Pub Date : 2023-10-01DOI: 10.3847/2041-8213/acf4fa
Renzhi Su, Minfeng Gu, S. J. Curran, Elizabeth K. Mahony, Ningyu Tang, James R. Allison, Di Li, Ming Zhu, J. N. H. S. Aditya, Hyein Yoon, Zheng Zheng, Zhongzu Wu
Abstract In this letter, we report the discovery of a fast neutral hydrogen outflow in SDSS J145239.38+062738.0, a merging radio galaxy containing an optical type I active galactic nucleus (AGN). This discovery was made through observations conducted by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) using redshifted 21 cm absorption. The outflow exhibits a blueshifted velocity likely up to ∼−1000 km s −1 with respect to the systemic velocity of the host galaxy with an absorption strength of ∼−0.6 mJy beam −1 corresponding to an optical depth of 0.002 at v = −500 km s −1 . The mass outflow rate ranges between 2.8 × 10 −2 and 3.6 M ⊙ yr −1 , implying an energy outflow rate ranging between 4.2 × 10 39 and 9.7 × 10 40 erg s −1 , assuming 100 K < T s < 1000 K. Plausible drivers of the outflow include the starbursts, AGN radiation, and radio jet, the last of which is considered the most likely culprit according to the kinematics. By analyzing the properties of the outflow, AGN, and jet, we find that if the H i outflow is driven by the AGN radiation, the AGN radiation does not seem powerful enough to provide negative feedback, whereas the radio jet shows the potential to provide negative feedback. Our observations contribute another example of a fast outflow detected in neutral hydrogen and demonstrate the capability of FAST in detecting such outflows.
在这封信函中，我们报告了在SDSS J145239.38+062738.0中发现的快速中性氢流出，这是一个合并的射电星系，包含一个光学型I活动星系核(AGN)。这一发现是通过500米口径球面射电望远镜(FAST)使用红移21厘米吸收进行的观测得出的。相对于宿主星系的系统速度，流出物的蓝移速度可能高达~−1000 km s−1，吸收强度为~−0.6 mJy光束−1，对应于v =−500 km s−1时的光学深度为0.002。质量流出率在2.8 × 10−2和3.6 M⊙yr−1之间，这意味着假设100 K <，能量流出率在4.2 × 10 39和9.7 × 10 40 erg s−1之间;这是<1000 K。流出的可能驱动因素包括星暴、AGN辐射和射电喷流，根据运动学，最后一个被认为是最有可能的罪魁祸首。通过分析外流、AGN和喷流的特性，我们发现，如果H i外流是由AGN辐射驱动的，那么AGN辐射似乎不足以提供负反馈，而射电喷流则显示出提供负反馈的潜力。我们的观测提供了在中性氢中检测到快速流出的另一个例子，并证明了fast在检测这种流出方面的能力。
{"title":"FAST Discovery of a Fast Neutral Hydrogen Outflow","authors":"Renzhi Su, Minfeng Gu, S. J. Curran, Elizabeth K. Mahony, Ningyu Tang, James R. Allison, Di Li, Ming Zhu, J. N. H. S. Aditya, Hyein Yoon, Zheng Zheng, Zhongzu Wu","doi":"10.3847/2041-8213/acf4fa","DOIUrl":"https://doi.org/10.3847/2041-8213/acf4fa","url":null,"abstract":"Abstract In this letter, we report the discovery of a fast neutral hydrogen outflow in SDSS J145239.38+062738.0, a merging radio galaxy containing an optical type I active galactic nucleus (AGN). This discovery was made through observations conducted by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) using redshifted 21 cm absorption. The outflow exhibits a blueshifted velocity likely up to ∼−1000 km s −1 with respect to the systemic velocity of the host galaxy with an absorption strength of ∼−0.6 mJy beam −1 corresponding to an optical depth of 0.002 at v = −500 km s −1 . The mass outflow rate ranges between 2.8 × 10 −2 and 3.6 M ⊙ yr −1 , implying an energy outflow rate ranging between 4.2 × 10 39 and 9.7 × 10 40 erg s −1 , assuming 100 K < T s < 1000 K. Plausible drivers of the outflow include the starbursts, AGN radiation, and radio jet, the last of which is considered the most likely culprit according to the kinematics. By analyzing the properties of the outflow, AGN, and jet, we find that if the H i outflow is driven by the AGN radiation, the AGN radiation does not seem powerful enough to provide negative feedback, whereas the radio jet shows the potential to provide negative feedback. Our observations contribute another example of a fast outflow detected in neutral hydrogen and demonstrate the capability of FAST in detecting such outflows.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135761394","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2023-10-01DOI: 10.3847/2041-8213/acffaf
Shubham Srivastav, T. Moore, M. Nicholl, M. R. Magee, S. J. Smartt, M. D. Fulton, S. A. Sim, J. M. Pollin, L. Galbany, C. Inserra, A. Kozyreva, Takashi J. Moriya, F. P. Callan, X. Sheng, K. W. Smith, J. S. Sommer, J. P. Anderson, M. Deckers, M. Gromadzki, T. E. Müller-Bravo, G. Pignata, A. Rest, D. R. Young
