Pub Date : 2025-02-21DOI: 10.3847/1538-4357/ada8a9
Michela Negro, Nicoló Cibrario, Eric Burns, Joshua Wood, Adam Goldstein and Tito Dal Canton
Gamma-ray bursts (GRBs) are one of the most energetic phenomena in the cosmos, whose study can probe physics extremes beyond the reach of laboratories on Earth. Our quest to unravel the origin of these events and understand their underlying physics is far from complete. Central to this pursuit is the rapid classification of GRBs to guide follow-up observations and analysis across the electromagnetic spectrum and beyond. Here, we introduce a compelling approach that can set a milestone toward a new and robust GRB prompt classification method. Leveraging self-supervised deep learning, we pioneer a previously unexplored data product to approach this task: GRB waterfalls.
{"title":"Prompt Gamma-Ray Burst Recognition through Waterfalls and Deep Learning","authors":"Michela Negro, Nicoló Cibrario, Eric Burns, Joshua Wood, Adam Goldstein and Tito Dal Canton","doi":"10.3847/1538-4357/ada8a9","DOIUrl":"https://doi.org/10.3847/1538-4357/ada8a9","url":null,"abstract":"Gamma-ray bursts (GRBs) are one of the most energetic phenomena in the cosmos, whose study can probe physics extremes beyond the reach of laboratories on Earth. Our quest to unravel the origin of these events and understand their underlying physics is far from complete. Central to this pursuit is the rapid classification of GRBs to guide follow-up observations and analysis across the electromagnetic spectrum and beyond. Here, we introduce a compelling approach that can set a milestone toward a new and robust GRB prompt classification method. Leveraging self-supervised deep learning, we pioneer a previously unexplored data product to approach this task: GRB waterfalls.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143462841","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}
Pub Date : 2025-02-21DOI: 10.3847/1538-4357/adabe1
Ying-Chi Hu, 英祈 胡, Chin-Fei Lee, 景輝 李, Zhe-Yu Daniel Lin, 哲宇 林, Zhi-Yun Li, John J. Tobin, Shih-Ping Lai and 詩萍 賴
Grain growth in disks around young stars plays a crucial role in the formation of planets. Early grain growth has been suggested in the HH 212 protostellar disk by previous polarization observations. To confirm it and to determine the grain size, we analyze high-resolution multiband observations of the disk obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) in bands 9 (0.4 mm), 7 (0.9 mm), 6 (1.3 mm), and 3 (3 mm), as well as with the Very Large Array (VLA) in band Ka (9 mm), and we present new VLA data in bands Q (7 mm), K (1.3 cm), and X (3 cm). We adopt a parameterized flared disk model to fit the continuum maps of the disk in these bands and derive the opacities, albedos, and opacity spectral index β of the dust in the disk, taking into account the dust scattering ignored in the previous work modeling the multiband data of this source. For the VLA bands, we only include the band Q data in our modeling to avoid free–free emission contamination. The obtained opacities, albedos, and opacity spectral index β (with a value of ∼1.2) suggest that the upper limit of maximum grain size in the disk should be ∼130 μm, consistent with that implied in the previous polarization observations in band 7, supporting the grain growth in this disk. The values of the absorption opacities further highlight the need for a new dust composition model for Class 0/I disks.
