A5014221816- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Cosmic Phenomena
- Astrophysics and Star Formation Studies
- Radio Astronomy Observations and Technology
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Adaptive optics and wavefront sensing
- Gyrotron and Vacuum Electronics Research
- Galaxies: Formation, Evolution, Phenomena
- Astro and Planetary Science
- Solar and Space Plasma Dynamics
- Particle Accelerators and Free-Electron Lasers
- Dark Matter and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Infrared Target Detection Methodologies
- Ionosphere and magnetosphere dynamics
- Space Exploration and Technology
- Atmospheric Ozone and Climate
- Pulsars and Gravitational Waves Research
- Precipitation Measurement and Analysis
- Material Science and Thermodynamics
- Radio Wave Propagation Studies
- History and Developments in Astronomy
Center for Theoretical Physics
2023-2024
Polish Academy of Sciences
2023-2024
Indian Institute of Astrophysics
2021-2022
Aryabhatta Research Institute of Observational Sciences
2006-2021
Deen Dayal Upadhyaya Gorakhpur University
2017-2020
Oil and Natural Gas Corporation (India)
2008
Udaipur Solar Observatory
1986-2002
Banaras Hindu University
1976
Context. FeII emission is a well-known contributor to the UV spectra of active galactic nuclei and modeling this part may affect results obtained for MgII λ 2800 emission, which one lines used black hole mass measurements cosmological applications. Aims. We tested different models when intermediate-redshift quasar HE 0413−4031 see how use specific template affects line properties measurement time delays with respect continuum. Methods. 11-year monitoring selected South African Large...
We have examined 40 NuSTAR light curves (LCs) of five TeV emitting high synchrotron peaked blazars: 1ES 0229+200, Mrk 421, 501, 1959+650 and PKS 2155-304. Four the blazars showed intraday variability in energy range 3-79 keV. Using an auto correlation function analysis we searched for timescales these LCs found indications several between 2.5 32.8 ks eight a timescale around 8.0 one LC 29.6 57.4 two The other blazars' do not show any evidence shorter than lengths those observations, however,...
Context: 3C 273, a well-studied active galactic nucleus (AGN), displays characteristics of both jetted-AGN and Seyfert galaxies, making it an excellent source to study the disc-jet connection in AGN. Aims: To investigate disk-jet scenario 273 using broadband (0.3--78 keV) X-ray spectra from {\it XMM-Newton} NuSTAR}. Methods: We used simultaneous NuSTAR} observations carried out between 2012 2024. The 0.3--78 keV were first fit with simple power-law (PL) then accretion-ejection-based JeTCAF...
We present the results of blazar 3C 273 obtained from simultaneous observations using XMM-Newton and NuSTAR satellites during period 2015-2019 in five epochs. When spectra are modeled with a power-law, significant residuals arise below 2 keV energy range 30-78 data. Residuals lower band represent soft X-ray excess while at higher energies it likely represents Compton reflection hump which might be weak component arising dense cold material. The presence faint iron line is observations....
The well-studied active galactic nucleus (AGN) 3C 273 displays characteristics of both jetted-AGNs and Seyfert galaxies, which makes it an excellent source to study the disc-jet connection in AGNs. We aim investigate scenario using broad-band (0.3--78 keV) X-ray spectra from XMM-Newton NuSTAR used simultaneous observations carried out between 2012 2024. 0.3--78 keV were first fitted with a simple power law (PL) then accretion-ejection-based model. model accounts for emission jet, extends up...
Abstract We present the results of blazar 3C 273 from simultaneous observations obtained using XMM-Newton and NuSTAR satellites during period 2015–2019 in five epochs. When spectra are modeled with a power law, significant residuals arise below ∼2 keV energy range 30–78 data. Residuals lower band represent soft X-ray excess, while at higher energies it likely represents Compton reflection hump, which might be weak component arising dense cold material. A faint iron line is observations....
