A multimessenger study of the Milky Way’s stellar disc and bulge with LISA, Gaia, and LSST

The upcoming LISA mission offers the unique opportunity to study the Milky Way through gravitational wave radiation from Galactic binaries. Among the variety of Galactic gravitational wave sources, LISA is expected to individually resolve signals from ∼105 ultra-compact double white dwarf (DWD) binaries. DWDs detected by LISA will be distributed across the Galaxy, including regions that are hardly accessible to electromagnetic observations such as the inner part of the Galactic disc, the bulge and beyond. We quantitatively show that the large number of DWD detections will allow us to use these systems as tracers of the Milky Way potential. We demonstrate that density profiles of DWDs detected by LISA may provide constraints on the scale length parameters of the baryonic components that are both accurate and precise, with statistical errors of a few percent to 10 percent level. Furthermore, the LISA sample is found to be sufficient to disentangle between different (commonly used) disc profiles, by well covering the disc out to sufficiently large radii. Finally, up to ∼80 DWDs can be detected through both electromagnetic and gravitational wave radiation. This enables multi-messenger astronomy with DWD binaries and allows one to extract their physical properties using both probes. We show that fitting the Galactic rotation curve constructed using distances inferred from gravitational waves {\it and} proper motions from optical observations yield a unique and competitive estimate of the bulge mass. Instead robust results for the stellar disc mass are contingent upon knowledge of the Dark Matter content

Constraining the Milky Way potential with Double White Dwarfs

The 21st European Workshop on White Dwarfs was held in Austin, TX from July 23rd to 27th of 2018The upcoming LISA mission is the only experiment that will allow us to study the Milky Way’s structure using gravitational wave signals from Galactic double white dwarfs (DWDs). The total number of expected detections exceeds 105. Furthermore, up to a hundred DWDs can be simultaneously detected in both gravitational and optical radiation (e.g. with Gaia and LSST as eclipsing), making DWDs ideal sources for performing a multi-messenger tomography of the Galaxy. We show that LISA will detect DWDs everywhere, mapping also the opposite side of the Galaxy. This complete coverage will : (1) provide precise and unbiased constraints on the scale radii of the Milky Way’s bulge and disc, and (2) allow us to compute the rotation curve and derive competitive estimates for the bulge and disc masses, when combining gravitational wave and optical observations.Astronom

Total spectrum of photon emission by an ultra-relativistic positron channeling in a periodically bent crystal

We present the results of numerical calculations of the channelling and undulator radiation generated by an ultra-relativistic positron channelling along a crystal plane, which is periodically bent. The bending might be due either to the propagation of a transverse acoustic wave through the crystal, or due to the static strain as it occurs in superlattices. The periodically bent crystal serves as an undulator. We investigate the dependence of the intensities of both the ordinary channelling and the undulator radiations on the parameters of the periodically bent channel with simultaneous account for the dechannelling effect of the positrons. We demonstrate that there is a range of parameters in which the undulator radiation dominates over the channelling one and the characteristic frequencies of both types of radiation are well separated. This result is important, because the undulator radiation can be used to create a tunable source of X-ray and gamma-radiation.Comment: published in J. Phys. G: Nucl. Part. Phys. 26 (2000) L87-L95, http://www.iop.org ; 12 pages, 4 figures, LaTe

Stable propagation of a modulated positron beam in a bent crystal channel

The propagation of a modulated positron beam in a planar crystal channel is investigated. It is demonstrated that the beam preserves its modulation at sufficiently large penetration depths which opens the prospect of using a crystalline undulator as a coherent source of hard x-rays. This finding is a crucial milestone in developing a new type of lasers radiating in the hard x-ray and gamma-ray range.Comment: 11 pages, 4 figures, iopar

The influence of the dechanneling process on the photon emission by an ultra-relativistc positron channeling in a periodically bent crystal

We investigate, both analytically and numerically, the influence of the dechanneling process on the parameters of undulator radiation generated by ultra-relativistic positron channelling along a crystal plane, which is periodically bent. The bending might be due either to the propagation of a transverse acoustic wave through the crystal, or due to the static strain as it occurs in superlattices. In either case the periodically bent crystal serves as an undulator which allows to generate X-ray and gamma-radiation. We propose the scheme for accurate quantitative treatment of the radiation in presence of the dechanneling. The scheme includes (i) the analytic expression for spectral-angular distribution which contains, as a parameter, the dechanneling length, (ii) the simulation procedure of the dechanneling process of a positron in periodically bent crystals. Using these we calculate the dechanneling lengths of 5 GeV positrons channeling in Si, Ge and W crystals, and the spectral-angular and spectral distributions of the undulator over broad ranges of the photons. The calculations are performed for various parameters of the channel bending.Comment: published in J. Phys. G: Nucl. Part. Phys. 27 (2001) 95-125, http://www.iop.or

Channeling of Positrons through Periodically Bent Crystals: on Feasibility of Crystalline Undulator and Gamma-Laser

The electromagnetic radiation generated by ultra-relativistic positrons channelling in a crystalline undulator is discussed. The crystalline undulator is a crystal whose planes are bent periodically with the amplitude much larger than the interplanar spacing. Various conditions and criteria to be fulfilled for the crystalline undulator operation are established. Different methods of the crystal bending are described. We present the results of numeric calculations of spectral distributions of the spontaneous radiation emitted in the crystalline undulator and discuss the possibility to create the stimulated emission in such a system in analogy with the free electron laser. A careful literature survey covering the formulation of all essential ideas in this field is given. Our investigation shows that the proposed mechanism provides an efficient source for high energy photons, which is worth to study experimentally.Comment: 52 pages, MikTeX, 14 figure

Hybridization-related correction to the jellium model for fullerenes

We introduce a new type of correction for a more accurate description of fullerenes within the spherically symmetric jellium model. This correction represents a pseudopotential which originates from the comparison between an accurate ab initio calculation and the jellium model calculation. It is shown that such a correction to the jellium model allows one to account, at least partly, for the sp2-hybridization of carbon atomic orbitals. Therefore, it may be considered as a more physically meaningful correction as compared with a structureless square-well pseudopotential which has been widely used earlier.Comment: 16 pages, 10 figure