Abstract We present optical photometric and spectroscopic observations of the 02es-like type Ia supernova (SN) 2022ywc. The transient occurred in the outskirts of an elliptical host galaxy and showed a striking double-peaked light curve with an early excess feature detected in the ATLAS orange and cyan bands. The early excess is remarkably luminous with an absolute magnitude ∼ − 19, comparable in luminosity to the subsequent radioactively driven second peak. The spectra resemble the hybrid 02es-like SN 2016jhr, which is considered to be a helium shell detonation candidate. We investigate different physical mechanisms that could power such a prominent early excess and rule out massive helium shell detonation, surface 56 Ni distribution, and ejecta–companion interaction. We conclude that SN ejecta interacting with circumstellar material (CSM) is the most viable scenario. Semianalytical modeling with MOSFiT indicates that SN ejecta interacting with ∼0.05 M ⊙ of CSM at a distance of ∼10 14 cm can explain the extraordinary light curve. A double-degenerate scenario may explain the origin of the CSM, by tidally stripped material from either the secondary white dwarf or disk-originated matter launched along polar axes following the disruption and accretion of the secondary white dwarf. A nonspherical CSM configuration could suggest that a small fraction of 02es-like events viewed along a favorable line of sight may be expected to display a very conspicuous early excess like SN 2022ywc.
{"title":"Unprecedented Early Flux Excess in the Hybrid 02es-like Type Ia Supernova 2022ywc Indicates Interaction with Circumstellar Material","authors":"Shubham Srivastav, T. Moore, M. Nicholl, M. R. Magee, S. J. Smartt, M. D. Fulton, S. A. Sim, J. M. Pollin, L. Galbany, C. Inserra, A. Kozyreva, Takashi J. Moriya, F. P. Callan, X. Sheng, K. W. Smith, J. S. Sommer, J. P. Anderson, M. Deckers, M. Gromadzki, T. E. Müller-Bravo, G. Pignata, A. Rest, D. R. Young","doi":"10.3847/2041-8213/acffaf","DOIUrl":"https://doi.org/10.3847/2041-8213/acffaf","url":null,"abstract":"Abstract We present optical photometric and spectroscopic observations of the 02es-like type Ia supernova (SN) 2022ywc. The transient occurred in the outskirts of an elliptical host galaxy and showed a striking double-peaked light curve with an early excess feature detected in the ATLAS orange and cyan bands. The early excess is remarkably luminous with an absolute magnitude ∼ − 19, comparable in luminosity to the subsequent radioactively driven second peak. The spectra resemble the hybrid 02es-like SN 2016jhr, which is considered to be a helium shell detonation candidate. We investigate different physical mechanisms that could power such a prominent early excess and rule out massive helium shell detonation, surface 56 Ni distribution, and ejecta–companion interaction. We conclude that SN ejecta interacting with circumstellar material (CSM) is the most viable scenario. Semianalytical modeling with MOSFiT indicates that SN ejecta interacting with ∼0.05 M ⊙ of CSM at a distance of ∼10 14 cm can explain the extraordinary light curve. A double-degenerate scenario may explain the origin of the CSM, by tidally stripped material from either the secondary white dwarf or disk-originated matter launched along polar axes following the disruption and accretion of the secondary white dwarf. A nonspherical CSM configuration could suggest that a small fraction of 02es-like events viewed along a favorable line of sight may be expected to display a very conspicuous early excess like SN 2022ywc.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135762653","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2023-10-01DOI: 10.3847/2041-8213/acfa03
Yan Liang, Peter Melchior, ChangHoon Hahn, Jeff Shen, Andy Goulding, Charlotte Ward
Abstract We present an unsupervised search for outliers in the Bright Galaxy Survey (BGS) data set from the DESI Early Data Release. This analysis utilizes an autoencoder to compress galaxy spectra into a compact, redshift-invariant latent space, and a normalizing flow to identify low-probability objects. The most prominent outliers show distinctive spectral features, such as irregular or double-peaked emission lines or originate from galaxy mergers, blended sources, and rare quasar types, including one previously unknown broad absorption line system. A significant portion of the BGS outliers are stars spectroscopically misclassified as galaxies. By building our own star model trained on spectra from the DESI Milky Way Survey, we have determined that the misclassification likely stems from the principle component analysis of stars in the DESI pipeline. To aid follow-up studies, we make the full probability catalog of all BGS objects and our pretrained models publicly available.