{"title":"Early Grain Growth in the Young Protostellar Disk HH 212 Supported by Dust Self-scattering Modeling","authors":"Ying-Chi Hu, 英祈 胡, Chin-Fei Lee, 景輝 李, Zhe-Yu Daniel Lin, 哲宇 林, Zhi-Yun Li, John J. Tobin, Shih-Ping Lai and 詩萍 賴","doi":"10.3847/1538-4357/adabe1","DOIUrl":"https://doi.org/10.3847/1538-4357/adabe1","url":null,"abstract":"Grain growth in disks around young stars plays a crucial role in the formation of planets. Early grain growth has been suggested in the HH 212 protostellar disk by previous polarization observations. To confirm it and to determine the grain size, we analyze high-resolution multiband observations of the disk obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) in bands 9 (0.4 mm), 7 (0.9 mm), 6 (1.3 mm), and 3 (3 mm), as well as with the Very Large Array (VLA) in band Ka (9 mm), and we present new VLA data in bands Q (7 mm), K (1.3 cm), and X (3 cm). We adopt a parameterized flared disk model to fit the continuum maps of the disk in these bands and derive the opacities, albedos, and opacity spectral index β of the dust in the disk, taking into account the dust scattering ignored in the previous work modeling the multiband data of this source. For the VLA bands, we only include the band Q data in our modeling to avoid free–free emission contamination. The obtained opacities, albedos, and opacity spectral index β (with a value of ∼1.2) suggest that the upper limit of maximum grain size in the disk should be ∼130 μm, consistent with that implied in the previous polarization observations in band 7, supporting the grain growth in this disk. The values of the absorption opacities further highlight the need for a new dust composition model for Class 0/I disks.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"81 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143462843","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}
Pub Date : 2025-02-21DOI: 10.3847/1538-4357/adaec0
Chuan Tian, 川 田, C. Megan Urry, Aritra Ghosh, Daisuke Nagai, Tonima T. Ananna, Meredith C. Powell, Connor Auge, Aayush Mishra, David B. Sanders, Nico Cappelluti and Kevin Schawinski
We present a composite machine learning framework to estimate posterior probability distributions of bulge-to-total light ratio, half-light radius, and flux for active galactic nucleus (AGN) host galaxies within z < 1.4 and m < 23 in the Hyper Supreme-Cam (HSC) Wide survey. We divide the data into five redshift bins: low (0 < z < 0.25), mid (0.25 < z < 0.5), high (0.5 < z < 0.9), extra (0.9 < z < 1.1), and extreme (1.1 < z < 1.4), and train our models independently in each bin. We use PSFGAN to decompose the AGN point-source light from its host galaxy, and invoke the Galaxy Morphology Posterior Estimation Network (GaMPEN) to estimate morphological parameters of the recovered host galaxy. We first trained our models on simulated data, and then fine-tuned our algorithm via transfer learning using labeled real data. To create training labels for transfer learning, we used GALFIT to fit ∼20,000 real HSC galaxies in each redshift bin. We comprehensively examined that the predicted values from our final models agree well with the GALFIT values for the vast majority of cases. Our PSFGAN + GaMPEN framework runs at least three orders of magnitude faster than traditional light-profile fitting methods, and can be easily retrained for other morphological parameters or on other data sets with diverse ranges of resolutions, seeing conditions, and signal-to-noise ratios, making it an ideal tool for analyzing AGN host galaxies from large surveys coming soon from the Rubin-LSST, Euclid, and Roman telescopes.
{"title":"Automatic Machine Learning Framework to Study Morphological Parameters of AGN Host Galaxies within z < 1.4 in the Hyper Supreme-Cam Wide Survey","authors":"Chuan Tian, 川 田, C. Megan Urry, Aritra Ghosh, Daisuke Nagai, Tonima T. Ananna, Meredith C. Powell, Connor Auge, Aayush Mishra, David B. Sanders, Nico Cappelluti and Kevin Schawinski","doi":"10.3847/1538-4357/adaec0","DOIUrl":"https://doi.org/10.3847/1538-4357/adaec0","url":null,"abstract":"We present a composite machine learning framework to estimate posterior probability distributions of bulge-to-total light ratio, half-light radius, and flux for active galactic nucleus (AGN) host galaxies within z < 1.4 and m < 23 in the Hyper Supreme-Cam (HSC) Wide survey. We divide the data into five redshift bins: low (0 < z < 0.25), mid (0.25 < z < 0.5), high (0.5 < z < 0.9), extra (0.9 < z < 1.1), and extreme (1.1 < z < 1.4), and train our models independently in each bin. We use PSFGAN to decompose the AGN point-source light from its host galaxy, and invoke the Galaxy Morphology Posterior Estimation Network (GaMPEN) to estimate morphological parameters of the recovered host galaxy. We first trained our models on simulated data, and then fine-tuned our algorithm via transfer learning using labeled real data. To create training labels for transfer learning, we used GALFIT to fit ∼20,000 real HSC galaxies in each redshift bin. We comprehensively examined that the predicted values from our final models agree well with the GALFIT values for the vast majority of cases. Our PSFGAN + GaMPEN framework runs at least three orders of magnitude faster than traditional light-profile fitting methods, and can be easily retrained for other morphological parameters or on other data sets with diverse ranges of resolutions, seeing conditions, and signal-to-noise ratios, making it an ideal tool for analyzing AGN host galaxies from large surveys coming soon from the Rubin-LSST, Euclid, and Roman telescopes.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"81 1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143462850","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}
