Ultraviolet emission from young and middle-aged pulsars     

Oleg Kargaltsev  George Pavlov 《Astrophysics and Space Science》2007,308(1-4):287-296

We present the UV spectroscopy and timing of three nearby pulsars (Vela, B0656+14 and Geminga) recently observed with the Space Telescope Imaging Spectrograph. We also review the optical and X-ray properties of these pulsars and establish their connection with the UV properties. We show that the multiwavelengths properties of neutron stars (NSs) vary significantly within the sample of middle-aged pulsars. Even larger differences are found between the thermal components of Geminga and B0656+14 as compared to those of radio-quiet isolated NSs. These differences could be attributed to different properties of the NS surface layers. This work was supported by STScI grants GO-9182 and GO-9797 and NASA grant NAG5-10865.  相似文献   

Evidence for a binary companion to the central compact object 1E 1207.4-5209     

Peter M. Woods  Vyacheslav E. Zavlin  George G. Pavlov 《Astrophysics and Space Science》2007,308(1-4):239-246

Unique among neutron stars, 1E 1207.4-5209 is an X-ray pulsar with a spin period of 424 ms that contains at least two strong absorption features in its energy spectrum. This neutron star is positionally coincident with the supernova remnant PKS 1209-51/52 and has been identified as a member of the growing class of radio-quiet compact central objects in supernova remnants. From previous observations with Chandra and XMM-Newton, it has been found that the 1E 1207.4-5209 is not spinning down monotonically as is common for young, isolated pulsars. The spin frequency history requires either strong, frequent glitches, the presence of a fall-back disk, or a binary companion. Here, we report on a sequence of seven XMM-Newton observations of 1E 1207.4-5209 performed during a 40 day window between 2005 June 22 and July 31. Due to unanticipated variance in the phase measurements during the observation period that was beyond the statistical uncertainties, we could not identify a unique phase-coherent timing solution. The three most probable timing solutions give frequency time derivatives of +0.9, ?2.6, and +1.6×10^?12 Hz s^?1 (listed in descending order of significance). We conclude that the local frequency derivative during our XMM-Newton observing campaign differs from the long-term spin-down rate by more than an order of magnitude. This measurement effectively rules out glitch models for 1E 1207.4-5209. If the long-term spin frequency variations are caused by timing noise, the strength of the timing noise in 1E 1207.4-5209 is much stronger than in other pulsars with similar period derivatives. Therefore, it is highly unlikely that the spin variations are caused by the same physical process that causes timing noise in other isolated pulsars. The most plausible scenario for the observed spin irregularities is the presence of a binary companion to 1E 1207.4-5209. We identified a family of orbital solutions that are consistent with our phase-connected timing solution, archival frequency measurements, and constraints on the companions mass imposed by deep IR and optical observations.  相似文献   

Radial velocities of the components of multiple star systems of Trapezium type. I     

G. Sh. Dzhavakhishvili  M. V. Pavlov  G. N. Salukvadze 《Astrophysics》1993,36(2):168-169

Translated fromAstrofizika, Vol. 36, No. 2, pp. 273–275, April–June 1993.  相似文献   

Peculiarities of Dynamic Slip Nucleation in a Thin Granular Layer     

Ostapchuk  A. A.  Kocharyan  G. G.  Morozova  K. G.  Pavlov  D. V.  Gridin  G. A. 《Izvestiya Physics of the Solid Earth》2021,57(5):659-670

Izvestiya, Physics of the Solid Earth - Abstract—Granular media determine the dynamics of many natural systems including faults in the Earth’s crust. The paper addresses the laboratory...  相似文献   

Effect of the Solar Activity Variations on the NmF2 Variability under Geomagnetically Quiet Conditions According to Ionosonde Data over Moscow     

Pavlov  A. V.  Pavlova  N. M. 《Geomagnetism and Aeronomy》2022,62(3):227-236

Geomagnetism and Aeronomy - Diurnal variations in the statistical characteristics of the day-to-day variability in the electron number density NmF2 of the ionospheric F2 layer maximum is studied...  相似文献   

Comparison of model electron densities and temperatures with Millstone Hill observations during undisturbed periods and the geomagnetic storms of 16–23 March and 6–12 April 1990     