{"title":"Outlier Detection in the DESI Bright Galaxy Survey","authors":"Yan Liang, Peter Melchior, ChangHoon Hahn, Jeff Shen, Andy Goulding, Charlotte Ward","doi":"10.3847/2041-8213/acfa03","DOIUrl":"https://doi.org/10.3847/2041-8213/acfa03","url":null,"abstract":"Abstract We present an unsupervised search for outliers in the Bright Galaxy Survey (BGS) data set from the DESI Early Data Release. This analysis utilizes an autoencoder to compress galaxy spectra into a compact, redshift-invariant latent space, and a normalizing flow to identify low-probability objects. The most prominent outliers show distinctive spectral features, such as irregular or double-peaked emission lines or originate from galaxy mergers, blended sources, and rare quasar types, including one previously unknown broad absorption line system. A significant portion of the BGS outliers are stars spectroscopically misclassified as galaxies. By building our own star model trained on spectra from the DESI Milky Way Survey, we have determined that the misclassification likely stems from the principle component analysis of stars in the DESI pipeline. To aid follow-up studies, we make the full probability catalog of all BGS objects and our pretrained models publicly available.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134977817","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2023-10-01DOI: 10.3847/2041-8213/acfa9e
Rui-Nan Li, Zhen-Yin Zhao, Zhifu Gao, Fa-Yin Wang
Abstract Recent observations discovered that some repeating fast radio bursts (FRBs) show a large value and complex variations of Faraday rotation measures (RMs). The binary systems containing a supermassive black hole and a neutron star can be used to explain such RM variations. Meanwhile, such systems produce low-frequency gravitational-wave (GW) signals, which are one of the primary interests of three proposed space-based GW detectors: the Laser Interferometer Space Antenna (LISA), Tianqin, and Taiji. These signals are known as extreme mass-ratio inspirals (EMRIs). Therefore, FRBs can serve as candidates of electromagnetic counterparts for EMRI signals. In this Letter, we study the EMRI signals in this binary system, which can be detected up to z ∼ 0.04 by LISA and Tianqin for the most optimistic case. Assuming the cosmic comb model for FRB production, the total event rate can be as high as ∼1 Gpc −3 yr −1 . EMRI signals associated with FRBs can be used to reveal the progenitor of FRBs. It is also a new type of standard siren, which can be used as an independent cosmological probe.