Pub Date : 2025-02-21DOI: 10.3847/1538-4357/adadf7
G. D. Muro, C. M. S. Cohen, Z. Xu, R. A. Leske, E. R. Christian, A. C. Cummings, G. De Nolfo, M. I. Desai, F. Fraschetti, J. Giacalone, A. Labrador, D. J. McComas, J. G. Mitchell, D. G. Mitchell, J. Rankin, N. A. Schwadron, M. Shen, M. E. Wiedenbeck, S. D. Bale, O. Romeo and A. Vourlidas
In the latter moments of 2023 July 17, the solar active region (AR) 13363, near the southwestern face of the Sun, was undergoing considerable evolution, which resulted in a significant solar energetic particle (SEP) event measured by Parker Solar Probe’s Integrated Science Investigation of the Sun (IS⊙IS) and near-Earth spacecraft. Remote observations from GOES and CHASE captured two M5.0+ solar flares that peaked at 23:34 and 00:06 UT from the source region. In tandem, STEREO COR2 first recorded a small, narrow coronal mass ejection (CME) emerging at 22:54 UT and then saw a major halo CME emerge at 23:43 UT with a bright, rapidly expanding core and CME-driven magnetic shock with an estimated speed of ∼1400 km s−1. Parker Solar Probe was positioned at 0.65 au, near-perfectly on the nominal Parker spiral magnetic field line, which connected Earth and the AR for a 537 km s−1 ambient solar wind speed at L1. This fortuitous alignment provided the opportunity to examine how the SEP velocity dispersion, energy spectra, elemental composition, and fluence varied from 0.65 to 1 au along a shared magnetic connection to the Sun. We find a strong radial gradient, which is best characterized for H and He as r−4.0, and most surprisingly, is stronger for O and Fe, which is better described by r−5.7.
{"title":"Radial Dependence of Ion Fluences in the 2023 July 17 Solar Energetic Particle Event from Parker Solar Probe to STEREO and ACE","authors":"G. D. Muro, C. M. S. Cohen, Z. Xu, R. A. Leske, E. R. Christian, A. C. Cummings, G. De Nolfo, M. I. Desai, F. Fraschetti, J. Giacalone, A. Labrador, D. J. McComas, J. G. Mitchell, D. G. Mitchell, J. Rankin, N. A. Schwadron, M. Shen, M. E. Wiedenbeck, S. D. Bale, O. Romeo and A. Vourlidas","doi":"10.3847/1538-4357/adadf7","DOIUrl":"https://doi.org/10.3847/1538-4357/adadf7","url":null,"abstract":"In the latter moments of 2023 July 17, the solar active region (AR) 13363, near the southwestern face of the Sun, was undergoing considerable evolution, which resulted in a significant solar energetic particle (SEP) event measured by Parker Solar Probe’s Integrated Science Investigation of the Sun (IS⊙IS) and near-Earth spacecraft. Remote observations from GOES and CHASE captured two M5.0+ solar flares that peaked at 23:34 and 00:06 UT from the source region. In tandem, STEREO COR2 first recorded a small, narrow coronal mass ejection (CME) emerging at 22:54 UT and then saw a major halo CME emerge at 23:43 UT with a bright, rapidly expanding core and CME-driven magnetic shock with an estimated speed of ∼1400 km s−1. Parker Solar Probe was positioned at 0.65 au, near-perfectly on the nominal Parker spiral magnetic field line, which connected Earth and the AR for a 537 km s−1 ambient solar wind speed at L1. This fortuitous alignment provided the opportunity to examine how the SEP velocity dispersion, energy spectra, elemental composition, and fluence varied from 0.65 to 1 au along a shared magnetic connection to the Sun. We find a strong radial gradient, which is best characterized for H and He as r−4.0, and most surprisingly, is stronger for O and Fe, which is better described by r−5.7.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143462848","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}
Pub Date : 2025-02-21DOI: 10.3847/1538-4357/adabc6
Sai Swagat Mishra, N. S. Kavya, P. K. Sahoo and V. Venkatesha
The H0 and S8 tensions highlight critical discrepancies in modern cosmology, challenging the standard Lambda cold dark matter model. The H0 tension arises from conflicting measurements between local probes and early-Universe predictions. Similarly, the S8 tension, related to the amplitude of matter clustering, exposes inconsistencies between cosmic microwave background data and weak gravitational lensing surveys. The primary goal of this work is to address these tensions by modifying the underlying geometric framework. Specifically, we test two f(T) gravity models using cosmic chronometers, baryonic acoustic oscillations, gamma-ray bursts, and Pantheon+SH0ES data sets and compare the results with gravitational-wave data for validation. Both teleparallel models demonstrate promising performance in simultaneously alleviating the H0 and S8 tensions.
