Pub Date : 2023-11-01DOI: 10.3847/1538-4357/acfc21
Qirong Jiao, Wenlong Liu, Dianjun Zhang, Jinbin Cao
Abstract Solar wind is important for the space environment between the Sun and the Earth and varies with the sunspot cycle, which is influenced by solar internal dynamics. We study the impact of latitude-dependent sunspot data on solar wind speed using the Granger causality test method and a machine-learning prediction approach. The results show that the low-latitude sunspot number has a larger effect on the solar wind speed. The time delay between the annual average solar wind speed and sunspot number decreases as the latitude range decreases. A machine-learning model is developed for the prediction of solar wind speed considering latitude and time effects. It is found that the model performs differently with latitude-dependent sunspot data. It is revealed that the timescale of the solar wind speed is more strongly influenced by low-latitude sunspots and that sunspot data have a greater impact on the 30 day average solar wind speed than on a daily basis. With the addition of sunspot data below 7.°2 latitude, the prediction of the daily and 30 day averages is improved by 0.23% and 12%, respectively. The best correlation coefficient is 0.787 for the daily solar wind prediction model.
{"title":"Relation between Latitude-dependent Sunspot Data and Near-Earth Solar Wind Speed","authors":"Qirong Jiao, Wenlong Liu, Dianjun Zhang, Jinbin Cao","doi":"10.3847/1538-4357/acfc21","DOIUrl":"https://doi.org/10.3847/1538-4357/acfc21","url":null,"abstract":"Abstract Solar wind is important for the space environment between the Sun and the Earth and varies with the sunspot cycle, which is influenced by solar internal dynamics. We study the impact of latitude-dependent sunspot data on solar wind speed using the Granger causality test method and a machine-learning prediction approach. The results show that the low-latitude sunspot number has a larger effect on the solar wind speed. The time delay between the annual average solar wind speed and sunspot number decreases as the latitude range decreases. A machine-learning model is developed for the prediction of solar wind speed considering latitude and time effects. It is found that the model performs differently with latitude-dependent sunspot data. It is revealed that the timescale of the solar wind speed is more strongly influenced by low-latitude sunspots and that sunspot data have a greater impact on the 30 day average solar wind speed than on a daily basis. With the addition of sunspot data below 7.°2 latitude, the prediction of the daily and 30 day averages is improved by 0.23% and 12%, respectively. The best correlation coefficient is 0.787 for the daily solar wind prediction model.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"19 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135765575","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2023-11-01DOI: 10.3847/1538-4357/acfa00
Salmoli Ghosh, P. Kharb, J. Baghel, S. Silpa
Abstract We present the polarization image of the hybrid morphology and broad absorption line quasar PG 1004+130 at 694 MHz obtained with the upgraded Giant Metrewave Radio Telescope. We detect linear polarization in this source’s core, jets, and lobes. The visible discontinuity in total intensity between the inner jets and the kiloparsec-scale lobes suggests that the source is restarted. The inferred poloidal magnetic ( B -) field structure in the inner jet is consistent with that observed in Fanaroff–Riley (FR) type II sources, as are the B -fields aligned with the lobe edges. Moreover, archival Chandra and XMM-Newton data indicate that PG 1004+130 displays several FRII-jetlike properties in X-rays. We conclude that PG 1004+130 is a restarted quasar, with both episodes of activity being FRII type. The spectral index images show the presence of an inverted spectrum core ( α = +0.30 ± 0.01) and a steep spectrum inner jet ( α = −0.62 ± 0.06) surrounded by much steeper lobe emission ( α ≈ −1.2 ± 0.1), consistent with the suggestion that the lobes are from a previous activity episode. The spectral age difference between the two activity episodes is likely to be small (<1.2 × 10 7 yr), in comparison to the lobe ages (∼3.3 × 10 7 yr). The inferred B -fields in the lobes are suggestive of turbulence and the mixing of plasma. This may account for the absence of X-ray cavities around this source, similar to what is observed in M87's radio halo region. The depolarization models reveal that thermal gas of mass ∼(2.4 ± 0.9) × 10 9 M ⊙ is mixed with the nonthermal plasma in the lobes of PG 1004+130.
