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X-WR-CALDESC:Division of Science, NAOJ のイベント
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DTSTART:20250101T000000
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BEGIN:VEVENT
DTSTART;TZID=Asia/Tokyo:20250514T153000
DTEND;TZID=Asia/Tokyo:20250514T163000
DTSTAMP:20260426T173646
CREATED:20250424T054416Z
LAST-MODIFIED:20250424T054416Z
UID:4968-1747236600-1747240200@sci.nao.ac.jp
SUMMARY:Talk by Margherita Grespan
DESCRIPTION:TBD
URL:https://sci.nao.ac.jp/main/event/talk-by-margherita-grespan
LOCATION:大セミナー室（すばる棟\, 国立天文台三鷹キャンパス）
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BEGIN:VEVENT
DTSTART;TZID=Asia/Tokyo:20250507T153000
DTEND;TZID=Asia/Tokyo:20250507T163000
DTSTAMP:20260426T173646
CREATED:20250424T053702Z
LAST-MODIFIED:20250502T034253Z
UID:4966-1746631800-1746635400@sci.nao.ac.jp
SUMMARY:Masafumi Niwano (NAOJ) : Study of the relationship between circumstellar disc evolution and Be donor activities in BeXBs
DESCRIPTION:=================\nMay. 7 Wed\n================= \nCampus: Mitaka\nSeminar: NAOJ Science Colloquium\nDate and time: 2025 May 7 (Wed.)\, 15:30-16:30 JST\nPlace: The large seminar room  / Zoom (hybrid) \nSpeaker: Masafumi Niwano\nAffiliation: NAOJ ADC/DoS\nTitle: Study of the relationship between circumstellar disc evolution and Be donor activities in BeXBs\nAbstract: The mechanism of X-ray outbursts in Be X-ray binaries remains a mystery\, and understanding their circumstellar discs is crucial for a solution of the mass-transfer problem. In particular\, it is important to identify the Be star activities (e.g. pulsations) that cause mass ejection and\, hence\, disc formation. Therefore\, we investigated the relationship between optical flux oscillations and the infrared (IR) excess in a sample of five Be X-ray binaries. Applying the Lomb-Scargle technique to high-cadence optical light curves from the Transiting Exoplanet Survey Satellite (TESS)\, we detected several significant oscillation modes in the 3-24 h period range for each source. We also measured the IR excess (a proxy for disc growth) of those five sources\, using J-band light curves from Palomar Gattini-IR. In four of the five sources\, we found anticorrelations between the IR excess and the amplitude of the main flux oscillation modes. This result is inconsistent with the conventional idea that non-radial pulsations drive mass ejections. We propose an alternative scenario where internal temperature variations in the Be star cause transitions between pulsation-active and mass-ejection-active states.
URL:https://sci.nao.ac.jp/main/event/talk-by-masafumi-niwano-naoj
LOCATION:大セミナー室（すばる棟\, 国立天文台三鷹キャンパス）
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BEGIN:VEVENT
DTSTART;TZID=Asia/Tokyo:20250423T153000
DTEND;TZID=Asia/Tokyo:20250423T163000
DTSTAMP:20260426T173646
CREATED:20250421T054619Z
LAST-MODIFIED:20250421T055539Z
UID:4946-1745422200-1745425800@sci.nao.ac.jp
SUMMARY:Is Stephen Hawking's evaporation of black holes wrong? - Black Hole as a new candidate for dark matter -
DESCRIPTION:=================\nApr. 23 Wed\n================= \nCampus: Mitaka\nSeminar: NAOJ Science Colloquium\nDate and time: 2025 April 23 (Wed.)\, 15:30-16:30 JST\nPlace: The insei seminar room of Subaru Building / Zoom (hybrid) \nSpeaker: Kazunori Kohri\nAffiliation: DoS\, NAOJ\nTitle: Is Stephen Hawking’s evaporation of black holes wrong? – Black Hole as a new candidate for dark matter –\nAbstract: Last year\, Prof. Gia Dvali\, an expert in quantum gravity theory\, criticized Stephen Hawking’s proposal for calculating the evaporation of black holes due to Hawking radiation\, insisting that the initial conditions assumed were not appropriate\, and if he added the back reaction (the Memory Burden Effect) from the entropy of Hawking radiation emitted by the black hole itself to the calculation\, the lifetime of the black hole should be extended even further. Researchers around the world were surprised. My group (Thoss\, Burkert and Kohri\, MNRAS\, 2024\, arXiv:2402.17823) was quick to incorporate this correction and pointed out that primordial black holes that have existed since the early Universe may have remained and become dark matter without evaporating. I will explain this topic\, which is still the subject of heated debate\, in an easy-to-understand way for non-experts in this seminar. https://arxiv.org/abs/2402.17823
URL:https://sci.nao.ac.jp/main/event/is-stephen-hawkings-evaporation-of-black-holes-wrong-black-hole-as-a-new-candidate-for-dark-matter
LOCATION:大セミナー室（すばる棟\, 国立天文台三鷹キャンパス）
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