Pub Date : 2024-06-30DOI: 10.1088/1674-4527/ad50b6
Aiying Duan, Yaoyu Xing and Chaowei Jiang
Solar active regions (ARs) are formed by the emergence of current-carrying magnetic flux tubes from below the photosphere. Although for an isolated flux tube the direct and return currents flowing along the tube should balance with each other, it remains controversial whether such a neutralization of currents is also maintained during the emergence process. Here we present a systematic survey of the degrees of the current neutralization in a large sample of flux-emerging ARs which appeared on the solar disk around the central meridian from 2010 to 2022. The vector magnetograms taken by Helioseismic and Magnetic Imager onboard Solar Dynamic Observatory are employed to calculate the distributions of the vertical current density at the photosphere. Focusing on the main phase of flux emergence, i.e., the phase in which the total unsigned magnetic flux is continuously increased, we statistically examined the ratios of direct to return currents in all the ARs. Such a large-sample statistical study suggests that most of the ARs were born with currents close to neutralization. The degree of current neutralization seems to be not affected by the active-region size, the active-region growing rate, and the total unsigned current. The only correlation of significance as found is that the stronger the magnetic field nonpotentiality is, the further the AR deviates from current neutrality, which supports previous event studies that eruption-productive ARs often have non-neutralized currents.
太阳活动区（AR）是由光球下方出现的载流磁通管形成的。虽然对于一个孤立的磁通管来说，沿磁通管流动的直流和回流应该相互平衡，但在出现过程中是否也能保持这种电流中和仍然存在争议。在此，我们对2010年至2022年期间出现在中央子午线附近太阳圆盘上的大样本通量萌发AR的电流中和程度进行了系统调查。我们利用太阳动力学观测站上的日震和磁成像仪拍摄的矢量磁图来计算光球的垂直电流密度分布。我们重点研究了磁通量出现的主要阶段，即无符号磁通量总量持续增加的阶段，并对所有 AR 中的直流与回流之比进行了统计。这种大样本的统计研究表明，大多数 AR 天生的电流接近中和。电流中和的程度似乎不受有源区大小、有源区增长率和无符号总电流的影响。唯一有意义的相关性是，磁场非潜在性越强，AR 偏离电流中性的程度就越大，这支持了之前的事件研究，即喷发产生的 AR 通常具有非中性化电流。
{"title":"Are Solar Active Regions Born with Neutralized Currents?","authors":"Aiying Duan, Yaoyu Xing and Chaowei Jiang","doi":"10.1088/1674-4527/ad50b6","DOIUrl":"https://doi.org/10.1088/1674-4527/ad50b6","url":null,"abstract":"Solar active regions (ARs) are formed by the emergence of current-carrying magnetic flux tubes from below the photosphere. Although for an isolated flux tube the direct and return currents flowing along the tube should balance with each other, it remains controversial whether such a neutralization of currents is also maintained during the emergence process. Here we present a systematic survey of the degrees of the current neutralization in a large sample of flux-emerging ARs which appeared on the solar disk around the central meridian from 2010 to 2022. The vector magnetograms taken by Helioseismic and Magnetic Imager onboard Solar Dynamic Observatory are employed to calculate the distributions of the vertical current density at the photosphere. Focusing on the main phase of flux emergence, i.e., the phase in which the total unsigned magnetic flux is continuously increased, we statistically examined the ratios of direct to return currents in all the ARs. Such a large-sample statistical study suggests that most of the ARs were born with currents close to neutralization. The degree of current neutralization seems to be not affected by the active-region size, the active-region growing rate, and the total unsigned current. The only correlation of significance as found is that the stronger the magnetic field nonpotentiality is, the further the AR deviates from current neutrality, which supports previous event studies that eruption-productive ARs often have non-neutralized currents.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"14 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141518208","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2024-06-26DOI: 10.1088/1674-4527/ad4fc2
Noam Soker
I further study the manner by which a pair of opposite jets shape the “keyhole” morphological structure of the core-collapse supernova (CCSN) SN 1997A, now the CCSN remnant (CCSNR) 1987A. By doing so, I strengthen the claim that the jittering-jet explosion mechanism accounts for most, likely all, CCSNe. The “keyhole” structure comprises a northern low-intensity zone closed with a bright rim on its front and an elongated low-intensity nozzle in the south. This rim-nozzle asymmetry is observed in some cooling flow clusters and planetary nebulae that are observed to be shaped by jets. I build a toy model that uses the planar jittering jets pattern, where consecutive pairs of jets tend to jitter in a common plane, implying that the accreted gas onto the newly born neutron star at the late explosion phase flows perpendicular to that plane. This allows for a long-lived jet-launching episode. This long-lasting jet-launching episode launches more mass into the jets that can inflate larger pairs of ears or bubbles, forming the main jets’ axis of the CCSNR that is not necessarily related to a possible pre-collapse core rotation. I discuss the relation of the main jets’ axis to the neutron star’s natal kick velocity.