{"title":"PG 1004+130: Hybrid Morphology Source or a Restarted FRII? A uGMRT Polarimetric Investigation","authors":"Salmoli Ghosh, P. Kharb, J. Baghel, S. Silpa","doi":"10.3847/1538-4357/acfa00","DOIUrl":"https://doi.org/10.3847/1538-4357/acfa00","url":null,"abstract":"Abstract We present the polarization image of the hybrid morphology and broad absorption line quasar PG 1004+130 at 694 MHz obtained with the upgraded Giant Metrewave Radio Telescope. We detect linear polarization in this source’s core, jets, and lobes. The visible discontinuity in total intensity between the inner jets and the kiloparsec-scale lobes suggests that the source is restarted. The inferred poloidal magnetic ( B -) field structure in the inner jet is consistent with that observed in Fanaroff–Riley (FR) type II sources, as are the B -fields aligned with the lobe edges. Moreover, archival Chandra and XMM-Newton data indicate that PG 1004+130 displays several FRII-jetlike properties in X-rays. We conclude that PG 1004+130 is a restarted quasar, with both episodes of activity being FRII type. The spectral index images show the presence of an inverted spectrum core ( α = +0.30 ± 0.01) and a steep spectrum inner jet ( α = −0.62 ± 0.06) surrounded by much steeper lobe emission ( α ≈ −1.2 ± 0.1), consistent with the suggestion that the lobes are from a previous activity episode. The spectral age difference between the two activity episodes is likely to be small (<1.2 × 10 7 yr), in comparison to the lobe ages (∼3.3 × 10 7 yr). The inferred B -fields in the lobes are suggestive of turbulence and the mixing of plasma. This may account for the absence of X-ray cavities around this source, similar to what is observed in M87's radio halo region. The depolarization models reveal that thermal gas of mass ∼(2.4 ± 0.9) × 10 9 M ⊙ is mixed with the nonthermal plasma in the lobes of PG 1004+130.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"18 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135765580","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2023-11-01DOI: 10.3847/1538-4357/ad0374
Ryoji Iwashita, Jun Kataoka, Yoshiaki Sofue
Abstract The North Polar Spur (NPS) is a giant structure that is clearly visible in both radio and X-ray all-sky maps. We analyzed broadband radio observations covering a range between 22 MHz and 70 GHz to systematically analyze the thermal/nonthermal emissions associated with the NPS. We demonstrate that the radio emission of the NPS comprises synchrotron, free–free, and dust emission; however, synchrotron emissions dominate over other emissions, especially at high Galactic latitudes. Moreover, the synchrotron spectra exhibit a power-law behavior with N ( γ ) ∝ γ − s ( s ≃ 1.8–2.4) up to a few GHz moderated by a turnover at ν brk ≃ 1 GHz, above which the spectral index s decreases by one. Assuming that the turnover is due to the electrons being cooled by synchrotron radiation before escaping (or advecting) from the emission region, the magnetic field strength can be estimated to be B ∼ 8 μ G if the NPS is a distant structure that is near the Galactic center (GC). However, an unreasonably strong B ∼ 114 μ G is required if the NPS is near the local supernova remnant (SNR). The corresponding nonthermal energy stored in the NPS is E n/th ≃ 4.4 × 10 55 erg in the GC scenario, whereas E n/th ≃ 4.1 × 10 52 erg is difficult to explain with a single local SNR. We also estimated the gamma-ray emission associated with the NPS through inverse Comptonization of the cosmic microwave background, which peaks at 100–1000 keV with a flux of ν F ν ∼ 10 −9 erg cm −2 s −1 sr −1 in the GC model, and may be a good candidate for detection by future X-ray/gamma-ray observatories.
