Observations of 79 comparison stars in the fields of seven Seyfert galaxies (Akn 79, Mrk 374, Mrk 382, Mrk 478, Mrk 493, Mrk 618, and Mrk 1513) and a single quasar (CTA 102) are reported. The ...observations were made with CCD photometry in the B, V, R, and I bands. The stellar magnitudes of these stars in the V band range from 12
m
.9 to 18
m
.4. The typical photometric uncertainties for magnitude 15 stars are 0
m
.008, 0
m
.011, 0
m
.009 and 0
m
.015 in the BVRI bands, respectively. For most of these stars the B, V, R, and I magnitudes have not been known previously. A variable star with brightness variations over a period of
P
= 0.1705 d was found in the field of the galaxy Mrk 478 and the sampled stars in the field of the galaxy Mrk 1513 include a variable with a period of
P
= 0.2211 d. These stars may be type W UMa contact binary systems with orbital periods of 0.341 and 0.4422 d, respectively. Finding charts for the comparison stars are included. These results can be used for differential photometry of the AGNs.
We present the final results from a high sampling rate, multi-month, spectrophotometric reverberation mapping campaign undertaken to obtain either new or improved H{beta} reverberation lag ...measurements for several relatively low-luminosity active galactic nuclei (AGNs). We have reliably measured the time delay between variations in the continuum and H{beta} emission line in six local Seyfert 1 galaxies. These measurements are used to calculate the mass of the supermassive black hole at the center of each of these AGNs. We place our results in context to the most current calibration of the broad-line region (BLR) R{sub BLR}-L relationship, where our results remove outliers and reduce the scatter at the low-luminosity end of this relationship. We also present velocity-resolved H{beta} time-delay measurements for our complete sample, though the clearest velocity-resolved kinematic signatures have already been published.
—
Deployment of the deep-sea neutrino telescope Baikal-GVD continues in Lake Baikal. By April 2022, ten telescope clusters, which include 2880 optical modules, were put into operation. One of the ...urgent tasks of the Baikal project is to study the possibility of increasing the detection efficiency of the detector based on the experience of its operation and the results obtained with other neutrino telescopes in recent years. In this paper, the authors consider a variant of optimizing the telescope configuration by installing an additional string of optical modules between the detector clusters (external string). An experimental version of the external garland was installed in Lake Baikal in April 2022. The paper presents the results from calculations of the efficiency of registration of neutrino events for a new setup configuration, the technical implementation of the system for recording and collecting data from the external garland, and the first results of its full-scale tests in Lake Baikal.
Neutrino astronomy offers a novel view of the non-thermal Universe and is complementary to other astronomical disciplines. The field has seen rapid progress in recent years, including the first ...detection of astrophysical neutrinos in the TeV–PeV energy range by IceCube and the first identified extragalactic neutrino source (TXS 0506+056). Further discoveries are aimed for with new cubic-kilometer telescopes in the Northern Hemisphere: Baikal-GVD, in Lake Baikal, and KM3NeT-ARCA, in the Mediterranean sea. The construction of Baikal-GVD proceeds as planned; the detector currently includes over 2000 optical modules arranged on 56 strings, providing an effective volume of 0.35 km
. We review the scientific case for Baikal-GVD, the construction plan, and first results from the partially built array.
Based on our
UBV RI
observations and X-ray data from the RXTE satellite, we have investigated the variability of the galaxy NGC 7469 over the period 1995–2009. In 1995–2000, the optical brightness of ...the galactic nucleus changed almost by 1
m
in the
U
band. In 2000–2009, the amplitude of the optical variations was considerably lower. Regular X-ray observations began only in 2003. The X-ray fractional variability amplitude is higher than the optical one. The optical variability amplitude decreases with increasing wavelength. The full width at half maximum of the X-ray and
B
-band autocorrelation functions is about 8 and 62 days, respectively. The structure functions (
SF
) in the X-ray range on time scales up to 7 days and in the optical range on time scales up to 100 days have the form of a power law
SF
(
τ
) ∼
τ
b
, where
τ
is the time shift. On time scales of more than a day, where both structure functions have been determined rather reliably, their slopes differ markedly:
b
= 1.34 ± 0.06 and
b
= 0.25 ± 0.05 for the optical and X-ray ranges, respectively. The X-ray and
B
-band structure functions begin to flatten, respectively, near 6–8 days and on time scales of about 90 days. The observed structure functions can be described by the model of a superposition of independent Gaussian flares whose number changes with duration
ω
as
n
(
ω
) ∼
ω
α
and whose amplitudes depend on duration as
A
(
ω
) ∼
ω
β
. The flux distribution and the flux-amplitude relation are consistent with the model of a light curve in the form of a superposition of random flares. Once the fast intensity variations have been filtered out on long time scales, the X-ray light curve correlates well with the optical one. No lag of the X-ray variations relative to those in the
B
band is detected. The light variations in the
R
and
I
bands lag behind those in the
B
band calculated from the centroid of the cross-correlation function by 2.6 and 3.5 days, respectively, at a 3
σ
confidence level.
Baikal-GVD is a 1 km
3
scale neutrino telescope now under construction in Lake Baikal. The sensitive volume of the detector is currently around 0.5 km
3
. Muons form through the exchange of W-bosons ...in the interaction between muon- and partial tau-neutrinos near the telescope. The muons then propagate to great distances in the lake’s water. Reconstructing their trajectory allows us to obtain the most accurate estimate of the direction of neutrinos at telescopes of this type. Angular resolution can be as good as 0.5° for fairly long muon tracks. The current state of affairs in analyzing track events at the Baikal-GVD is discussed.
The main goal of the Baikal-GVD deep-sea neutrino telescope is to detect high-energy neutrinos of astrophysical origin by reconstructing muon tracks or showers of particles generated in interactions ...of neutrino with water. Since 2020, Baikal-GVD has been monitoring IceCube telescope alerts about detecting neutrinos with energies of more than 100 TeV. This work presents results from searching for matches between Baikal-GVD events and IceCube neutrino alerts from September 2020 to April 2022.
The Baikal-GVD deep underwater neutrino experiment participates in the international multi-messenger program to detect the astrophysical sources of high- and ultrahigh-energy cosmic-ray particles, ...being at the stage of array deployment and a step-by-step increase of the telescope’s effective volume to the scale of a cubic kilometer. At present, the telescope consists of seven clusters containing 2016 photodetectors. The effective volume of the detector has reached 0.35 km
for the selection of shower events from neutrino interactions in Baikal water. The experimental data have been accumulated in a continuous exposure mode since 2015, allowing a prompt data analysis and a celestial-sphere monitoring program to be implemented in real time. We discuss the structure of the data acquisition system, describe the physical event reconstruction procedure in the mode of fast response to alerts, and present the results of our analysis of nine alerts from the polar IceCube telescope from early September to late October 2020.
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