Publications of the Astronomical Society of Japan最新文献

{"title":"Identifying hot subdwarf stars from photometric data using a Gaussian mixture model and graph neural network","authors":"Wei Liu, Yude Bu, Xiaoming Kong, Zhenping Yi, Meng Liu","doi":"10.1093/pasj/psae013","DOIUrl":"https://doi.org/10.1093/pasj/psae013","url":null,"abstract":"Hot subdwarf stars are very important for understanding stellar evolution, stellar astrophysics, and binary star systems. Identifying more such stars can help us better understand their statistical distribution, properties, and evolution. In this paper, we present a new method to search for hot subdwarf stars in photometric data (BP, RP, G, g, r, i, z, y) using a machine-learning algorithm, a graph neural network, and a Gaussian mixture model. We use a Gaussian mixture model and Markov distance to build the graph structure, and on the graph structure we use a graph neural network to identify hot subdwarf stars from a dataset containing 31838 stars, with the recall, precision, and F1 score maximized on the original, weight, and synthetic minority oversampling technique datasets. Finally, to validate the model, we selected about 2116 hot subdwarf candidates from the Gaia Data Release 3 database and compared them with the studies by Culpan et al. (2022, A&A, 662, A40) and Geier et al. (2019, A&A, 621, A38).","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"147 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140575913","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}

{"title":"Radio emission from SN 1181 hosting a white dwarf merger product","authors":"Takatoshi Ko, Daichi Tsuna, Bunyo Hatsukade, Toshikazu Shigeyama","doi":"10.1093/pasj/psae023","DOIUrl":"https://doi.org/10.1093/pasj/psae023","url":null,"abstract":"The remnant of the historical supernova 1181 is claimed to be associated with a white dwarf merger remnant J005311. The supernova remnant (SNR) shock, and a termination shock expected to be formed by the intense wind of J005311, are potential sites for radio emission via synchrotron emission from shock-accelerated electrons. In this paper, we estimate the radio emission from these two shocks, and find the peak radio flux to be 0.1–10 mJy (at 0.01–1 GHz) in the outer SNR shock and 0.01–0.1 mJy (at 1–10 GHz) in the inner termination shock. We also search for radio emission from this source in the archival data of the Karl G. Jansky Very Large Array (VLA) Sky Survey at 3 GHz, the NRAO VLA Sky Survey at 1.4 GHz and the Canadian Galactic Plane Survey at 408 MHz, finding no significant detection. While targeted observations with higher sensitivity are desired, we particularly encourage those at higher frequency and angular resolution to probe the inner termination shock and its evolution.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"8 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140575967","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}

{"title":"Sub-parsec-scale jet-driven water maser with possible gravitational acceleration in the radio galaxy NGC 1052","authors":"Seiji Kameno, Yuichi Harikane, Satoko Sawada-Satoh, Tsuyoshi Sawada, Toshiki Saito, Kouichiro Nakanishi, Elizabeth Humphreys, C M Violette Impellizzeri","doi":"10.1093/pasj/psae015","DOIUrl":"https://doi.org/10.1093/pasj/psae015","url":null,"abstract":"We report sub-parsec-scale observations of the 321 GHz H2O emission line in the radio galaxy NGC 1052. The H2O line emitter size is constrained in <0.6 mas distributed on the continuum core component. The brightness temperature exceeding 106 K and the intensity variation indicate certain evidence for maser emission. The maser spectrum consists of redshifted and blueshifted velocity components spanning ∼400 km s−1, separated by a local minimum around the systemic velocity of the galaxy. The spatial distribution of maser components shows a velocity gradient along the jet direction, implying that the population-inverted gas is driven by the jets interacting with the molecular torus. We identified a significant change of the maser spectra between two sessions separated by 14 days. The maser profile showed a radial velocity drift of 127 ± 13 km s−1 yr−1 implying inward gravitational acceleration at 5000 Schwarzschild radii. The results demonstrate the feasibility of future very long baseline interferometry observations to resolve the jet–torus interacting region.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"121 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140196624","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}