{"title":"Broadband Radio Study of the North Polar Spur: Origin of the Spectral Turnover with Insights into the X-Ray and Gamma-Ray Spectra","authors":"Ryoji Iwashita, Jun Kataoka, Yoshiaki Sofue","doi":"10.3847/1538-4357/ad0374","DOIUrl":"https://doi.org/10.3847/1538-4357/ad0374","url":null,"abstract":"Abstract The North Polar Spur (NPS) is a giant structure that is clearly visible in both radio and X-ray all-sky maps. We analyzed broadband radio observations covering a range between 22 MHz and 70 GHz to systematically analyze the thermal/nonthermal emissions associated with the NPS. We demonstrate that the radio emission of the NPS comprises synchrotron, free–free, and dust emission; however, synchrotron emissions dominate over other emissions, especially at high Galactic latitudes. Moreover, the synchrotron spectra exhibit a power-law behavior with N ( γ ) ∝ γ − s ( s ≃ 1.8–2.4) up to a few GHz moderated by a turnover at ν brk ≃ 1 GHz, above which the spectral index s decreases by one. Assuming that the turnover is due to the electrons being cooled by synchrotron radiation before escaping (or advecting) from the emission region, the magnetic field strength can be estimated to be B ∼ 8 μ G if the NPS is a distant structure that is near the Galactic center (GC). However, an unreasonably strong B ∼ 114 μ G is required if the NPS is near the local supernova remnant (SNR). The corresponding nonthermal energy stored in the NPS is E n/th ≃ 4.4 × 10 55 erg in the GC scenario, whereas E n/th ≃ 4.1 × 10 52 erg is difficult to explain with a single local SNR. We also estimated the gamma-ray emission associated with the NPS through inverse Comptonization of the cosmic microwave background, which peaks at 100–1000 keV with a flux of ν F ν ∼ 10 −9 erg cm −2 s −1 sr −1 in the GC model, and may be a good candidate for detection by future X-ray/gamma-ray observatories.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"26 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135765726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2023-11-01DOI: 10.3847/1538-4357/acfa96
Carlos Allende Prieto, David S. Aguado, Jonay I. González Hernández, Rafael Rebolo, Joan Najita, Christopher J. Manser, Constance Rockosi, Zachary Slepian, Mar Mezcua, Monica Valluri, Rana Ezzeddine, Sergey E. Koposov, Andrew P. Cooper, Arjun Dey, Boris T. Gänsicke, Ting S. Li, Katia Cunha, Siwei Zou, Jessica Nicole Aguilar, Steven Ahlen, David Brooks, Todd Claybaugh, Shaun Cole, Sarah Eftekharzadeh, Kevin Fanning, Jaime Forero-Romero, Satya Gontcho A Gontcho, Klaus Honscheid, Pascale Jablonka, Robert Kehoe, Theodore Kisner, Martin Landriau, Axel de la Macorra, Aaron Meisner, Ramón Miquel, John Moustakas, Jundan Nie, Claire Poppett, Francisco Prada, Mehdi Rezaie, Graziano Rossi, Eusebio Sánchez, Michael Schubnell, Ray Sharples, Malgorzata Siudek, Verne V. Smith, Gregory Tarlé, Fiorenzo Vincenzo, Benjamin Alan Weaver, Zhimin Zhou, Hu Zou
Abstract The observations from the Dark Energy Spectroscopic Instrument (DESI) will significantly increase the numbers of known extremely metal-poor stars by a factor of ∼10, improving the sample statistics to study the early chemical evolution of the Milky Way and the nature of the first stars. In this paper we report follow-up observations with high signal-to-noise ratio of nine metal-poor stars identified during the DESI commissioning with the Optical System for Imaging and Low-Resolution Integrated Spectroscopy (OSIRIS) instrument on the 10.4 m Gran Telescopio Canarias. The analysis of the data using a well-vetted methodology confirms the quality of the DESI spectra and the performance of the pipelines developed for the data reduction and analysis of DESI data.
