A5003620163- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astrophysical Phenomena and Observations
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Solar and Space Plasma Dynamics
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Adaptive optics and wavefront sensing
- Geophysics and Gravity Measurements
- Magnetic confinement fusion research
- Galaxies: Formation, Evolution, Phenomena
- Particle accelerators and beam dynamics
- Radio Astronomy Observations and Technology
- Ionosphere and magnetosphere dynamics
- High-pressure geophysics and materials
- Magnetic Bearings and Levitation Dynamics
- Acoustic Wave Resonator Technologies
- Calibration and Measurement Techniques
- Particle Accelerators and Free-Electron Lasers
- Geomagnetism and Paleomagnetism Studies
- Innovation Policy and R&D
- Streptococcal Infections and Treatments
Aryabhatta Research Institute of Observational Sciences
2015-2024
Indian Institute of Technology BHU
2024
Banaras Hindu University
2024
Indian Institute of Astrophysics
2019
Sapienza University of Rome
2015
Astronomical Observatory
2010
Tata Institute of Fundamental Research
2007-2008
ABSTRACT OJ 287 is a quasi-periodic quasar with roughly 12 year optical cycles. It displays prominent outbursts that are predictable in binary black hole model. The model predicted major outburst 2015 December. We found the did occur within expected time range, peaking on December 5 at magnitude 12.9 R -band. Based Swift /XRT satellite measurements and polarization data, we find it included thermal component. Its timing provides an accurate estimate for spin of primary hole, . present also...
Abstract Results from regular monitoring of relativistic compact binaries like PSR 1913+16 are consistent with the dominant (quadrupole) order emission gravitational waves (GWs). We show that observations associated binary black hole (BBH) central engine blazar OJ 287 demand inclusion radiation reaction effects beyond quadrupolar order. It turns out even certain hereditary contributions to GW required predict impact flare timings 287. develop an approach incorporates this effect into BBH...
Abstract We present the results of our power spectral density analysis for BL Lac object OJ 287, utilizing Fermi -LAT survey at high-energy γ -rays, Swift -XRT in X-rays, several ground-based telescopes and Kepler satellite optical, radio GHz frequencies. The light curves are modeled terms continuous-time autoregressive moving average (CARMA) processes. Owing to inclusion data, we were able construct first time optical variability spectrum a blazar without any gaps across ∼6 dex temporal Our...
We present an analysis of seven flares detected from five RS CVn-type binaries (UZ Lib, \sigma Gem, \lambda And, V711 Tau and EI Eri) observed with XMM-Newton observatory. The quiescent state X-ray luminosities in the energy band 0.3-10.0 keV these stars were found to be 10^{30.7-30.9} erg/s. exponential decay time all sample range ~ 1 8 hrs. luminosity at peak 10^{30.8} - 10^{31.8} great sensitivity XMM-EPIC instruments allowed us perform resolved spectral during also subsquent phases....
Abstract Using long-term X-ray observations, we present short-term and variability analysis of the ultrafast rotating active star AB Dor. Flaring events are common in observations Dor occupy a substantial portion total observation time, averaging at around 57% ± 23%. The flare-free light curves show rotational modulation, indicating presence highly regions star's corona. We have developed light-curve inversion code to image corona fast stars. results coronal imaging reveal two different...
Deep optical photometric data on the NGC 7538 region were collected and combined with archival sets from $Chandra$, 2MASS {\it Spitzer} surveys in order to generate a new catalog of young stellar objects (YSOs) including those not showing IR excess emission. This is complete down 0.8 M$_\odot$. The nature YSOs associated their spatial distribution are used study star formation process resultant mass function (MF) region. Out 419 YSOs, $\sim$91\% have ages between 0.1 2.5 Myr $\sim$86\%...
We present temporal and spectral characteristics of X-ray flares observed from six late-type G–K active dwarfs (V368 Cep, XI Boo, IM Vir, V471 Tau, CC Eri EP Eri) using data observations with the XMM–Newton observatory. All stars were found to be flaring frequently altogether a total 17 detected above 'quiescent' state emission which varied 0.5 8.3 × 1029erg s−1. The largest flare was in low-activity dwarf Boo decay time 10 ks ratio peak luminosity 2. have studied changes during by...
We present multi-wavelength linear polarimetric observations for 44 stars of the NGC 1893 young open cluster region along with V-band other four clusters located between l ~160 to ~175 degree. found evidence presence two dust layers at a distance ~170 pc and ~360 pc. The produce polarization Pv ~2.2%. It is evident from studied in work that, Galactic longitude range 175 degree within plane (|b| < 2 degree), angles remain almost constant, mean ~163 dispersion 6 small angle could be due...
We report the observations of X-ray oscillations during flare in a cool active star XI Boo for first time. was observed by EPIC/MOS XMM-Newton satellite. The light curve is investigated with wavelet and periodogram analyses. Both analyses clearly show period 1019 s. interpret these as fundamental fast-kink mode magnetoacoustic waves.
We present a comprehensive analysis of the detailed chemical abundances for sample 11 metal-poor, very metal-poor and extremely stars ([Fe/H] = -1.65 to [Fe/H] -3.0) as part HESP-GOMPA (Galactic survey Of Metal Poor stArs) survey. The abundance determinations encompass range elements, including C, Na, Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Ba, with subset brighter objects allowing measurement additional key elements. Notably, relatively bright highly r-process-enhanced...