Abstract We present a set of new theoretical Fe ii templates for bright quasars covering wavelength range 1000–10000 Å based on the recent atomic database available in C23.00 version photoionization code CLOUDY . compute grid models incident photon flux, gas density, and multiple microturbulence velocities. examine equivalent widths ratios emission over various wave bands compare them with observations. Our key results are as follows: (1) The flux generated from shielded side cloud is...
Contamination from singly ionized iron emission is one of the greatest obstacles to determining intensity lines in UV and optical wavelength ranges. This study presents a comprehensive analysis ii bright quasar RM 102, based on most recent version CLOUDY software, with goal understanding nature origin emission. We employ constant pressure model for emitting clouds, instead customary density assumption. The allowed parameter range broad, metallicity up 50 times solar value turbulent velocity...
Observations of the extraordinarily bright optical afterglow (OA) GRB 991208 started 2.1 d after event. The flux decay constant OA in R-band is -2.30 +/- 0.07 up to 5 d, which very likely due jet effect, and that it followed by a much steeper with -3.2 0.2, fastest one ever seen OA. A negative detection several all-sky films taken simultaneously event implies either previous additional break prior 2 occurrence (as expected from effect). existence second might indicate steepening electron...
We report the results of multiband optical photometric monitoring two well-known blazars, S5 0716+714 and BL Lacertae, carried out during 1996 2000–01 with an aim to study variations on time-scales ranging from minutes hours longer. The light curves were derived relative comparison stars present CCD frames. Night-to-night intensity ≥0.1 mag observed in a campaign about 2 weeks 1996. A good correlation between different bands was found for both inter-night intra-night observations. In all,...
We present recent optical photometric observations of the blazar OJ 287 taken during September 2015 -- May 2016. Our intense started in November and continued until 2016 included detection large outburst December that was predicted using binary black hole model for 287. For our observing campaign, we used a total 9 ground based telescopes which one is Japan, India, three are Bulgaria, Serbia, Georgia, two USA. These were carried out 102 nights with ~ 1000 image frames BVRI bands, though...
In order to study the relation between core and corona in galactic star clusters, spatial structure of 38 rich open clusters has been studied using radial density profiles derived from photometric data Digital Sky Survey.The shape profile indicates that corona, most probably, is outer region around cluster.It can exist very beginning cluster formation dynamical evolution not reason for its occurrence.The does find any size age but with galacto-centric distances >9.5 kpc have larger...
Since many years we know that dust in the form of dusty-molecular torus is responsible for obscuration active galactic nuclei (AGN) at large viewing angles and thus classification AGN. Recently, gained some observational theoretical insight into geometry region role dynamics outflow failed winds. We will briefly touch on all these aspects, including our dust-based model (FRADO - Failed Radiatively Accelerated Dusty Outflow) formation Balmer lines
Abstract In this review, the third one in series focused on a small two-band UV-photometry mission, we assess possibilities for UV photometry mission studying accreting supermassive black holes (SMBHs; mass range $\sim 10^{6}$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>∼</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mn>6</mml:mn> </mml:msup> </mml:math> – $10^{10}\,M_{\odot }$ <mml:mspace /> <mml:msub> <mml:mi>M</mml:mi> <mml:mo>⊙</mml:mo>...
We present the results of our optical (VRI) observations TeV blazar PG 1553+113 over eight nights in 2016 April. monitored quasi-simultaneously V and R bands each night examined light curves (LCs) for intraday flux color variations using two most powerful tests; power-enhanced F-test nested ANOVA test. The source was found to be significantly (> 99%) variable both only on April 13, while clear band LCs were seen 8 12. No temporal variation during observation period. did not find any...