{"title":"Supernova 1987A’s Keyhole: A Long-lived Jet-pair in the Final Explosion Phase of Core-collapse Supernovae","authors":"Noam Soker","doi":"10.1088/1674-4527/ad4fc2","DOIUrl":"https://doi.org/10.1088/1674-4527/ad4fc2","url":null,"abstract":"I further study the manner by which a pair of opposite jets shape the “keyhole” morphological structure of the core-collapse supernova (CCSN) SN 1997A, now the CCSN remnant (CCSNR) 1987A. By doing so, I strengthen the claim that the jittering-jet explosion mechanism accounts for most, likely all, CCSNe. The “keyhole” structure comprises a northern low-intensity zone closed with a bright rim on its front and an elongated low-intensity nozzle in the south. This rim-nozzle asymmetry is observed in some cooling flow clusters and planetary nebulae that are observed to be shaped by jets. I build a toy model that uses the planar jittering jets pattern, where consecutive pairs of jets tend to jitter in a common plane, implying that the accreted gas onto the newly born neutron star at the late explosion phase flows perpendicular to that plane. This allows for a long-lived jet-launching episode. This long-lasting jet-launching episode launches more mass into the jets that can inflate larger pairs of ears or bubbles, forming the main jets’ axis of the CCSNR that is not necessarily related to a possible pre-collapse core rotation. I discuss the relation of the main jets’ axis to the neutron star’s natal kick velocity.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"34 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141509081","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2024-06-23DOI: 10.1088/1674-4527/ad44f1
Wei-Nan Wang, Jin-Song Ping, Ming-Yuan Wang, Wen-Zhao Zhang, Han-Lin Ye, Xing-Wei Han and Song-Feng Kou
Lunar optical polarization is a fascinating phenomenon that occurs when sunlight reflects off the surface of the Moon and becomes polarized. This study employs a novel split-focus plane polarimetric camera to conduct the initial white light polarimetric observations on the near side of the Moon. We obtained the linear degree of polarization (DOP) parameters of white light by observation from the eastern and western hemispheres of the Moon. The findings indicate that the white light polarization is lower in the lunar highland than in the lunar maria overall. Combining the analysis of lunar soil samples, we noticed and determined that the DOP parameters of white light demonstrate high consistency with iron oxide on the Moon. This study may serve as a new diagnostic tool for the Moon.
