On the Possibility of Observing the Shapiro Effect for Pulsars in Globular Clusters

For pulsars in globular clusters, we suggest using observations of the relativistic time delay of their radiation in the gravitational eld of a massive body (the Shapiro effect) located close to the line of sight to detect and identify invisible compact objects and to study the distribution of both visible and dark matter in globular clusters and various components of the Galaxy. We have derived the dependences of the event probability on the Galactic latitude and longitude of sources for two models of the mass distribution in the Galaxy: the classical Bahcall-Soneira model and the more recent Dehnen-Binney model. Using three globular clusters (M15, 47 Tuc, Terzan 5) as an example, we show that the ratios of the probability of the events due to the passages of massive Galactic objects close to the line of sight to the parameter f2 for pulsars in the globular clusters 47 Tuc and M15 are comparable to those for close passages of massive objects in the clusters themselves and are considerably higher than those for the cluster Terzan 5. We have estimated the rates of such events. We have determined the number of objects near the line of sight toward the pulsar that can produce a modulation of its pulse arrival times characteristic of the effect under consideration; the population of brown dwarfs in the Galactic disk, whose concentration is comparable to that of the disk stars, has been taken into account for the first time.Comment: 26 pages, 9 figure

Observations of Lensed Relativistic Jets as a Tool of Constraining Lens Galaxy Parameters

The possibility of using lensed relativistic jets on very small angular scales to construct proper models of spiral lens galaxies and to independently determine the Hubble constant is considered. The system B0218+357 is used as an example to illustrate that there exists a great choice of model parameters adequately reproducing its observed large-scale properties but leading to a significant spread in the Hubble constant. The jet image position angle is suggested as an additional parameter that allows the range of models under consideration to be limited. It is shown that the models for which the jet image position angles differ by at least $40^o$ can be distinguished between themselves during observations on very small angular scales. The possibility of observing the geometric properties of lensed relativistic jets and measuring the superluminal velocities of knot images on time scales of several months with very long baseline space interferometers is discussed.Comment: 11 pages, 3 figures, Will be published in the Astronomy Letters, V.37, PP.483-490, 201

Orientation dependence of superelasticity in quenched high-nickel Ti51.8Ni single crystals

The orientation dependence of the functional and mechanical properties of quenched Ti-51.8at.%Ni single crystals, undergoing a strain-glass transition upon cooling/heating was investigated. It was found that a compressive stress above 800 MPa leads to the B2-B190 martensitic transformation (MT), regardless of orientation. In the high-strength [0 0 1]-orientation, superelasticity (SE) was observed at 203–248 K, with a reversible strain of 2.3%. Degradation of SE at deforming stresses r > 1000 MPa was associated with the formation of {1 1 3}B2 twins during the reverse MT. In the low-strength 1 1 1-orientation, the formation of stress-induced B190 -martensite occurred simultaneously with the plastic deformation of the B2-phase (due to the formation of reorientation bands and dislocation slip) and a reversible strain was not observed

Prospects for Detecting Dark Matter Halo Substructure with Pulsar Timing

One of the open questions of modern cosmology is the nature and properties of the Dark Matter halo and its substructures. In this work we study the gravitational effect of dark matter substructures on pulsar timing observations. Since millisecond pulsars are stable and accurate emitters, they have been proposed as plausible astrophysical tools to probe the gravitational effects of dark matter structures. We study this effect on pulsar timing through Shapiro time delay (or Integrated Sachs-Wolfe (ISW) effect) and Doppler effects statistically, showing that the latter dominates the signal. For this task, we relate the power spectrum of pulsar frequency change to the matter power spectrum on small scales, which we compute using the stable clustering hypothesis. We compare this power spectrum with the reach of current and future observations of pulsar timing designed for gravitational wave (GW) detection. Our results show that while current observations are unable to detect these signals, the sensitivity of the upcoming Square Kilometer Array (SKA) is only a factor of few weaker than our optimistic predictions.Comment: 12 pages, 10 figures. Final Versio

Review of scientific topics for Millimetron space observatory

This paper describes outstanding issues in astrophysics and cosmology that can be solved by astronomical observations in a broad spectral range from far infrared to millimeter wavelengths. The discussed problems related to the formation of stars and planets, galaxies and the interstellar medium, studies of black holes and the development of the cosmological model can be addressed by the planned space observatory Millimetron (the "Spectr-M" project) equipped with a cooled 10-m mirror. Millimetron can operate both as a single-dish telescope and as a part of a space-ground interferometer with very long baseline.Comment: The translation of the original article in Physics Uspekhi http://ufn.ru/ru/articles/2014/12/c

Modeling the Images of Relativistic Jets Lensed by Galaxies with Different Mass Surface Density Distributions

The images of relativistic jets from extragalactic sources produced by gravitational lensing by galaxies with different mass surface density distributions are modeled. In particular, the following models of the gravitational lens mass distribution are considered: a singular isothermal ellipsoid, an isothermal ellipsoid with a core, two- and three-component models with a galactic disk, halo, and bulge. The modeled images are compared both between themselves and with available observations. Different sets of parameters are shown to exist for the gravitationally lensed system B0218+357 in multicomponent models. These sets allow the observed geometry of the system and the intensity ratio of the compact core images to be obtained, but they lead to a significant variety in the Hubble constant determined from the modeling results.Comment: 26 pages, 9 figures, will be published in the Astronomy Letters, 2011, v.37, N4, pp. 233-24

