Astronomy Letters-A Journal of Astronomy and Space Astrophysics最新文献

{"title":"X-ray Halo of the Pulsar 4U 1538–52 from SRG Data","authors":"A. E. Shtykovsky,&nbsp;A. A. Lutovinov,&nbsp;R. A. Krivonos,&nbsp;M. R. Gilfanov,&nbsp;P. S. Medvedev,&nbsp;I. A. Mereminskiy,&nbsp;V. A. Arefiev,&nbsp;S. V. Molkov,&nbsp;R. A. Sunyaev","doi":"10.1134/S1063773723050031","DOIUrl":"10.1134/S1063773723050031","url":null,"abstract":"<p>We present the first results of the SRG observation of the pulsar 4U 1538–52 based on ARC-XC and eROSITA data. An extended emission in the form of a halo is detected around the source in the 0.5–8 keV energy band. Our simulation has shown that its surface brightness distribution can be described by a two-component model composed of a flat disk <span>({sim}250^{primeprime})</span> in radius and a <span>(beta)</span>-model with a characteristic size <span>({sim}480^{primeprime})</span>. We have constructed a broadband spectrum of 4U 1538–52 in the energy range 0.5–30 keV, which can be fitted by a weakly absorbed (<span>(N_{textrm{H}}simeq 0.7times 10^{22})</span> cm<span>({}^{-2})</span>) power law with a high-energy cutoff. In addition, iron emission lines are detected in the pulsar spectrum at 6–7 keV. We show that the observed halo spectrum is considerably softer (a power-law index <span>({simeq}2.8)</span>) than the pulsar spectrum (a power-law index <span>({simeq}0.9)</span>), consistent with the predictions of theoretical models for the X-ray scattering by dust.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"49 5","pages":"240 - 248"},"PeriodicalIF":0.9,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50447186","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":"Properties of the Flare Energy Release in Force-Free Magnetic Flux Ropes","authors":"A. A. Solov’ev,&nbsp;E. A. Kirichek","doi":"10.1134/S1063773723050055","DOIUrl":"10.1134/S1063773723050055","url":null,"abstract":"<p>A straight cylindrical, electrically shielded magnetic flux rope is considered as the upper part of a weakly curved magnetic loop whose footpoints are fixed in the photosphere. All parameters of the flux rope depend on one variable—the distance <span>(r)</span> from the axis of its symmetry. As the flux rope rises into the rarefied solar atmosphere, the external pressure keeping the flux rope from lateral expansion drops continuously. At some critical value of it the longitudinal magnetic field of the flux rope vanishes on the magnetic surface where the longitudinal electric current changes its sign in accordance with the requirement for the total current to be shielded. At the same time, the azimuthal current and the force-free parameter near this surface grow indefinitely. Because of this growth, the electron drift velocity near this surface exceeds the ion-sound speed, leading to the excitation of a plasma ion-sound instability as a trigger of flare energy release. The plasma conductivity in the region of plasma turbulence drops by seven orders of magnitude. Rapid magnetic energy dissipation at the anomalous resistivity generates an inductive electric field in the plasma that exceeds considerably the Dreicer limit. This explains the efficient acceleration of particles in the region where the magnetic field weakens rapidly.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"49 5","pages":"257 - 269"},"PeriodicalIF":0.9,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50447190","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":"Theoretical Mass Estimates for the Mira-Type Variable R Hydrae","authors":"Yu. A. Fadeyev","doi":"10.1134/S1063773723040023","DOIUrl":"10.1134/S1063773723040023","url":null,"abstract":"<p>Calculations of stellar evolution at initial abundances of helium <span>(Y=0.28)</span> and heavier elements <span>(Z=0.014)</span> were done for stars with masses on the main sequence <span>(1.7;M_{odot}leq M_{textrm{ZAMS}}leq 5.2;M_{odot})</span>. Evolutionary sequences corresponding to the AGB stage were used for modelling the pulsation period decrease observed for almost two centuries in the Mira-type variable R Hya. Diminution of the period from <span>(Piapprox)</span> 495 d in the second half of the eighteenth century to <span>(Piapprox 380)</span> d in the 1950s is due to stellar radius decrease accompanying dissipation of the radiation–diffusion wave generated by the helium flash. For all the history of its observations R Hya was the fundamental mode pulsator. The best agreement with observations is obtained for eight evolutionary models with initial mass <span>(M=4.8;M_{odot})</span> and the mass loss rate parameter of the Blöcker formula <span>(0.03leqeta_{textrm{B}}leq 0.07)</span>. Theoretical mass estimates of R Hya are in the range <span>(4.44;M_{odot}leq Mleq 4.63;M_{odot})</span>, whereas the mean stellar radius (<span>(421;R_{odot}leqbar{R}leq 445;R_{odot})</span>) corresponding to the pulsation period <span>(Piapprox 380)</span> d agrees well with measurements of the angular diameter by methods of the optical interferometric imaging.