DSpace community: 天文研究所

Seasonal exposure of carbon dioxide ice on the nucleus of comet 67P/Churyumov-Gerasimenko

Tue, 21 Apr 2026 07:00:39 GMT

title: Seasonal exposure of carbon dioxide ice on the nucleus of comet 67P/Churyumov-Gerasimenko abstract: 摘要： Rosetta observes sublimating surface icesComets are “dirty snowballs” made of ice and dust, but they are dark because the ice sublimates away, leaving some of the dust behind on the surface. The Rosetta spacecraft has provided a close-up view of the comet 67P/Churyumov-Gerasimenko as it passes through its closest point to the Sun (see the Perspective by Dello Russo). Filacchioneet al.detected the spectral signature of solid CO2(dry ice) in small patches on the surface of the nucleus as they emerged from local winter. By modeling how the CO2sublimates, they constrain the composition of comets and how ices generate the gaseous coma and tail. Fornasieret al.studied images of the comet and discovered bright patches on the surface where ice was exposed, which disappeared as the ice sublimated. They also saw frost emerging from receding shadows. The surface of the comet was noticeably less red just after local dawn, indicating that icy material is removed by sunlight during the local day.Science, this issue p.1563, p.1566; see also p.1536 其他題名： Science 出版者： United States: American Association for the Advancement of Science (AAAS) 出版日期： 2016-12-23 出處： Science, 2016-12, Vol.354 (6319), p.1563-1566 資源來源： American Association for the Advancement of Science 版權： Copyright © 2016 American Association for the Advancement of Science 版權： Copyright © 2016, American Association for the Advancement of Science. 版權： Copyright © 2016, American Association for the Advancement of Science 版權： CC0 1.0 - Universal 識別號： ISSN: 0036-8075 識別號： EISSN: 1095-9203 識別號： DOI: 10.1126/science.aag3161 識別號： PMID: 27856846 識別號： CODEN: SCIEAS

Rosetta's comet 67P/Churyumov- Gerasimenko sheds its dusty mantle to reveal its icy nature

Tue, 21 Apr 2026 07:00:30 GMT

title: Rosetta's comet 67P/Churyumov- Gerasimenko sheds its dusty mantle to reveal its icy nature abstract: 摘要： Rosetta observes sublimating surface icesComets are “dirty snowballs” made of ice and dust, but they are dark because the ice sublimates away, leaving some of the dust behind on the surface. The Rosetta spacecraft has provided a close-up view of the comet 67P/Churyumov-Gerasimenko as it passes through its closest point to the Sun (see the Perspective by Dello Russo). Filacchioneet al.detected the spectral signature of solid CO2(dry ice) in small patches on the surface of the nucleus as they emerged from local winter. By modeling how the CO2sublimates, they constrain the composition of comets and how ices generate the gaseous coma and tail. Fornasieret al.studied images of the comet and discovered bright patches on the surface where ice was exposed, which disappeared as the ice sublimated. They also saw frost emerging from receding shadows. The surface of the comet was noticeably less red just after local dawn, indicating that icy material is removed by sunlight during the local day.Science, this issue p.1563, p.1566; see also p.1536 其他題名： Science 出版者： United States: American Association for the Advancement of Science (AAAS) 出版日期： 2016-12-23 出處： Science, 2016-12, Vol.354 (6319), p.1566-1570 資源來源： American Association for the Advancement of Science 版權： Copyright © 2016 American Association for the Advancement of Science 版權： Copyright © 2016, American Association for the Advancement of Science. 版權： Copyright © 2016, American Association for the Advancement of Science 版權： licence_http://creativecommons.org/publicdomain/zero 識別號： ISSN: 0036-8075 識別號： ISSN: 1095-9203 識別號： EISSN: 1095-9203 識別號： DOI: 10.1126/science.aag2671 識別號： PMID: 27856849 識別號： CODEN: SCIEAS