{"title":"Impact of Teleparallelism on Addressing Current Tensions and Exploring the GW Cosmology","authors":"Sai Swagat Mishra, N. S. Kavya, P. K. Sahoo and V. Venkatesha","doi":"10.3847/1538-4357/adabc6","DOIUrl":"https://doi.org/10.3847/1538-4357/adabc6","url":null,"abstract":"The H0 and S8 tensions highlight critical discrepancies in modern cosmology, challenging the standard Lambda cold dark matter model. The H0 tension arises from conflicting measurements between local probes and early-Universe predictions. Similarly, the S8 tension, related to the amplitude of matter clustering, exposes inconsistencies between cosmic microwave background data and weak gravitational lensing surveys. The primary goal of this work is to address these tensions by modifying the underlying geometric framework. Specifically, we test two f(T) gravity models using cosmic chronometers, baryonic acoustic oscillations, gamma-ray bursts, and Pantheon+SH0ES data sets and compare the results with gravitational-wave data for validation. Both teleparallel models demonstrate promising performance in simultaneously alleviating the H0 and S8 tensions.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"127 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143462842","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}
Pub Date : 2025-02-21DOI: 10.3847/1538-4357/adac60
Gerald H. Share, Ronald J. Murphy, Brian R. Dennis and Justin D. Finke
Significant improvements in our understanding of nuclear γ-ray line production and instrument performance allow us to better characterize the continuum emission from electrons at energies ≳300 keV during solar flares. We represent this emission by the sum of a power-law (PL) extension of hard X-rays and a power law times an exponential function (PLexp). We fit the γ-ray spectra in 25 large flares observed over 40 yr with this continuum and the calculated spectra of all known nuclear components. The PLexp is separated spectroscopically from the other components, and its presence is required with >99% confidence in 18 of the flares. Its distinct origin is suggested by significant differences between its time histories and those of the PL and nuclear components in 18 of the flares. RHESSI imaging/spectroscopy of the 2005 January 20 flare reveals that the PL and nuclear components come from the footpoints, while the PLexp component comes from the corona. While the index and flux of the anisotropic PL component are dependent on the flare’s heliocentric angle, the PLexp parameters do not show comparable dependences with 99.5% confidence. The PLexp spectrum is flat at low energies and rolls over at a few megaelectronvolts (MeV). Such a shape can be produced by thin-target bremsstrahlung from electrons with a spectrum that peaks between 3 and 5 MeV and by inverse Compton scattering of soft X-rays by 10–20 MeV electrons, or by a combination of the two. These electrons can produce radiation detectable at other wavelengths.
