A5011491933- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astrophysics and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Planetary Science and Exploration
- Atmospheric Ozone and Climate
- Radio Astronomy Observations and Technology
- Particle Accelerators and Free-Electron Lasers
- Isotope Analysis in Ecology
- Adaptive optics and wavefront sensing
- Galaxies: Formation, Evolution, Phenomena
- Solar and Space Plasma Dynamics
- Calibration and Measurement Techniques
- Spacecraft and Cryogenic Technologies
- Space Exploration and Technology
- Gyrotron and Vacuum Electronics Research
- Geophysics and Gravity Measurements
- Pulsars and Gravitational Waves Research
- Ionosphere and magnetosphere dynamics
- Dark Matter and Cosmic Phenomena
- SAS software applications and methods
Physical Research Laboratory
2015-2024
Yes Technologies (United States)
2020
Institut d'Astrophysique de Paris
1999-2008
Centre National de la Recherche Scientifique
1999-2003
Raman Research Institute
2002
Southern Illinois University Carbondale
1992
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...
Over the course of three hours on 27 December 2008 we obtained optical (R-band) observations blazar S5 0716+714 at a very fast cadence 10 s. Using several different techniques find fluctuations with an approximately 15-minute quasi-period to be present in first portion that data > 3 sigma confidence level. This is fastest QPO has been claimed observed any wavelength. While this insufficient strongly constrain models for such fluctuations, presence short timescale when source not low state...
Many body gravity (MBG) is an alternate theory of gravity, which has been able to explain the galaxy rotation curves, radial acceleration relation (RAR) and wide binary stars (WBS). The genesis MBG a novel theory, models systems with thermal gradients, by recasting variation in temperature as metric. Merging above concept Einstein's leads 5-D space-time-temperature. Thermal when generalized for partially thermalized systems, results many gravity. bullet cluster supposed be smoking gun...
We have studied three most recent precursor flares in the light curve of blazar OJ 287 while invoking presence a precessing binary black hole system to explain nature these flares. Precursor flare timings from historical curves are compared with theoretical predictions our model that incorporate effects an accretion disk and post-Newtonian description for orbit. find coincide secondary descending towards primary observed side, mean z-component approximately z_c = 4000 AU. use this predict...
We present results derived from four stellar occultations by the plutino object (208996) 2003~AZ$_{84}$, detected at January 8, 2011 (single-chord event), February 3, 2012 (multi-chord), December 2, 2013 (single-chord) and November 15, 2014 (multi-chord). Our observations rule out an oblate spheroid solution for 2003~AZ$_{84}$'s shape. Instead, assuming hydrostatic equilibrium, we find that a Jacobi triaxial with semi axes $(470 \pm 20) \times (383 10) (245 8)$~km % axis ratios $b/a= 0.82...
The ISOGAL project is an infrared survey of specific regions sampling the Galactic Plane selected to provide information on structure, stellar populations, mass-loss and recent star formation history inner disk Bulge Galaxy. combines 7 15 μm ISOCAM observations – with a resolution 6″ at worst DENIS IJKs data determine nature sources interstellar extinction. We have observed about 16 square degrees sensitivity approaching 10–20 mJy, detecting ~105 sources, mostly AGB stars, red giants young...
The ISO galactic survey provides images of the inner disk in two broad filters (around 7 and 15 μm) over some square degrees, away from brightest star forming regions. A multiresolution analysis leads to a catalogue infrared dark clouds, most which are condensed cores large molecular several kpc Sun, seen absorption front diffuse emission. longitude distributions background emission clouds correlate with known tracers young population components. We analyse morphology intensity fluctuations...
Context. In about 2000, the south pole of Triton experienced an extreme summer solstice that occurs every ∼650 years, when subsolar latitude reached 50°S. Bracketing this epoch, a few occultations probed atmosphere in 1989, 1995, 1997, 2008, and 2017. A recent ground-based stellar occultation observed on 6 October 2022 provides new measurement atmospheric pressure Triton. This is presented here. Aims. The goal to constrain volatile transport models (VTMs) atmosphere. basically vapor...
By cross-correlating the results of two recent large-scale surveys, general properties a well-defined sample semiregular variable stars have been determined. ISOGAL mid-infrared photometry (7 and 15 μm) MACHO V R light curves are assembled for approximately 300 in Baade's windows low extinction toward Galactic bulge. These mainly giants late M spectral type, evolving along asymptotic giant branch (AGB). They found to possess wide continuous distribution pulsation periods obey an approximate...
We report rapid optical variability for the blazar S5 0716+71 during 2010 March 08-10 & 19-20 in CCD observations made from Mt.Abu Infrared Observatory. The light curves are constructed duration longer than 3-hours each night, with very high temporal resolution(~ 45 seconds R-band). During 08 source smoothly decayed by about 0.15 mag 2.88 hours, apart a fast flicker lasting 30 mins. brightened up 09 and 10 showing activity while it was relatively faint (> 14 R) albeit variable 19-20. 9 10,...
