A5054909336- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Adaptive optics and wavefront sensing
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Photonic and Optical Devices
- Astrophysics and Star Formation Studies
- Optical Coatings and Gratings
- Gamma-ray bursts and supernovae
- Optical Systems and Laser Technology
- Solar and Space Plasma Dynamics
- Photonic Crystals and Applications
- Photorefractive and Nonlinear Optics
- Advanced Fiber Laser Technologies
- Advanced Measurement and Metrology Techniques
- Calibration and Measurement Techniques
- Optical Polarization and Ellipsometry
- Spectroscopy and Laser Applications
- Advanced optical system design
- Advanced Optical Imaging Technologies
- Metamaterials and Metasurfaces Applications
- Advanced Fluorescence Microscopy Techniques
- Photoreceptor and optogenetics research
- Satellite Image Processing and Photogrammetry
- Advanced Frequency and Time Standards
Indian Institute of Astrophysics
2014-2024
University of Göttingen
2013
Northeastern University
2007-2010
Correlations between the occurrence rate of exoplanets and their host star properties provide important clues about planet formation processes. We studied dependence observed (radius, mass, orbital period) as a function metallicity. analyzed planetary radii periods over 2800 $Kepler$ candidates from latest data release DR25 (Q1-Q17) with revised based on $Gaia$~DR2 metallicity (from Q1-Q17 (DR25) stellar catalog). With much larger sample improved radius measurements, we are able to reconfirm...
Nanoporous oxide coatings, such as anodic aluminum (AAO), are utilized drug-release platforms for up to weeks of delivery (see picture doxorubicin, Dox). A burst-release phase is followed by sustained release, the kinetics which described an activated surface-density-dependent desorption model. Detailed facts importance specialist readers published "Supporting Information". Such documents peer-reviewed, but not copy-edited or typeset. They made available submitted authors. Please note: The...
We show that a nonresonant planar waveguide consisting of conventional dielectric cladded with single-negative materials supports degenerate propagating modes for which the group velocity and total energy flow can be zero if media are lossless. Absorptive losses will destroy zero-group condition real frequency/complex wave vector modes. by incorporating gain G into core dielectric, there exists critical value Gc at we recover velocity, so light pulses stopped stored. This structure is...
Directly imaged planets are self-luminous companions of pre-main sequence and young main stars. They reside in wider orbits ($\sim10\mathrm{s}-1000\mathrm{s}$~AU) generally more massive compared to the close-in ($\lesssim 10$~AU) planets. Determining host star properties these outstretched planetary systems is important understand discern various planet formation evolution scenarios. We present stellar parameters metallicity ([Fe/H]) for a subsample 18 stars known discovered by direct...
ABSTRACT Exomoons have so far eluded ongoing searches. Several studies exploited transit and timing variations high-resolution spectroscopy to identify potential exomoon candidates. One method of detecting confirming these exomoons is search for signals planet-moon interactions. In this work, we present the first radio observations candidate system WASP-69b. Based on detection alkali metals in transmission spectra WASP-69b, it was deduced that might be hosting an exomoon. WASP-69b also one...
State-of-the-art Doppler experiments require wavelength calibration with precision at the cm/s level. A low-finesse Fabry-Perot interferometer (FPI) can provide a comb very large bandwidth as required for astronomical experiments, but unavoidable spectral drifts are difficult to control. Instead of actively controlling FPI cavity, we propose passively stabilize and track time-dependent cavity length drift externally. dual-finesse allows tracking during observation. The is monitored in...
Abstract There is growing evidence from stellar kinematics and galactic chemical evolution suggesting that giant planets ( M P ≥ 0.3 J ) are relatively young compared to the most commonly occurring population of small < ). To further test validity these results, we analyzed ages for a large number 2336 exoplanet hosting stars determined using three different but well-established isochrone fitting models, namely, PARSEC, MIST, Yonsei Yale. As input parameters, used Gaia DR3 parallaxes,...
In this paper, an opto-thermal analysis of a moderately heated lightweighted solar telescope mirror is carried out using 3D finite element (FEA). A physically realistic heat transfer model developed to account for the radiative heating and energy exchange with surroundings. The numerical simulations show non-uniform temperature distribution associated thermo-elastic distortions blank clearly mimicking underlying discrete geometry substrate. computed mechanical deformation data analyzed...
