Vol 49, No 11 (2023)

In the fall of 2019, during the in-flight calibration phase of the SRG observatory, the
onboard eROSITA and Mikhail Pavlinsky ART-XC telescopes carried out a series of observations of
PG1634+706—one of the most luminous (an X-ray luminosity ∼1046 erg s−1) quasars in the Universe at
z < 2. Approximately at the same dates this quasar was also observed by the XMM-Newton observatory.
Although the object had already been repeatedly studied in X-rays previously, its new observations allowed
its energy spectrumto be measuredmore accurately in the wide range 1–30 keV (in the quasar rest frame).
Its spectrum can be described by a two-component model that consists of a power-law continuum with a
slope Γ ≈ 1.9 and a broadened iron emission line at an energy of about 6.4 keV. The X-ray variability of the
quasar was also investigated. On time scales of the order of several hours (here and below, in the source
rest frame) the X-ray luminosity does not exhibit a statistically significant variability. However, it changed
noticeably from observation to observation in the fall of 2019, having increased approximately by a factor
of 1.5 in 25 days. A comparison of the new SRG and XMM-Newton measurements with the previous
measurements of other X-ray observatories has shown that in the entire 17-year history of observations
of the quasar PG 1634+706 its X-ray luminosity has varied by no more than a factor of 2.5, while the
variations on time scales of several weeks and several years are comparable in amplitude.

We present new three-dimensional (3D) interstellar extinctionmaps in the V and Gaia G filters
within 2 kpc of the Sun, a 3D differential extinction (dust density) map along the line of sight in the same
space, a 3D map of variations in the ratio of the extinctions in the V and Gaia G filters within 800 pc
of the Sun, and a 2D map of total Galactic extinction through the entire dust half-layer from the Sun to
extragalactic space for Galactic latitudes |b| > 13◦. The 3D maps have a transverse resolution from 3.6
to 11.6 pc and a radial resolution of 50 pc. The 2D map has an angular resolution of 6.1 arcmin. We
have produced these maps based on the Gaia DR3 parallaxes and Gaia, Pan-STARRS1, SkyMapper,
2MASS, andWISE photometry for ∼ 100 million stars. We have paid special attention to the space within
200 pc of the Sun and high Galactic latitudes as regions where the extinction estimates have had a large
relative uncertainty so far. Our maps estimate the extinction within the Galactic dust layer from the Sun
to an extended object or through the entire dust half-layer from the Sun to extragalactic space with an
accuracy σ(AV) = 0.06 mag. This gives a high relative accuracy of extinction estimates even at high
Galactic latitudes, where, according to our estimates, the median total Galactic extinction through the
entire dust half-layer from the Sun to extragalactic objects is AV = 0.12 ± 0.06 mag. We have shown that
the presented maps are among the best ones in data volume, space size, resolution, accuracy, and other
properties.

We have carried out a comprehensive study of the poorly investigated eclipsing polar
1RXS J184542.4+483134 with a short orbital period Porb ≈ 79 min. An analysis of its long-term light
curves points to a change in the position and sizes of the accretion spot as the accretion rate changes.
Narrow and broad components, which are probably formed on the ballistic segment of the accretion stream
and on the magnetic trajectory, respectively, are identified in the emission line profiles. An inversion of
the line profiles from emission to absorption due to the obscuration of the accretion spot by the accretion
stream is observed. Based on the eclipse duration and the radial velocities of the narrow line component,
we impose constraints on the white dwarf mass, 0.49 ≤ M1/M  ≤ 0.89, and the orbital inclination,
79.7◦ ≤ i ≤ 84.3◦. An analysis of the cyclotron spectra points to the presence of two accretion spots
with magnetic field strengths B1 = 28.4+0.1
−0.2 MG and B2 = 30 − 36 MG. The main spot has a complex
structure that apparently has a dense core and a less dense periphery emitting a spectrum with cyclotron
harmonics. Polarization observations reveal a circular polarization sign reversal during the orbital period
and an anticorrelation of the polarization with the brightness of the polar. Our modeling of polarization
observations using the simple model of an accreting white dwarf shows that the polarization properties
can be interpreted in terms of two-pole accretion with different optical depths of the accretion spots
(τ1/τ2 ∼ 10). An analysis of the Swift/XRT observations points to a predominance of bremsstrahlung
in the X-ray radiation from the system.

The detection of radio emission from solar flares at frequencies below ∼2 GHz allows the upper
limits for the characteristic size of the soft X-ray (SXR) source L(t) to be estimated under the assumption
that the density n(t) is determined by the plasma frequency νp. If the SXR source with a higher density is
inside the radio source, then the size of the SXR source will be L(t) < (EM(t)/2n(t)2)1/3, where EM(t)
is the emission measure. For three flares (C7.2 on December 22, 2009, M2.9 on July 6, 2012, and X1.1 on
July 6, 2012) we calculate the expansion speeds of the SXR source V (t) ∼ dL(t)/dt, which are compared
with the estimates of the sound speed and the Alfve´ n speed. By “magnetic detonation” wemean the process
of the propagation of magnetic reconnectionwith a supersonic speed in eruptive flares. Magnetic detonation
and the succeeding coronal mass ejection (CME) were realized in the December 22, 2009 C7.2 and July 6,
2012 X1.1 flares, in which supersonic and super-Alfve´ n speeds were reached if the density of the SXR
source was lower than 2.1 × 109 and 7.4 × 108 cm−3 (νp < 410 and < 245 MHz), respectively. There were
no magnetic detonation and CME in the July 6, 2012 M2.9 flare, whose radio emission frequencies were
only above 1415 MHz (n > 2.5 × 1010 cm−3). For magnetic detonation in the July 6, 2012 X1.1 flare we
have estimated the magnetic field strength, the reconnection electric field strength, the plasma flow, and the
CME mass.

Helioseismology has revealed an increase in the rotation rate with depth in a thin (∼30 Mm)
near-surface layer. The normalized rotational shear in this layer does not depend on latitude. This rotational
state is shown to be a consequence of the short characteristic time of near-surface convection compared
to the rotation period and radial anisotropy of convective turbulence. Analytical calculations within meanfield
hydrodynamics reproduce the observed normalized rotational shear and are consistent with numerical
experiments on radiative hydrodynamics of solar convection. The near-surface shear layer is the source of
global meridional flow important for the solar dynamo.