mihoko, et al.
(författare)
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A substellar companion to Pleiades HII 3441
- 2016
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Ingår i: Publications of the Astronomical Society of Japan. - : Oxford University Press (OUP). - 0004-6264 .- 2053-051X. ; 68:6
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Tidskriftsartikel (refereegranskat)abstract
- We find a new substellar companion to the Pleiades member star, Pleiades HII 3441, using the Subaru telescope with adaptive optics. The discovery is made as part of the high-contrast imaging survey to search for planetary-mass and substellar companions in the Pleiades and young moving groups. The companion has a projected separation of 0.'' 49 +/- 0.'' 02 (66 +/- 2 au) and a mass of 68 +/- 5 M-J based on three observations in the J-, H-, and K-s-bands. The spectral type is estimated to be M7 (similar to 2700 K), and thus no methane absorption is detected in the H band. Our Pleiades observations result in the detection of two substellar companions including one previously reported among 20 observed Pleiades stars, and indicate that the fraction of substellar companions in the Pleiades is about 10.0(-8.8)(+26.1)%. This is consistent with multiplicity studies of both the Pleiades stars and other open clusters.
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| 28. |
- Lim, Wanggi, et al.
(författare)
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Star cluster formation in Orion A
- 2021
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Ingår i: Publication of the Astronomical Society of Japan. - : Oxford University Press (OUP). - 2053-051X .- 0004-6264. ; 73, s. S239-S255
-
Tidskriftsartikel (refereegranskat)abstract
- We introduce new analysis methods for studying the star cluster formation processes in Orion A, especially examining the scenario of a cloud-cloud collision. We utilize the CARMA-NRO Orion survey (CO)-C-13 (1-0) data to compare molecular gas to the properties of young stellar objects from the SDSS III IN-SYNC survey. We show that the increase of v(13CO) - v(YSO) and Sigma scatter of older YSOs can be signals of cloud-cloud collision. SOFIA-upGREAT 158 mu m [C II] archival data toward the northern part of Orion A are also compared to the (CO)-C-13 data to test whether the position and velocity offsets between the emission from these two transitions resemble those predicted by a cloud-cloud collision model. We find that the northern part of Orion A, including regions ONC-OMC-1, OMC-2, OMC-3, and OMC-4, shows qualitative agreements with the cloud-cloud collision scenario, while in one of the southern regions, NGC 1999, there is no indication of such a process in causing the birth of new stars. On the other hand, another southern cluster, L 1641 N, shows slight tendencies of cloud-cloud collision. Overall, our results support the cloud-cloud collision process as being an important mechanism for star cluster formation in Orion A.
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| 29. |
- Momose, Munetake, et al.
(författare)
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Detailed structure of the outer disk around HD169142 with polarized light in H-band
- 2015
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Ingår i: Nippon Tenmon Gakkai obun kenkyu hokoku. - : Oxford University Press (OUP). - 0004-6264. ; 67:5
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Tidskriftsartikel (refereegranskat)abstract
- Coronagraphic imagery of the circumstellar disk around HD 169142 in H-band polarized intensity (PI) with Subaru/HiCIAO is presented. The emission scattered by dust particles at the disk surface in 0.2 <= r <= 1.2, or 29 <= r <= 174 AU, is successfully detected. The azimuthally-averaged radial profile of the PI shows a double power-law distribution, in which the PIs in r=29-52 AU and r=81.2-145 AU respectively show r(-3)-dependence. These two power-law regions are connected smoothly with a transition zone (TZ), exhibiting an apparent gap in r=40-70 AU. The PI in the inner power-law region shows a deep minimum whose location seems to coincide with the point source at lambda = 7 mm. This can be regarded as another sign of a protoplanet in TZ. The observed radial profile of the PI is reproduced by a minimally flaring disk with an irregular surface density distribution or with an irregular temperature distribution or with the combination of both. The depletion factor of surface density in the inner power-law region (r<50 AU) is derived to be >= 0.16 from a simple model calculation. The obtained PI image also shows small scale asymmetries in the outer power-law region. Possible origins for these asymmetries include corrugation of the scattering surface in the outer region, and shadowing effect by a puffed up structure in the inner power-law region.
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| 30. |
- Morokuma, Tomoki, et al.
(författare)
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Kiso Supernova Survey (KISS) : Survey strategy
- 2014
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Ingår i: Nippon Tenmon Gakkai obun kenkyu hokoku. - : Oxford University Press (OUP). - 0004-6264. ; 66:6
-
Tidskriftsartikel (refereegranskat)abstract
- lThe Kiso Supernova Survey (KISS) is a high-cadence optical wide-field supernova (SN) survey. The primary goal of the survey is to catch the very early light of a SN, during the shock breakout phase. Detection of SN shock breakouts combined with multi-band photometry obtained with other facilities would provide detailed physical information on the progenitor stars of SNe. The survey is performed using a 2 degrees.2 x 2 degrees.2 field-of-view instrument on the 1.05-m Kiso Schmidt telescope, the Kiso Wide Field Camera (KWFC). We take a 3-min exposure in g-band once every hour in our survey, reaching magnitude g similar to 20-21. About 100 nights of telescope time per year have been spent on the survey since 2012 April. The number of the shock breakout detections is estimated to be of the order of 1 during our three-year project. This paper summarizes the KISS project including the KWFC observing setup, the survey strategy, the data reduction system, and CBET-reported SNe discovered so far by KISS.
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