In this report, we present an overview of the 3rd BINA workshop hosted by ARIES, Nainital on a broad theme Scientific potential Indo-Belgian co-operation. Further, introduction proceedings is also delineated along with possible areas where there to extend cooperation in current era multi-wavelength astronomy. These contain total 94 articles that are based results presented form 35 oral and 59 poster presentations during workshop. The participants strongly recommend further continuation...
We present new B, V and R linear polarimetric observations for 61 stars towards the region of young open cluster NGC 654. In this study we found evidence presence at least two layers dust along line sight to cluster. The distances are estimated be ~ 200 pc 1 kpc which located much closer Sun than (~ 2.4 kpc). Both have their local magnetic field orientation nearly parallel direction Galactic plane. foreground layer is a ring morphology with central hole coinciding center grains suggested...
ABSTRACT We present the R-band polarimetry of two low-latitude Lynd’s clouds L1495 and L1498 acquired with AIMPOL at Aryabhatta Research Institute Observational Sciences, Nainital, India. The estimated polarization across regions is typically in range ∼1–5 per cent position angle ∼100°–137° from which we infer morphologies corresponding magnetic field envelope region ($\theta_{\rm B}^{\rm env}$). In both clouds, fields are found to be aligned galactic (θGP). Due their close proximity plane,...
We present the $UBVR_cI_c$ broad band optical photometry of Type Ic supernova SN 2002ap obtained during 2002 February 06 -- March 23 in early decline phases and also later on 15 August. Combining these data with published ones, general light curve development is studied. The time luminosity peak brightness width are estimated. There a flattening about 30 days after $B$ maximum. flux rates before 0.127$\pm$0.005, 0.082$\pm$0.001, 0.074$\pm$0.001, 0.062$\pm$0.001 0.040$\pm$0.001 mag day$^{-1}$...
We present BVR polarimetric study of the cool active star LO Pegasi (LO Peg) for first time. Peg was found to be highly polarized among stars. Our observations yield average values polarization in Peg: PB= 0.387 ± 0.004 per cent, θB= 88°± 1°; PV= 0.351 θV= 91°± 1° and PR= 0.335 0.003 θR= 1°. Both degree position angle are variable. The semi-amplitude variability B, V R bands is 0.18 0.02, 0.13 0.01 0.10 0.02 respectively. suggest that levels observed could result scattering an anisotropic...
We present the first observational evidence of multiple slow acoustic oscillations in post-flaring loops corona Proxima Centauri using XMM-Newton observations. find signature periodic localized decay phase flare its soft (0.3–10.0 keV) X-ray emissions. Using standard wavelet tool, we periodicities 1261 s and 687 s. These bursty persist for durations 90 minutes 50 minutes, respectively, more than three cycles. The intensity with a period may be fundamental mode magnetoacoustic waves speed 119...
We present analyses of archival X-ray data obtained from the XMM-Newton satellite and optical photometric 1 m class telescopes ARIES, Nainital a magnetic cataclysmic variable (MCV) Paloma. Two persistent periods at 156 $\pm$ minutes 130 are in data, which we interpret as orbital spin periods, respectively. These similar to those previous well new observations. The soft-X-ray excess seen spectrum Paloma averaged spectra fitted by two-temperature plasma models with temperatures...
We present a detailed X-ray analysis and imaging of stellar coronae five coronally connected eclipsing binaries, namely, 44 Boo, DV Psc, ER Vul, XY UMa, TX Cnc. Both components these binaries are found to be active. The light curves detached semidetached type systems show eclipsed-like features, whereas no evidence for coronal is shown by the contact systems. curve Psc shows O'Connell-like effect where first maximum brighter than that second. Results using three-dimensional deconvolution all...
We present multiwavelength linear polarimetric observations of 104 stars towards the region young open cluster NGC 6823. The polarization 6823 is dominated by foreground dust grains and we found evidence for presence several layers line sight. first layer located approximately within 200 pc cluster, which much closer to Sun than (~ 2.1 kpc). radial distribution position angles member are show a systematic change while reduce outer parts average angle coronal very close inclination Galactic...
ABSTRACT We present the analyses of intense X-ray flares detected on active fast rotator AB Dor using observations from XMM–Newton. A total 21 are detected, and 13 analysed in detail. The energy these is found to be range 1034−36 erg, which peak flare flux increased up 34 times pre-/post-flaring states for strongest observed flare. duration flaring events 0.7 5.8 h. quiescent state spectra explained by a three-temperature plasma with average temperatures 0.29, 0.95, 1.9 keV, respectively....
We present a multiwavelength study of the NGC 281 complex which contains young cluster IC 1590 at center, using deep wide-field optical UBVI_c photometry, slitless spectroscopy along with archival data sets in near-infrared (NIR) and X-ray. The extent is estimated to be ~6.5 pc. region shows relatively small amount differential reddening. majority identified stellar objects (YSOs) are low mass PMS stars having age <1-2 Myr 0.5-3.5 M_\odot. slope (\Gamma) function for 1590, range 2 <...
We present analyses of optical photometric, spectroscopic, polarimetric and X-ray observations the K5V binary star, V1147 Tau. Nearly 20 yr show that Tau is a periodic variable with photometric period 1.4845 ± 0.0001 d. Light curves observed at 16 epochs changes in minima, amplitude shape indicating variability due to presence surface inhomogeneities. The coverage spots was found be range 9–22 per cent. Most time, were resolved as two active longitudes. Switching dominant longitudes also...