{"title":"The First Ground-based White Light Lunar Polarization Imaging: A New Kind of FeO Observation on the Near Side of the Moon","authors":"Wei-Nan Wang, Jin-Song Ping, Ming-Yuan Wang, Wen-Zhao Zhang, Han-Lin Ye, Xing-Wei Han and Song-Feng Kou","doi":"10.1088/1674-4527/ad44f1","DOIUrl":"https://doi.org/10.1088/1674-4527/ad44f1","url":null,"abstract":"Lunar optical polarization is a fascinating phenomenon that occurs when sunlight reflects off the surface of the Moon and becomes polarized. This study employs a novel split-focus plane polarimetric camera to conduct the initial white light polarimetric observations on the near side of the Moon. We obtained the linear degree of polarization (DOP) parameters of white light by observation from the eastern and western hemispheres of the Moon. The findings indicate that the white light polarization is lower in the lunar highland than in the lunar maria overall. Combining the analysis of lunar soil samples, we noticed and determined that the DOP parameters of white light demonstrate high consistency with iron oxide on the Moon. This study may serve as a new diagnostic tool for the Moon.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"41 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141509082","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
Infrared (IR) spectral energy distribution (SED) is the major tracer of protoplanetary disks. It was recently proposed to use the near-to-mid IR (or K-24) SED slope α defined between 2 and 24μm as a potential quantitative tracer of disk age. We critically examine the viability of this idea and confront it with additional statistics of IR luminosities and SED shapes. We point out that, because the statistical properties of most of the complicated physical factors involved in disk evolution are still poorly understood in a quantitative sense, the only viable way is to assume them to be random so that an idealized “average disk” can be defined, which allows the α histogram to trace its age. We confirm that the statistics of the zeroth order (luminosity), first order (slope α), and second order characteristics (concavity) of the observed K-24 SEDs indeed carry useful information upon the evolutionary processes of the “average disk”. We also stress that intrinsic diversities in K-24 SED shapes and luminosities are always large at the level of individual stars so that the application of the evolutionary path of the “average disk” to individual stars must be done with care. The data of most curves in plots are provided on GitHub (Disk-age package https://github.com/starage/disk-age/).
红外光谱能量分布（SED）是原行星盘的主要示踪剂。最近有人提出利用定义在 2 到 24μm 之间的近中红外（或 K-24）SED 斜率 α 作为磁盘年龄的潜在定量示踪。我们对这一想法的可行性进行了严格的审查，并用红外亮度和 SED 形状的其他统计资料来加以证实。我们指出，由于涉及磁盘演化的大多数复杂物理因素的统计特性在定量意义上仍不甚明了，唯一可行的办法是假定它们是随机的，这样就可以定义一个理想化的 "平均磁盘"，从而可以用α直方图来追踪其年龄。我们证实，观测到的 K-24 SED 的零阶（光度）、一阶（斜率 α）和二阶（凹度）特征的统计数据确实包含了 "平均圆盘 "演化过程的有用信息。我们还强调，在单个恒星的层面上，K-24 SED 的形状和亮度的内在多样性总是很大的，因此将 "平均圆盘 "的演化路径应用到单个恒星上时必须小心谨慎。图中大多数曲线的数据都在 GitHub 上提供（Disk-age 软件包 https://github.com/starage/disk-age/）。
{"title":"Can near-to-mid Infrared Spectral Energy Distribution Quantitatively Trace Protoplanetary Disk Evolution?","authors":"Mingchao Liu, 明超 刘, Jinhua He, 金华 何, Zhen Guo, Jixing Ge, 继兴 葛, Yuping Tang and 雨平 唐","doi":"10.1088/1674-4527/ad4b5c","DOIUrl":"https://doi.org/10.1088/1674-4527/ad4b5c","url":null,"abstract":"Infrared (IR) spectral energy distribution (SED) is the major tracer of protoplanetary disks. It was recently proposed to use the near-to-mid IR (or K-24) SED slope α defined between 2 and 24μm as a potential quantitative tracer of disk age. We critically examine the viability of this idea and confront it with additional statistics of IR luminosities and SED shapes. We point out that, because the statistical properties of most of the complicated physical factors involved in disk evolution are still poorly understood in a quantitative sense, the only viable way is to assume them to be random so that an idealized “average disk” can be defined, which allows the α histogram to trace its age. We confirm that the statistics of the zeroth order (luminosity), first order (slope α), and second order characteristics (concavity) of the observed K-24 SEDs indeed carry useful information upon the evolutionary processes of the “average disk”. We also stress that intrinsic diversities in K-24 SED shapes and luminosities are always large at the level of individual stars so that the application of the evolutionary path of the “average disk” to individual stars must be done with care. The data of most curves in plots are provided on GitHub (Disk-age package https://github.com/starage/disk-age/).","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"146 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141529813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2024-06-18DOI: 10.1088/1674-4527/ad48d1