{"title":"Fast Radio Bursts: Electromagnetic Counterparts to Extreme Mass-ratio Inspirals","authors":"Rui-Nan Li, Zhen-Yin Zhao, Zhifu Gao, Fa-Yin Wang","doi":"10.3847/2041-8213/acfa9e","DOIUrl":"https://doi.org/10.3847/2041-8213/acfa9e","url":null,"abstract":"Abstract Recent observations discovered that some repeating fast radio bursts (FRBs) show a large value and complex variations of Faraday rotation measures (RMs). The binary systems containing a supermassive black hole and a neutron star can be used to explain such RM variations. Meanwhile, such systems produce low-frequency gravitational-wave (GW) signals, which are one of the primary interests of three proposed space-based GW detectors: the Laser Interferometer Space Antenna (LISA), Tianqin, and Taiji. These signals are known as extreme mass-ratio inspirals (EMRIs). Therefore, FRBs can serve as candidates of electromagnetic counterparts for EMRI signals. In this Letter, we study the EMRI signals in this binary system, which can be detected up to z ∼ 0.04 by LISA and Tianqin for the most optimistic case. Assuming the cosmic comb model for FRB production, the total event rate can be as high as ∼1 Gpc −3 yr −1 . EMRI signals associated with FRBs can be used to reveal the progenitor of FRBs. It is also a new type of standard siren, which can be used as an independent cosmological probe.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135605276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2023-10-01DOI: 10.3847/2041-8213/acf71a
Apurba Bera, Nissim Kanekar, Jayaram N. Chengalur, Jasjeet S. Bagla
Abstract Star-forming galaxies are believed to replenish their atomic gas reservoir, which is consumed in star formation, through accretion of gas from their circumgalactic mediums (CGMs). However, there are few observational constraints today on the gas accretion rate in external galaxies. Here, we use our recent measurement of the scaling relation between the atomic hydrogen (H i ) mass M H I and the stellar mass M * in star-forming galaxies at z ≈ 0.35, with the relations between the star formation rate (SFR) and M * , and the molecular gas mass M Mol and M * , and the assumption that star-forming galaxies evolve along the main sequence, to determine the evolution of the neutral gas reservoir and the average net gas accretion rate onto the disks of star-forming galaxies over the past 4 Gyr. For galaxies with M * ≳ 10 9 M ⊙ today, we find that both M * and M H I in the disk have increased, while M Mol has decreased, since z ≈ 0.35. The average gas accretion rate onto the disk over the past 4 Gyr is similar to the average SFR over this period, implying that main-sequence galaxies have maintained a stable H i reservoir, despite the consumption of gas in star formation. We obtain an average net gas accretion rate (over the past 4 Gyr) of ≈6 M ⊙ yr −1 for galaxies with the stellar mass of the Milky Way. At low redshifts, z ≲ 0.4, the reason for the decline in the cosmic SFR density thus appears to be the inefficiency in the conversion of atomic gas to molecular gas, rather than insufficient gas accretion from the CGM.
{"title":"The Gas Accretion Rate of Star-forming Galaxies over the Last 4 Gyr","authors":"Apurba Bera, Nissim Kanekar, Jayaram N. Chengalur, Jasjeet S. Bagla","doi":"10.3847/2041-8213/acf71a","DOIUrl":"https://doi.org/10.3847/2041-8213/acf71a","url":null,"abstract":"Abstract Star-forming galaxies are believed to replenish their atomic gas reservoir, which is consumed in star formation, through accretion of gas from their circumgalactic mediums (CGMs). However, there are few observational constraints today on the gas accretion rate in external galaxies. Here, we use our recent measurement of the scaling relation between the atomic hydrogen (H i ) mass M H I and the stellar mass M * in star-forming galaxies at z ≈ 0.35, with the relations between the star formation rate (SFR) and M * , and the molecular gas mass M Mol and M * , and the assumption that star-forming galaxies evolve along the main sequence, to determine the evolution of the neutral gas reservoir and the average net gas accretion rate onto the disks of star-forming galaxies over the past 4 Gyr. For galaxies with M * ≳ 10 9 M ⊙ today, we find that both M * and M H I in the disk have increased, while M Mol has decreased, since z ≈ 0.35. The average gas accretion rate onto the disk over the past 4 Gyr is similar to the average SFR over this period, implying that main-sequence galaxies have maintained a stable H i reservoir, despite the consumption of gas in star formation. We obtain an average net gas accretion rate (over the past 4 Gyr) of ≈6 M ⊙ yr −1 for galaxies with the stellar mass of the Milky Way. At low redshifts, z ≲ 0.4, the reason for the decline in the cosmic SFR density thus appears to be the inefficiency in the conversion of atomic gas to molecular gas, rather than insufficient gas accretion from the CGM.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"2015 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135607005","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2023-10-01DOI: 10.3847/2041-8213/acfcab
Hai-Ming Zhang, Yi-Yun Huang, Ruo-Yu Liu, Xiang-Yu Wang
Abstract Recently, LHAASO reported the detection of the brightest-of-all-time GRB 221009A, revealing the early onset of a TeV afterglow. We analyze the spectral evolution of the X-ray/gamma-ray emission of GRB 221009A measured by the Fermi Gamma-ray Burst Monitor (GBM) during the dips of two prompt emission pulses (i.e., intervals T 0 + [300–328] s and T 0 + [338–378] s, where T 0 is the GBM trigger time). We find that the spectra at the dips transit from the Band function to a power-law function, indicating a transition from the prompt emission to the afterglow. After ∼ T 0 + 660 s, the spectrum is well described by a power-law function, and the afterglow becomes dominant. Remarkably, the underlying afterglow emission at the dips smoothly connect with the afterglow after ∼ T 0 + 660 s. The entire afterglow emission measured by GBM can be fitted by a power-law function F ∼ t −0.95±0.05 , where t is the time since the first main pulse at T * = T 0 + 226 s, consistent with the TeV afterglow decay measured by LHAASO. The start time of this power-law decay indicates that the afterglow peak of GRB 221009A should be earlier than T 0 + 300 s. We also test the possible presence of a jet break in the early afterglow light curve, finding that both the jet break model and single power-law decay model are consistent with the GBM data. The two models cannot be distinguished with the GBM data alone because the inferred jet break time is quite close to the end of the GBM observations.