A. V. Pavlov  M. J. Buonsanto 《Annales Geophysicae》1997,15(3):327-344

Measurements of F-region electron density and temperature at Millstone Hill are compared with results from the IZMIRAN time-dependent mathematical model of the Earths ionosphere and plasmasphere during the periods 16–23 March and 6–12 April 1990. Each of these two periods included geomagnetically quiet intervals followed by major storms. Satisfactory agreement between the model and the data is obtained during the quiet intervals, provided that the recombination rate of O⁺(⁴S) ions was decreased by a factor of 1.5 at all altitudes during the nighttime periods 17–18 March, 19–20 March, 6–8 April and 8–9 April in order to increase the NmF2 at night better to match observations. Good model/data agreement is also obtained during the storm periods when vibrationally excited N₂ brings about factor-of-2-4 reductions in daytime NmF2. Model calculations are carried out using different expressions for the O⁺ – O collision frequency for momentum transfer, and the best agreement between the electron-density measurements and the model results is obtained when the CEDAR interim standard formula for the O⁺ – O collision frequency is used. Deviations from the Boltzmann distribution for the first five vibrational levels of NI were calculated. The calculated distribution is highly non-Boltzmann at vibrational levels j > 2, and the Boltzmann distribution assumption results in the increase of 10–30% in calculated NmF2 during the storm-time periods. During the March storm at solar maximum the model results obtained using the EUVAC solar flux model agree a little better with the observations in comparison with the EUV94 solar flux model. For the April storm period of moderate solar activity the EUV94X model results agree better with the observations in comparison to the EUVAC model.  相似文献   

The algorithms for calculating synthetic seismograms from a dipole source using the derivatives of Green’s function     

V. M. Pavlov 《Izvestiya Physics of the Solid Earth》2017,53(4):556-564

The problem of calculating complete synthetic seismograms from a point dipole with an arbitrary seismic moment tensor in a plane parallel medium composed of homogeneous elastic isotropic layers is considered. It is established that the solutions of the system of ordinary differential equations for the motion–stress vector have a reciprocity property, which allows obtaining a compact formula for the derivative of the motion vector with respect to the source depth. The reciprocity theorem for Green’s functions with respect to the interchange of the source and receiver is obtained for a medium with cylindrical boundary. The differentiation of Green’s functions with respect to the coordinates of the source leads to the same calculation formulas as the algorithm developed in the previous work (Pavlov, 2013). A new algorithm appears when the derivatives with respect to the horizontal coordinates of the source is replaced by the derivatives with respect to the horizontal coordinates of the receiver (with the minus sign). This algorithm is more transparent, compact, and economic than the previous one. It requires calculating the wavenumbers associated with Bessel function’s roots of order 0 and order 1, whereas the previous algorithm additionally requires the second order roots.  相似文献   

Formation Mechanisms of the Spring–Autumn Asymmetry of the Midlatitudinal <Emphasis Type="Italic">NmF</Emphasis>2 under Daytime Quiet Geomagnetic Conditions at Low Solar Activity     

A. V. Pavlov  N. M. Pavlova 《Geomagnetism and Aeronomy》2018,58(3):383-393

Formation mechanism of the spring–autumn asymmetry of the F2-layer peak electron number density of the midlatitudinal ionosphere, NmF2, under daytime quiet geomagnetic conditions at low solar activity are studied. We used the ionospheric parameters measured by the ionosonde and incoherent scatter radar at Millstone Hill on March 3, 2007, March 29, 2007, September 12, 2007, and September 18, 1984. The altitudinal profiles of the electron density and temperature were calculated for the studied conditions using a one-dimensional, nonstationary, ionosphere–plasmasphere theoretical model for middle geomagnetic latitudes. The study has shown that there are two main factors contributing to the formation of the observed spring–autumn asymmetry of NmF2: first, the spring–autumn variations of the plasma drift along the geomagnetic field due to the corresponding variations in the components of the neutral wind velocity, and, second, the difference between the composition of the neutral atmosphere under the spring and autumn conditions at the same values of the universal time and the ionospheric F2-layer peak altitude. The seasonal variations of the rate of O⁺(⁴S) ion production, which are associated with chemical reactions with the participation of the electronically excited ions of atomic oxygen, does not significantly affect the studied NmF2 asymmetry. The difference in the degree of influence of O⁺(⁴S) ion reactions with vibrationally excited N₂ and O₂ on NmF2 under spring and autumn conditions does not significantly change the spring–autumn asymmetry of NmF2.  相似文献   