Jiangang Kang, Chang-Zhi Lu, Tong-Jie Zhang and Ming Zhu
This study presents results on detecting neutral atomic hydrogen (H i) 21 cm absorption in the spectrum of PKS PKS1413+13 at redshift z = 0.24670041. The observation was conducted by FAST, with a spectral resolution of 10 Hz, using 10 minutes of observing time. The global spectral profile is examined by modeling the absorption line using a single Gaussian function with a resolution of 10 kHz within a 2 MHz bandwidth. The goal is to determine the rate of the latest cosmic acceleration by directly measuring the redshift evolution of the H i 21 cm absorption line with Hubble flow toward a common background quasar over a decade or longer time span. This will serve as a detectable signal generated by the accelerated expansion of the Universe at redshift z < 1, referred to as redshift drift or the SL effect. The measured H i gas column density in this DLA system is approximately equivalent to the initial observation value, considering uncertainties of the spin temperature of a spiral host galaxy. The high signal-to-noise ratio of 57, obtained at a 10 kHz resolution, strongly supports the feasibility of using the H i 21 cm absorption line in DLA systems to accurately measure the redshift drift rate at a precision level of around 10−10 per decade.
本研究介绍了在红移 z = 0.24670041 的 PKS PKS1413+13 的光谱中探测到中性原子氢（H i）21 厘米吸收的结果。观测由 FAST 进行，光谱分辨率为 10 Hz，观测时间为 10 分钟。通过在 2 MHz 带宽内使用分辨率为 10 kHz 的单高斯函数对吸收线进行建模，对全局光谱剖面进行了研究。我们的目标是通过直接测量 H i 21 厘米吸收线的红移演变，确定最近宇宙加速的速率。这将作为红移 z < 1 时宇宙加速膨胀产生的可探测信号，即红移漂移或 SL 效应。考虑到螺旋宿主星系自旋温度的不确定性，在这个 DLA 系统中测得的 H i 气体柱密度大约相当于最初的观测值。在 10 kHz 分辨率下获得的 57 的高信噪比，有力地支持了在 DLA 系统中利用 H i 21 cm 吸收线精确测量红移漂移率的可行性，精确度约为每十年 10-10。
{"title":"Toward a Direct Measurement of the Cosmic Acceleration: The Pilot Observation of HI 21 cm Absorption Line at FAST","authors":"Jiangang Kang, Chang-Zhi Lu, Tong-Jie Zhang and Ming Zhu","doi":"10.1088/1674-4527/ad48d1","DOIUrl":"https://doi.org/10.1088/1674-4527/ad48d1","url":null,"abstract":"This study presents results on detecting neutral atomic hydrogen (H i) 21 cm absorption in the spectrum of PKS PKS1413+13 at redshift z = 0.24670041. The observation was conducted by FAST, with a spectral resolution of 10 Hz, using 10 minutes of observing time. The global spectral profile is examined by modeling the absorption line using a single Gaussian function with a resolution of 10 kHz within a 2 MHz bandwidth. The goal is to determine the rate of the latest cosmic acceleration by directly measuring the redshift evolution of the H i 21 cm absorption line with Hubble flow toward a common background quasar over a decade or longer time span. This will serve as a detectable signal generated by the accelerated expansion of the Universe at redshift z < 1, referred to as redshift drift or the SL effect. The measured H i gas column density in this DLA system is approximately equivalent to the initial observation value, considering uncertainties of the spin temperature of a spiral host galaxy. The high signal-to-noise ratio of 57, obtained at a 10 kHz resolution, strongly supports the feasibility of using the H i 21 cm absorption line in DLA systems to accurately measure the redshift drift rate at a precision level of around 10−10 per decade.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"223 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141518209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2024-06-07DOI: 10.1088/1674-4527/ad4598
Jun-Yu Shen, Bi-Wen Bao, Li Zhang
