Vikram Rana
A5087351960- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- High-pressure geophysics and materials
- Particle Detector Development and Performance
- Astronomical Observations and Instrumentation
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Mechanics and Biomechanics Studies
- Galaxies: Formation, Evolution, Phenomena
- Particle Accelerators and Free-Electron Lasers
- Nuclear Physics and Applications
- Advanced Semiconductor Detectors and Materials
- Advanced X-ray Imaging Techniques
- Solar and Space Plasma Dynamics
- Scientific Measurement and Uncertainty Evaluation
- Laser-Plasma Interactions and Diagnostics
- Astrophysics and Star Formation Studies
- Calibration and Measurement Techniques
- Neutrino Physics Research
- Geophysics and Gravity Measurements
- Astro and Planetary Science
- Geotechnical and Geomechanical Engineering
- SAS software applications and methods
Raman Research Institute
2018-2024
California Institute of Technology
2009-2017
Schlumberger (British Virgin Islands)
2016
Space Micro (United States)
2014
Tata Institute of Fundamental Research
2003-2007
Indian Institute of Science Bangalore
2003-2006
The Nuclear Spectroscopic Telescope Array (NuSTAR) mission, launched on 2012 June 13, is the first focusing high-energy X-ray telescope in orbit. NuSTAR operates band from 3 to 79 keV, extending sensitivity of far beyond ∼10 keV cutoff achieved by all previous satellites. inherently low background associated with concentrating light enables probe hard sky a more than 100-fold improvement over collimated or coded mask instruments that have operated this bandpass. Using its unprecedented...
ABSTRACT We report the detection of coherent pulsations from ultraluminous X-ray source (ULX) NGC 7793 P13. The ≈0.42 s nearly sinusoidal were initially discovered in broadband observations using XMM-Newton and NuSTAR taken 2016. subsequently also found archival data 2013 2014. significant (≫5 σ ) demonstrates that compact object P13 is a neutron star, given observed peak luminosity ≈10 40 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>erg</mml:mi>...
We present the calibration of Nuclear Spectroscopic Telescope Array (NuSTAR) X-ray satellite. used Crab as primary effective area calibrator and constructed a piece-wise linear spline function to modify vignetting response. The achieved residuals for all off-axis angles energies, compared assumed spectrum, are typically better than ±2% up 40 keV 5%–10% above due limited counting statistics. An empirical adjustment theoretical two-dimensional point-spread (PSF) was found using several strong...
We report the results of a multi-band observing campaign on famous blazar 3C 279 conducted during phase increased activity from 2013 December to 2014 April, including first observations it with NuSTAR. The $\gamma$-ray emission source measured by Fermi-LAT showed multiple distinct flares reaching highest flux level in this object since beginning Fermi mission, $F(E > 100\,{\rm MeV})$ $10^{-5}$ photons cm$^{-2}$ s$^{-1}$, and doubling time scale as short 2 hours. spectrum one was very hard,...
We present broadband (radio, optical, and X-ray) light curves spectra of the afterglows four long-duration gamma-ray bursts (GRBs; GRBs 090323, 090328, 090902B, 090926A) detected by Gamma-Ray Burst Monitor Large Area Telescope (LAT) instruments on Fermi satellite. With its wide spectral bandpass, extending to GeV energies, is sensitive with very large isotropic energy releases (1054 erg). Although rare, these events are particularly important for testing GRB central-engine models. When...
Stellar metals shine toward our eyes only Taking a different look at familiar star may still yield surprises. Boggs et al. trained the x-ray vision of NuSTAR observatory on well-studied supernova 1987A. Core-collapse explosions such as SN 1987A produce titanium isotope, 44 Ti, whose radioactive decay yields hard emission lines. All associated with 44Ti appears to be from material moving us, none away. This implies that explosion was not symmetric. These findings help explain mechanics and...
We present the results of NuSTAR and XMM-Newton observations two ultraluminous X-ray sources (ULX) NGC 1313 X-1 X-2. The combined spectral bandpass satellites enables us to produce first spectrum between 0.3 30 keV, while X-2 is not significantly detected by above 10 keV. data demonstrate that has a clear cutoff whose presence was only marginally detectable with previous observations. This rules out interpretation as black hole in standard low/hard state, it deeper than predicted for...
We present coordinated multiwavelength observations of the bright, nearby BL Lac object Mrk 421 taken in 2013 January-March, involving GASP-WEBT, Swift, NuSTAR, Fermi-LAT, MAGIC, VERITAS, and other collaborations instruments, providing data from radio to very-high-energy (VHE) gamma-ray bands. NuSTAR yielded previously unattainable sensitivity 3-79 keV range, revealing that spectrum softens when source is dimmer until X-ray spectral shape saturates into a steep power law with photon index...
The distribution of elements produced in the inner-most layers a supernova explosion is key diagnostic for studying collapse massive stars. Here we present results 2.4 Ms \textit{NuSTAR} observing campaign aimed at remnant Cassiopeia A (Cas A). We perform spatially-resolved spectroscopic analyses $^{44}$Ti ejecta which use to determine Doppler shift and thus three-dimensional (3D) velocities ejecta. find an initial mass 1.54 $\pm$ 0.21 $\times 10^{-4}$ M$_{\odot}$ has day average momentum...
