A5089519043- Stellar, planetary, and galactic studies
- Astrophysical Phenomena and Observations
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Solar and Space Plasma Dynamics
- Gamma-ray bursts and supernovae
- Adaptive optics and wavefront sensing
- Advanced X-ray Imaging Techniques
- X-ray Spectroscopy and Fluorescence Analysis
- High-pressure geophysics and materials
- Calibration and Measurement Techniques
- History and Developments in Astronomy
- Optical Systems and Laser Technology
- Astrophysics and Cosmic Phenomena
- Geophysics and Gravity Measurements
- Galaxies: Formation, Evolution, Phenomena
- Atomic and Molecular Physics
- Pulsars and Gravitational Waves Research
- Optical Coatings and Gratings
- Magnetic confinement fusion research
- Nuclear Physics and Applications
- Medical Imaging Techniques and Applications
- Advanced Measurement and Metrology Techniques
Massachusetts Institute of Technology
2015-2024
Kavli Institute for Particle Astrophysics and Cosmology
2006-2024
Vassar College
2008-2023
IIT@MIT
2020
Trinity House
2013
Pennsylvania State University
1984-2010
Observatoire astronomique de Strasbourg
2010
California Institute of Technology
2010
Osservatorio Astronomico di Palermo
2010
Association for Language Learning
2009
The CIAO (<i>Chandra</i> Interactive Analysis of Observations) software package was first released in 1999 following the launch <i>Chandra</i> X-ray Observatory and is used by astronomers across world to analyze data as well from other telescopes. From earliest design discussions, planned a general-purpose scientific analysis system optimized for astronomy, consists mainly command line tools (allowing easy pipelining scripting) with parameter-based interface layered on flexible manipulation...
Eclipsing systems of massive stars allow one to explore the properties their components in great detail. We perform a multi-wavelength, non-LTE analysis three multiple system $\delta$ Ori A, focusing on fundamental stellar properties, winds, and X-ray characteristics system. The primary's distance-independent parameters turn out be characteristic for its spectral type (O9.5 II), but usage ${\rm \it Hipparcos}$ parallax yields surprisingly low values mass, radius, luminosity. Consistent...
We present high-resolution X-ray spectra of the X-ray-bright classical T Tauri star, TW Hydrae, covering wavelength range 1.5-25 Å. The differential emission measure derived from fluxes temperature-sensitive lines shows a plasma with sharply peaked temperature distribution, peaking at log = 6.5. Abundance anomalies are apparent, iron very deficient relative to oxygen, while neon is enhanced oxygen. Density-sensitive line ratios Ne IX and O VII indicate densities near ne 13. A flare rapid (~1...
Details of the design, fabrication, ground and flight calibration High Energy Transmission Grating, HETG, on Chandra X-ray Observatory are presented after five years experience. Specifics include theory phased transmission gratings as applied to Rowland design spectrometer, details grating fabrication techniques, results testing HETG. For nearly six HETG has operated essentially designed, although it some subtle effects.
MARX is a portable ray-trace program that was originally developed to simulate event data from the trans- mission grating spectrometers on-board Chandra X-ray Observatory (CXO). has since evolved include detailed models of all CXO science instruments and been further modified serve as an simulator for future observatory design concepts. We first review number applications demonstrate roles such could play throughout life mission, including its calibration, production input products...
High-resolution spectra of the active binary Capella (G8 III + G1 III) covering energy range 0.4-8.0 keV (1.5-30 Å) show a large number emission lines, demonstrating performance High-Energy Transmission Grating Spectrometer. A preliminary application plasma diagnostics provides information on coronal temperatures and densities. Lines arising from different elements in ionization states indicate that has with broad temperatures, log T = 6.3 to 7.2, generally consistent recent results...
The Chandra Transmission Grating Data Archive and Catalog (TGCat) provides easy access to analysis-ready products, specifically, high-resolution X-ray count spectra their corresponding calibrations. web interface makes it find observations of a particular object, type or observation; quickly assess the quality potential usefulness from pre-computed summary plots; customize view with an interactive plotter, optionally combining over multiple orders observations. responses can be downloaded as...
We investigate the structure of wind in neutron star X-ray binary system Vela X-1 by analyzing its flaring behavior. shows constant flaring, with some flares reaching fluxes more than 3.0 Crab between 20–60 keV for several 100 s, while average flux is around 250 mCrab. analyzed all archival <i>INTEGRAL<i/> data, calculating brightness distribution band, which, as we show, closely follows a log-normal distribution. Orbital resolved analysis that strongly variable, explainable shocks and...
