Abstract
It is widely believed that the cool gas clouds traced by Mg ii
absorption, within a velocity offset of 5000 km s−1 relative to the background quasar are mostly associated with the quasar ...itself, whereas the absorbers seen at larger velocity offsets towards us are intervening absorber systems and hence their existence is completely independent of the background quasar. Recent evidence by Bergeron et al. (hereinafter BBM) has seriously questioned this paradigm, by showing that the number density of intervening Mg ii absorbers towards the 45 blazars in their sample is nearly two times the expectation based on the Mg ii
absorption systems seen towards normal quasars (QSOs). Given its serious implications, it becomes important to revisit this finding, by enlarging the blazar sample and subjecting it to an independent analysis. Here, we first report the outcome of our re-analysis of the available spectroscopic data for the BBM sample itself. Our analysis of the BBM sample reproduces their claimed factor of 2 excess of dN/dz along blazar sightlines, vis-à-vis normal QSOs. We have also assembled an approxmately three times larger sample of blazars, albeit with moderately sensitive optical spectra. Using this sample together with the BBM sample, our analysis shows that the dN/dz of the Mg ii absorbers statistically matches that known for normal QSO sightlines. Further, the analysis indicates that associated absorbers might be contributing significantly to the estimated dN/dz up to offset speeds Δv ∼ 0.2c relative to the blazar.
The three-dimensional structure of recombinant nicking endonuclease S11C Cys-free Nt.BspD6I was determined at 1.85 Å resolution. Nickase S11C Cys-free Nt.BspD6I was produced by the reversion back to ...Cys11 in Cys-free Nt.BspD6I using site-directed mutagenesis. An analysis of the crystal structure of nickase S11C Cys-free Nt.BspD6I demonstrated that the reversion back to Cys11 induces significant conformational changes in the recognition domain of nickase, which are accompanied by changes in its functions, such as a decrease in the affinity to DNA, the loss of the ability to undergo oligomerization, and high activity of restriction endonuclease S11C Cys-free R.BspD6I.
—This paper presents a method for searching for polar candidates using mid-band filters. One of the spectral features of polars is the HeII λ4686 strong emission line. We selected the Edmund Optics ...color filters with central wavelengths of 470, 540, and 656 nm and a transmission bandwidth of 10 nm. These filters cover the regions of the HeII λ4686 line, continuum, and the Hα line respectively. We constructed a color diagram based on the available spectra of polars and objects with a zero redshift from the SDSS archive. We show that most polars make a group with unique color indices. In practice, the method is implemented in SAO RAS at the Zeiss-1000 telescope with a new multi-mode photometer-polarimeter (MMPP). Approbation of the method with the known polars allowed us to develop two criteria to select candidates with an efficiency of up to 75%.
We present a study of the influence of magnetically induced control of external convection in stars of different types, in particular white dwarfs, on their thermal evolution. In the work preceding ...this study, we argued that for the cooling down white dwarf stars that have exhausted the sources of thermonuclear combustion, cessation of convection by a magnetic field significantly slows down their cooling. To test this asertion, we performed an observational program to search for new highly magnetized white dwarfs. The program is described in detail in the same issue of the journal. Our observations, together with the observations of other researchers, allowed us to construct the observed luminosity function of strongly magnetized white dwarfs with stopped convection and compare it with the well-known similar luminosity function of white dwarfs with weak fields that allow effective convective heat removal from their insides. As a result of the model analysis of these functions, the hypothesis that strongly magnetized white dwarfs cool down slower than weakly magnetic ones is confirmed. The article also qualitatively examines the effect of magnetic braking of convection in solar-type stars and cool M-dwarf stars of the Main Sequence on the periodicity of their radiation activity. The geophysical aspect of the problem and the practical application of magnetic field control of the heat removal in electrically conductive media are discussed.
We present the results of observations within the program for the search for new highly magnetized white dwarfs among evolutionary old stars of this class. The program was carried out for two years ...at the 1-m telescope of the SAO RAS. As a result, new white dwarf candidates of different ages with super-strong (several megagauss, tens, hundreds of megagauss) magnetic fields were discovered. These observations, along with the observations of other authors made it possible to make a new estimate of the frequency of occurrence of magnetic white dwarfs among old stars. Our results confirm our earlier assumptions that the frequency of occurrence of far-evolved magnetic white dwarfs with magnetic fields of several megagauss or higher and with the temperatures of less than 10 000 K is at the level of 15% or higher, while the frequency of occurrence of such stars among young white dwarfs does not exceed 4–6%. This fact means that the thermal evolution of the physical properties of magnetic white dwarfs differs from the thermal evolution of their weakly magnetic counterparts.
