The Astrophysical Journal Letters最新文献

{"title":"Bolometric Corrections for FU Ori Object Accretion Disk Luminosities","authors":"Adolfo S. Carvalho and Lynne A. Hillenbrand","doi":"10.3847/2041-8213/ad8cdf","DOIUrl":"https://doi.org/10.3847/2041-8213/ad8cdf","url":null,"abstract":"The accretion luminosity of an FU Ori disk is a fundamental system parameter, but a challenging one to estimate for all but the most well-studied systems. FU Ori objects are dynamically evolving accretion disks, especially close in time to the outburst epoch. They have a complex multitemperature disk structure that results in distinctly shaped, broad spectral energy distributions (SEDs). Detailed spectroscopic analysis is required for simultaneous constraint on relevant physical parameters such as the central stellar mass, inner disk radius, disk inclination, and disk accretion rate. However, outbursting systems that are deeply embedded and/or distant may be limited to only photometric measurement and over only a narrow range of wavelengths. The bolometric corrections necessary to estimate accretion luminosities are not straightforward and in particular cannot be adopted from existing literature on isotropically radiating stars. We present bolometric corrections specific to astrophysical accretion disks for a variety of filters in ongoing and upcoming all-sky surveys.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142601433","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New Results on the Onset of a Coronal Mass Ejection from 5303 Å Emission Line Observations with VELC/ADITYA-L1","authors":"R. Ramesh, V. Muthu Priyal, Jagdev Singh, K. Sasikumar Raja, P. Savarimuthu and Priya Gavshinde","doi":"10.3847/2041-8213/ad8c45","DOIUrl":"https://doi.org/10.3847/2041-8213/ad8c45","url":null,"abstract":"We report on the onset of a coronal mass ejection (CME) using spectroscopic observations in the 5303 Å coronal emission line with the Visible Emission Line Coronagraph (VELC) onboard ADITYA-L1, the recently launched first Indian space solar mission. The CME was observed on 2024 July 16 in association with an X1.9 class soft X-ray flare from heliographic location S05W85. The VELC observations were near the west limb of the Sun during the CME. The results obtained helped to constrain the onset time of the CME. In addition, they indicate a ≈50% decrease in the coronal intensity near the source region of the CME due to mass depletion, a ≈15% enhancement in the emission line width, and a redshifted Doppler velocity of about ≈10 km s−1. The nonthermal velocity associated with the line broadening is ≈24.87 km s−1.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142600900","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Green Monster Hiding in Front of Cas A: JWST Reveals a Dense and Dusty Circumstellar Structure Pockmarked by Ejecta Interactions","authors":"Ilse De Looze, Dan Milisavljevic, Tea Temim, Danielle Dickinson, Robert Fesen, Richard G. Arendt, Jeremy Chastenet, Salvatore Orlando, Jacco Vink, Michael J. Barlow, Florian Kirchschlager, Felix D. Priestley, John C. Raymond, Jeonghee Rho, Nina S. Sartorio, Tassilo Scheffler, Franziska Schmidt, William P. Blair, Ori Fox, Christopher Fryer, Hans-Thomas Janka, Bon-Chul Koo, J. Martin Laming, Mikako Matsuura, Dan Patnaude, Mónica Relaño, Armin Rest, Judy Schmidt, Nathan Smith and Niharika Sravan","doi":"10.3847/2041-8213/ad855d","DOIUrl":"https://doi.org/10.3847/2041-8213/ad855d","url":null,"abstract":"JWST observations of the young Galactic supernova remnant Cassiopeia A revealed an unexpected structure seen as a green emission feature in colored composite MIRI F1130W and F1280W images—hence dubbed the Green Monster—that stretches across the central parts of the remnant in projection. Combining the kinematic information from NIRSpec and the MIRI Medium Resolution Spectrograph with the multiwavelength imaging from NIRCam and MIRI, we associate the Green Monster with circumstellar material (CSM) that was lost during an asymmetric mass-loss phase. MIRI images are dominated by dust emission, but their spectra show emission lines from Ne, H, and Fe with low radial velocities indicative of a CSM nature. An X-ray analysis of this feature in a companion paper supports its CSM nature and detects significant blueshifting, thereby placing the Green Monster on the nearside, in front of the Cas A supernova remnant. The most striking features of the Green Monster are dozens of almost perfectly circular 1″–3″ sized holes, most likely created by interaction between high-velocity supernova ejecta material and the CSM. Further investigation is needed to understand whether these holes were formed by small 8000–10,500 km s−1 N-rich ejecta knots that penetrated and advanced out ahead of the remnant’s 5000–6000 km s−1 outer blast wave or by narrow ejecta fingers that protrude into the forward-shocked CSM. The detection of the Green Monster provides further evidence of the highly asymmetric mass loss that Cas A’s progenitor star underwent prior to its explosion.