{"title":"GTC Follow-up Observations of Very Metal-poor Star Candidates from DESI","authors":"Carlos Allende Prieto, David S. Aguado, Jonay I. González Hernández, Rafael Rebolo, Joan Najita, Christopher J. Manser, Constance Rockosi, Zachary Slepian, Mar Mezcua, Monica Valluri, Rana Ezzeddine, Sergey E. Koposov, Andrew P. Cooper, Arjun Dey, Boris T. Gänsicke, Ting S. Li, Katia Cunha, Siwei Zou, Jessica Nicole Aguilar, Steven Ahlen, David Brooks, Todd Claybaugh, Shaun Cole, Sarah Eftekharzadeh, Kevin Fanning, Jaime Forero-Romero, Satya Gontcho A Gontcho, Klaus Honscheid, Pascale Jablonka, Robert Kehoe, Theodore Kisner, Martin Landriau, Axel de la Macorra, Aaron Meisner, Ramón Miquel, John Moustakas, Jundan Nie, Claire Poppett, Francisco Prada, Mehdi Rezaie, Graziano Rossi, Eusebio Sánchez, Michael Schubnell, Ray Sharples, Malgorzata Siudek, Verne V. Smith, Gregory Tarlé, Fiorenzo Vincenzo, Benjamin Alan Weaver, Zhimin Zhou, Hu Zou","doi":"10.3847/1538-4357/acfa96","DOIUrl":"https://doi.org/10.3847/1538-4357/acfa96","url":null,"abstract":"Abstract The observations from the Dark Energy Spectroscopic Instrument (DESI) will significantly increase the numbers of known extremely metal-poor stars by a factor of ∼10, improving the sample statistics to study the early chemical evolution of the Milky Way and the nature of the first stars. In this paper we report follow-up observations with high signal-to-noise ratio of nine metal-poor stars identified during the DESI commissioning with the Optical System for Imaging and Low-Resolution Integrated Spectroscopy (OSIRIS) instrument on the 10.4 m Gran Telescopio Canarias. The analysis of the data using a well-vetted methodology confirms the quality of the DESI spectra and the performance of the pipelines developed for the data reduction and analysis of DESI data.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"43 9-10","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135272742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Abstract We develop a novel approach to measure the dust attenuation properties of galaxies, including the dust opacity, the shape of the attenuation curve, and the strength of the 2175 Å absorption feature. From an observed spectrum, the method uses a model-independent approach to derive a relative attenuation curve with an absolute amplitude calibrated using NIR photometry. The dust-corrected spectrum is fitted with stellar population models to derive the dust-free model spectrum, which is compared with the observed SED/spectrum from NUV to NIR to determine the dust attenuation properties. We apply this method to investigate dust attenuation on kiloparsec scales using a sample of 134 galaxies with integral field spectroscopy from MaNGA, NIR imaging from 2MASS, and NUV imaging from Swift/UVOT. We find that the attenuation curve slope and the 2175 Å bump in both the optical and NUV span a wide range at kiloparsec scales. The slope is shallower at higher optical opacity, regardless of the specific star formation rate (sSFR), the minor-to-major axis ratio ( b / a ) of the galaxies, and the location of spaxels within individual galaxies. The 2175 Å bump presents a strong negative correlation with the sSFR, while the correlations with the optical opacity, b / a , and the locations within individual galaxies are all weak. All of these trends appear to be independent of the stellar mass of the galaxies. Our results support the scenario that the variation of the 2175 Å bump is driven predominantly by processes related to star formation, such as the destruction of small dust grains by UV radiation in star-forming regions.
{"title":"Mapping Dust Attenuation and the 2175 Å Bump at Kiloparsec Scales in Nearby Galaxies","authors":"Shuang Zhou, Cheng Li, Niu Li, Houjun Mo, Renbin Yan, Michael Eracleous, Mallory Molina, Caryl Gronwall, Nikhil Ajgaonkar, Zhuo Cheng, Ruonan Guo","doi":"10.3847/1538-4357/acfb80","DOIUrl":"https://doi.org/10.3847/1538-4357/acfb80","url":null,"abstract":"Abstract We develop a novel approach to measure the dust attenuation properties of galaxies, including the dust opacity, the shape of the attenuation curve, and the strength of the 2175 Å absorption feature. From an observed spectrum, the method uses a model-independent approach to derive a relative attenuation curve with an absolute amplitude calibrated using NIR photometry. The dust-corrected spectrum is fitted with stellar population models to derive the dust-free model spectrum, which is compared with the observed SED/spectrum from NUV to NIR to determine the dust attenuation properties. We apply this method to investigate dust attenuation on kiloparsec scales using a sample of 134 galaxies with integral field spectroscopy from MaNGA, NIR imaging from 2MASS, and NUV imaging from Swift/UVOT. We find that the attenuation curve slope and the 2175 Å bump in both the optical and NUV span a wide range at kiloparsec scales. The slope is shallower at higher optical opacity, regardless of the specific star formation rate (sSFR), the minor-to-major axis ratio ( b / a ) of the galaxies, and the location of spaxels within individual galaxies. The 2175 Å bump presents a strong negative correlation with the sSFR, while the correlations with the optical opacity, b / a , and the locations within individual galaxies are all weak. All of these trends appear to be independent of the stellar mass of the galaxies. Our results support the scenario that the variation of the 2175 Å bump is driven predominantly by processes related to star formation, such as the destruction of small dust grains by UV radiation in star-forming regions.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"42 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135371275","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2023-11-01DOI: 10.3847/1538-4357/acf831