{"title":"GRB 221009A: Revealing a Hidden Afterglow during the Prompt Emission Phase with Fermi-GBM Observations","authors":"Hai-Ming Zhang, Yi-Yun Huang, Ruo-Yu Liu, Xiang-Yu Wang","doi":"10.3847/2041-8213/acfcab","DOIUrl":"https://doi.org/10.3847/2041-8213/acfcab","url":null,"abstract":"Abstract Recently, LHAASO reported the detection of the brightest-of-all-time GRB 221009A, revealing the early onset of a TeV afterglow. We analyze the spectral evolution of the X-ray/gamma-ray emission of GRB 221009A measured by the Fermi Gamma-ray Burst Monitor (GBM) during the dips of two prompt emission pulses (i.e., intervals T 0 + [300–328] s and T 0 + [338–378] s, where T 0 is the GBM trigger time). We find that the spectra at the dips transit from the Band function to a power-law function, indicating a transition from the prompt emission to the afterglow. After ∼ T 0 + 660 s, the spectrum is well described by a power-law function, and the afterglow becomes dominant. Remarkably, the underlying afterglow emission at the dips smoothly connect with the afterglow after ∼ T 0 + 660 s. The entire afterglow emission measured by GBM can be fitted by a power-law function F ∼ t −0.95±0.05 , where t is the time since the first main pulse at T * = T 0 + 226 s, consistent with the TeV afterglow decay measured by LHAASO. The start time of this power-law decay indicates that the afterglow peak of GRB 221009A should be earlier than T 0 + 300 s. We also test the possible presence of a jet break in the early afterglow light curve, finding that both the jet break model and single power-law decay model are consistent with the GBM data. The two models cannot be distinguished with the GBM data alone because the inferred jet break time is quite close to the end of the GBM observations.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"205 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135705862","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2023-10-01DOI: 10.3847/2041-8213/acfdaa
Zhongtian Zhang
Abstract Isotopic studies of meteorites suggest that planetesimals were formed as two distinct populations: noncarbonaceous (NC) and carbonaceous (CC) reservoirs. A recent model explains this dichotomy by considering planetesimal formation at the snowline during its migration in the protoplanetary disk, suggesting that NC planetesimals were formed during the outward migration and CC planetesimals were formed during the inward migration. This model has been suggested to contradict meteorite observations because planetesimals formed at the snowline are expected to be rich in H 2 O and, therefore, develop more oxidizing environments than those inferred from NC iron meteorites. However, if the accreted ice sublimates into vapor without transitioning into a liquid state, the planetesimals may lose most water without being oxidized because reactions between vapor and solids are negligibly slow at temperatures relevant to direct ice sublimation. Here, we investigate the transport of vapor inside a planetesimal and suggest that the pore pressure would have been sufficiently low for direct ice sublimation if (1) the planetesimals were formed during the outward snowline migration (such that they lay inside the snowline after formation and had surfaces permeable to water vapor), (2) these planetesimals were formed by dust-aggregate boulders through “streaming instabilities” instead of being formed directly by submicrometer dust grains, and (3) the boulders were between a few centimeters to ~10 m in size. With these results, the snowline model for NC/CC planetesimal formation may be reconciled with the observations of iron meteorite oxidation states.