{"title":"Measurement of the zodiacal light absolute intensity through Fraunhofer line spectroscopy of the night sky with the Hale telescope","authors":"Masaki Hanzawa, Shuji Matsuura, Aoi Takahashi, Ranga-Ram Chary, Kei Sano, Kohji Takimoto, Yuto Tome","doi":"10.1093/pasj/psae016","DOIUrl":"https://doi.org/10.1093/pasj/psae016","url":null,"abstract":"Measuring the absolute brightness of the zodiacal light (ZL), which is the sunlight scattered by interplanetary dust particles, is important not only for understanding the physical properties of the dust but also for constraining the extragalactic background light (EBL) by subtracting the ZL foreground. We describe the results of high-resolution spectroscopic observations of the night sky in the wavelength range of 300–900 nm with the double spectrograph on the Hale telescope to determine the absolute brightness of the ZL continuum spectra from the Fraunhofer absorption line intensities. The observed fields are part of the fields observed by the Spitzer Space Telescope for the EBL study. Assuming that the spectral shape of the zodiacal light is identical to the solar spectrum in a narrow region around the Fraunhofer lines, we decomposed the observed sky brightness into multiple emission components by amplitude parameter fitting with spectral templates of the airglow, ZL, diffuse Galactic light, integrated starlight, and other isotropic components including EBL. As a result, the ZL component with the Ca ii λλ 393.3, 396.8 nm Fraunhofer lines around 400 nm is clearly separated from the others in all fields with uncertainties around 20%, mainly due to the template errors and the time variability of the airglow. The observed ZL brightness in most of the observed fields is consistent with the modeled ZL brightness calculated by combining the most conventional ZL model at 1250 nm based on the Diffuse Infrared Background Experiment and the observational ZL template spectrum based on the Hubble Space Telescope. However, the ecliptic plane observation is considerably fainter than the ZL model, and this discrepancy is discussed in terms of the optical properties of the interplanetary dust accreted in the ecliptic plane.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"27 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140196668","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}

{"title":"Optical and soft X-ray light-curve analysis during the 2022 eruption of U Scorpii: Structural changes in the accretion disk","authors":"Katsuki Muraoka, Naoto Kojiguchi, Junpei Ito, Daisaku Nogami, Taichi Kato, Yusuke Tampo, Kenta Taguchi, Keisuke Isogai, Teofilo Arranz, John Blackwell, David Blane, Stephen M Brincat, Graeme Coates, Walter Cooney, Shawn Dvorak, Charles Galdies, Daniel Glomski, Franz-Josef Hambsch, Barbara Harris, John Hodge, Jose L Hernández-Verdejo, Marco Iozzi, Hiroshi Itoh, Seiichiro Kiyota, Darrell Lee, Magnus Larsson, Tapio Lahtinen, Gordon Myers, Berto Monard, Mario Morales Aimar, Masayuki Moriyama, Masanori Mizutani, Kazuo Nagai, Thabet AlQaissieh, Aldrin B Gabuya, Mohammad Odeh, Carlos Perello, Andrew Pearce, Juan Miguel Perales, David Quiles, Filipp D Romanov, David J Lane, Michael Richmond, Nello Ruocco, Yasuo Sano, Mark Spearman, Richard Schmidt, Tonny Vanmunster, Pavol A Dubovsky, Richard Wagner, Guido Wollenhaupt, Joachim Lorenz, Gerhard Lehmann, Andrea Salewski, Guy Williamson","doi":"10.1093/pasj/psae010","DOIUrl":"https://doi.org/10.1093/pasj/psae010","url":null,"abstract":"We present our optical photometric observations of the 2022 eruption of the recurrent nova U Scorpii (U Sco) using 49152 data points over 70 d following the optical peak. We have also analyzed its soft X-ray (0.3–1 keV) light curve by the Neil Gehrels Swift Observatory. During the 2022 eruption, the optical plateau stage started 13.8–15.0 d and ended 23.8–25.0 d after the optical peak. The soft X-ray stage started 14.6–15.3 d and ended 38.7–39.5 d after the optical peak. Both stages started later and had shorter durations, and the soft X-ray light curve peaked earlier and was less luminous compared to those during the U Sco 2010 eruption. These points suggest that there were differences in the envelope mass between the different cycles of the nova eruption. Furthermore, we have analyzed the optical eclipses during the 2022 eruption. The primary eclipse was first observed 10.4–11.6 d after the optical peak, earlier than the beginning of the optical plateau stage. This sequence of events can be explained by the receding ejecta photosphere associated with the expanding nova ejecta. We have determined the ingress and egress phases of the primary eclipses and estimated the outer radius of the optical light source centered at the white dwarf (WD). During the optical plateau stage, the source radius remained ∼1.2 times larger than the Roche volume radius of the primary WD, being close to the L1 point. When the optical plateau stage ended, the source radius drastically shrank to the tidal truncation radius within a few orbital periods. This previously unresolved phenomenon can be interpreted as a structural change in U Sco where the temporarily expanded accretion disk due to the nova wind returned to a steady state.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"102 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140073912","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}