B. O’Connor, J. Brink, D. A. H. Buckley, K. Mukai, C. Kouveliotou, E. Göğüş, S. B. Potter, P. Woudt, A. Lien, A. Levan, O. Kargaltsev, M. G. Baring, E. Bellm, S. B. Cenko, P. A. Evans, J. Granot, C. Hailey, F. Harrison, D. Hartmann, A. J. van der Horst, D. Huppenkothen, L. Kaper, J. A. Kennea, P. O. Slane, D. Stern, E. Troja, R. A. M. J. Wijers, G. Younes
Abstract We present the results of our X-ray, ultraviolet, and optical follow-up campaigns of 1RXS J165424.6-433758, an X-ray source detected with the Swift Deep Galactic Plane Survey. The source X-ray spectrum (Swift and NuSTAR) is described by thermal bremsstrahlung radiation with a temperature of kT = 10.1 ± 1.2 keV, yielding an X-ray (0.3–10 keV8) luminosity L X = (6.5 ± 0.8) × 10 31 erg s −1 at a Gaia distance of 460 pc. Spectroscopy with the Southern African Large Telescope revealed a flat continuum dominated by emission features, demonstrating an inverse Balmer decrement, the λ 4640 Bowen blend, almost a dozen He i lines, and He ii λ 4541, λ 4686, and λ 5411. Our high-speed photometry demonstrates a preponderance of flickering and flaring episodes, and revealed the orbital period of the system, P orb = 2.87 hr, which fell well within the cataclysmic variable (CV) period gap between 2 and 3 hr. These features classify 1RXS J165424.6-433758 as a nearby polar magnetic CV.
{"title":"Identification of 1RXS J165424.6-433758 as a Polar Cataclysmic Variable","authors":"B. O’Connor, J. Brink, D. A. H. Buckley, K. Mukai, C. Kouveliotou, E. Göğüş, S. B. Potter, P. Woudt, A. Lien, A. Levan, O. Kargaltsev, M. G. Baring, E. Bellm, S. B. Cenko, P. A. Evans, J. Granot, C. Hailey, F. Harrison, D. Hartmann, A. J. van der Horst, D. Huppenkothen, L. Kaper, J. A. Kennea, P. O. Slane, D. Stern, E. Troja, R. A. M. J. Wijers, G. Younes","doi":"10.3847/1538-4357/acf831","DOIUrl":"https://doi.org/10.3847/1538-4357/acf831","url":null,"abstract":"Abstract We present the results of our X-ray, ultraviolet, and optical follow-up campaigns of 1RXS J165424.6-433758, an X-ray source detected with the Swift Deep Galactic Plane Survey. The source X-ray spectrum (Swift and NuSTAR) is described by thermal bremsstrahlung radiation with a temperature of kT = 10.1 ± 1.2 keV, yielding an X-ray (0.3–10 keV8) luminosity L X = (6.5 ± 0.8) × 10 31 erg s −1 at a Gaia distance of 460 pc. Spectroscopy with the Southern African Large Telescope revealed a flat continuum dominated by emission features, demonstrating an inverse Balmer decrement, the λ 4640 Bowen blend, almost a dozen He i lines, and He ii λ 4541, λ 4686, and λ 5411. Our high-speed photometry demonstrates a preponderance of flickering and flaring episodes, and revealed the orbital period of the system, P orb = 2.87 hr, which fell well within the cataclysmic variable (CV) period gap between 2 and 3 hr. These features classify 1RXS J165424.6-433758 as a nearby polar magnetic CV.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135371872","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2023-11-01DOI: 10.3847/1538-4357/acffbb
Dong Zheng, Zhongxiang Wang
Abstract Teraelectronvolt halos have been suggested to be a common phenomenon associated with middle-aged pulsars. Based on our recent work on the middle-aged pulsar J0631+1036, which is the only known source positionally coincident with a hard teraelectronvolt γ -ray source and likely powers the latter as a teraelectronvolt halo, we select three candidate teraelectronvolt halos from the first Large High Altitude Air Shower Observatory (LHAASO) catalog of γ -ray sources. The corresponding pulsars, given by the positional coincidences and property similarities, are PSR J1958+2846, PSR J2028+3332, and PSR J1849-0001. We analyze the gigaelectronvolt γ -ray data obtained with the Large Area Telescope on board the Fermi Gamma-ray Space Telescope for the first two pulsars, as the last is γ -ray quiet. We remove the pulsed emissions of the pulsars from the source regions from timing analysis, and determine that there are no residual gigaelectronvolt emissions in the regions as any possible counterparts to the teraelectronvolt sources. Considering the previous observational results for the source regions and comparing the two pulsars to Geminga (and Monogem), the LHAASO-detected teraelectronvolt sources are likely the pulsars’ respective teraelectronvolt halos. We find that the candidate and identified teraelectronvolt halos, including that of PSR J1849-0001, have luminosities at 50 TeV (estimated from the differential fluxes) approximately proportional to the spin-down energy Ė of the pulsars, and the ratios of the former to the latter are ∼6 × 10 −4 .
