A. A. Arkharov
A5071707185- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Radio Astronomy Observations and Technology
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Dark Matter and Cosmic Phenomena
- Neutrino Physics Research
- Solar and Space Plasma Dynamics
- Calibration and Measurement Techniques
- Pulsars and Gravitational Waves Research
- Atmospheric Ozone and Climate
- Gyrotron and Vacuum Electronics Research
- Geophysics and Gravity Measurements
- History and Developments in Astronomy
- Particle physics theoretical and experimental studies
- Particle Accelerators and Free-Electron Lasers
- Galaxies: Formation, Evolution, Phenomena
- Spectroscopy and Laser Applications
- Space Exploration and Technology
- Spectroscopy Techniques in Biomedical and Chemical Research
- Ionosphere and magnetosphere dynamics
Pulkovo Observatory
2014-2023
St Petersburg University
2008-2018
Russian Academy of Sciences
2006-2015
Southampton City Council
2015
Astronomical Observatory
2002
(Abridged) We have conducted a detailed investigation of the broad-band spectral properties \gamma-ray selected blazars Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated gamma-ray spectra with Swift, radio, infra-red, optical and other hard X-ray/gamma-ray data, collected within three months LBAS data taking period, we were able to assemble high-quality quasi-simultaneous Spectral Energy Distributions (SED) for 48 blazars.The SED these sources is similar that...
We present the results of one-year long observational campaign type II plateau SN 2005cs, which exploded in nearby spiral galaxy M51 (the Whirlpool galaxy). This extensive data set makes 2005cs best observed low-luminosity, 56Ni-poor event so far and one core-collapse supernovae ever. The optical near-infrared spectra show narrow P-Cygni lines characteristic this family, are indicative a very low expansion velocity (about 1000 km s−1) ejected material. light curves cover both phase late-time...
We present time-resolved broad-band observations of the quasar 3C 279 obtained from multi-wavelength campaigns conducted during first two years Fermi Gamma-ray Space Telescope mission. While investigating previously reported gamma-ray/optical flare accompanied by a change in optical polarization, we found that emission appears delayed with respect to gamma-ray about 10 days. X-ray reveal pair `isolated' flares separated ~90 days, only weak counterparts. The spectral structure measured...
We analyze the multifrequency behavior of quasar 3C 454.3 during three prominent \gamma-ray outbursts: 2009 Autumn, 2010 Spring, and Autumn. The data reveal a repeating pattern, including triple flare structure, in properties each outburst, which implies similar mechanism(s) location for all events. multi-frequency indicates that lower frequency events are co-spatial with outbursts, although emission varies on shortest timescales. determine variability from UV to IR wavelengths an outburst...
We present new optical and near infrared (NIR) photometry spectroscopy of the type IIP supernova, SN 2004et. In combination with already published data, this provides one most complete studies NIR data for any from just after explosion to +500 days. The contribution flux bolometric light curve is estimated increase 15% at around 50% end plateau then declines 40% 300 2004et luminous SNe which has been well studied, a luminosity log L = 42.3 erg/s, it 2 times brighter than 1999em. provide...
The radio quasar 3C 454.3 underwent an exceptional optical outburst lasting more than 1 year and culminating in spring 2005. maximum brightness detected was R = 12.0, which represents the most luminous state thus far observed (M_B ~ -31.4). In order to follow emission behaviour of source detail, a large multiwavelength campaign organized by Whole Earth Blazar Telescope (WEBT). Continuous optical, near-IR monitoring performed several bands. ToO pointings Chandra INTEGRAL satellites provided...
We present photometric and spectroscopic observations at optical near-infrared wavelengths of the nearby type Ic SN 2007gr. These represent most extensive data-set to date any supernova this sub-type, with frequent coverage from shortly after discovery more than one year post-explosion. deduce a rise time B-band maximum 11.5 \pm 2.7 days. find peak magnitude M_B=-16.8, light curves which are remarkably similar so-called 'hypernova' 2002ap. In contrast, spectra SNe 2007gr 2002ap show marked...
We report the first results of a long term infrared monitoring campaign known and candidate galactic Luminous Blue Variables (LBVs). In particular, we are able to confirm LBV nature G24.73+0.69, luminous mid-B supergiant associated with dusty ejection nebula. find that prior 2003 September G24.73+0.69 exhibited low amplitude ( mag) variability, but in ~200 day period between September–2004 April it abruptly brightened by ~0.7 mag broadband J filter. Subsequently, further ~0.4 increase was...
We present optical and infrared observations of the unusual Type Ia supernova (SN) 2004eo. The light curves spectra closely resemble those prototypical SN 1992A, luminosity at maximum (M_B = -19.08) is close to average for a Ia. However, ejected 56Ni mass derived by modelling bolometric curve (about 0.45 solar masses) lies near lower limit distribution observed in normal SNe Accordingly, 2004eo shows relatively rapid post-maximum decline (Delta m_(B) 1.46), small expansion velocities ejecta,...
Aims. Since the CGRO operation in 1991–2000, one of primary unresolved questions about blazar γ-ray emission has been its possible correlation with low-energy (in particular optical) emission. To help answer this problem, Whole Earth Blazar Telescope (WEBT) consortium organized GLAST-AGILE Support Program (GASP) to provide optical-to-radio monitoring data be compared detections by AGILE and GLAST satellites. This new WEBT project started early September 2007, just before a strong detection...