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142600904","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Composition Variation of the 2023 May 16 Solar Energetic Particle Event Observed by SolO and PSP","authors":"Z. G. Xu, C. M. S Cohen, R. A. Leske, G. D. Muro, A. C. Cummings, D. J. McComas, N. A. Schwadron, E. R. Christian, M. E. Wiedenbeck, R. L. McNutt, D. G. Mitchell, G. M. Mason, A. Kouloumvakos, R. F. Wimmer-Schweingruber, G. C. Ho and J. Rodriguez-Pacheco","doi":"10.3847/2041-8213/ad8b18","DOIUrl":"https://doi.org/10.3847/2041-8213/ad8b18","url":null,"abstract":"In this study, we employ the combined charged particle measurements from Integrated Science Investigation of the Sun on board the Parker Solar Probe (PSP) and Energetic Particle Detector on board the Solar Orbiter (SolO) to study the composition variation of the solar energetic particle (SEP) event occurring on 2023 May 16. During the event, SolO and PSP were located at a similar radial distance of ∼0.7 au and were separated by ∼60° in longitude. The footpoints of both PSP and SolO were west of the flare region, but the former was much closer (18° versus 80°). Such a distribution of observers is ideal for studying the longitudinal dependence of the ion composition with the minimum transport effects of particles along the radial direction. We focus on H, He, O, and Fe measured by both spacecraft in sunward and antisunward directions. Their spectra are in a double power-law shape, which is fitted best by the Band function. Notably, the event was Fe rich at PSP, where the mean Fe/O ratio at energies of 0.1–10 Mev nuc−1 was 0.48, higher than the average Fe/O ratio in previous large SEP events. In contrast, the mean Fe/O ratio at SolO over the same energy range was considerably lower at 0.08. The Fe/O ratio between 0.5 and 10 MeV nuc−1 at both spacecraft is nearly constant. Although the He/H ratio shows energy dependence, decreasing with increasing energy, the He/H ratio at PSP is still about twice as high as that at SolO. Such a strong longitudinal dependence of element abundances and the Fe-rich component in the PSP data could be attributed to the direct flare contribution. Moreover, the temporal profiles indicate that differences in the Fe/O and He/H ratios between PSP and SolO persisted throughout the entire event rather than only at the start.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142599118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Large Eruptive and Confined Flares in Relation to the Solar Active Region Evolution","authors":"Fuyu Li, Changhui Rao, Huaning Wang, Xinhua Zhao, Nanbin Xiang, Linhua Deng, Haitang Li and Yu Liu","doi":"10.3847/2041-8213/ad8c37","DOIUrl":"https://doi.org/10.3847/2041-8213/ad8c37","url":null,"abstract":"Solar active regions (ARs) provide the required magnetic energy and the topology configuration for flares. Apart from conventional static magnetic parameters, the evolution of AR magnetic flux systems should have nonnegligible effects on magnetic energy store and the trigger mechanism of eruptions, which would promote the prediction for the flare using photospheric observations conveniently. Here we investigate 322 large (M- and X-class) flares from 2010 to 2019, almost the whole solar cycle 24. The flare occurrence rate is obviously higher in the developing phase, which should be due to the stronger shearing and complex configurations caused by affluent magnetic emergences. However, the probability of flare eruptions in decaying phases of ARs is obviously higher than that in the developing phase. The confined flares were in nearly equal counts to eruptive flares in developing phases, whereas the eruptive flares were half over confined flares in decaying phases. Yearly looking at flare eruption rates demonstrates the same conclusion. The relationship between sunspot group areas and confined/erupted flares also suggested that the strong field make constraints on the mass ejection, though it can contribute to flare productions. The flare indexes also show a similar trend. It is worth mentioning that all the X-class flares in the decaying phase were erupted, without the strong field constraint. The decaying of magnetic flux systems had facilitation effects on flare eruptions, which may be consequent on the splitting of magnetic flux systems.