{"title":"Two Candidate Pulsar TeV Halos Identified from Property-similarity Studies","authors":"Dong Zheng, Zhongxiang Wang","doi":"10.3847/1538-4357/acffbb","DOIUrl":"https://doi.org/10.3847/1538-4357/acffbb","url":null,"abstract":"Abstract Teraelectronvolt halos have been suggested to be a common phenomenon associated with middle-aged pulsars. Based on our recent work on the middle-aged pulsar J0631+1036, which is the only known source positionally coincident with a hard teraelectronvolt γ -ray source and likely powers the latter as a teraelectronvolt halo, we select three candidate teraelectronvolt halos from the first Large High Altitude Air Shower Observatory (LHAASO) catalog of γ -ray sources. The corresponding pulsars, given by the positional coincidences and property similarities, are PSR J1958+2846, PSR J2028+3332, and PSR J1849-0001. We analyze the gigaelectronvolt γ -ray data obtained with the Large Area Telescope on board the Fermi Gamma-ray Space Telescope for the first two pulsars, as the last is γ -ray quiet. We remove the pulsed emissions of the pulsars from the source regions from timing analysis, and determine that there are no residual gigaelectronvolt emissions in the regions as any possible counterparts to the teraelectronvolt sources. Considering the previous observational results for the source regions and comparing the two pulsars to Geminga (and Monogem), the LHAASO-detected teraelectronvolt sources are likely the pulsars’ respective teraelectronvolt halos. We find that the candidate and identified teraelectronvolt halos, including that of PSR J1849-0001, have luminosities at 50 TeV (estimated from the differential fluxes) approximately proportional to the spin-down energy <?CDATA $dot{E}$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:mover accent=\"true\"> <mml:mrow> <mml:mi>E</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:math> of the pulsars, and the ratios of the former to the latter are ∼6 × 10 −4 .","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"41 5-6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135372421","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2023-11-01DOI: 10.3847/1538-4357/acf2f4
Mu-Tian 牧天 Wang 王, Gregory J. 雷歌 Herczeg 沈, Hui-Gen 慧根 Liu 刘, Min 敏 Fang 房, Doug Johnstone, Ho-Gyu Lee, Frederick M. Walter, Franz-Josef Hambsch, Carlos Contreras Peña, Jeong-Eun Lee, Mervyn Millward, Andrew Pearce, Berto Monard, Lihang 立杭 Zhou 周
Abstract EX Lup is the archetype for the class of young stars that undergoes repeated accretion outbursts of ∼5 mag at optical wavelengths that last for months. Despite extensive monitoring that dates back 130 yr, the accretion history of EX Lup remains mostly qualitative and has large uncertainties. We assess historical accretion rates of EX Lup by applying correlations between optical brightness and accretion, developed on multi-band magnitude photometry of the ∼2 mag optical burst in 2022. Two distinct classes of bursts occur: major outbursts (Δ V ∼ 5 mag) have year-long durations, are rare, reach accretion rates of Ṁacc∼10−7 M ⊙ yr −1 at peak, and have a total accreted mass of around 0.1 Earth mass. The characteristic bursts (Δ V ∼ 2 mag) have durations of ∼2–3 months, are more common, reach accretion rates of Ṁacc∼10−8 M ⊙ yr −1 at peak, and have a total accreted mass of around 10 −3 Earth masses. The distribution of total accreted mass in the full set of bursts is poorly described by a power law, which suggests different driving causes behind the major outburst and characteristic bursts. The total mass accreted during two classes of bursts is around 2 times the masses accreted during quiescence. Our analysis of the light curves reveals a color-dependent time lag in the 2022 post-burst light curve, attributed to the presence of both hot and cool spots on the stellar surface.
