| 1. |
- De La Fuente, Eduardo, et al.
(författare)
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Detection of a new molecular cloud in the LHAASO J2108+5157 region supporting a hadronic PeVatron scenario
- 2023
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Ingår i: Publication of the Astronomical Society of Japan. - 2053-051X .- 0004-6264. ; 75:3, s. 546-566
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Tidskriftsartikel (refereegranskat)abstract
- PeVatrons are the most powerful naturally occurring particle accelerators in the Universe. The identification of counterparts associated to astrophysical objects such as dying massive stars, molecular gas, star-forming regions, and star clusters is essential to clarify the underlying nature of the PeV emission, i.e., hadronic or leptonic. We present 12,13CO (J = 2→1) observations made with the 1.85 m radio-Telescope of the Osaka Prefecture University toward the Cygnus OB7 molecular cloud, which contains the PeVatron candidate LHAASO J2108+5157. We investigate the nature of the sub-PeV (gamma-ray) emission by studying the nucleon density determined from the content of H i and H2, derived from the CO observations. In addition to MML[2017]4607, detected via the observations of the optically thick 12CO (J = 1→0) emission, we infer the presence of an optically thin molecular cloud, named [FKT-MC]2022, whose angular size is 1-1 ± 0.}^\circ}}2. We propose this cloud as a new candidate to produce the sub-PeV emission observed in LHAASO J2108+5157. Considering a distance of 1.7 kpc, we estimate a nucleon (H i + H2) density of 37 ± 14 cm-3, and a total nucleon mass(H i + H2) of 1.5 ± 0.6 × 104 M·. On the other hand, we confirm that Kronberger 82 is a molecular clump with an angular size of 0°1, a nucleon density ∼103 cm-3, and a mass ∼103 M·. Although Kronberger 82 hosts the physical conditions to produce the observed emission of LHAASO J2108+5157, [FKT-MC]2022 is located closer to it, suggesting that the latter could be the one associated to the sub-PeV emission. Under this scenario, our results favour a hadronic origin for the emission.
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| 2. |
- de la Fuente, Eduardo, et al.
(författare)
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The symbiotic and bipolar nebula M2-9: Morphological variability of the collimated ionized wind arising from the core
- 2022
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Ingår i: Publication of the Astronomical Society of Japan. - : Oxford University Press (OUP). - 2053-051X .- 0004-6264. ; 74:3, s. 594-601
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Tidskriftsartikel (refereegranskat)abstract
- We studied the central region of bipolar nebula M 2-9 using radio-continuum observations obtained from the Jansky Very Large Array (JVLA) and the Atacama Large Millimeter Array (ALMA) interferometers. This work presents new images at similar to 43 GHz (similar to 7.0 mm) and similar to 345 GHz (similar to 0.9 mm) with angular resolutions of similar to 0 ''.047 and 0 ''.09, respectively. The continuum emission at similar to 43 GHz shows an elongated jet-like structure perpendicular to the similar to 345 GHz observation. We conclude that both emissions could correspond to tracing an isothermal collimated fast wind with constant expansion velocity and being driven by the circumstellar ring traced by ALMA. Although this configuration has been discussed within the scope of planetary nebulae models, there is a remarkable fact: the collimated fast wind shows morphological spatial variability. This supports the idea of a symbiotic binary system within the innermost part of M 2-9, which would be composed of a white dwarf and an AGB star. The latter could explain the mirror symmetry observed at larger scales due to their orbital motion.
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| 3. |
- Fukui, Akihiko, et al.