{"title":"Ice Sublimation in Planetesimals Formed at the Outward Migrating Snowline","authors":"Zhongtian Zhang","doi":"10.3847/2041-8213/acfdaa","DOIUrl":"https://doi.org/10.3847/2041-8213/acfdaa","url":null,"abstract":"Abstract Isotopic studies of meteorites suggest that planetesimals were formed as two distinct populations: noncarbonaceous (NC) and carbonaceous (CC) reservoirs. A recent model explains this dichotomy by considering planetesimal formation at the snowline during its migration in the protoplanetary disk, suggesting that NC planetesimals were formed during the outward migration and CC planetesimals were formed during the inward migration. This model has been suggested to contradict meteorite observations because planetesimals formed at the snowline are expected to be rich in H 2 O and, therefore, develop more oxidizing environments than those inferred from NC iron meteorites. However, if the accreted ice sublimates into vapor without transitioning into a liquid state, the planetesimals may lose most water without being oxidized because reactions between vapor and solids are negligibly slow at temperatures relevant to direct ice sublimation. Here, we investigate the transport of vapor inside a planetesimal and suggest that the pore pressure would have been sufficiently low for direct ice sublimation if (1) the planetesimals were formed during the outward snowline migration (such that they lay inside the snowline after formation and had surfaces permeable to water vapor), (2) these planetesimals were formed by dust-aggregate boulders through “streaming instabilities” instead of being formed directly by submicrometer dust grains, and (3) the boulders were between a few centimeters to ~10 m in size. With these results, the snowline model for NC/CC planetesimal formation may be reconciled with the observations of iron meteorite oxidation states.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135706833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2023-10-01DOI: 10.3847/2041-8213/acfa97
María Jesús Martínez González, Tanausú del Pino Alemán, Adur Pastor Yabar, Carlos Quintero Noda, Andrés Asensio Ramos
Abstract Ca ii K grains, i.e., intermittent, short-lived (about 1 minute), periodic (2–4 minutes), pointlike chromospheric brightenings, are considered to be the manifestations of acoustic waves propagating upward from the solar surface and developing into shocks in the chromosphere. After the simulations of Carlsson and Stein, we know that hot shocked gas moving upward interacting with the downflowing chromospheric gas (falling down after having been displaced upward by a previous shock) nicely reproduces the spectral features of the Ca ii K profiles observed in such grains, i.e., a narrowband emission-like feature at the blue side of the line core. However, these simulations are one-dimensional and cannot explain the location or the pointlike shape of the grains. Here, we report on the magnetic nature of these events. Furthermore, we report on similar events occurring at the largest flux concentrations, though they are longer-lived (up to 8 minutes) and exhibit the typical signature of steep velocity gradients traveling across the atmosphere. The spectral signatures of the studied events resemble their counterparts in sunspots, the umbral flashes. We then propose that magnetohydrodynamical waves are not only channeled through the magnetic field in sunspots, but they pervade the whole atmosphere. The propagation along magnetic fields can explain the pointlike appearance of the calcium grains observed in the quiet chromosphere.
Ca ii K颗粒，即间歇性的、短暂的(约1分钟)、周期性的(2-4分钟)、点状的色球亮，被认为是声波从太阳表面向上传播并在色球层发展成激波的表现。在Carlsson和Stein的模拟之后，我们知道向上移动的热激波气体与向下流动的色球气体相互作用(在被先前的激波向上取代后下降)很好地再现了在这些颗粒中观察到的Ca ii K剖面的光谱特征，即线核蓝色一侧的窄带发射样特征。然而，这些模拟是一维的，不能解释颗粒的位置或点状形状。在这里，我们报道这些事件的磁性。此外，我们报告了在最大通量浓度下发生的类似事件，尽管它们持续时间较长(长达8分钟)，并表现出穿越大气的陡峭速度梯度的典型特征。所研究事件的光谱特征与太阳黑子的对应物——本影闪光相似。然后我们提出磁流体动力波不仅在太阳黑子的磁场中传播，而且遍及整个大气。沿着磁场的传播可以解释在安静色球中观察到的钙颗粒的点状外观。