Shapiro Effect as a Possible Cause of the Low-Frequency Pulsar Timing Noise in Globular Clusters

A prolonged timing of millisecond pulsars has revealed low-frequency uncorrelated noise, presumably of astrophysical origin, in the pulse arrival time (PAT) residuals for some of them. In most cases, pulsars in globular clusters show a low-frequency modulation of their rotational phase and spin rate. The relativistic time delay of the pulsar signal in the curved space time of randomly distributed and moving globular cluster stars (the Shapiro effect) is suggested as a possible cause of this modulation. Given the smallness of the aberration corrections that arise from the nonstationarity of the gravitational field of the randomly distributed ensemble of stars under consideration, a formula is derived for the Shapiro effect for a pulsar in a globular cluster. The derived formula is used to calculate the autocorrelation function of the low-frequency pulsar noise, the slope of its power spectrum, and the behavior of the $\sigma_z$ statistic that characterizes the spectral properties of this noise in the form of a time function. The Shapiro effect under discussion is shown to manifest itself for large impact parameters as a low-frequency noise of the pulsar spin rate with a spectral index of n=-1.8 that depends weakly on the specific model distribution of stars in the globular cluster. For small impact parameters, the spectral index of the noise is n=-1.5.Comment: 23 pages, 6 figure

Objectives of the Millimetron Space Observatory science program and technical capabilities of its realization

We present the scientific program of the Spectr-M project aimed at the creation and operation of the Millimetron Space Observatory (MSO) planned for launch in the late 2020s. The unique technical capabilities of the observatory will enable broadband observations of astronomical objects from 50 μm to 10 mm wavelengths with a record sensitivity (up to ~ 0.1 μJy) in the single-dish mode and with an unprecedented high angular resolution (~ 0.1 μas) in the ground-space very long baseline interferometer (SVLBI) regime. The program addresses fundamental priority issues of astrophysics and physics in general that can be solved only with the MSO capabilities: 1) the study of physical processes in the early Universe up to redshifts z ~ 2 × 106 through measuring μ-distortions of the cosmic microwave background (CMB) spectrum, and investigation of the structure and evolution of the Universe at redshifts z < 15 by measuring y-distortions of the CMB spectrum; 2) the investigation of the geometry of space-time around supermassive black holes (SMBHs) in the center of our Galaxy and M87 by imaging surrounding shadows, the study of plasma properties in the shadow formation regions, and the search for observational manifestations of wormholes; 3) the study of observational manifestations of the origin of life in the Universe - the search for water and biomarkers in the Galactic interstellar medium. Moreover, the technical capabilities of the MSO can help solve related problems, including the birth of the first galaxies and SMBHs (z ≳ 10), alternative approaches to measuring the Hubble constant, the physics of SMBHs in 'dusty' galactic nuclei, the study of protoplanetary disks and water transport in them, and the study of 'ocean worlds' in the Solar System

Objectives of the Millimetron Space Observatory Science Program and Technical Capabilities of Its Realization

We present the scientific program of the Spectr-M project aimed at the creation and operation of the Millimetron Space Observatory (MSO) planned for launch in the late 2020s. The unique technical capabilities of the observatory will enable broadband observations of astronomical objects from 50 μm to 10 mm wavelengths with a record sensitivity (up to ∼0.1 μJy) in the single-dish mode and with an unprecedented high angular resolution (∼0.1 μas) in the ground-space very long baseline interferometer (SVLBI) regime. The program addresses fundamental priority issues of astrophysics and physics in general that can be solved only with the MSO capabilities: 1) the study of physical processes in the early Universe up to redshifts z ∼ 2 106 through measuring μ-distortions of the cosmic microwave background (CMB) spectrum, and investigation of the structure and evolution of the Universe at redshifts z<15 by measuring y-distortions of the CMB spectrum; 2) the investigation of the geometry of space-time around supermassive black holes (SMBHs) in the center of our Galaxy and M87 by imaging surrounding shadows, the study of plasma properties in the shadow formation regions, and the search for observational manifestations of wormholes; 3) the study of observational manifestations of the origin of life in the Universe - the search for water and biomarkers in the Galactic interstellar medium. Moreover, the technical capabilities of the MSO can help solve related problems, including the birth of the first galaxies and SMBHs (z ⪆ 10), alternative approaches to measuring the Hubble constant, the physics of SMBHs in 'dusty' galactic nuclei, the study of protoplanetary disks and water transport in them, and the study of 'ocean worlds' in the Solar System. © 2021 Uspekhi Fizicheskikh Nauk, Russian Academy of Sciences and IOP Publishing.We appreciate the referees for their critical notes.Thestudy was partially supported by the project New Scientific Groups of LPI, no. 41-2020. AP thanks the RSF for its support (project 19-72-00064). AB is supported by RSF grant 18-12-00351 and by the State Target FEUZ-2020-0038. The work by IZ (Section 4) is supported by RFBR grant 18-02-00660. DV was supported by a grant from the Russian Government and Ministry of Higher Education and Science, 075-15-2020-780 (no. 13.1902.21.0039). The work by VSh (Section 4.4) was supported by a grant from the Russian Government for research by leading scientists under the program Studies of Stars with Exoplanets (agreement 075-15-2019-1875)