Peter Shternin

Two-color two-photon excited fluorescence of indole: Determination of wavelength-dependent molecular parameters

We present a detailed study of two-color two-photon excited fluorescence in indole dissolved in propylene glycol. Femtosecond excitation pulses at effective wavelengths from 268 to 293.33 nm were used to populate the two lowest indole excited states (1)La and (1)Lb and polarized fluorescence was then detected. All seven molecular parameters and the two-photon polarization ratio Ω containing information on two-photon absorption dynamics, molecular lifetime τf, and rotation correlation time τrot have been determined from experiment and analyzed as a function of the excitation wavelength. The analysis of the experimental data has shown that (1)Lb-(1)La inversion occurred under the conditions of our experiment. The two-photon absorption predominantly populated the (1)La state at all excitation wavelengths but in the 287-289 nm area which contained an absorption hump of the (1)Lb state 0-0 origin. The components of the two-photon excitation tensor S were analyzed giving important information on the principal tensor axes and absorption symmetry. The results obtained are in a good agreement with the results reported by other groups. The lifetime τf and the rotation correlation time τrot showed no explicit dependence on the effective excitation wavelength. Their calculated weighted average values were found to be τf = 3.83 ± 0.14 ns and τrot = 0.74 ± 0.06 ns.

Nuclear Reactions in the Crusts of Accreting Neutron Stars

X-ray observations of transiently accreting neutron stars during quiescence provide information about the structure of neutron star crusts and the properties of dense matter. Interpretation of the observational data requires an understanding of the nuclear reactions that heat and cool the crust during accretion, and define its nonequilibrium composition. We identify here in detail the typical nuclear reaction sequences down to a depth in the inner crust where the mass density is 2E12 g/cm^3 using a full nuclear reaction network for a range of initial compositions. The reaction sequences differ substantially from previous work. We find a robust reduction of crust impurity at the transition to the inner crust regardless of initial composition, though shell effects can delay the formation of a pure crust somewhat to densities beyond 2E12 g/cm^3. This naturally explains the small inner crust impurity inferred from observations of a broad range of systems. The exception are initial compositions with A >= 102 nuclei, where the inner crust remains impure with an impurity parameter of Qimp~20 due to the N = 82 shell closure. In agreement with previous work we find that nuclear heating is relatively robust and independent of initial composition, while cooling via nuclear Urca cycles in the outer crust depends strongly on initial composition. This work forms a basis for future studies of the sensitivity of crust models to nuclear physics and provides profiles of composition for realistic crust models.

Observations of the

We present the analysis of the archival Suzaku and Swift X-ray observations of the young

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-ray pulsar J1932+1916 in X-rays

-ray pulsar J1932+1916 field. The data revealed a point-like object at the

Nuclear physics of the outer layers of accreting neutron stars

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Proper motion of the radio pulsar B1727−47 and its association with the supernova remnant RCW 114

-ray position of the pulsar and diffuse X-ray emission around it. Spectra of the point-like source and diffuse emission are well-described by absorbed power-law models with spectral parameters typical for pulsar plus pulsar wind nebula systems. Therefore we suggest that Suzaku and Swift detected the X-ray counterpart of PSR J1932+1916. Assuming this interpretation, we constrain the distance to the pulsar in the range of 2-6 kpc. We also suggest possible association of the pulsar with the nearby supernova remnant G54.4-0.3 and discuss its implications for the pulsar proper motion, age and distance.

International conference “Physics of neutron stars – 2017. 50 years after”

Now 50 years since the existence of the neutron star crust was proposed, we review the current understanding of the nuclear physics of the outer layers of accreting neutron stars. Nuclei produced during nuclear burning replace the nascent composition of the neutron star ocean and crust. Non-equilibrium nuclear reactions driven by compression alter the outer thermal structure and chemical composition, leaving observable imprints on astronomical phenomena. As observations of bursting neutron stars and cooling neutron stars have increased, the recent volume of astronomical data allows new insights into the microphysics of the neutron star interior and the possibility to test nuclear physics input in model calculations. Despite numerous advances in our understanding of neutron star interiors and observed neutron star phenomena, many challenges remain in the astrophysics theory of accreting neutron stars, the nuclear theory of neutron-rich nuclei, and the reach and precision of terrestrial nuclear physics experiments.

X-ray Analysis of the Bright Source in the Supernova Remnant G350.0-2.0 Field

We report preliminary results of the analysis of the proper motion of the bright radio pulsar B1727

Radio-interferometric and near-IR observations of PSR J1357—6429

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