The Tolud Burst of Seismicity and the Earthquake of November 30, 2012 (<Emphasis Type="Italic">M</Emphasis><Subscript>C</Subscript> = 5.4, <Emphasis Type="Italic">M</Emphasis><Subscript>W</Subscript> = 4.8) that Accompanied the Start of the 2012‒2013 Tolbachik Eruption     

Yu. A. Kugaenko  V. M. Pavlov  E. I. Ivanova  I. R. Abubakirov  V. A. Saltykov 《Journal of Volcanology and Seismology》2017,11(6):419-433

This paper reports a study of the Tolud earthquake sequence; the sequence was a burst of shallow seismicity between November 28 and December 7, 2012; it accompanied the initial phase in the Tolbachik Fissure Eruption of 2012?2013. The largest earthquake (the Tolud earthquake of November 30, 2012, to be referred to as the Tolud Earthquake in what follows, with K_S = 11.3, M_L = 4.9, M_C = 5.4, and M_W = 4.8) is one of the five larger seismic events that have been recorded at depths shallower than 10 km beneath the entire Klyuchevskoi Volcanic Cluster in 1961?2015. It was found that the Tolud earthquake sequence was the foreshock–aftershock process of the Tolud Earthquake. This is one of the larger seismicity episodes ever to have occurred in the volcanic areas of Kamchatka. Data of the Kamchatka seismic stations were used to compute some parameters for the Tolud Earthquake and its largest (M_L = 4.3) aftershock; the parameters include the source parameters and mechanisms, and the moment magnitudes, since no information on these is available at the world seismological data centers. The focal mechanisms for the Tolud Earthquake and for its aftershock are consistent with seismic ruptures at a tension fault in the rift zone. Instrumental data were used to estimate the intensity of shaking due to the Tolud Earthquake. We discuss the sequence of events that was a signature of the time-dependent seismic and volcanic activity that took place in the Tolbachik zone in late November 2012 and terminated in the Tolud burst of seismicity. Based on the current ideas of the tectonics and magma sources for the Tolbachik volcanic zone, we discuss possible causes of these earthquakes.  相似文献   

On the Prospect of Detecting the Process of Earthquake Preparation in the Spectrum of Seismic Noise: A Laboratory Experiment     

G. G. Kocharyan  A. A. Ostapchuk  D. V. Pavlov  A. M. Budkov 《Izvestiya Physics of the Solid Earth》2018,54(6):914-925

The results of laboratory experiments aimed at studying the pattern of the transition process of a model fault into a metastable state are presented. The experiments are conducted on a slider model installed onto a long granite base wherein vibrations are excited. The idea of the experiments is that the mechanical properties of the fault change under the transition into the metastable state. These changes can be detected by the detailed examination of the parameters of microseismic noise. The conducted experiments show that, despite the low Q-factor of the block–fault mechanical system, the spectrum of the recorded oscillations definitely contains the harmonic components corresponding to the eigenmodes of this system. In the model with the interblock contact filled with quartz sand, the fundamental mode of the free oscillations alters most noticeably in the frequency band 1000–1200 Hz, where the clear effect of the spectral peak’s migration towards lower frequencies is observed as the contact approaches the moment of dynamic failure, and the approximately initial value is recovered after the sliding stops. The revealed effect gives hope that the changes in the stress–strain state of the fault zone at the final stage of earthquake preparation can be detected by analyzing the parameters of low-frequency seismic noise. The segment of the record during and after the passage of surface waves from remote earthquakes is perhaps amongst the most favorable for determining the characteristic values of the region under study. These oscillations with a period of a few dozen seconds have significant amplitudes and durations, which promotes the excitation of the resonant vibrations of the blocks.  相似文献