{"title":"The Accretion History of EX Lup: A Century of Bursts, Outbursts, and Quiescence","authors":"Mu-Tian 牧天 Wang 王, Gregory J. 雷歌 Herczeg 沈, Hui-Gen 慧根 Liu 刘, Min 敏 Fang 房, Doug Johnstone, Ho-Gyu Lee, Frederick M. Walter, Franz-Josef Hambsch, Carlos Contreras Peña, Jeong-Eun Lee, Mervyn Millward, Andrew Pearce, Berto Monard, Lihang 立杭 Zhou 周","doi":"10.3847/1538-4357/acf2f4","DOIUrl":"https://doi.org/10.3847/1538-4357/acf2f4","url":null,"abstract":"Abstract EX Lup is the archetype for the class of young stars that undergoes repeated accretion outbursts of ∼5 mag at optical wavelengths that last for months. Despite extensive monitoring that dates back 130 yr, the accretion history of EX Lup remains mostly qualitative and has large uncertainties. We assess historical accretion rates of EX Lup by applying correlations between optical brightness and accretion, developed on multi-band magnitude photometry of the ∼2 mag optical burst in 2022. Two distinct classes of bursts occur: major outbursts (Δ V ∼ 5 mag) have year-long durations, are rare, reach accretion rates of <?CDATA ${dot{M}}_{mathrm{acc}}sim {10}^{-7}$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:msub> <mml:mrow> <mml:mover accent=\"true\"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>acc</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∼</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>7</mml:mn> </mml:mrow> </mml:msup> </mml:math> M ⊙ yr −1 at peak, and have a total accreted mass of around 0.1 Earth mass. The characteristic bursts (Δ V ∼ 2 mag) have durations of ∼2–3 months, are more common, reach accretion rates of <?CDATA ${dot{M}}_{mathrm{acc}}sim {10}^{-8}$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:msub> <mml:mrow> <mml:mover accent=\"true\"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>acc</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∼</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>8</mml:mn> </mml:mrow> </mml:msup> </mml:math> M ⊙ yr −1 at peak, and have a total accreted mass of around 10 −3 Earth masses. The distribution of total accreted mass in the full set of bursts is poorly described by a power law, which suggests different driving causes behind the major outburst and characteristic bursts. The total mass accreted during two classes of bursts is around 2 times the masses accreted during quiescence. Our analysis of the light curves reveals a color-dependent time lag in the 2022 post-burst light curve, attributed to the presence of both hot and cool spots on the stellar surface.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"26 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135456362","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2023-11-01DOI: 10.3847/1538-4357/acfa6e
Marzieh Farhang, Nima Khosravi
Abstract In this work we extend our earlier phenomenological model for a gravitational phase transition and its generalization to early times by letting the modifications in the linearly perturbed Einstein equations be scale dependent. These modifications are characterized as deviations of the parameters μ ( z , k ) and γ ( z , k ) from their values in general relativity (GR). The scale-dependent amplitudes of modified μ ( z , k ) and γ ( z , k ) and the parameters defining the phase transition, along with the standard cosmological parameters, are measured by various data combinations. Out of the perturbation parameters, we construct gravity eigenmodes that represent patterns of perturbations best detectable by data. We detect no significant deviation from GR in these parameters. However, the larger parameter space produced due to the new degrees of freedom allows for the reconciliation of various data sets that are in tension in ΛCDM. In particular, we find H 0 = 71.9 ± 9.2 from anisotropies of the cosmic microwave background as measured by Planck (and various measurements of the baryonic acoustic oscillations, in agreement with local Hubble measurements). We also find that the σ 8 tension between the measurements of the Dark Energy Survey and Planck is reduced to less than 1 σ .