(författare)
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TOI-2285b: A 1.7 Earth-radius planet near the habitable zone around a nearby M dwarf
- 2022
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Ingår i: Publication of the Astronomical Society of Japan. - : Oxford University Press (OUP). - 2053-051X .- 0004-6264. ; 74:1, s. L1-L8
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Tidskriftsartikel (refereegranskat)abstract
- We report the discovery of TO1-2285b, a sub-Neptune-sized planet transiting a nearby (42 pc) M dwarf with a period of 27.3 d. We identified the transit signal from the Transiting Exoplanet Survey Satellite photometric data, which we confirmed with ground-based photometric observations using the multiband imagers MuSCAT2 and MuSCAT3. Combining these data with other follow-up observations including high-resolution spectroscopy with the Tillinghast Reflector Echelle Spectrograph, high-resolution imaging with the SPeckle Polarimeter, and radial velocity (RV) measurements with the InfraRed Doppler instrument, we find that the planet has a radius of 1.74 +/- 0.08 R-circle plus, a mass of <19.5 M-circle plus + (95% c.I.), and an insolation flux of 1.54 +/- 0.14 times that of the Earth. Although the planet resides just outside the habitable zone for a rocky planet, if the planet harbors an H2O layer under a hydrogen-rich atmosphere, then liquid water could exist on the surface of the H2O layer depending on the planetary mass and water mass fraction. The bright host star in the near-infrared (K-s = 9.0) makes this planet an excellent target for further RV and atmospheric observations to improve our understanding of the composition, formation, and habitability of sub-Neptune-sized planets.
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| 4. |
- Harakawa, Hiroki, et al.
(författare)
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A super-Earth orbiting near the inner edge of the habitable zone around the M4.5 dwarf Ross 508
- 2022
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Ingår i: Publications of the Astronomical Society of Japan. - : Oxford University Press (OUP). - 0004-6264 .- 2053-051X. ; 74:4, s. 904-922
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Tidskriftsartikel (refereegranskat)abstract
- We report the near-infrared radial velocity (RV) discovery of a super-Earth planet on a 10.77 d orbit around the M4.5 dwarf Ross 508 (Jmag = 9.1). Using precision RVs from the Subaru Telescope IRD (InfraRed Doppler) instrument, we derive a semi-amplitude of 3.92ms−1, corresponding to a planet with a minimum mass msini=4.00M⊕. We find no evidence of significant signals at the detected period in spectroscopic stellar activity indicators or MEarth photometry. The planet, Ross 508 b, has a semi-major axis of 0.05366au. This gives an orbit-averaged insolation of ≈1.4 times the Earth’s value, placing Ross 508 b near the inner edge of its star’s habitable zone. We have explored the possibility that the planet has a high eccentricity and its host is accompanied by an additional unconfirmed companion on a wide orbit. Our discovery demonstrates that the near-infrared RV search can play a crucial role in finding a low-mass planet around cool M dwarfs like Ross 508.
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| 5. |
- Hayakawa, Ryota, et al.
(författare)
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X-ray hot spots in the eastern ear of the supernova remnant W 50 and the microquasar SS 433 system
- 2022
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Ingår i: Publications of the Astronomical Society of Japan. - : Oxford University Press (OUP). - 0004-6264 .- 2053-051X. ; 74:3, s. 510-520
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Tidskriftsartikel (refereegranskat)abstract
- We examined the X-ray and radio spatial structure at the eastern ear of the W 50/SS 433 system to clarify a characteristic feature of the termination region of the SS 433 jet, and found that a hot spot ahead of the filament structure, which is considered to be a terminal shock of the SS 433 eastern jet, is clearly different from a single point source. The detailed spatial structure of the X-ray emission is finely resolved by Chandra observations, showing that there are two sources. By comparing the point-spread function of Chandra with the radial profiles of the two sources, the northern one is clearly more extended than a point source while the other seems marginally extended. Since there are no point sources nearby, the northern hot spot is likely a localized diffuse source. The northern hot spot spatially corresponds to the peak of the radio emission. Its spatial correlation is confirmed by an X-ray image using XMM-Newton. The X-ray spectra of the two sources are reproduced by a single absorbed power-law but the column density of the northern part is larger by a factor of ∼3. When a radiation model comprising synchrotron emission and inverse Compton emission is applied to the spectral energy distribution of the northern hot spot, the emission from this spot can be explained by the radiation from an electron population accelerated up to 30 TeV in a magnetic field strength of B ≲ 50 μG. This model also agrees with the radio and X-ray data, as well as the upper limit of gamma-ray emission obtained by the Fermi satellite.
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| 6. |
- 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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| 7. |
- 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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| 8. |
- 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
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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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