Research in Astronomy and Astrophysics最新文献

{"title":"A Comprehensive Classification and Analysis of Geomagnetic Storms Over Solar Cycle 24","authors":"Raja Adibah Raja Halim Shah, Nurul Shazana Abdul Hamid, Mardina Abdullah, Adlyka Annuar, Idahwati Sarudin, Zahira Mohd Radzi and Akimasa Yoshikawa","doi":"10.1088/1674-4527/ad5b34","DOIUrl":"https://doi.org/10.1088/1674-4527/ad5b34","url":null,"abstract":"A geomagnetic storm is a global disturbance of Earth's magnetosphere, occurring as a result of the interaction with magnetic plasma ejected from the Sun. Despite considerable research, a comprehensive classification of storms for a complete solar cycle has not yet been fully developed, as most previous studies have been limited to specific storm types. This study, therefore, attempted to present complete statistics for solar cycle 24, detailing the occurrence of geomagnetic storm events and classifying them by type of intensity (moderate, intense, and severe), type of complete interval (normal or complex), duration of the recovery phase (rapid or long), and the number of steps in the storm's development. The analysis was applied to data from ground-based magnetometers, which measured the Dst index as provided by the World Data Center for Geomagnetism, Kyoto, Japan. This study identified 211 storm events, comprising moderate (177 events), intense (33 events), and severe (1 event) types. About 36% of ICMEs and 23% of CIRs are found to be geoeffective, which caused geomagnetic storms. Up to four-step development of geomagnetic storms was exhibited during the main phase for this solar cycle. Analysis showed the geomagnetic storms developed one or more steps in the main phase, which were probably related to the driver that triggered the geomagnetic storms. A case study was additionally conducted to observe the variations of the ionospheric disturbance dynamo (Ddyn) phenomenon that resulted from the geomagnetic storm event of 2015 July 13. The attenuation of the Ddyn in the equatorial region was analyzed using the H component of geomagnetic field data from stations in the Asian sector (Malaysia and India). The variations in the Ddyn signatures were observed at both stations, with the TIR station (India) showing higher intensity than the LKW station (Malaysia).","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"44 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141780847","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}

{"title":"Perturbing the Stable Accretion Disk in Kerr and 4D Einstein–Gauss–Bonnet Gravities: Comprehensive Analysis of Instabilities and Dynamics","authors":"Orhan Donmez","doi":"10.1088/1674-4527/ad5b9e","DOIUrl":"https://doi.org/10.1088/1674-4527/ad5b9e","url":null,"abstract":"The study of a disturbed accretion disk holds great significance in the realm of astrophysics, as such events play a crucial role in revealing the nature of disk structure, the release of energy, and the generation of shock waves. Consequently, they can help explain the causes of X-ray emissions observed in black hole accretion disk systems. In this paper, we perturb the stable disk formed by spherical accretion around Kerr and Einstein–Gauss–Bonnet (EGB) black holes. This perturbation reveals one- and two-armed spiral shock waves around the black hole. We find a strong connection between these waves and the black hole spin parameter (a/M) and the EGB coupling constant (α). Specifically, we find that as α increases in the negative direction, the dynamics of the disk and the waves become more chaotic. Additionally, we observe that the angular momentum of the perturbing matter significantly affects mass accretion and the oscillation of the arising shock waves. This allows us to observe changes in QPO frequencies, particularly, perturbations with angular momentum matching the observed C−type low-frequency QPOs of the GRS 1915+105 source. Thus, we conclude that the possibility of the occurrence of shock waves within the vicinity of GRS 1915+105 is substantial.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"26 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141746195","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}

{"title":"Simulation Study on Constraining Gravitational Wave Propagation Speed by Gravitational Wave and Gamma-ray Burst Joint Observation on Binary Neutron Star Mergers","authors":"Jin-Hui Rao, Shu-Xu Yi, Lian Tao and Qing-Wen Tang","doi":"10.1088/1674-4527/ad5d8b","DOIUrl":"https://doi.org/10.1088/1674-4527/ad5d8b","url":null,"abstract":"Theories of modified gravity suggest that the propagation speed of gravitational waves (GW) vg may deviate from the speed of light c. A constraint can be placed on the difference between c and vg with a simple method that uses the arrival time delay between GW and electromagnetic wave simultaneously emitted from a burst event. We simulated the joint observation of GW and short gamma-ray burst signals from binary neutron star merger events in different observation campaigns, involving advanced LIGO (aLIGO) in design sensitivity and Einstein Telescope (ET) joint-detected with Fermi/GBM. As a result, the relative precision of constraint on vg can reach ∼10−17 (aLIGO) and ∼10−18 (ET), which are one and two orders of magnitude better than that from GW170817, respectively. We continue to obtain the bound of graviton mass mg ≤ 7.1(3.2) × 10−20 eV with aLIGO (ET). Applying the Standard-Model Extension test framework, the constraint on vg allows us to study the Lorentz violation in the nondispersive, nonbirefringent limit of the gravitational sector. We obtain the constraints of the dimensionless isotropic coefficients at mass dimension d = 4, which are for aLIGO and for ET.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"28 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141746363","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}