We present results from the coordinated broadband X-ray observations of extreme ultraluminous source Holmberg IX X-1 performed by NuSTAR, XMM-Newton and Suzaku in late 2012. These provide first high-quality spectra above 10 keV to date, extending coverage this remarkable up ~30 keV. Broadband were undertaken at two epochs, between which exhibited both flux strong spectral variability, increasing luminosity Lx = (1.90+/-0.03)e40 erg/s (3.35+/-0.03)e40 erg/s. Neither epoch exhibits a spectrum...
The <i>Nuclear Spectroscopic Telescope Array (NuSTAR)</i> is a NASA Small Explorer mission that will carry the first focusing hard X-ray (6 - 80 keV) telescope to orbit. <i>NuSTAR</i> offer factor 50 100 sensitivity improvement compared previous collimated or coded mask imagers have operated in this energy band. In addition, provides sub-arcminute imaging with good spectral resolution over 12-arcminute eld of view. After launch, out two-year primary science focuses on four key programs:...
ABSTRACT We present broadband, multi-epoch X-ray spectroscopy of the pulsating ultra-luminous source (ULX) in NGC 5907. Simultaneous XMM-Newton and NuSTAR data from 2014 are best described by a multicolor blackbody model with temperature gradient as function accretion disk radius significantly flatter than expected for standard thin ( <?CDATA $T(r)\propto {r}^{-p}$?> , $p={0.608}_{-0.012}^{+0.014}$?> ). Additionally, we detect hard power-law tail at energies above 10 keV, which interpret...
ABSTRACT We report the detection of a 78.1 ± 0.5 day period in X-ray light curve extreme ultraluminous source NGC 5907 ULX1 ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mi mathvariant="normal">X,peak</mml:mi> </mml:msub> <mml:mo>∼</mml:mo> <mml:mn>5</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mn>40</mml:mn> </mml:msup> </mml:math> erg s −1 ), discovered during an extensive...
We present results for two Ultraluminous X-ray Sources (ULXs), IC 342 X-1 and X-2, using epochs of XMM-Newton NuSTAR observations separated by $\sim$7 days. observe little spectral or flux variability above 1 keV between epochs, with unabsorbed 0.3--30 luminosities being $1.04^{+0.08}_{-0.06} \times 10^{40}$ erg s$^{-1}$ $7.40\pm0.20 10^{39}$ so that both were observed in a similar, luminous state. Both sources have high absorbing column excess the Galactic value. Neither source has spectrum...
Following a serendipitous detection with the NuSTAR observatory, we present multi-epoch spectral and temporal analysis of an extreme ultraluminous X-ray source (ULX) located in outskirts Circinus galaxy, hereafter ULX5, including coordinated follow-up observations XMM-Newton NuSTAR. The data presented here represent one first instances ULX reliably detected at hard (E>10 keV) X-rays. ULX5 is variable on long timescales by least factor ~5 flux, was caught historically bright state during our...
We report on an observation of the neutron star low-mass X-ray binary Serpens X-1, made with NuSTAR. The extraordinary sensitivity afforded by NuSTAR facilitated detection a clear, robust, relativistic Fe K emission line from inner disk. A profile is required over single Gaussian any charge state at 5-sigma level confidence, and two Gaussians equal width same confidence. Compton back-scattering "hump" peaking in 10-20 keV band detected for first time binary. Fits relativistically-blurred...
We present the first broadband 0.3-25.0 kev X-ray observations of bright ultraluminous source (ULX) Holmberg II X-1, performed by NuSTAR, XMM-Newton and Suzaku in September 2013. The NuSTAR data provide X-1 above 10 keV, reveal a very steep high-energy spectrum, similar to other ULXs observed date. These further demonstrate that exhibit spectral states are not typically seen Galactic black hole binaries. Comparison with sources implies accretes at high fraction its Eddington accretion rate,...
We present results obtained from two broadband X-ray observations of the extreme ultraluminous source (ULX) NGC 5907 ULX1, known to have a peak luminosity ∼5 × 1040 erg s−1. These XMM-Newton and NuSTAR observations, separated by only ∼4 days, revealed an level short-term flux variability. In first epoch, ULX1 was undetected NuSTAR, weakly detected (if at all) with XMM-Newton, while in second clearly high both missions. This implies increase ∼2 orders magnitude or more during this day window....
We present first results from a series of $NuSTAR$ observations the black hole X-ray binary V404 Cyg obtained during its summer 2015 outburst, primarily focusing on height this outburst activity. The data show extreme variability in both flux and spectral properties source. This is partly driven by strong variable line-of-sight absorption, similar to previous outbursts. latter stages observation are dominated flares, reaching luminosities close Eddington. During these central source appears...
We present a timing analysis of multiple XMM-Newton and NuSTAR observations the ultra-luminous pulsar NGC 7793 P13 spread over its 65 d variability period. use measured pulse periods to determine orbital ephemeris, confirm long period with P orb = 63.9 +0.5 −0.6 d, find an eccentricity e ≤ 0.15. The signature is imprinted on top secular spin-up, which seems get faster as source becomes brighter. also analyze data from dense monitoring Swift optical photometric ± 0.5 X-ray flux 66.8 0.4 d....
ABSTRACT We present the 3–8 keV and 8–24 number counts of active galactic nuclei (AGNs) identified in Nuclear Spectroscopic Telescope Array ( NuSTAR ) extragalactic surveys. has now resolved 33%–39% X-ray background band, directly identifying AGNs with obscuring columns up to <?CDATA $\sim {10}^{25}\,{\mathrm{cm}}^{-2}$?> . In softer band are general agreement those measured by XMM-Newton Chandra over flux range $5\times {10}^{-15}\,\lesssim $?> S (3–8 keV)/...