Using an effective adiabatic index γeff to mimic the feedback of efficient shock acceleration, we simulate the temporal evolution of a young type Ia supernova remnant (SNR) with two different background magnetic field (BMF) topologies: a uniform and a turbulent BMF. The density distribution and magnetic-field characteristics of our benchmark SNR are studied with two-dimensional cylindrical magnetohydrodynamic simulations. When γeff is considered, we find that: (1) the two-shock structure shrinks and the downstream magnetic-field orientation is dominated by the Rayleigh–Taylor instability structures; (2) there exists more quasi-radial magnetic fields inside the shocked region; and (3) inside the intershock region, both the quasi-radial magnetic energy density and the total magnetic energy density are enhanced: in the radial direction, with γeff = 1.1, they are amplified about 10–26 times more than those with γeff = 5/3. While in the angular direction, the total magnetic energy densities could be amplified about 350 times more than those with γeff = 5/3, and there are more grid cells within the intershock region where the magnetic energy density is amplified by a factor greater than 100.
{"title":"Feedback of Efficient Shock Acceleration on Magnetic-field Structure Inside Young Type Ia Supernova Remnants","authors":"Jun-Yu Shen, Bi-Wen Bao, Li Zhang","doi":"10.1088/1674-4527/ad4598","DOIUrl":"https://doi.org/10.1088/1674-4527/ad4598","url":null,"abstract":"Using an effective adiabatic index <italic toggle=\"yes\">γ</italic>\u0000<sub>eff</sub> to mimic the feedback of efficient shock acceleration, we simulate the temporal evolution of a young type Ia supernova remnant (SNR) with two different background magnetic field (BMF) topologies: a uniform and a turbulent BMF. The density distribution and magnetic-field characteristics of our benchmark SNR are studied with two-dimensional cylindrical magnetohydrodynamic simulations. When <italic toggle=\"yes\">γ</italic>\u0000<sub>eff</sub> is considered, we find that: (1) the two-shock structure shrinks and the downstream magnetic-field orientation is dominated by the Rayleigh–Taylor instability structures; (2) there exists more quasi-radial magnetic fields inside the shocked region; and (3) inside the intershock region, both the quasi-radial magnetic energy density and the total magnetic energy density are enhanced: in the radial direction, with <italic toggle=\"yes\">γ</italic>\u0000<sub>eff</sub> = 1.1, they are amplified about 10–26 times more than those with <italic toggle=\"yes\">γ</italic>\u0000<sub>eff</sub> = 5/3. While in the angular direction, the total magnetic energy densities could be amplified about 350 times more than those with <italic toggle=\"yes\">γ</italic>\u0000<sub>eff</sub> = 5/3, and there are more grid cells within the intershock region where the magnetic energy density is amplified by a factor greater than 100.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"32 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141518210","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2024-06-03DOI: 10.1088/1674-4527/ad44f0
Y. El jariri, F.L. Sefyani, A. Benhida, Z. Benkhaldoun, K. Kolenberg, K. Chafouai, A. Habib and M. Sabil
The Van Hoof effect is a phase shift existing between the radial velocity curves of hydrogen and metallic lines within the atmosphere of pulsating stars. In this article, we present a study of this phenomenon through the spectra of the brightest pulsating star RR Lyr of RR Lyrae stars recorded for 22 yr. We based ourselves, on the one hand, on 1268 spectra (41 nights of observation) recorded between the years 1994 and 1997 at the Observatory of Haute Provence (OHP, France) previously observed by Chadid and Gillet, and on the other hand on 1569 spectra (46 nights of observation) recorded at our Oukaimeden Observatory (Morocco) between 2015 and 2016. Through this study, we have detected information on atmospheric dynamics that had not previously been detected. Indeed, the Van Hoof effect which results in a clear correlation between the radial velocities of hydrogen and those of the metallic lines has been observed and analyzed at different Blazhko phases. A correlation between the radial velocities of different metallic lines located in the lower atmosphere has been observed as well. For the first time, we were able to show that the amplitude of the radial velocity curves deduced from the lines of hydrogen and that of Fe ii (λ4923.921 Å) increases toward the minimum of the Blazhko cycle and decreases toward the maximum of the same Blazhko cycle. Furthermore, we found that the Van Hoof effect is also modulated by the Blazhko effect. Thus, toward the minimum of the Blazhko cycle the Van Hoof effect is more visible and at the maximum of the Blazhko cycle, this effect is minimal. We also observed the temporal evolution of the amplitudes of the radial velocities of the lower and upper atmosphere. When observed over a long time, we can interpret it as a function of the Blazhko phases.