{"title":"Investigation of WZ Sge-type Dwarf Nova ASASSN-19oc: Optical Spectroscopy and Multicolor Light Curve Analysis","authors":"Viktoriia Krushevska, Sergey Shugarov, Paolo Ochner, Yuliana Kuznyetsova, Mykola Petrov and Peter Kroll","doi":"10.1088/1674-4527/ad59ec","DOIUrl":"https://doi.org/10.1088/1674-4527/ad59ec","url":null,"abstract":"In this study, we present an investigation of the newly discovered dwarf nova ASASSN-19oc during its superoutburst on 2019 June 2. We carried out detailed UBVRcIc-photometric observations and also obtained a spectrum on day 7 of the outburst, which shows the presence of hydrogen absorption lines commonly found in dwarf nova outbursts. Analysis of photometric data reveals the occurrence of early superhumps in the initial days of observations, followed by ordinary and late superhumps. We have accurately calculated the period of the ordinary superhumps as Pord = 0.05681(10) days and determined the periods at different stages, as well as the rate of change of the superhump period (Pdot = /P = 8.1 × 10−5). Additionally, we have derived the mass ratio of the components (q = 0.09), and estimated the color temperature during the outburst as ∼11,000 K, the distance to the system (d = 560 pc) and absolute magnitude of the system in outburst (MV = 5.3). We have shown that outbursts of this star are very rare: based on brightness measurements on 600 archival photographic plates, we found only one outburst that occurred in 1984. This fact, as well as the properties listed above, convincingly shows that the variable ASASSN-19oc is a dwarf nova of WZ Sge type.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"22 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141746194","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}

{"title":"Calculating the Excitation Temperature for H2CO Absorption Lines in Molecular Clouds","authors":"Jia Bu, Jarken Esimbek, Jianjun Zhou, Toktarkhan Komesh, Xindi Tang, Dalei Li, Yuxin He, Kadirya Tursun, Dongdong Zhou, Ernar Imanaly and Serikbek Sailanbek","doi":"10.1088/1674-4527/ad5b36","DOIUrl":"https://doi.org/10.1088/1674-4527/ad5b36","url":null,"abstract":"The excitation temperature Tex for molecular emission and absorption lines is an essential parameter for interpreting the molecular environment. This temperature can be obtained by observing multiple molecular transitions or hyperfine structures of a single transition, but it remains unknown for a single transition without hyperfine structure lines. Earlier H2CO absorption experiments for a single transition without hyperfine structures adopted a constant value of Tex, which is not correct for molecular regions with active star formation and H ii regions. For H2CO, two equations with two unknowns may be used to determine the excitation temperature Tex and the optical depth τ, if other parameters can be determined from measurements. Published observational data of the 4.83 GHz (λ = 6 cm) H2CO (110−111) absorption line for three star formation regions, W40, M17 and DR17, have been used to verify this method. The distributions of Tex in these sources are in good agreement with the contours of the H110α emission of the H ii regions in M17 and DR17 and with the H2CO (110−111) absorption in W40. The distributions of Tex in the three sources indicate that there can be significant variation in the excitation temperature across star formation and H ii regions and that the use of a fixed (low) value results in misinterpretation.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"152 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141584638","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}