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142598495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Small-scale Current Sheets and Associated Switchback Activity in the Inner Heliosphere","authors":"Sydney Furman, Alexandros Chasapis, David Malaspina, Peter Tatum, Benjamin Short, Harriet George and Mihailo Martinović","doi":"10.3847/2041-8213/ad8c38","DOIUrl":"https://doi.org/10.3847/2041-8213/ad8c38","url":null,"abstract":"Several long-standing theories postulate that turbulent dissipation can heat solar wind protons in situ. Turbulent dissipation can occur via current sheets, which are small-scale structures embedded in the solar wind magnetic field. This study examines the role that switchbacks—intermediate-scale reversals in the interplanetary magnetic field—may play in heating the solar wind by generating current sheets. We explore this possible relationship by analyzing the characteristics of current sheets within and around switchback regions. Previous studies investigated current sheet properties during Parker Solar Probe's first solar encounter, analyzed current sheets using a wide range of statistics, and explored trends that switchbacks follow with radial distance from the Sun. The present study builds on these works by analyzing the distribution and maximum values of solar wind current sheets using the Partial Variance of Increments method and focusing on how these properties correlate with the presence of switchbacks to better understand how switchbacks contribute to current sheet activity. We conclude that there are no increased current sheet populations observed within and around switchbacks, with most current sheets being observed outside switchbacks. We find a consistent distribution of current sheets regardless of whether there is concurrent switchback activity. We also observe that current sheets follow a uniform occurrence rate with increased distance from the Sun, while switchback regions significantly evolve with larger radial distances. Our findings suggest that local turbulence may be responsible for generating solar wind current sheets and does so with the same efficiency inside and outside of switchback regions.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142598496","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Predicting the Energy Spectra of Solar Energetic Particles with a Machine Learning Regression Algorithm","authors":"Jiajun Liu, Zhendi Huang, Jingnan Guo, Yubao Wang, Jiajia Liu","doi":"10.3847/2041-8213/ad8bbc","DOIUrl":"https://doi.org/10.3847/2041-8213/ad8bbc","url":null,"abstract":"Solar energetic particles (SEPs) are a major source of space radiation, especially within the inner heliosphere. These particles, originating from solar flares and coronal mass ejections (CMEs), propagate primarily along interplanetary magnetic fields. The energy spectra of SEP events are crucial for assessing radiation effects and understanding the acceleration and propagation mechanisms in their source regions. In this study, we employed a decision tree regression algorithm with cost complexity pruning to predict SEP energy spectra, including peak flux and integral fluence spectra. This approach uses only solar flares, CMEs, and solar wind data as input parameters and demonstrates strong performance to accurately predict SEP spectra. This method holds significant real-time application value for monitoring and forecasting radiation risks in both deep space and near-Earth environments.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142597312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Detection of Very High-energy Gamma-Ray Emission from the Radio Galaxy M87 with LHAASO","authors":"Zhen Cao, F. Aharonian, Axikegu, Y. X. Bai, Y. W. Bao, D. Bastieri, X. J. Bi, Y. J. Bi, W. Bian, A. V. Bukevich, Q. Cao, W. Y. Cao, Zhe Cao, J. Chang, J. F. Chang, A. M. Chen, E. S. Chen, H. X. Chen, Liang Chen, Lin Chen, Long Chen, M. J. Chen, M. L. Chen, Q. H. Chen, S. Chen, S. H. Chen, S. Z. Chen, T. L. Chen, Y. Chen, N. Cheng, Y. D. Cheng, M. C. Chu, M. Y. Cui, S. W. Cui, X. H. Cui, Y. D. Cui, B. Z. Dai, H. L. Dai, Z. G. Dai, Danzengluobu, X. Q. Dong, K. K. Duan, J. H. Fan, Y. Z. Fan, J. Fang, J. H. Fang, K. Fang, C. F. Feng, H. Feng, L. Feng, S. H. Feng, X. T. Feng, Y. Feng, Y. L. Feng, S. Gabici, B. Gao, C. D. Gao, Q. Gao, W. Gao, W. K. Gao, M. M. Ge, T. T. Ge, L. S. Geng, G. Giacinti, G. H. Gong, Q. B. Gou, M. H. Gu, F. L. Guo, J. Guo, X. L. Guo, Y. Q. Guo, Y. Y. Guo, Y. A. Han, O. A. Hannuksela, M. Hasan, H. H. He, H. N. He, J. Y. He, Y. He, Y. K. Hor, B. W. Hou, C. Hou, X. Hou, H. B. Hu, Q. Hu, S. C. Hu, C. Huang, D. H. Huang, T. Q. Huang, W. J. Huang, X. T. Huang, X..","doi":"10.3847/2041-8213/ad8921","DOIUrl":"https://doi.org/10.3847/2041-8213/ad8921","url":null,"abstract":"The nearby radio galaxy M87 is a very high-energy (VHE) gamma-ray emitter established by observations with ground-based gamma-ray detectors. Here we report the long-term monitoring of M87 from 2021 to 2024 with the Large High Altitude Air Shower Observatory (LHAASO). M87 has been detected by LHAASO