{"title":"Solar Gamma-Ray Evidence for a Distinct Population of >1 MeV Flare-accelerated Electrons","authors":"Gerald H. Share, Ronald J. Murphy, Brian R. Dennis and Justin D. Finke","doi":"10.3847/1538-4357/adac60","DOIUrl":"https://doi.org/10.3847/1538-4357/adac60","url":null,"abstract":"Significant improvements in our understanding of nuclear γ-ray line production and instrument performance allow us to better characterize the continuum emission from electrons at energies ≳300 keV during solar flares. We represent this emission by the sum of a power-law (PL) extension of hard X-rays and a power law times an exponential function (PLexp). We fit the γ-ray spectra in 25 large flares observed over 40 yr with this continuum and the calculated spectra of all known nuclear components. The PLexp is separated spectroscopically from the other components, and its presence is required with >99% confidence in 18 of the flares. Its distinct origin is suggested by significant differences between its time histories and those of the PL and nuclear components in 18 of the flares. RHESSI imaging/spectroscopy of the 2005 January 20 flare reveals that the PL and nuclear components come from the footpoints, while the PLexp component comes from the corona. While the index and flux of the anisotropic PL component are dependent on the flare’s heliocentric angle, the PLexp parameters do not show comparable dependences with 99.5% confidence. The PLexp spectrum is flat at low energies and rolls over at a few megaelectronvolts (MeV). Such a shape can be produced by thin-target bremsstrahlung from electrons with a spectrum that peaks between 3 and 5 MeV and by inverse Compton scattering of soft X-rays by 10–20 MeV electrons, or by a combination of the two. These electrons can produce radiation detectable at other wavelengths.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"50 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143462844","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}
Pub Date : 2025-02-21DOI: 10.3847/1538-4357/adae90
Yunlu Gong, Liancheng Zhou, Qi Xia, Haiyun Zhang, Jun Fang and Li Zhang
The pulsar wind nebula CTB 87 (G74.9+1.2) is one of the sources emitting γ-rays with energies higher than 10 TeV, as measured by the Very Energetic Radiation Imaging Telescope Array System telescope. In this study, we undertake a reanalysis of the GeV emission from the CTB 87 region, utilizing ∼16 yr of high-energy γ-ray data collected with the Fermi Large Area Telescope. In the energy range of 0.03–1 TeV, the spectrum can be adequately described by a power-law model with an index of 1.34 ± 0.18, and the integral energy flux is calculated to be (7.25 ± 1.36) × 10−13 erg cm−2 s−1. Based on the multiband data, we have employed a time-dependent model to investigate the nonthermal emission properties of CTB 87. In the model, it is assumed that particles with broken power-law energy distributions are continuously injected into the nebula. This results in multiband nonthermal emission being produced by relativistic leptons via synchrotron radiation and inverse Compton processes. Furthermore, the model suggests an energy of approximately 2.4 PeV for the most energetic particle in the nebula.
{"title":"Multiband Nonthermal Radiative Properties of the Pulsar Wind Nebula CTB 87","authors":"Yunlu Gong, Liancheng Zhou, Qi Xia, Haiyun Zhang, Jun Fang and Li Zhang","doi":"10.3847/1538-4357/adae90","DOIUrl":"https://doi.org/10.3847/1538-4357/adae90","url":null,"abstract":"The pulsar wind nebula CTB 87 (G74.9+1.2) is one of the sources emitting γ-rays with energies higher than 10 TeV, as measured by the Very Energetic Radiation Imaging Telescope Array System telescope. In this study, we undertake a reanalysis of the GeV emission from the CTB 87 region, utilizing ∼16 yr of high-energy γ-ray data collected with the Fermi Large Area Telescope. In the energy range of 0.03–1 TeV, the spectrum can be adequately described by a power-law model with an index of 1.34 ± 0.18, and the integral energy flux is calculated to be (7.25 ± 1.36) × 10−13 erg cm−2 s−1. Based on the multiband data, we have employed a time-dependent model to investigate the nonthermal emission properties of CTB 87. In the model, it is assumed that particles with broken power-law energy distributions are continuously injected into the nebula. This results in multiband nonthermal emission being produced by relativistic leptons via synchrotron radiation and inverse Compton processes. Furthermore, the model suggests an energy of approximately 2.4 PeV for the most energetic particle in the nebula.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"65 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143462846","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}
Pub Date : 2025-02-21DOI: 10.3847/1538-4357/ada774
Jin Qin, Hua Feng and Lian Tao
The short-term X-ray variability of Cyg X-1 can be interpreted as a random occurrence of mini-flares known as the shots, whose physical nature is still unclear. We propose a new algorithm for shot identification in the X-ray light curve, based on baseline detection and template fitting. Compared with previous techniques, our algorithm allows us to detect shots with lower amplitudes and shorter time separations. With NICER observations, we find that, after correction for detection sensitivity, both the shot amplitude and recurrence rate are positively scaled with the mean count rate, while the recurrence rate has a much higher dependence on the count rate. These suggest that a higher mass accretion rate will drive more and slightly larger shots. We also find that the abrupt hardening near the shot peak found in previous studies is attributed to different shot profiles in different energy bands; there is no need to involve a rapid physical process to suddenly harden the emitting spectrum.