We propose a dual cavity Fabry–Perot interferometer as wavelength calibrator and stability tracking device for astronomical spectrograph. The FPI consists of two adjoining cavities engraved on low expansion monoblock spacer. A low-finesse astro-cavity is intended generating uniform grid reference lines to calibrate the spectrograph high-finesse lock-cavity meant using optical frequency standards. differential length changes in due temperature vibration perturbations are quantitatively...
HISPEC (High-resolution Infrared Spectrograph for Exoplanet Characterization) is a proposed diffraction-limited spectrograph the W.M. Keck Observatory, and pathfinder MODHIS facility project (Multi-Object Diffraction-limited High-resolution Spectrograph) on Thirty Meter Telescope. HISPEC/MODHIS builds designs which rely adaptively corrected single-mode fiber feeds. Seeing-limited high-resolution spectrographs, by virtue of conservation beam etendue, grow in volume following D^3 power law (D...
We conducted the first dedicated search for signatures of exoplanet-exomoon interactions using Giant Metrewave Radio Telescope (GMRT) as part radio-loud survey (RLEES). Due to stellar tidal heating, irradiation, and subsequent atmospheric escape, candidate `exo-Io' systems are expected emit up $10^6$ times more plasma flux than Jupiter-Io DC circuit. This can induce detectable radio emission from system. analyze three stars: WASP-49, HAT-P 12, HD 189733. perform 12-hour phase-curve...
We demonstrate experimentally negative refraction by a photonic crystal prism and imaging of point source slab at 1.5 microm wavelength. The structures were nanofabricated in InGaAsP/InP heterostructure platform, optical characterization was performed using near-field scanning microscope. By designing suitable lens surface termination, an image spot size 0.12lambda2 achieved, demonstrating superlens with subwavelength resolution well below Abbe's diffraction limit (0.5lambda2).
Abstract The imprints of stellar nucleosynthesis and chemical evolution the galaxy can be seen in different populations, with older generation stars showing higher α -element abundances later generations becoming enriched iron-peak elements. evolutionary connections characteristics circumstellar disks, stars, their planetary companions inferred by studying interdependence host star properties. Numerous studies past have confirmed that high-mass giant planets are commonly found around...
Abstract The GAIA space mission is impacting astronomy in many significant ways by providing a uniform, homogeneous, and precise data set for over 1 billion stars other celestial objects the Milky Way beyond. Exoplanet science has greatly benefited from unprecedented accuracy of stellar parameters obtained GAIA. In this study, we combine photometric, astrometric, spectroscopic most recent Gaia DR3 to examine kinematic chemical age proxies large sample 2611 exoplanets hosting whose have been...
Refraction at a smooth interface is accompanied by momentum transfer normal to the interface.We show that corrugating an initially smooth, totally reflecting, non-metallic provides kick parallel surface, which can be used refract light negatively or positively.This new mechanism of negative refraction demonstrated visible and microwave experiments on grisms (grating-prisms).Single-beam all-angle-negative-refraction achieved incorporating surface grating flat multilayered material.This create...
We present the design of SCALES (Slicer Combined with Array Lenslets for Exoplanet Spectroscopy) a new 2-5 micron coronagraphic integral field spectrograph under construction Keck Observatory. enables low-resolution (R∼50) spectroscopy, as well medium-resolution (R∼4,000) spectroscopy goal discovering and characterizing cold exoplanets that are brightest in thermal infrared. Additionally, has 12x12" field-of-view imager will be used general adaptive optics science at Keck. SCALES's...
Abstract The correlation between host star iron abundance and the exoplanet occurrence rate is well established arrived at in several studies. Similar correlations may be present for most abundant elements, such as carbon oxygen, which also control dust chemistry of protoplanetary disk. In this paper, using a large number stars Kepler field observed by LAMOST survey, it has been possible to estimate planet with respect abundance. Carbon abundances are derived synthetic spectra fit CH - G...
We report experiments with nonlinear-absorption-based, high-contrast, all-optical switching in photochromic bacteriorhodopsin (BR) films. The action is accomplished by control of the transmission a weak probe beam through BR sample help strong pump illumination at 532 nm wavelength. found that properties films depend on several experimentally controllable parameters such as wavelength, intensity, and excitation rate. A comparative study behavior other practical use was carried out three...