{"title":"On the Magnetic Nature of Quiet-Sun Chromospheric Grains","authors":"María Jesús Martínez González, Tanausú del Pino Alemán, Adur Pastor Yabar, Carlos Quintero Noda, Andrés Asensio Ramos","doi":"10.3847/2041-8213/acfa97","DOIUrl":"https://doi.org/10.3847/2041-8213/acfa97","url":null,"abstract":"Abstract Ca ii K grains, i.e., intermittent, short-lived (about 1 minute), periodic (2–4 minutes), pointlike chromospheric brightenings, are considered to be the manifestations of acoustic waves propagating upward from the solar surface and developing into shocks in the chromosphere. After the simulations of Carlsson and Stein, we know that hot shocked gas moving upward interacting with the downflowing chromospheric gas (falling down after having been displaced upward by a previous shock) nicely reproduces the spectral features of the Ca ii K profiles observed in such grains, i.e., a narrowband emission-like feature at the blue side of the line core. However, these simulations are one-dimensional and cannot explain the location or the pointlike shape of the grains. Here, we report on the magnetic nature of these events. Furthermore, we report on similar events occurring at the largest flux concentrations, though they are longer-lived (up to 8 minutes) and exhibit the typical signature of steep velocity gradients traveling across the atmosphere. The spectral signatures of the studied events resemble their counterparts in sunspots, the umbral flashes. We then propose that magnetohydrodynamical waves are not only channeled through the magnetic field in sunspots, but they pervade the whole atmosphere. The propagation along magnetic fields can explain the pointlike appearance of the calcium grains observed in the quiet chromosphere.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134934297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Many particles are accelerated during solar flares. To understand the acceleration and propagation processes of electrons, we require the pitch-angle distributions of the particles. The pitch angle of accelerated electrons has been estimated from the propagation velocity of a nonthermal microwave source archived in Nobeyama Radioheliograph data. We analyzed a flare event (an M-class flare on 2014 October 22) showing cyclical microwave brightenings at the two footpoint regions. Assuming that the brightenings were caused by the accelerated electrons, we approximated the velocity parallel to the magnetic field of the accelerated electrons as 77,000 and 90,000 km/s. The estimated pitch angle of the accelerated electrons is 69-80 degrees and the size of the loss cone at the footpoint (estimated from the magnetic field strength in the nonlinear force-free field model) is approximately 43 degrees. Most of the accelerated electrons could be reflected at the footpoint region. This feature can be interpreted as brightenings produced by bouncing motion of the accelerated electrons.
{"title":"Characteristics of the Accelerated Electrons Moving along the Loop Derived from Cyclical Microwave Brightenings at the Footpoints","authors":"Keitarou Matsumoto, Satoshi Masuda, Takafumi Kaneko","doi":"10.3847/2041-8213/acf99c","DOIUrl":"https://doi.org/10.3847/2041-8213/acf99c","url":null,"abstract":"Many particles are accelerated during solar flares. To understand the acceleration and propagation processes of electrons, we require the pitch-angle distributions of the particles. The pitch angle of accelerated electrons has been estimated from the propagation velocity of a nonthermal microwave source archived in Nobeyama Radioheliograph data. We analyzed a flare event (an M-class flare on 2014 October 22) showing cyclical microwave brightenings at the two footpoint regions. Assuming that the brightenings were caused by the accelerated electrons, we approximated the velocity parallel to the magnetic field of the accelerated electrons as 77,000 and 90,000 km/s. The estimated pitch angle of the accelerated electrons is 69-80 degrees and the size of the loss cone at the footpoint (estimated from the magnetic field strength in the nonlinear force-free field model) is approximately 43 degrees. Most of the accelerated electrons could be reflected at the footpoint region. This feature can be interpreted as brightenings produced by bouncing motion of the accelerated electrons.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"124 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134934300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2023-10-01DOI: 10.3847/2041-8213/acfaff