{"title":"Impulsive gas fueling to the galactic center in a barred galaxy due to falls of gas clouds","authors":"Hidenori Matsui, Toshiyasu Masakawa, Asao Habe, Takayuki R Saitoh","doi":"10.1093/pasj/psae009","DOIUrl":"https://doi.org/10.1093/pasj/psae009","url":null,"abstract":"We have studied the evolution of the central hundred parsec region of barred galaxies by performing numerical simulations realizing the multi-phase nature of gas. Our simulations have shown that a stellar bar produces an oval gas ring, namely the x-2 ring, within 1 kpc as the bar grows. The ring is self-gravitationally unstable enough to trigger the formation of gas clouds. Although the gas clouds initially rotate in the x-2 ring, cloud–cloud collisions and$/$or energy injections into the gas ring by Type II supernovae causes some of the clouds to deviate from the ring orbit. After the deviation, the deviated clouds repeat collisions with the other clouds, which rotate in the x-2 ring, during several rotations. These processes effectively reduce the angular momentum of the deviated gas cloud. As a result, the gas cloud finally falls into the galactic center, and episodic gas supply to the galactic center takes place.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"49 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140074046","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}

{"title":"Peak energy–isotropic luminosity correlation and jet opening angle evolution in Swift-BAT short GRBs with soft-tail emission","authors":"Naoki Ogino, Daisuke Yonetoku, Makoto Arimoto, Tatsuya Sawano, Hamid Hamidani","doi":"10.1093/pasj/psae018","DOIUrl":"https://doi.org/10.1093/pasj/psae018","url":null,"abstract":"Some short gamma-ray bursts (SGRBs) exhibit a short-duration and spectral hard emission (referred to as a “hard spike”) followed by a slightly longer soft emission (known as a “soft tail”). We identified nine SGRBs with the known redshift in the Swift/BAT gamma-ray burst catalog by specifically searching for the soft tail. We found that the spectra of these SGRBs can be described as a cutoff power-law model for the hard spike and the soft tail, and both show a time variation keeping the Epeak–Liso correlation. This suggests that the emission mechanisms of both phenomena are identical. Furthermore, we found a trend of luminosity evolution as a function of redshift. This phenomenon suggests that these bursts originate from sources that are intrinsically bright and/or energy-density-concentrated within a narrower jet at higher redshift. We demonstrate that the average jet opening angle, derived from the jet break, can be explained by considering a model based on a strongly redshift-dependent jet opening angle.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"60 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140054344","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}