{"title":"A New Algorithm for Detecting X-Ray Shots in Cyg X-1","authors":"Jin Qin, Hua Feng and Lian Tao","doi":"10.3847/1538-4357/ada774","DOIUrl":"https://doi.org/10.3847/1538-4357/ada774","url":null,"abstract":"The short-term X-ray variability of Cyg X-1 can be interpreted as a random occurrence of mini-flares known as the shots, whose physical nature is still unclear. We propose a new algorithm for shot identification in the X-ray light curve, based on baseline detection and template fitting. Compared with previous techniques, our algorithm allows us to detect shots with lower amplitudes and shorter time separations. With NICER observations, we find that, after correction for detection sensitivity, both the shot amplitude and recurrence rate are positively scaled with the mean count rate, while the recurrence rate has a much higher dependence on the count rate. These suggest that a higher mass accretion rate will drive more and slightly larger shots. We also find that the abrupt hardening near the shot peak found in previous studies is attributed to different shot profiles in different energy bands; there is no need to involve a rapid physical process to suddenly harden the emitting spectrum.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"50 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143462839","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}
Pub Date : 2025-02-21DOI: 10.3847/1538-4357/adb0cb
Evelyn Macdonald, Kristen Menou, Christopher Lee and Adiv Paradise
Our recent work shows how M-Earth climates and transmission spectra depend on the amount of ice-free ocean on the planet’s dayside and the mass of N2 in its atmosphere. M-Earths with more ice-free ocean and thicker atmospheres are hotter and more humid and have larger water vapor features in their transmission spectra. In this paper, we describe a climate transition in high-pN2 simulations from the traditional “eyeball” M-Earth climate, in which only the substellar region is temperate, to a “temperate nightside” regime, in which both the dayside and the nightside are entirely ice-free. Between these two states, there is a “transition” regime with partial nightside ice cover. We use 3D climate simulations to describe the climate transition from frozen to deglaciated nightsides. We attribute this transition to increased advection and heat transport by water vapor in thicker atmospheres. We find that the nightside transitions smoothly back and forth between frozen and ice-free when the instellation or pCO2 is perturbed, with no hysteresis. We also find an analogous transition in colder planets: those with thin atmospheres can have a dayside hot spot when the instellation is low, whereas those with more massive atmospheres are more likely to be in the “snowball” regime, featuring a completely frozen dayside, due to the increased advection of heat away from the substellar point. We show how both of these climate transitions are sensitive to instellation, land cover, and atmosphere mass. We generate synthetic transmission spectra and phase curves for the range of climates in our simulations.