M31N 2008-12a - The REMARKABLE RECURRENT NOVA in M31: PANCHROMATIC OBSERVATIONS of the 2015 ERUPTION

Tue, 21 Apr 2026 07:00:18 GMT

title: M31N 2008-12a - The REMARKABLE RECURRENT NOVA in M31: PANCHROMATIC OBSERVATIONS of the 2015 ERUPTION abstract: 摘要： ABSTRACT The Andromeda Galaxy recurrent nova M31N 2008-12a had been observed in eruption 10 times, including yearly eruptions from 2008 to 2014. With a measured recurrence period of days (we believe the true value to be half of this) and a white dwarf very close to the Chandrasekhar limit, M31N 2008-12a has become the leading pre-explosion supernova type Ia progenitor candidate. Following multi-wavelength follow-up observations of the 2013 and 2014 eruptions, we initiated a campaign to ensure early detection of the predicted 2015 eruption, which triggered ambitious ground- and space-based follow-up programs. In this paper we present the 2015 detection, visible to near-infrared photometry and visible spectroscopy, and ultraviolet and X-ray observations from the Swift observatory. The LCOGT 2 m (Hawaii) discovered the 2015 eruption, estimated to have commenced at August 28.28 0.12 UT. The 2013-2015 eruptions are remarkably similar at all wavelengths. New early spectroscopic observations reveal short-lived emission from material with velocities ∼13,000 km s−1, possibly collimated outflows. Photometric and spectroscopic observations of the eruption provide strong evidence supporting a red giant donor. An apparently stochastic variability during the early supersoft X-ray phase was comparable in amplitude and duration to past eruptions, but the 2013 and 2015 eruptions show evidence of a brief flux dip during this phase. The multi-eruption Swift/XRT spectra show tentative evidence of high-ionization emission lines above a high-temperature continuum. Following Henze et al. (2015a), the updated recurrence period based on all known eruptions is days, and we expect the next eruption of M31N 2008-12a to occur around 2016 mid-September. 其他題名： APJ 其他題名： Astrophys. J 出版者： Philadelphia: The American Astronomical Society 出版日期： 2016-12-20 出處： The Astrophysical journal, 2016-12, Vol.833 (2), p.149 資源來源： IoP Science journals 版權： 2016. The American Astronomical Society. All rights reserved. 版權： Copyright IOP Publishing Dec 20, 2016 識別號： ISSN: 0004-637X 識別號： ISSN: 1538-4357 識別號： EISSN: 1538-4357 識別號： DOI: 10.3847/1538-4357/833/2/149

THE PALOMAR TRANSIENT FACTORY and RR LYRAE: The METALLICITY-LIGHT CURVE RELATION BASED on AB-TYPE RR LYRAE in the KEPLER FIELD

Tue, 21 Apr 2026 07:00:13 GMT

title: THE PALOMAR TRANSIENT FACTORY and RR LYRAE: The METALLICITY-LIGHT CURVE RELATION BASED on AB-TYPE RR LYRAE in the KEPLER FIELD abstract: 摘要： ABSTRACT The wide-field synoptic sky surveys, known as the Palomar Transient Factory (PTF) and the intermediate Palomar Transient Factory (iPTF), will accumulate a large number of known and new RR Lyrae. These RR Lyrae are good tracers to study the substructure of the Galactic halo if their distance, metallicity, and galactocentric velocity can be measured. Candidates of halo RR Lyrae can be identified from their distance and metallicity before requesting spectroscopic observations for confirmation. This is because both quantities can be obtained via their photometric light curves, because the absolute V-band magnitude for RR Lyrae is correlated with metallicity, and the metallicity can be estimated using a metallicity-light curve relation. To fully utilize the PTF and iPTF light-curve data in related future work, it is necessary to derive the metallicity-light curve relation in the native PTF/iPTF R-band photometric system. In this work, we derived such a relation using the known ab-type RR Lyrae located in the Kepler field, and it is found to be (where P is pulsational period and is one of the Fourier parameters describing the shape of the light curve), with a dispersion of 0.118 dex. We tested our metallicity-light curve relation with new spectroscopic observations of a few RR Lyrae in the Kepler field, as well as several data sets available in the literature. Our tests demonstrated that the derived metallicity-light curve relation could be used to estimate metallicities for the majority of the RR Lyrae, which are in agreement with the published values. 其他題名： APJS 其他題名： Astrophys. J. Suppl 出版者： United States: The American Astronomical Society 出版日期： 2016-12-01 出處： The Astrophysical journal. Supplement series, 2016-12, Vol.227 (2), p.30 資源來源： Institute of Physics Journals 版權： 2016. The American Astronomical Society. All rights reserved. 識別號： ISSN: 0067-0049 識別號： EISSN: 1538-4365 識別號： DOI: 10.3847/1538-4365/227/2/30