{"title":"Analysis of the Impact of the Blazhko Effect Both on the Van Hoof Effect and Radial Velocity Amplitude in the Star RR Lyr","authors":"Y. El jariri, F.L. Sefyani, A. Benhida, Z. Benkhaldoun, K. Kolenberg, K. Chafouai, A. Habib and M. Sabil","doi":"10.1088/1674-4527/ad44f0","DOIUrl":"https://doi.org/10.1088/1674-4527/ad44f0","url":null,"abstract":"The Van Hoof effect is a phase shift existing between the radial velocity curves of hydrogen and metallic lines within the atmosphere of pulsating stars. In this article, we present a study of this phenomenon through the spectra of the brightest pulsating star RR Lyr of RR Lyrae stars recorded for 22 yr. We based ourselves, on the one hand, on 1268 spectra (41 nights of observation) recorded between the years 1994 and 1997 at the Observatory of Haute Provence (OHP, France) previously observed by Chadid and Gillet, and on the other hand on 1569 spectra (46 nights of observation) recorded at our Oukaimeden Observatory (Morocco) between 2015 and 2016. Through this study, we have detected information on atmospheric dynamics that had not previously been detected. Indeed, the Van Hoof effect which results in a clear correlation between the radial velocities of hydrogen and those of the metallic lines has been observed and analyzed at different Blazhko phases. A correlation between the radial velocities of different metallic lines located in the lower atmosphere has been observed as well. For the first time, we were able to show that the amplitude of the radial velocity curves deduced from the lines of hydrogen and that of Fe ii (λ4923.921 Å) increases toward the minimum of the Blazhko cycle and decreases toward the maximum of the same Blazhko cycle. Furthermore, we found that the Van Hoof effect is also modulated by the Blazhko effect. Thus, toward the minimum of the Blazhko cycle the Van Hoof effect is more visible and at the maximum of the Blazhko cycle, this effect is minimal. We also observed the temporal evolution of the amplitudes of the radial velocities of the lower and upper atmosphere. When observed over a long time, we can interpret it as a function of the Blazhko phases.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"24 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141255752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2024-05-28DOI: 10.1088/1674-4527/ad4599
Xue-Feng Lu, Li-Ming Song, Ming-Yu Ge, Shuang-Nan Zhang, Jin-Lu Qu, Ce Cai, Cong-Zhan Liu, Cheng-Kui Li, Yu-Cong Fu and Ying-Chen Xu
In October 2022, the magnetar SGR J1935+2154 entered the active outburst state. During the episode, the Insight-HXMT satellite carried out a long observation that lasted for 20 days. More than 300 bursts were detected, and a certain amount of persistent radiation signals were also accumulated. This paper mainly introduces the results of persistent radiation profile folding and period search based on Insight-HXMT data. At the same time, the burst phase distribution characteristics, spectral lag results of burst, the spectral characteristics of zero-lag bursts and the time-resolved spectral evolution characteristics of high-flux bursts are reported. We found that there is no significant delay feature during different energy bands for the bursts of SGR J1935+2154. The observed zero-lag burst does not have a unique spectrum. The time-resolved spectrum of the individual burst has consistent spectral types and spectral parameters at different time periods of the burst. We also find that the burst number phase distribution and the burst photon phase distribution have the same tendency to concentrate in specific regions of the persistent emission profile.