{"title":"Identifying Three New AGNs among Fermi Unidentified Gigaelectronvolt Sources","authors":"Shun-Hao Ji, Zhong-Xiang Wang, Qiang-Meng Huang and Ruo-Heng Yang","doi":"10.1088/1674-4527/ad5ada","DOIUrl":"https://doi.org/10.1088/1674-4527/ad5ada","url":null,"abstract":"We report our identification of three gigaelectronvolt γ-ray sources, 4FGL J0502.6+0036, 4FGL J1055.9+6507, and 4FGL J1708.2+5519, as Active Galactic Nuclei (AGNs). They are listed in the latest Fermi-Large Area Telescope source catalog as unidentified ones. We find that the sources all showed γ-ray flux variations in recent years. Using different survey catalogs, we are able to find a radio source within the error circle of each source’s position. Further analysis of optical sources in the fields allows us to determine the optical counterparts, which showed similar variation patterns to those seen in γ-rays. The optical counterparts have reported redshifts of 0.6, 1.5, and 2.3, respectively, estimated from photometric measurements. In addition, we also obtain an X-ray spectrum of 4FGL J0502.6+0036 and a flux upper limit on the X-ray emission of 4FGL J1055.9+6507 by analyzing the archival data. The broadband spectral energy distributions of the three sources from radio to γ-rays are constructed. Comparing mainly the γ-ray properties of the three sources with those of different sub-classes of AGNs, we tentatively identify them as blazars. Followup optical spectroscopy is highly warranted for obtaining their spectral features and thus verifying the identification.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"1 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141609794","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}

{"title":"Astrometric Observations of NEA 1998 HH49 Using the Daocheng 50 cm Telescope","authors":"Huan Xu, Xiang-Ming Cheng, Yi-Gong Zhang, Teng-Fei Song, Zhen-Jun Zhang, Qing-Yu Peng","doi":"10.1088/1674-4527/ad50b8","DOIUrl":"https://doi.org/10.1088/1674-4527/ad50b8","url":null,"abstract":"This study details an astrometric observation campaign of the Near-Earth Asteroid 1998 HH49, conducted with the aim of refining our understanding of its physical characteristics. Utilizing the 50 cm telescope located at the Wumingshan Mountain in Daocheng, Sichuan, images were obtained over four nights, from 2023 October 19 to October 22. These observations were processed using Astrometrica software, facilitating the precise determination of the asteroid’s position. The observational results were compared with the ephemerides from three distinct sources to verify accuracy: the Jet Propulsion Laboratory (JPL) Horizons System, the Institut de Mécanique Céleste et de Calcul des Éphémérides (IMCCE) Miriade, and the Near-Earth Objects Dynamic Site (NEODyS-2). When compared with the JPL ephemeris, a mean observed-minus-calculated (<italic toggle=\"yes\">O</italic>-<italic toggle=\"yes\">C</italic>) result of 0.″07 in the R.A. direction and −0.″35 in the decl. direction was yielded. Furthermore, the comparison with the IMCCE ephemeris yielded mean <italic toggle=\"yes\">O</italic>-<italic toggle=\"yes\">C</italic> results of 0.″08 in the R.A. direction and −0.″06 in the decl. direction. The comparison with the NEODyS-2 ephemeris yielded the mean <italic toggle=\"yes\">O</italic>-<italic toggle=\"yes\">C</italic> results of 0.″06 in R.A. and −0.″49 in decl. direction. The study’s findings demonstrate a general consistency between the observed data and the ephemeris predictions, with minor discrepancies observed across the data sets. Notably, both the JPL and NEODyS-2 ephemerides show that the residuals in the decl. direction exceed those in the R.A. direction. The disparities may result from atmospheric differential color refraction, ephemeris discrepancies, observational errors, and other factors. Additionally, it is worth noting that further investigation is required due to the potential influence of additional factors. Overall, the Daocheng 50 cm Telescope exhibits the ability to conduct high-precision positional measurements.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"38 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141576797","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}

{"title":"Design and Application of an S-band Fast Radio Bursts Search Pipeline for the Nanshan 26 m Radio Telescope","authors":"Yan-Ling Liu, Mao-Zheng Chen, Jian Li, Jian-Ping Yuan, Rai Yuen, Zhi-Yong Liu, Hao Yan, Wen-Long Du, Nan-Nan Zhai","doi":"10.1088/1674-4527/ad52c5","DOIUrl":"https://doi.org/10.1088/1674-4527/ad52c5","url":null,"abstract":"Fast radio bursts (FRBs) are among the most studied radio transients in astrophysics, but their origin and radiation mechanism are still unknown. It is a challenge to search for FRB events in a huge amount of observational data with high speed and high accuracy. With the rapid advancement of the FRB research process, FRB searching has changed from archive data mining to either long-term monitoring of the repeating FRBs or all-sky surveys with specialized equipments. Therefore, establishing a highly efficient and high quality FRB search pipeline is the primary task in FRB research. Deep learning techniques provide new ideas for FRB search processing. We have detected radio bursts from FRB 20201124A in the <italic toggle=\"yes\">L</italic>-band observational data of the Nanshan 26 m radio telescope (NSRT-26m) using the constructed deep learning based search pipeline named dispersed dynamic spectra search (DDSS). Afterwards, we further retrained the deep learning model and applied the DDSS framework to <italic toggle=\"yes\">S</italic>-band observations. In this paper, we present the FRB observation system and search pipeline using the <italic toggle=\"yes\">S</italic>-band receiver. We carried out search experiments, and successfully detected the radio bursts from the magnetar SGR J1935+2145 and FRB 20220912A. The experimental results show that the search pipeline can complete the search efficiently and output the search results with high accuracy.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"27 3 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141576798","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}

