Damghan University PressIranian Journal of Astronomy and Astrophysics2322-49248120210301Dust Acoustic Shock Waves in Strongly Coupled Dusty Plasmas with Superthermal Electrons and Ions11321810.22128/ijaa.2021.482.1104ENHamid Reza PakzadDepartment of Physics, Ferdowsi University of Mashhad, 91775-1436, Mashhad, Iran0000-0001-8514-3155Journal Article20211212We use reductive perturbation method and derive the Kordeweg-de Vries-Burgers (KdV-Burgers) equation in coupled dusty plasmas containing ions and electrons obeying superthermal distribution. We discuss the effect of the plasma parameters on the shock wave structure. It is simply shown how soliton profile is converted into shock structure when the coupling force increases. In fact as long as the dispersive term and the dissipative term as well as the nonlinear term are balanced, the shock wave structure forms; otherwise, the soliton forms due to the balance between the dispersive term and the nonlinear term. We show that the effect of superthermal electrons is more influence in comparison with the superthermal ions on the behavior of the shock waves. It is also seen that increasing relative density ( ) decreases the amplitude of shock wave except for very small value of . Our investigation is of wide relevance to astronomers and space scientists working on interstellar space plasmas.https://ijaa.du.ac.ir/article_218_71503b51380626bddf29336c5e5a30ba.pdfDamghan University PressIranian Journal of Astronomy and Astrophysics2322-49248120210301Constraints of Anisotropy on Warm Power-Law Ination in Light of Planck Results152823910.22128/ijaa.2021.479.1103ENZahra GhadirySanandaj Branch, Islamic Azad, Sanandaj, IranAli AghamohammadiDepartment of physics, Sanandaj Branch, Islamic Azad University, Sanandaj , Iran0000-0002-0229-8651Abdollah RefaeiSanandaj Branch, Islamic Azad, Sanandaj, IranJournal Article20211120In this article, we examine the effects of anisotropy on a model of canonical warm inflation with the power-law potential. And we have compared the limitations of this model with Planck's results. Using a conventional local scalar field in the Bianchi type I metric, we have estimated the slow-roll conditions and the suitable regions in which the specific free parameters obtained from the theoretical calculations are in good agreement with the Planck results. Here, as is the usual calculation method in warm inflation, we examine the early universe in two different dissipative regimes, including the weak dissipative regime and the strong dissipative regime, and obtain the field equations. Then we calculate the slow-roll parameters and observational indexes in both regimes and finally, we show that this model has been able to make a good agreement by comparing the theoretical results and observational data obtained from cosmic microwave background and Planck satellites 2013 and 2015https://ijaa.du.ac.ir/article_239_d1e10a987e15a449e8ec2c846f6fd91f.pdfDamghan University PressIranian Journal of Astronomy and Astrophysics2322-49248120210301Simulation of Electron Acoustic Wave Propagation in Non-Uniform Magnetized Plasma293424010.22128/ijaa.2021.500.1108ENHamid Reza PakzadDepartment of Physics, Bojnourd Branch, Islamic Azad University, Bojnourd, Iran.0000-0001-8514-3155Journal Article20220213The Propagation of electron acoustic solitary waves is studied in a plasmas consisting of hot and cold electrons and stationary ions and in the presence of nonuniform external magnetic field. Our simulation results in this paper show that the electron acoustic solitary waves radiate some amount of energy during their traveling through the varying magnetic field. The important point is that we do not have other dissipative sources like particle interaction or viscosity effects, in this model. We also find that the electron density waves moves with a small wavelets around the central electron density even if the external magnetic field is constant.<br /><br />We propose to perform a laboratory experiment which will be able to identify the special new features of the electron acoustic waves propagation in a magnetized plasma with external varying magnetic field in which have been predicted in this investigation. Furthermore, our theoretical analysis brings a possibility to develop more refined theories of nonlinear acoustic waves that may occur in astrophysical nonuniform magnetixed plasmas.https://ijaa.du.ac.ir/article_240_e03fe530e1a71fd902775f11b80a7580.pdfDamghan University PressIranian Journal of Astronomy and Astrophysics2322-49248120210301A Dynamical Stability Study of Triple-Star Systems Using Physical and Geometrical Parameters354724110.22128/ijaa.2021.510.1111ENReza PazhouheshPhysics Department, Faculty of Sciences, University of Birjand0000-0002-9160-1666Hasan Hamedi NasabPhysics Department, Faculty of Sciences, University of BirjandKazem Yoosefi RoobiatPhysics department, faculty of sciences, university of Birjand, Birjand, Iran.0000-0002-7359-0625Journal Article20220309The dynamical stability of 141 triple-star