{"title":"Model of a “Warm Corona” as the origin of the soft X-ray excess of active galactic nuclei","authors":"Norita Kawanaka, Shin Mineshige","doi":"10.1093/pasj/psae012","DOIUrl":"https://doi.org/10.1093/pasj/psae012","url":null,"abstract":"The soft X-ray excess in the spectra of active galactic nuclei is characterized by similar electron temperatures of 0.1–0.3 keV and similar photon indices around 2.2–3, if fitted with inverse Comptonization. It remains a puzzle why both values are not sensitive to the black hole mass nor the accretion rate. Supposing that the scattering-dominated surface layer of an accretion disk can act as a warm corona, we construct a vertical one-zone model to understand what determines its temperature. By solving the equations of (1) the condition for the effective optical depth, (2) the energy balance, and (3) the dominance of the Compton cooling over the bound–free cooling, we could reproduce the basic observational features of the soft excess, provided that anomalous heating (excess heating other than what is expected by local energy dissipation) takes place in the warm corona in agreement with similar studies done so far. The similar temperatures can be understood, since both the anomalous heating and Compton cooling rates are proportional to the dissipation rate of the accretion energy, while similar photon indices are a natural consequence of the fact that observed photons are finally emitted from the layer of Compton y ∼ 1. The soft excess is not observed in black hole binaries, since disk temperatures are too high for the Compton scattering to work as cooling. The derived temperatures are somewhat of an underestimation, however. This may indicate a necessity of multi-zone corona structure. The stability of the warm corona and its consequences are briefly discussed.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"51 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140002039","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}

{"title":"Discovery of diffuse radio source in Abell 1060","authors":"Kohei Kurahara, Takuya Akahori, Aika Oki, Yuki Omiya, Kazuhiro Nakazawa","doi":"10.1093/pasj/psae011","DOIUrl":"https://doi.org/10.1093/pasj/psae011","url":null,"abstract":"Non-thermal components in the intra-cluster medium (ICM), such as turbulence, magnetic field, and cosmic rays, imprint the past and current energetic activities of jets from active galactic nuclei (AGN) of member galaxies as well as disturbance caused by galaxy cluster mergers. Meter- and centimeter-radio observations of synchrotron radiation allow us to diagnose the nonthermal component. Here we report on our discovery of an unidentified diffuse radio source, named the Flying Fox, near the center of the Abell 1060 field. The Flying Fox has an elongated ring-like structure and a central bar shape, but there is no obvious host galaxy. The average spectral index of the Flying Fox is −1.4, which is steeper than that for radio sources seen at meter wavelengths. We discussed the possibilities of radio lobes, phoenixes, radio halos and relics, and an odd radio circle. In conclusion, the Flying Fox is not clearly explained by known radio sources.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"8 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139950102","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}

{"title":"Near-ultraviolet radiation toward molecular cloud N4 in W 50/SS 433: Evidence for direct interaction of the jet with molecular cloud","authors":"Hiroaki Yamamoto, Tatsumi Ishikawa, Tsutomu T Takeuchi","doi":"10.1093/pasj/psae007","DOIUrl":"https://doi.org/10.1093/pasj/psae007","url":null,"abstract":"We compared the molecular clouds in the western part of SS 433 with near-ultraviolet radiation data obtained from GALEX. Near-ultraviolet radiation is prominently confirmed toward only N4, while no near-ultraviolet radiation is detected toward N1, N2, or N3. The radiative region of near-ultraviolet radiation is nearly the same as the CO-emitting region in N4, and does not extend beyond the jet seen in X-ray radiation. Near-ultraviolet radiation cannot be explained solely by broad-band continuous radiation and may originate from line emissions. The intensity of near-ultraviolet radiation exhibits an anti-correlation with that of 13CO(J = 3–2) emission. This anti-correlation, along with strong far-infrared radiation in the region with weaker near-ultraviolet radiation intensity compared to its surroundings, suggests that near-ultraviolet radiation originates from behind the molecular cloud, heating up the interstellar dust in N4. Subsequently, the dust in N4 reradiates in the far-infrared band. In the same region, a high peak TMB ratio of 12CO(J = 3–2)$/$12CO(J = 1–0) of ∼0.9, and a high kinetic temperature of Tk ∼ 56 K in the molecular cloud, indicate that CO molecules are highly excited, and the molecular cloud is heated through photoelectric heating. This heating results from electrons released due to the photoelectric effect caused by the phenomenon where interstellar dust absorbs near-ultraviolet radiation. In terms of the timescale of near-ultraviolet radiation originating from line emissions, near-ultraviolet radiation towards N4 cannot be explained by the shock of the blast wave from a supernova that created W 50. These findings also suggest that N4 directly interacts with the jet from SS 433. As a result of this direct interaction, near-ultraviolet radiation is emitted from an interacting layer between the jet and N4.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"48 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139903484","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}