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"49 4","pages":"167 - 174"},"PeriodicalIF":0.9,"publicationDate":"2023-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47221506","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":"The Cepheids V371 Per and OGLE-LMC-CEP-2132: The First Crossing of the Instability Strip","authors":"L. N. Berdnikov,&nbsp;E. N. Pastukhova","doi":"10.1134/S1063773723040011","DOIUrl":"10.1134/S1063773723040011","url":null,"abstract":"<p>For both periods of the double-mode Cepheid V371 Per and for the Cepheid OGLE-LMC-CEP-2132 we have constructed <span>(O-C)</span> diagrams spanning a time interval of 126 and 119 years, respectively. The <span>(O-C)</span> diagrams have the shape of parabolas, which has allowed us for the first time to determine the quadratic light elements and to calculate the rates of evolutionary changes in their periods: <span>(dP_{Fu}/dt=1.085({pm}{0.007}))</span> s yr<span>({}^{-1})</span> and <span>(dP_{1O}/dt=0.923({pm}{0.003}))</span> s yr<span>({}^{-1})</span> for the fundamental mode and the first overtone of V371 Per, respectively, and <span>(dP/dt=15.304({pm}{0.048}))</span> s yr<span>({}^{-1})</span> for OGLE-LMC-CEP-2132, in agreement with the results of theoretical calculations for the first crossing of the instability strip. The pulsation stability test proposed by Lombard and Koen has confirmed that the increase in the periods is real.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"49 4","pages":"175 - 190"},"PeriodicalIF":0.9,"publicationDate":"2023-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49213665","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":"Secular Dynamics of a Number of Planets from the TESS Catalog Detected in Binary Star Systems","authors":"A. V. Mel’nikov,&nbsp;Yu. G. Kopylova","doi":"10.1134/S1063773723040035","DOIUrl":"10.1134/S1063773723040035","url":null,"abstract":"<p>We have investigated the stability of the orbital dynamics of a number of planets detected in binary star systems based on the analysis of data from the TESS orbital observatory. For 20 circumstellar planets we have obtained typical estimates of the Lyapunov time (the time of predictable dynamics). The secular orbital dynamics of 18 planets considered is stable with Lyapunov times greater than 6000 years. For the planets TOI-905b and TOI-1634b the calculated Lyapunov times (less than 3000 years) correspond to unstable dynamics and point to possible inaccuracies in the parameters of the planets found. A detailed analysis of the stability of the secular dynamics of the circumbinary planets TOI-1338 and TIC 172900988 has shown that on the stability diagrams the planets are located in regions with relatively large Lyapunov times (more than 7000 years), confirming the reliability of the derived parameters of the planets.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"49 4","pages":"191 - 199"},"PeriodicalIF":0.9,"publicationDate":"2023-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41621648","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":"Collisional Plasma Temperature and Betatron Acceleration of Quasi-thermal Electrons in Solar Flares","authors":"Yu. T. Tsap,&nbsp;V. F. Melnikov","doi":"10.1134/S1063773723040059","DOIUrl":"10.1134/S1063773723040059","url":null,"abstract":"<p>Based on the model of a collapsing magnetic trap, we consider the influence of the temperature of a Maxwellian flare plasma on the efficiency of the betatron acceleration of quasi-thermal fast electrons in the cusp region of coronal loops. We show that an increase in the temperature causes a sharp growth (by 6–8 orders of magnitude) in the number density of quasi-thermal electrons which are capable of overcoming the ‘‘Coulomb loss barrier.’’ This suggests the necessity of background plasma preheating in the cusp region to <span>({gtrsim}10)</span> MK, for which the betatron mechanism can be responsible. We discuss the connection between the impulsive phase of flare energy release and the X-ray precursors of solar flares.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"49 4","pages":"200 - 208"},"PeriodicalIF":0.9,"publicationDate":"2023-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42725611","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":"SDSS-IV MaNGA: Ionization Sources of the Extra-planar Diffuse Ionized Gas","authors":"V. K. Postnikova,&nbsp;D. Bizyaev","doi":"10.1134/S1063773723040047","DOIUrl":"10.1134/S1063773723040047","url":null,"abstract":"<p>We investigate the ionization sources of the diffuse gas at various galactic heights in galaxies with various stellar masses, H<span>(alpha)</span> luminosities, and specific star formation rates. For this purpose, we use the SDSS-IV MaNGA DR16 data and the theoretical models of photoionization and shock ionization from the Mexican Million Models database (3MdB). Our final sample contains 239 edge-on galaxies, which makes the results statistically significant and allows even great galactic heights to be investigated using the spectra stacking procedure. Using diagnostic diagrams, we show that for galaxies of all the types being investigated the behavior of the diffuse ionized gas is adequately described by the models of photoionization by young OB stars and hot low-mass evolved stars. However, in galaxies with high stellar masses or passive star formation shocks can also contribute to the ionization. For galaxies of all the types being investigated we find that the flux from OB stars and the ionization parameter decrease with height, while the relative contribution of hot low-mass evolved stars to the ionization increases. The greatest difference of the contributions from these sources to the gas ionization is observed between galaxies with different specific star formation rates and different stellar masses: hot low-mass evolved stars are the main source of gas ionization in galaxies with passive star formation (and with high stellar masses), whereas in galaxies with active star formation (and with lower stellar masses) OB stars are a decisive factor of the diffuse gas ionization.