with a statistical significance ∼ 9σ. The observed energy spectrum extends to 20 TeV, with a possible hardening at ∼20 TeV and then a clear softening at higher energies. Assuming that the intrinsic spectrum is described by a single power law up to 20 TeV, a tight upper bound on the extragalactic background light intensity is obtained. A strong VHE flare lasting 8 days, with a rise time of days and decay time of days, was found in early 2022. A possible GeV flare is seen also in Fermi Large Area Telescope data during the VHE flare period. The variability time as short as 1 day seen in the LHAASO data suggests a compact emission region with a size of ∼3 × 1015δ cm (δ being the Doppler factor of the emitting region), corresponding to a few Schwarzschild radii of the central supermassive black hole in M87. The continuous monitoring of the source reveals a duty cycle of ∼1% for VHE flares with a flux above 10−11 erg cm−2 s−1.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142597310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Out of the Darkness: High-resolution Detection of CO Absorption on the Nightside of WASP-33b","authors":"Georgia Mraz, Antoine Darveau-Bernier, Anne Boucher, Nicolas B. Cowan, David Lafrenière, Charles Cadieux","doi":"10.3847/2041-8213/ad8438","DOIUrl":"https://doi.org/10.3847/2041-8213/ad8438","url":null,"abstract":"We observed the ultrahot Jupiter WASP-33b with the SpectroPolarimètre InfraRouge on the Canada–France–Hawaii Telescope. Previous observations of the dayside of WASP-33b show evidence of CO and Fe emission indicative of a thermal inversion. We observed its nightside over five Earth nights to search for spectral signatures of CO in the planet’s thermal emission. Our three pretransit observations and two posttransit observations are sensitive to regions near the morning or evening terminators, respectively. From spectral retrievals, we detect CO molecular absorption in the planet’s emission spectrum after transit at ∼6.6<italic toggle=\"yes\">σ</italic>. This is the strongest ground-based detection of nightside thermal emission from an exoplanet and only the third ever. CO appearing in absorption suggests that the nightside near the evening terminator does not have a temperature inversion; this makes sense if the dayside inversion is driven by absorption of stellar radiation. On the contrary, we do not detect CO from the morning terminator. This may be consistent with heat advection by an eastward jet. Phase-resolved high-resolution spectroscopy offers an economical alternative to space-based full-orbit spectroscopic phase curves for studying the vertical and horizontal atmospheric temperature profiles of short-period exoplanets.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142597313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Measuring Black Hole Light Echoes with Very Long Baseline Interferometry","authors":"George N. Wong, Lia Medeiros, Alejandro Cárdenas-Avendaño and James M. Stone","doi":"10.3847/2041-8213/ad8650","DOIUrl":"https://doi.org/10.3847/2041-8213/ad8650","url":null,"abstract":"Light passing near a black hole can follow multiple paths from an emission source to an observer due to strong gravitational lensing. Photons following different paths take different amounts of time to reach the observer, which produces an echo signature in the image. The characteristic echo delay is determined primarily by the mass of the black hole, but it is also influenced by the black hole spin and inclination to the observer. In the Kerr geometry, echo images are demagnified, rotated, and sheared copies of the direct image and lie within a restricted region of the image. Echo images have exponentially suppressed flux, and temporal correlations within the flow make it challenging to directly detect light echoes from the total light curve. In this Letter, we propose a novel method to search for light echoes by correlating the total light curve with the interferometric signal at high spatial frequencies, which is a proxy for indirect emission. We explore the viability of our method using numerical general relativistic magnetohydrodynamic simulations of a near-face-on accretion system scaled to M87-like parameters. We demonstrate that our method can be used to directly infer the echo delay period in simulated data. An echo detection would be clear evidence that we have captured photons that have circled the black hole, and a high-fidelity echo measurement would provide an independent measure of fundamental black hole parameters. Our results suggest that detecting echoes may be achievable through interferometric observations with a modest space-based very long baseline interferometry mission.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142594698","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}