{"title":"Probing the Galactic Halo with RR Lyrae Stars. VI. The Radial Velocity Curve Templates of RRc Stars","authors":"Yue Huang, Min Fang, Gaochao Liu, Xianzhong Zheng, Sarah Ann Bird, Yang Huang, Jianrong Shi, Jiangtao Wang, Huawei Zhang, Haijun Tian, Haotong Zhang","doi":"10.1088/1674-4527/ad50b5","DOIUrl":"https://doi.org/10.1088/1674-4527/ad50b5","url":null,"abstract":"We present radial velocity (RV) curve templates of RR Lyrae first-overtone (RRc) stars constructed with the Mg <sc>i</sc> b triplet and H<italic toggle=\"yes\">α</italic> lines using time-domain Medium-Resolution Survey spectra of seven RRc stars from Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Data Release 9. Additionally, we derive the relation between the stellar RV curve amplitudes and <italic toggle=\"yes\">g</italic>-band light curve amplitudes from Zwicky Transient Facility (ZTF) public survey. For those RRc stars without ZTF <italic toggle=\"yes\">g</italic>-band light curves, we provide the conversions from the light curve amplitudes in ZTF <italic toggle=\"yes\">r</italic>- and <italic toggle=\"yes\">i</italic>-bands, Gaia <italic toggle=\"yes\">G</italic>-band, and <italic toggle=\"yes\">V</italic>-band from the All-Sky Automated Survey for Supernovae to those in ZTF <italic toggle=\"yes\">g</italic>-band. We validate our RV curve templates using the RRc star SV Scl and find the uncertainties of systemic RV are less than 2.11 km s ⁻¹ and 6.08 km s ⁻¹ based on the Mg <sc>i</sc> b triplet and H<italic toggle=\"yes\">α</italic> lines, respectively. We calculate the systemic RVs of 30 RRc stars using the RV curve templates constructed with the Mg <sc>i</sc> b triplet and H<italic toggle=\"yes\">α</italic> lines and find the systemic RVs are comparable with each other. This RV curve template will be particularly useful for obtaining the systemic RV of RRc using the LAMOST spectroscopy.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"144 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141576800","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}

{"title":"Evolution of High-energy Electron Distribution in Pulsar Wind Nebulae","authors":"Yi-Ming Liu, Hou-Dun Zeng, Yu-Liang Xin, Si-Ming Liu and Yi Zhang","doi":"10.1088/1674-4527/ad50b7","DOIUrl":"https://doi.org/10.1088/1674-4527/ad50b7","url":null,"abstract":"In this paper, we analyze the spectral energy distributions of 17 powerful (with a spin-down luminosity greater than 1035 erg s−1) young (with an age less than 15,000 yr) pulsar wind nebulae (PWNe) using a simple time-independent one-zone emission model. Our aim is to investigate correlations between model parameters and the ages of the corresponding PWNe, thereby revealing the evolution of high-energy electron distributions within PWNe. Our findings are as follows: (1) The electron distributions in PWNe can be characterized by a double power-law with a super-exponential cutoff. (2) As PWNe evolve, the high-energy end of the electron distribution spectrum becomes harder with the index decreasing from approximately 3.5 to 2.5, while the low-energy end spectrum index remains constant near 1.5. (3) There is no apparent correlation between the break energy or cutoff energy and the age of PWNe. (4) The average magnetic field within PWNe decreases with age, leading to a positive correlation between the energy loss timescale of electrons at the break energy or the high-energy cutoff, and the age of the PWN. (5) The total electron energy within PWNe remains constant near 2 × 1048 erg, while the total magnetic energy decreases with age.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"33 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141548269","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}