systems is investigated. These systems are selected from the updated catalog of multiple stars systems (i.e., the MSC catalog). The distribution of eccentricity for inner and outer orbits is plotted. This diagram shows that the inner orbits are almost circular while the outer ones are oval, indicating higher eccentricity. This confirms that triple-star systems are also hierarchical. The dynamical stability of all systems is investigated using five different criteria. Observational stability parameters and their critical values are calculated using orbital values and the masses of components. In addition, the stability margin against the eccentricity of the outer orbit is plotted. This diagram shows that by increasing the eccentricity of the outer orbit, the distance from the stability limit also increases. Therefore, the higher the eccentricity of the outer orbit is, the more unstable the system becomes. Furthermore, by some investigations, we found that the dependence on the eccentricity of the inner orbit through the factor 1=(1 − ein) stabilizes many systems in some criteria, and this modifies the corresponding criteria. The results of the investigations show that almost all triple-star systems are stable and have a hierarchical structure. Only five systems (with WDS indexes: 18126-7340, 06467+0822, 02022- 2402, 08391-5557, and 00247-2653) are unstable in at least three criteria. The reasons for the instability of these systems are most likely the observational errors or the unreal theoretical criteria. Finally, the introduced five criteria are ordered according to their credibility and precision.https://ijaa.du.ac.ir/article_241_404f4bfa43e3f447ea0599c804919197.pdfDamghan University PressIranian Journal of Astronomy and Astrophysics2322-49248120210301The Main Ionization Sources of Gas in Several Nearby Star Forming Galaxies495624310.22128/ijaa.2021.513.1113ENBehjat Zarei JalalabadiDepartment of Physics, University of Birjand, Birjand, Iran;Abbas AbediDepartment of physics, Faculty of science, University of Birjand, Birjand, IranAlexei VMoiseevSpecial Astrophysical Observatory, Russian Academy of Sciences, Nizhnij Arkhyz, 369167, Russia;
Space Research Institute, Russian Academy of Sciences, Moscow, 117997 Russia;Journal Article20220310The emission-line intensity ratios are used to distinguish the main sources of gas ionization to study the state of galactic interstellar medium (ISM). In intermediate cases, when the contributions of radiation from OB stars and from shock waves mix, the identification becomes uncertain. As an extra parameter, the gas velocity dispersion in the line-of-sight can be added to classical diagnostic diagrams (i.e., "BPT-σ" relations) to help finding an appropriate solution. The minimum distance from the curve that bounds the H II-type ionization region for each point in BPT-ρ diagram can be used to characterize the excitation mechanism of the ionized gas. The shock excitation in the diffuse ionized gas (DIG) can be realized by the correlation between ρ and σ, while the H II regions with low level turbulent motions can be characterized by the absence of this correlation. We consider the "BPT-σ" relation and the correlation between σ and ρ to determine the ionized gas excitation in several nearby star-forming galaxies. Distributions of the velocity dispersion are obtained from the scanning Fabry-Perot interferometer observations at the SAO RAS 6-m telescope, whereas the emission-line ratios are calculated from the archival long-slit spectroscopic data. The results of this study are reported for Mrk 370, NGC 4068, UGC 8313, and UGC 8508.https://ijaa.du.ac.ir/article_243_9aa428caa3ee6c42c6feece907ad45d8.pdfDamghan University PressIranian Journal of Astronomy and Astrophysics2322-49248120210301Heating and Cooling Studies of Relativistic Accretion Disks Around the Non-Rotating Black with A Simple Model576124510.22128/ijaa.2021.514.1114ENMahboobe MoeenScience department,Faculty member, Kosar University of Bojnord, IranJournal Article20220312In this paper, the relativistic accretion disks around the non- rotating black holes are studied. In these disks, we study the fluids with influences of stress viscosity and heat flux in the ignorable magnetic field. In this paper, the reformed conservation equations with the influences of heat flux are used. We use the simple model of heat flux, in which the heat flux is proportional to temperature. Then the thermodynamic quantities are derived. We use the radial form for the radial component of four velocity in the locally non rotating frame and Keplerian angular momentum. So, the viscous heating and heat flux cooling are derived. Also, the figures of viscous heating and heat flux cooling are derived by various parameters such as the viscous coefficient and the thermal conductivity. Therefore, the energy balance can be study in the relativistic accretion disks. So, we see the region which have the energy balance.https://ijaa.du.ac.ir/article_245_73ae58c9f443f7045b7beda85dd15dfb.pdf