{"title":"Temporal and Spectral Characteristics of Persistent Emission and Special Bursts of Magnetar SGR J1935+2154 Based on Insight-HXMT","authors":"Xue-Feng Lu, Li-Ming Song, Ming-Yu Ge, Shuang-Nan Zhang, Jin-Lu Qu, Ce Cai, Cong-Zhan Liu, Cheng-Kui Li, Yu-Cong Fu and Ying-Chen Xu","doi":"10.1088/1674-4527/ad4599","DOIUrl":"https://doi.org/10.1088/1674-4527/ad4599","url":null,"abstract":"In October 2022, the magnetar SGR J1935+2154 entered the active outburst state. During the episode, the Insight-HXMT satellite carried out a long observation that lasted for 20 days. More than 300 bursts were detected, and a certain amount of persistent radiation signals were also accumulated. This paper mainly introduces the results of persistent radiation profile folding and period search based on Insight-HXMT data. At the same time, the burst phase distribution characteristics, spectral lag results of burst, the spectral characteristics of zero-lag bursts and the time-resolved spectral evolution characteristics of high-flux bursts are reported. We found that there is no significant delay feature during different energy bands for the bursts of SGR J1935+2154. The observed zero-lag burst does not have a unique spectrum. The time-resolved spectrum of the individual burst has consistent spectral types and spectral parameters at different time periods of the burst. We also find that the burst number phase distribution and the burst photon phase distribution have the same tendency to concentrate in specific regions of the persistent emission profile.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"6 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141190192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2024-05-19DOI: 10.1088/1674-4527/ad3ec8
An-Xu Luo, Hong-Li Liu, Guang-Xing Li, Sirong Pan and Dong-Ting Yang
To explore the potential role of gravity, turbulence and magnetic fields in high-mass star formation in molecular clouds, this study revisits the velocity dispersion–size (σ–L) and density–size (ρ–L) scalings and the associated turbulent energy spectrum using an extensive data sample. The sample includes various hierarchical density structures in high-mass star formation clouds, across scales of 0.01–100 pc. We observe σ ∝ L0.26 and ρ ∝ L−1.54 scalings, converging toward a virial equilibrium state. A nearly flat virial parameter–mass (αvir−M) distribution is seen across all density scales, with αvir values centered around unity, suggesting a global equilibrium maintained by the interplay between gravity and turbulence across multiple scales. Our turbulent energy spectrum (E(k)) analysis, based on the σ–L and ρ–L scalings, yields a characteristic E(k) ∝ k−1.52. These findings indicate the potential significance of gravity, turbulence, and possibly magnetic fields in regulating dynamics of molecular clouds and high-mass star formation therein.