{"title":"Reconstruction of a Scale-dependent Gravitational Phase Transition","authors":"Marzieh Farhang, Nima Khosravi","doi":"10.3847/1538-4357/acfa6e","DOIUrl":"https://doi.org/10.3847/1538-4357/acfa6e","url":null,"abstract":"Abstract In this work we extend our earlier phenomenological model for a gravitational phase transition and its generalization to early times by letting the modifications in the linearly perturbed Einstein equations be scale dependent. These modifications are characterized as deviations of the parameters μ ( z , k ) and γ ( z , k ) from their values in general relativity (GR). The scale-dependent amplitudes of modified μ ( z , k ) and γ ( z , k ) and the parameters defining the phase transition, along with the standard cosmological parameters, are measured by various data combinations. Out of the perturbation parameters, we construct gravity eigenmodes that represent patterns of perturbations best detectable by data. We detect no significant deviation from GR in these parameters. However, the larger parameter space produced due to the new degrees of freedom allows for the reconciliation of various data sets that are in tension in ΛCDM. In particular, we find H 0 = 71.9 ± 9.2 from anisotropies of the cosmic microwave background as measured by Planck (and various measurements of the baryonic acoustic oscillations, in agreement with local Hubble measurements). We also find that the σ 8 tension between the measurements of the Dark Energy Survey and Planck is reduced to less than 1 σ .","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"16 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135510573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2023-11-01DOI: 10.3847/1538-4357/acf99a
Nina Bizien, Thierry Dudok de Wit, Clara Froment, Marco Velli, Anthony W. Case, Stuart D. Bale, Justin Kasper, Phyllis Whittlesey, Robert MacDowall, Davin Larson
Abstract Switchbacks are sudden and large deflections in the magnetic field that Parker Solar Probe frequently observes in the inner heliosphere. Their ubiquitous occurrence has prompted numerous studies to determine their nature and origin. Our goal is to describe the boundary of these switchbacks using a series of events detected during the spacecraft’s first encounter with the Sun. Using FIELDS and SWEAP data, we investigate different methods for determining the boundary normal. The observed boundaries are arc-polarized structures with a rotation that is always contained in a plane. Classical minimum variance analysis gives misleading results and overestimates the number of rotational discontinuities. We propose a robust geometric method to identify the nature of these discontinuities, which involves determining whether or not the plane that contains them also includes the origin ( B = 0). Most boundaries appear to have the same characteristics as tangential discontinuities in the context of switchbacks, with little evidence for having rotational discontinuities. We find no effect of the size of the Parker spiral deviation. Furthermore, the thickness of the boundary is within MHD scales. We conclude that most of the switchback boundaries observed by Parker Solar Probe are likely to be closed, in contrast to previous studies. Our results suggest that their erosion may be much slower than expected.
{"title":"Are Switchback Boundaries Observed by Parker Solar Probe Closed?","authors":"Nina Bizien, Thierry Dudok de Wit, Clara Froment, Marco Velli, Anthony W. Case, Stuart D. Bale, Justin Kasper, Phyllis Whittlesey, Robert MacDowall, Davin Larson","doi":"10.3847/1538-4357/acf99a","DOIUrl":"https://doi.org/10.3847/1538-4357/acf99a","url":null,"abstract":"Abstract Switchbacks are sudden and large deflections in the magnetic field that Parker Solar Probe frequently observes in the inner heliosphere. Their ubiquitous occurrence has prompted numerous studies to determine their nature and origin. Our goal is to describe the boundary of these switchbacks using a series of events detected during the spacecraft’s first encounter with the Sun. Using FIELDS and SWEAP data, we investigate different methods for determining the boundary normal. The observed boundaries are arc-polarized structures with a rotation that is always contained in a plane. Classical minimum variance analysis gives misleading results and overestimates the number of rotational discontinuities. We propose a robust geometric method to identify the nature of these discontinuities, which involves determining whether or not the plane that contains them also includes the origin ( B = 0). Most boundaries appear to have the same characteristics as tangential discontinuities in the context of switchbacks, with little evidence for having rotational discontinuities. We find no effect of the size of the Parker spiral deviation. Furthermore, the thickness of the boundary is within MHD scales. We conclude that most of the switchback boundaries observed by Parker Solar Probe are likely to be closed, in contrast to previous studies. Our results suggest that their erosion may be much slower than expected.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"7 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135516409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
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