We have carried out optical (R band) intraday variability (IDV) monitoring of a sample 10 bright low energy peaked blazars (LBLs). 40 photometric observations, an average ∼4 h each, were made between 2008 September and 2009 June using two telescopes in India. Measurements with good signal-to-noise ratios typically obtained within 1–3 min, allowing the detection weak, fast variations N-star differential photometry. employed both structure function discrete correlation analysis methods to...
ABSTRACT This paper presents a comprehensive analysis of two pairs binary clusters (NGC 5617 and Trumpler 22) 3293 NGC 3324) located in the fourth quadrant our Galaxy. For this purpose, we use different data taken from VVV survey, WISE, VPHAS, APASS, GLIMPSE along with Gaia EDR3 astrometric data. We identified 584, 429, 692, 273 most probable cluster members membership probability higher than $80 {{\ \rm per\ cent}}$ towards region 5617, 22, 3293, 3324. estimated value...
<i>Aims. <i/>We derive a new map of the interstellar extinction near Galactic Centre (GC), extending to much higher values <i>A<i/><sub><i>V<i/><sub/> than previously available, and use results obtained better characterise long-period variable star population region.<i>Methods. take Spitzer IRAC catalogue GC point sources (Ramírez et al. 2008, ApJS, 175, 147) combine it with isochrones (Marigo A&A, 482, 883) extinctions based on photometry red giants asymptotic giant branch (AGB) stars. We...
Aims: With this paper we want to investigate the highly variable afterglow light curve and environment of gamma-ray burst (GRB) 060526 at $z=3.221$. Methods: We present one largest photometric datasets ever obtained for a GRB afterglow, consisting multi-color data from ultraviolet near infrared. The set contains 412 points in total which add additional literature. Furthermore, low-resolution high signal-to-noise spectra afterglow. is modeled with both an analytical model using broken power...
We present a $UBVI$ photometric study of the open clusters Berkeley 24 (Be 24) and Czernik 27 (Cz 27). The radii are determined as 2\farcm7 2\farcm3 for Be Cz 27, respectively. use Gaia Data Release 2 (GDR2) catalogue to estimate mean proper motions clusters. found motion $0.35\pm0.06$ mas yr$^{-1}$ $1.20\pm0.08$ in right ascension declination $-0.52\pm0.05$ $-1.30\pm0.05$ 27. used probable cluster members selected from data estimation fundamental parameters. infer reddenings $E(B-V)$ =...
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...
The ISOGAL mid-infrared survey of areas close to the Galactic plane aims determine stellar content those areas, and its possible bearing on history Galaxy. NGC 6522 Sgr I Baade's Windows low obscuration towards inner parts bulge represent ideal places in which calibrate understand colour-magnitude diagrams, are more difficult interpret heavily reddened fields. observations were made with ISOCAM instrument ISO satellite. filter bands chosen LW2 (∼7 μm) LW3 (∼15 μm). results presented here...
We present version 1.0 of the ISOGAL–DENIS Point Source Catalogue (PSC), containing more than 100 000 point sources detected at 7 and/or 15 μm in ISOGAL survey inner Galaxy with ISOCAM instrument on board Infrared Space Observatory (ISO). These are cross-identified, wherever possible, near-infrared (0.8–2.2 μm) data from DENIS survey. The overall surface covered by is about 16 square degrees, mostly (95%) distributed near Galactic plane (), where source extraction can become confusion...
We present the results from a multiwavelength study of flaring activity in HBL, 1ES 1959+650, during January 2015-June 2016. The source underwent significant flux enhancements showing two major outbursts (March 2015 and October 2015) optical, UV, X-rays gamma-rays. Normally, HBLs are not very active but 1959+650 has shown exceptional outburst across whole electromagnetic spectrum (EMS). used data Fermi-LAT, Swift-XRT & UVOT optical Mt. Abu InfraRed Observatory (MIRO) along with archival...
We present a study of known OH/IR stars in the inner bulge, observed by ISOGAL survey at m and m. Bolometric corrections luminosities are computed, based on near mid-infrared data. The vast majority sources exhibit mass-loss rates range: up to few times /year. bolometric magnitude distribution peaks . There is no clear evidence that luminosity related expansion velocity envelope for sample bulge ISOGAL. find do not follow period-luminosity (PL) law they systematically less luminous than...
The continuum polarization observations, spread over a period from October 1996 to May 1997, of the coma region comet Hale Bopp are made at various phase angles, varying 17.1 47.4 degrees, using IAU/IHW filter set. linear measured through 3650, 4845 and 6840 Å bands shows stronger wavelength dependence as compared what is seen in Halley similar angles. Comparisons with Comet properties it inferred that has smaller grains than those found for Halley. However, this similarity so far albedo...
Aims.To study the nature of Bulge AGB stars and in particular their circumstellar dust, we have analysed mid-infrared spectra obtained with ISOCAM CVF spectrometer three fields.
Context: L-type ultra-cool dwarfs and brown have cloudy atmospheres that could host weather-like phenomena. The detection of photometric or spectral variability would provide insight into unresolved atmospheric heterogeneities, such as holes in a global cloud deck. Aims: It has been proposed growth heterogeneities the deck may account for L- to T-type transition dwarf photospheres evolve from clear conditions. Such mechanism is compatible with variability. We searched spectra five L6 T6...