{"title":"What is the Role of Gravity, Turbulence and Magnetic Fields in High-mass Star Formation Clouds?","authors":"An-Xu Luo, Hong-Li Liu, Guang-Xing Li, Sirong Pan and Dong-Ting Yang","doi":"10.1088/1674-4527/ad3ec8","DOIUrl":"https://doi.org/10.1088/1674-4527/ad3ec8","url":null,"abstract":"To explore the potential role of gravity, turbulence and magnetic fields in high-mass star formation in molecular clouds, this study revisits the velocity dispersion–size (σ–L) and density–size (ρ–L) scalings and the associated turbulent energy spectrum using an extensive data sample. The sample includes various hierarchical density structures in high-mass star formation clouds, across scales of 0.01–100 pc. We observe σ ∝ L0.26 and ρ ∝ L−1.54 scalings, converging toward a virial equilibrium state. A nearly flat virial parameter–mass (αvir−M) distribution is seen across all density scales, with αvir values centered around unity, suggesting a global equilibrium maintained by the interplay between gravity and turbulence across multiple scales. Our turbulent energy spectrum (E(k)) analysis, based on the σ–L and ρ–L scalings, yields a characteristic E(k) ∝ k−1.52. These findings indicate the potential significance of gravity, turbulence, and possibly magnetic fields in regulating dynamics of molecular clouds and high-mass star formation therein.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"67 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141149815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2024-05-19DOI: 10.1088/1674-4527/ad3c6f
Keyu Lu, Yue-Lin Sming Tsai, Qiang Yuan and Le Zhang
We investigate the impact of inelastic collisions between dark matter (DM) and heavy cosmic ray (CR) nuclei on CR propagation. We approximate the fragmentation cross-sections for DM-CR collisions using collider-measured proton-nuclei scattering cross-sections, allowing us to assess how these collisions affect the spectra of CR boron and carbon. We derive new CR spectra from DM-CR collisions by incorporating their cross-sections into the source terms and solving the diffusion equation for the complete network of reactions involved in generating secondary species. In a specific example with a coupling strength of bχ = 0.1 and a DM mass of mχ = 0.1 GeV, considering a simplified scenario where DM interacts exclusively with oxygen, a notable modification in the boron-to-carbon spectrum due to the DM-CR interaction is observed. Particularly, the peak within the spectrum, spanning from 0.1 to 10 GeV, experiences an enhancement of approximately 1.5 times. However, in a more realistic scenario where DM particles interact with all CRs, this peak can be amplified to twice its original value. Utilizing the latest data from AMS-02 and DAMPE on the boron-to-carbon ratio, we estimate a 95% upper limit for the effective inelastic cross-section of DM-proton as a function of DM mass. Our findings reveal that at mχ ≃ 2 MeV, the effective inelastic cross-section between DM and protons must be less than .
{"title":"Inelastic Scattering of Dark Matter with Heavy Cosmic Rays","authors":"Keyu Lu, Yue-Lin Sming Tsai, Qiang Yuan and Le Zhang","doi":"10.1088/1674-4527/ad3c6f","DOIUrl":"https://doi.org/10.1088/1674-4527/ad3c6f","url":null,"abstract":"We investigate the impact of inelastic collisions between dark matter (DM) and heavy cosmic ray (CR) nuclei on CR propagation. We approximate the fragmentation cross-sections for DM-CR collisions using collider-measured proton-nuclei scattering cross-sections, allowing us to assess how these collisions affect the spectra of CR boron and carbon. We derive new CR spectra from DM-CR collisions by incorporating their cross-sections into the source terms and solving the diffusion equation for the complete network of reactions involved in generating secondary species. In a specific example with a coupling strength of bχ = 0.1 and a DM mass of mχ = 0.1 GeV, considering a simplified scenario where DM interacts exclusively with oxygen, a notable modification in the boron-to-carbon spectrum due to the DM-CR interaction is observed. Particularly, the peak within the spectrum, spanning from 0.1 to 10 GeV, experiences an enhancement of approximately 1.5 times. However, in a more realistic scenario where DM particles interact with all CRs, this peak can be amplified to twice its original value. Utilizing the latest data from AMS-02 and DAMPE on the boron-to-carbon ratio, we estimate a 95% upper limit for the effective inelastic cross-section of DM-proton as a function of DM mass. Our findings reveal that at mχ ≃ 2 MeV, the effective inelastic cross-section between DM and protons must be less than .","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"28 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141149810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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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