Marco Tavani, Giovanni Piano, Andrea Bulgarelli, Luca Foffano, Alessandro Ursi, Francesco Verrecchia, Carlotta Pittori, Claudio Casentini, Andrea Giuliani, Francesco Longo, Gabriele Panebianco, Ambra Di Piano, Leonardo Baroncelli, Valentina Fioretti, Nicolò Parmiggiani, Andrea Argan, Alessio Trois, Stefano Vercellone, Martina Cardillo, Lucio Angelo Antonelli, Guido Barbiellini, Patrizia Caraveo, Paolo W. Cattaneo, Andrew W. Chen, Enrico Costa, Ettore Del Monte, Guido Di Cocco, Immacolata Donnarumma, Yuri Evangelista, Marco Feroci, Fulvio Gianotti, Claudio Labanti, Francesco Lazzarotto, Paolo Lipari, Fabrizio Lucarelli, Martino Marisaldi, Sandro Mereghetti, Aldo Morselli, Luigi Pacciani, Alberto Pellizzoni, Francesco Perotti, Piergiorgio Picozza, Maura Pilia, Massimo Rapisarda, Andrea Rappoldi, Alda Rubini, Paolo Soffitta, Massimo Trifoglio, Valerio Vittorini, Fabio D’Amico
Abstract Gamma-ray emission in the MeV–GeV range from explosive cosmic events is of invaluable relevance to understanding physical processes related to the formation of neutron stars and black holes. Here we report on the detection by the AGILE satellite in the MeV–GeV energy range of the remarkable long-duration gamma-ray burst GRB 221009A. The AGILE onboard detectors have good exposure to GRB 221009A during its initial crucial phases. Hard X-ray/MeV emission in the prompt phase lasted hundreds of seconds, with the brightest radiation being emitted between 200 and 300 s after the initial trigger. Very intense GeV gamma-ray emission is detected by AGILE in the prompt and early afterglow phase up to 10,000 s. Time-resolved spectral analysis shows time-variable MeV-peaked emission simultaneous with intense power-law GeV radiation that persists in the afterglow phase. The coexistence during the prompt phase of very intense MeV emission together with highly nonthermal and hardening GeV radiation is a remarkable feature of GRB 221009A. During the prompt phase, the event shows spectrally different MeV and GeV emissions that are most likely generated by physical mechanisms occurring in different locations. AGILE observations provide crucial flux and spectral gamma-ray information regarding the early phases of GRB 221009A during which emission in the TeV range was reported.
{"title":"AGILE Gamma-Ray Detection of the Exceptional GRB 221009A","authors":"Marco Tavani, Giovanni Piano, Andrea Bulgarelli, Luca Foffano, Alessandro Ursi, Francesco Verrecchia, Carlotta Pittori, Claudio Casentini, Andrea Giuliani, Francesco Longo, Gabriele Panebianco, Ambra Di Piano, Leonardo Baroncelli, Valentina Fioretti, Nicolò Parmiggiani, Andrea Argan, Alessio Trois, Stefano Vercellone, Martina Cardillo, Lucio Angelo Antonelli, Guido Barbiellini, Patrizia Caraveo, Paolo W. Cattaneo, Andrew W. Chen, Enrico Costa, Ettore Del Monte, Guido Di Cocco, Immacolata Donnarumma, Yuri Evangelista, Marco Feroci, Fulvio Gianotti, Claudio Labanti, Francesco Lazzarotto, Paolo Lipari, Fabrizio Lucarelli, Martino Marisaldi, Sandro Mereghetti, Aldo Morselli, Luigi Pacciani, Alberto Pellizzoni, Francesco Perotti, Piergiorgio Picozza, Maura Pilia, Massimo Rapisarda, Andrea Rappoldi, Alda Rubini, Paolo Soffitta, Massimo Trifoglio, Valerio Vittorini, Fabio D’Amico","doi":"10.3847/2041-8213/acfaff","DOIUrl":"https://doi.org/10.3847/2041-8213/acfaff","url":null,"abstract":"Abstract Gamma-ray emission in the MeV–GeV range from explosive cosmic events is of invaluable relevance to understanding physical processes related to the formation of neutron stars and black holes. Here we report on the detection by the AGILE satellite in the MeV–GeV energy range of the remarkable long-duration gamma-ray burst GRB 221009A. The AGILE onboard detectors have good exposure to GRB 221009A during its initial crucial phases. Hard X-ray/MeV emission in the prompt phase lasted hundreds of seconds, with the brightest radiation being emitted between 200 and 300 s after the initial trigger. Very intense GeV gamma-ray emission is detected by AGILE in the prompt and early afterglow phase up to 10,000 s. Time-resolved spectral analysis shows time-variable MeV-peaked emission simultaneous with intense power-law GeV radiation that persists in the afterglow phase. The coexistence during the prompt phase of very intense MeV emission together with highly nonthermal and hardening GeV radiation is a remarkable feature of GRB 221009A. During the prompt phase, the event shows spectrally different MeV and GeV emissions that are most likely generated by physical mechanisms occurring in different locations. AGILE observations provide crucial flux and spectral gamma-ray information regarding the early phases of GRB 221009A during which emission in the TeV range was reported.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135810843","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：