{"title":"Climate Transition to Temperate Nightside at High Atmosphere Mass","authors":"Evelyn Macdonald, Kristen Menou, Christopher Lee and Adiv Paradise","doi":"10.3847/1538-4357/adb0cb","DOIUrl":"https://doi.org/10.3847/1538-4357/adb0cb","url":null,"abstract":"Our recent work shows how M-Earth climates and transmission spectra depend on the amount of ice-free ocean on the planet’s dayside and the mass of N2 in its atmosphere. M-Earths with more ice-free ocean and thicker atmospheres are hotter and more humid and have larger water vapor features in their transmission spectra. In this paper, we describe a climate transition in high-pN2 simulations from the traditional “eyeball” M-Earth climate, in which only the substellar region is temperate, to a “temperate nightside” regime, in which both the dayside and the nightside are entirely ice-free. Between these two states, there is a “transition” regime with partial nightside ice cover. We use 3D climate simulations to describe the climate transition from frozen to deglaciated nightsides. We attribute this transition to increased advection and heat transport by water vapor in thicker atmospheres. We find that the nightside transitions smoothly back and forth between frozen and ice-free when the instellation or pCO2 is perturbed, with no hysteresis. We also find an analogous transition in colder planets: those with thin atmospheres can have a dayside hot spot when the instellation is low, whereas those with more massive atmospheres are more likely to be in the “snowball” regime, featuring a completely frozen dayside, due to the increased advection of heat away from the substellar point. We show how both of these climate transitions are sensitive to instellation, land cover, and atmosphere mass. We generate synthetic transmission spectra and phase curves for the range of climates in our simulations.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143462852","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}
Pub Date : 2025-02-21DOI: 10.3847/1538-4357/ada603
Junyao Li, John D. Silverman, Yue Shen, Marta Volonteri, Knud Jahnke, Ming-Yang Zhuang, Matthew T. Scoggins, Xuheng Ding, Yuichi Harikane, Masafusa Onoue and Takumi S. Tanaka
JWST is revealing a remarkable new population of high-redshift (z ≳ 4), low-luminosity active galactic nuclei in deep surveys and detecting the host galaxy's stellar light in the most luminous and massive quasars at z ∼ 6 for the first time. Recent findings claim that supermassive black holes (SMBHs) in these systems are significantly more massive than predicted by the local black hole (BH) mass–stellar mass ( ) relation and that this is not due to sample selection effects. Through detailed statistical modeling, we demonstrate that the coupled effects of selection biases (i.e., finite detection limit and requirements for detecting broad lines) and measurement uncertainties can largely explain the reported offset and flattening in the observed relation toward the upper envelope of the local relation, even for those at . We further investigate the possible evolution of the relation at z ≳ 4 with careful treatment of observational biases and consideration of the degeneracy between intrinsic evolution and dispersion in this relation. The bias-corrected intrinsic relation in the low-mass regime ( ) suggests a large population of low-mass BHs ( ), possibly originating from lighter seeds, may remain undetected or unidentified. These results underscore the importance of forward modeling observational biases to better understand BH seeding and SMBH–galaxy coevolution mechanisms in the early universe, even with the deepest JWST surveys.
{"title":"Tip of the Iceberg: Overmassive Black Holes at 4 < z < 7 Found by JWST Are Not Inconsistent with the Local M BH ...","authors":"Junyao Li, John D. Silverman, Yue Shen, Marta Volonteri, Knud Jahnke, Ming-Yang Zhuang, Matthew T. Scoggins, Xuheng Ding, Yuichi Harikane, Masafusa Onoue and Takumi S. Tanaka","doi":"10.3847/1538-4357/ada603","DOIUrl":"https://doi.org/10.3847/1538-4357/ada603","url":null,"abstract":"JWST is revealing a remarkable new population of high-redshift (z ≳ 4), low-luminosity active galactic nuclei in deep surveys and detecting the host galaxy's stellar light in the most luminous and massive quasars at z ∼ 6 for the first time. Recent findings claim that supermassive black holes (SMBHs) in these systems are significantly more massive than predicted by the local black hole (BH) mass–stellar mass ( ) relation and that this is not due to sample selection effects. Through detailed statistical modeling, we demonstrate that the coupled effects of selection biases (i.e., finite detection limit and requirements for detecting broad lines) and measurement uncertainties can largely explain the reported offset and flattening in the observed relation toward the upper envelope of the local relation, even for those at . We further investigate the possible evolution of the relation at z ≳ 4 with careful treatment of observational biases and consideration of the degeneracy between intrinsic evolution and dispersion in this relation. The bias-corrected intrinsic relation in the low-mass regime ( ) suggests a large population of low-mass BHs ( ), possibly originating from lighter seeds, may remain undetected or unidentified. These results underscore the importance of forward modeling observational biases to better understand BH seeding and SMBH–galaxy coevolution mechanisms in the early universe, even with the deepest JWST surveys.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143462835","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}
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