We report on the multi-wavelength observations of PKS 1510-089 (a flat spectrum radio quasar (FSRQ) at z = 0.361) during its high activity period between 2008 September and 2009 June. During this 11 month period, source was characterized by a complex variability optical, UV, γ-ray bands, timescales down to 6–12 hr. The brightest isotropic luminosity, recorded March 26, ≃2 × 1048 erg s−1. in Fermi Large Area Telescope energy range shows mild curvature described well log-parabolic law, can be...
We report on 18 months of multiwavelength observations the blazar 3C 454.3 (Crazy Diamond) carried out in July 2007-January 2009. show results AGILE campaigns which took place May-June 2008, July-August and October 2008-January During May 2009 period, source average flux was highly variable, from an gamma-ray F(E>100MeV) > 200E-8 ph/cm2/s to F(E>100MeV)~80E-8 The spectrum between 100 MeV 1 GeV can be fit by a simple power law (Gamma_GRID ~ 2.0 2.2). Only 3-sigma upper limits derived 20-60...
Since 2005, the blazar 3C 454.3 has shown remarkable flaring activity at all frequencies, and during last four years it exhibited more than one γ-ray flare per year, becoming most active in sky. We present for first time multi-wavelength AGILE, Swift, INTEGRAL, GASP-WEBT data collected order to explain extraordinary of which occurred 2010 November. On November 20 (MJD 55520), reached a peak flux (E >100 MeV) Fpγ = (6.8 ± 1.0) × 10−5 photons cm−2 s−1 on timescale about 12 hr, factor six...
Aims. The Whole Earth Blazar Telescope (WEBT) consortium has been monitoring the blazar 3C 454.3 from radio to optical bands since 2004 study its emission variability properties.
<i>Aims. <i/>We aim to characterise the properties of a third massive, red supergiant dominated galactic cluster.<i>Methods. <i/>To accomplish this we utilised combination near/mid- IR photometry and spectroscopy identify classify cluster members, statistical arguments determine mass cluster.<i>Results. found total 16 strong candidates for membership, which formal classification subset yields spectral types from K3–M4 Ia luminosities between –4.8 an adopted distance kpc. For age in range...
We present the results of polarimetric (R-band) and multicolor photometric (BH RI J H K) observations blazar AO 0235+16 during an outburst in 2006 December. The data reveal a short timescale variability (several hours), which increases from optical to near-IR wavelengths; even shorter variations are detected polarization. flux density correlates with degree polarization, at maximum polarization electric vector tends align parsec-scale jet direction. find that variable component steady...
The GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) monitored BL Lacertae in 2008-2009 at radio, near-IR, and optical frequencies. During this period, high-energy observations were performed by XMM-Newton, Swift, Fermi. We analyse these data with particular attention to calibration Swift UV data, apply a helical jet model interpret source broad-band variability. GASP-WEBT show an flare 2008 February-March, oscillations several tenths mag on few-day time scale...
<i>Context. <i/>Since 2001, the radio quasar 3C 454.3 has undergone a period of high optical activity, culminating in brightest state ever observed, during 2004-2005 outburst. The Whole Earth Blazar Telescope (WEBT) consortium carried out several multifrequency campaigns to follow source behaviour.<i>Aims. <i/>The GLAST-AGILE Support Program (GASP) was born from WEBT provide long-term continuous optical-to-radio monitoring sample <i>γ<i/>-loud blazars, operation AGILE and GLAST (now known as...
Since 1997, BL Lacertae has undergone a phase of high optical activity, with the occurrence several prominent outbursts. Starting from 1999, Whole Earth Blazar Telescope (WEBT) consortium organized various multifrequency campaigns on this blazar, collecting tens thousands data points. One main issues in study huge dataset been search for correlations between and radio flux variations, possible periodicities light curves. The analysis assembled during first four (comprising also archival to...
We present multiwavelength observations of 3C 454.3 from April 2008 to March 2010. The radio optical data are mostly the GASP-WEBT, UV and X-ray Swift, gamma-ray AGILE Fermi satellites. improved calibration optical-UV UVOT OM instruments estimated Lyalpha flux disentangle contributions different components in this spectral region. reveal prominent variability above 8 GHz. In band, amplitude decreases with increasing frequency due a steadier radiation both broad line region an accretion disc....
We report on the extreme gamma-ray activity from FSRQ PKS 1510-089 observed by AGILE in March 2009. In same period a radio-to-optical monitoring of source was provided GASP-WEBT and REM. Moreover, several Swift ToO observations were triggered, adding important information behaviour optical/UV to hard X-rays. paid particular attention calibration Swift/UVOT data make it suitable blazars spectra. Simultaneous radio gamma rays allowed us study detail correlation among emission variability at...
We present the results of a comparison between classical and newly identified EXor based on literature data aimed at recognizing possible differences or similarities categories. Optical near-IR two-color diagrams, modalities fluctuations, derived values mass accretion rates are indicative strong two samples. demonstrate how difference outburst quiescence spectral energy distribution all can be well fitted with single blackbody, as if an additional thermal component appears during outbursting...
The quasar-type blazar 4C 38.41 (B3 1633+382) experienced a large outburst in 2011, which was detected throughout the entire electromagnetic spectrum. We present results of low-energy multifrequency monitoring by GASP project WEBT consortium and collaborators, as well those spectropolarimetric/spectrophotometric at Steward Observatory. also analyse high-energy observations Swift Fermi satellites. In optical-UV band, several indicate that there is contribution from QSO-like emission...