We present an optical-to-radio study of the BL Lac object S4 0954+658 observations during 1998–2023. The measurements were obtained with the SAO RAS Zeiss-1000 and AS-500/2 0.5-m telescopes in ...2003–2023, with the RATAN-600 radio telescope at 1.25 (0.96, 1.1), 2.3, 4.7 (3.7, 3.9), 8.2 (7.7), 11.2, 22.3 (21.7) GHz in 1998–2023, with the IAA RAS RT-32 Zelenchukskaya and Badary telescopes at 5.05 and 8.63 GHz in 2020–2023, and with the RT-22 single-dish telescope of CrAO RAS at 36.8 GHz in 2009–2023. In this period the blazar was showing extremely high broadband activity with the variability amplitude of the flux densities up to 70–100
both in the optical and radio domains. During the period of 2014–2023 the blazar displayed extremely high activity in the radio wavelengths, and we detected multiple radio flares of varying amplitude and duration. The large flares last on average from 0.3 to 1 year at 22–36.8 GHz and slightly longer at 5–11.2 GHz. The optical flares are shorter and last 7–50 days. The characteristic time scale
of variation at 5–22 GHz is about 100 days in the most active epoch of 2014–2023 and about 1000 days for the state with lower activity in 2009–2014. We found a general correlation between the optical, radio, and
-ray flux variations, which suggesting that we observe the same photon population from different emission regions. We estimated the linear size of this region as 0.5–2 pc for different conditions. A broadband radio spectrum with two components of the S4 0954+658 jet was modeled using both electrons and protons as emitting particles. The results suggest that the synchrotron radio waves in this AGN may be produced by relativistic protons.
Eight Exoplanet Candidates in SAO Survey Yakovlev, O. Ya; Valeev, A. F.; Valyavin, G. G. ...
Astrophysical bulletin,
03/2023, Volume:
78, Issue:
1
Journal Article
Peer reviewed
Open access
We report eight new exoplanet candidates discovered at the Special Astrophysical Observatory of the Russian Academy of Sciences using the transit technique. Photometric observations were performed ...with a 50-cm robotic telescope during the second half of 2020. Transits with depths of
and periods
were detected in
–
stars. All the stars considered are dwarfs with radii
(with an uncertainty of up to
for a single star). We use simulations to estimate the candidate radii (all are greater than 1.4 times the Jovian radius), semi-major axes of their orbits (0.012–0.035 AU), and other orbital parameters. We report the transit light curves for two stars obtained in 2022 based on individual observations.
We present the results of the first year of searching for polar candidates within the 3BS (3-Band Survey) program using medium-band filters. Observational data for 84 selected objects from the ...catalog of cataclysmic variables of the CRTS DR1 sky survey were obtained while implementing the program. A dwarf nova during its outburst and a polar were detected. The available archival data are analyzed. The dwarf nova is of the U Gem or Z Cam type and contains a massive secondary component with
. For the polar found we have estimated the orbital period
and calculated the magnetic field strength of the white dwarf
MG.
We report the results of long-term photometric observations of the magnetic white dwarfs WD 2047+372 and WD 0009+501, aimed to search for and study regular brightness variability in these stars. The ...data in the
V
band of the Johnson filter revealed signs of irregular variability in the convectively inactive white dwarf WD 2047+372 at times from hours to 1–3 days with characteristic amplitudes of about 0
m
. 005. This variability can be due to both irregular proper pulsations of the star or even the debris disk and reasons of unidentified instrumental nature. We have not found the brightness variability of WD 2047+372 at the level of greater than 0
m
. 005. As distinct from WD 2047+372, the convectively active magnetic white dwarf WD 0009+501 shows stable photometric variability associated with the proper rotation of the object and correlating with the variability of its magnetic properties. The variability amplitude is about 0
m
. 01. Based on comparison of the observations of these two targets, we concluded on the photometric variability of magnetic dwarfs located in the thermal convection zone. We noticed the stable variability on long-term timescales (years, decades, and over).
We present broad band photometry and spectroscopic observations of the host galaxy of GRB 030329. Analysis of the spectral emission lines shows that the host is likely a low metallicity galaxy (Z 6 ...0.004). The spectral energy distribution (SED) constructed with the photometric points has been fitted using synthetic and observational templates. The best SED fit is obtained with a starburst template with an age of 6150 Myr and an extinction Av 6 0.6. We find that the GRB 030329 host galaxy is a subluminous galaxy (L 6 0.016 L*) with a stellar mass of 108 M. Three independent diagnostics, based on the restframe UV continuum, the O II, and the Balmer emission lines, provide a consistent unextinguished star formation rate of 60.6 M yr-1, implying a high unextinguished specific star formation rate (634 M yr-1 (L/L*)-1). We estimate that the unextinguished specific star formation rate of the GRB 030329 host is higher than 693.5% of the galaxies at a similar redshift.
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