We have performed a detailed analysis of the Czernik 3 (Cz3) open cluster by using deep near-infrared photometry taken with TIRCAM2 on 3.6m Devasthal optical telescope along recently available high quality proper motion data from {\it Gaia} DR2 and photometric Pan-STARRS1. The has highly elongated morphology fractal distribution stars. core radii are estimated as 0.5 pc 1.2 pc, respectively. identified 45 stars members data. distance age found to be $3.5\pm0.9$ kpc $0.9^{+0.3}_{-0.1}$ Gyr,...
We present optical photometric and polarimetric observations of stars towards NGC 1931 with the aim to derive cluster parameters such as distance, reddening, age luminosity/mass function well understand dust properties star formation in region. The distance is found be 2.3$\pm$0.3 kpc reddening E(B-V) region variable. stellar density contours reveal two clustering suggest differing law within Polarization efficiency grains direction less than that for general diffuse interstellar medium...
Abstract We present 12 new transit light curves of the hot-Jupiter TrES-3b observed during 2012−2018 to probe timing variation (TTV). By combining midtransit times determined from these data with those reestimated through uniform procedure 71 available in literature, we derive linear ephemeris and obtain residuals that suggest possibility TTV TrES-3 system. However, frequency analysis shows possible is unlikely be periodic, indicating absence an additional body this To explore other origins...
Context. We present the wavelength-resolved reverberation mapping (RM) of combined Mg II and UV Fe broad-line emissions for two intermediate-redshift ( z ∼ 1), luminous quasars, HE 0413-4031 0435-4312, monitored by Southern African Large Telescope (SALT) 1m class telescopes between 2012 2022. Aims. Using a technique, we aim to disentangle emission regions build radius–luminosity (R–L) relation emission, which has so far remained unconstrained. Methods. applied several time-delay...
Based on an extensive site survey conducted during 1980-1990 in the Shivalik Hills of Central Himalayan range, a promising Devasthal has been identified. The longitude and latitude Peak are 79° 41′ E 29° 23′ N. It is situated at altitude 2540 m about 50 km by road from Nainital towards East. surroundings thinly populated it logistically well suited for establishing modern optical observational facilities. prevailing wind direction NW. For large fraction night time, variation ambient...
Abstract We report the first results of timing and spectral studies Nuclear Spectroscopic Telescope Array observations six TeV-emitting high-frequency peaked blazars: 1ES 0347-121, 0414+009, RGB J0710+591, 1101-232, 1218+304, H 2356-309. Two out these TeV blazars, 1101−232 showed strong evidence intraday variations in 3–79 keV energy range during those observations. also found a hint an variability timescale 23.5 ks light curve 1218+304 using autocorrelation function analysis. obtained...
We present an extensive study of 72 archival Chandra light curves the high-frequency-peaked type blazar Mrk 421, first strong extragalactic object to be detected at TeV energies. Between 2000 and 2015 421 often displayed intraday variability in 0.3-10.0 keV energy range, as quantified through fractional amplitudes that range up 21.3 per cent. A duty cycle ~84 cent is these data. Variability timescales, with values ranging from 5.5 30.5 ks, appear seven observations. Discrete correlation...
We present Cousins R and I band photometry of variable stars in a region the disk M 31 galaxy, obtained during 141 nights. Of 26 Cepheid variables region, two are newly discovered, 11 classified as Cepheids for first time 13 confirmed Cepheids. The extensive these enabled us to determine precise phase amplitude pulsation which ranges from 0.11 0.48 mag band. period variability ~7.5 56 days. period-luminosity diagram is used derive distance modulus galaxy. also report 333 other stars, them,...
Colour excesses and photometric distances of open clusters compiled by Janes & Adler Lyngå have been used to study the distribution interstellar matter within a few kiloparsecs Sun. In general reddening material is highly concentrated near galactic plane. It found that plane defined inclined formal an angle |$0_{.}^{\circ}8\pm0_{.}^{\circ}2$| shows maximum upward tilt towards l~60°. The scale height be 0.16±0.02 kpc. Based on whole matter, Sun situated at distance about 10 pc above symmetry...