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"49 4","pages":"151 - 166"},"PeriodicalIF":0.9,"publicationDate":"2023-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50451044","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":"Chromatic Afterglow of GRB 200829A","authors":"N. S. Pankov,&nbsp;A. S. Pozanenko,&nbsp;P. Yu. Minaev,&nbsp;S. O. Belkin,&nbsp;A. A. Volnova,&nbsp;I. V. Reva,&nbsp;A. V. Serebryanskii,&nbsp;M. A. Krugov,&nbsp;S. A. Naroenkov,&nbsp;A. O. Novichonok,&nbsp;A. A. Zhornichenko,&nbsp;V. V. Rumyantsev,&nbsp;K. A. Antonyuk,&nbsp;Sh. A. Egamberdiev,&nbsp;O. A. Burkhonov,&nbsp;E. V. Klunko,&nbsp;A. S. Moskvitin,&nbsp;I. E. Molotov,&nbsp;R. Ya. Inasaridze","doi":"10.1134/S1063773723030052","DOIUrl":"10.1134/S1063773723030052","url":null,"abstract":"<p>We present the results of our analysis of multiwavelength observations for the long gamma-ray burst GRB 200829A. The burst redshift <span>(zapprox 1.29pm 0.04)</span> has been determined photometrically at the afterglow phase. In gamma rays the event is one of the brightest (in isotropic equivalent), <span>(E_{textrm{iso}}gtrsim 10^{54})</span> erg. The multicolor light curve of the GRB 200829A afterglow is characterized by chromatic behavior and the presence of a plateau gradually transitioning into a power-law decay that can also be interpreted as a quasi-synchronous inhomogeneity (flare). We assume that the presence of a chromatic inhomogeneity in the early afterglow is consistent with the model of a structured jet.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"49 3","pages":"81 - 109"},"PeriodicalIF":0.9,"publicationDate":"2023-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42840130","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":"First Adiabatic Invariant and the Brightness Temperature of Relativistic Jets","authors":"V. S. Beskin,&nbsp;T. I. Khalilov,&nbsp;V. I. Pariev","doi":"10.1134/S1063773723030015","DOIUrl":"10.1134/S1063773723030015","url":null,"abstract":"<p>Assuming that the first adiabatic invariant for radiating particles in relativistic jets is conserved, we investigate the change in brightness temperature along the jet axis. We show that in this case the observed break in the dependence of the brightness temperature on the distance to the ‘‘central engine’’ can be explained.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"49 3","pages":"119 - 128"},"PeriodicalIF":0.9,"publicationDate":"2023-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47749588","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":"High-precision Astrometric Observations of the SRG Space Observatory with RTT-150 for Orbit Correction Control","authors":"I. M. Khamitov,&nbsp;I. F. Bikmaev","doi":"10.1134/S1063773723030039","DOIUrl":"10.1134/S1063773723030039","url":null,"abstract":"<p>The Russian–Turkish 1.5-m telescope (hereafter RTT-150) takes an active part in the work on the ground optical support of observations by the Russian Spectrum–Röntgen–Gamma (SRG) observatory (with the participation of Germany) aimed at the identification and classification of new X-ray sources detected by the SRG telescopes. The instrumental capabilities of RTT-150 (occasionally, without any significant usage of telescope time and detriment for astrophysical programs) are used in astrometric observations to control the correction of the orbit of the SRG space observatory itself. In these cases, RTT-150 provides the Ballistic Center of the Keldysh Institute of Applied Mathematics of the Russian Academy of Sciences with high-precision astrometric measurements of the SRG position, which have been used to successfully keep it in its operational orbit for more than three years of its exploitation. Beginning from the stage of flight to the zone of the Lagrange point <span>(L_{2})</span> in July 2019 and at the main phase of the all-sky survey mission until March 2023, 96 sets (with a duration of about 30 min each) of high-precision positional observations with more than 5000 astrometric and photometric measurements were carried out at the RTT-150 observing facility. In most cases, the positional accuracy of the measurements dependent on seeing and apparent SRG brightness agrees with the accuracy of the provided ephemerides, <span>(0.10^{primeprime})</span> and <span>(0.15^{primeprime})</span> in declination and right ascension, respectively. In the summer months in projection onto the central region of the Galaxy in fields extremely rich in sources, the astrometric accuracy is <span>(1^{primeprime})</span>, sufficient for the SRG detection after the corrections and subsequent refinements of its trajectory. Geographically, RTT-150 is the southernmost instrument among the Russian telescopes for the ground astrophysical support of SRG. This fact is also extremely important in positional SRG observations at the lowest positions in declination <span>(DECsim{-}30^{circ})</span>. We present the results of our astrometric and photometric observations with RTT-150 and our astrometric data reduction technique in various fields up to those extremely rich in sources.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"49 3","pages":"141 - 150"},"PeriodicalIF":0.9,"publicationDate":"2023-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47045023","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}