We report here the first results of a multi-wavelength campaign focusing on magnetospheric accretion processes within close binary system V4046 Sgr, hosting two partly convective classical T Tauri stars masses ≃0.9 M⊙ and age ≃12 Myr. In this paper, we present time-resolved spectropolarimetric observations collected in 2009 September with ESPaDOnS at Canada–France–Hawaii Telescope (CFHT) covering full span 7 d or ≃2.5 orbital/rotational cycles Sgr. Small circularly polarized Zeeman...
Arcus will be proposed to the NASA Explorer program as a free-flying satellite mission that enable high-resolution soft X-ray spectroscopy (8-50) with unprecedented sensitivity – effective areas of >500 sq cm and spectral resolution >2500. The key science goals are (1) determine how baryons cycle in out galaxies by measuring effects structure formation imprinted upon hot gas is predicted lie extended halos around galaxies, groups, clusters, (2) black holes influence their surroundings...
We have obtained high-resolution X-ray spectra of the coronally active binary II Pegasi (HD 224085), covering wavelength range 1.5-25 Å. For first half our 44 ks observation, source was in a quiescent state with constant flux, after which it flared, reaching twice flux 12 ks, then decreased. analyze emission-line spectrum and continuum during flaring states. The differential emission measure derived from lines fluxes shows hot corona continuous distribution temperature. During nonflare...
We have analyzed Chandra High-Energy Transmission Grating spectra of the active RS CVn-type binary V711 Tauri (HR 1099; HD 22468) in order to examine chemical composition its coronae. Observed fluxes and flux upper limits for spectral lines from a range charge states iron, covering species Fe XVI-Fe XXV, been used determine emission measure distribution as function temperature, while observed line-to-continuum ratio has absolute iron abundance, Fe/H. Abundances elements O, Ne, Mg, Si, S, Ar...
\mu\ Columbae is a prototypical weak-wind O-star for which we have obtained high-resolution X-ray spectrum with the Chandra LETG/ACIS-S instrument and low resolution Suzaku. This allows us, first time, to investigate role of X-rays on wind structure in bona fide system determine whether there actually massive, hot wind. The emission measure indicates that outflow an order magnitude greater than derived from UV lines commensurate nominal wind-luminosity relationship O-stars. Therefore,...
We present a first emission-line analysis of high-resolution X-ray spectrum the stellar wind θ1 Ori C obtained with High-Energy Transmission Grating Spectrometer on board Chandra X-Ray Observatory. The spectra are resolved into large number emission lines from H- and He-like O, Ne, Mg, Si, S, Ar, Fe ions. XXV Li-like XXIV appear quite strong, indicating very hot emitting regions. From H/He flux ratios as well He/Li measure ratios, we deduce temperatures ranging 0.5 to 6.1 × 107 K. He...
We observed the coronally active eclipsing binary, AR Lac, with High Energy Transmission Grating on Chandra for a total of 97 ks, spaced over five orbits, at quadratures and conjunctions. Contemporaneous simultaneous EUV spectra photometry were also obtained Extreme Ultraviolet Explorer. Significant variability in both X-ray fluxes observed, dominated by least one flare flare. saw no evidence primary or secondary eclipses. flux modulation was largest high temperature, indicative heating...
High-resolution X-ray spectroscopy with the diffraction gratings of Chandra and XMM-Newton offers new chances to study a large variety stellar coronal phenomena. A popular calibration target is Capella, which has been observed all significant exposure times. We gathered together available data High Energy Transmission Grating Spectrometer (HETGS; 155 ks), Low (LETGS; 219 Reflection (RGS; 53 ks) for comparative analysis, focusing on Ne IX triplet at around 13.5 Å, region that severely blended...
We analyzed high resolution X-ray spectra in the wavelength range of 1.5 -- 25 A three its brightest members obtained with High Energy Transmission Grating Spectrometer (HETGS) on-board Chandra Observatory. The DEM derived from over 80 emission lines spectrum Theta Ori C indicates peaks located at 7.9 MK, and 66 MK. measure varies 15.4 day wind period star. For two phases observed, low temperature remains stable, while shows significant differences. line widths seem to show a similar...
In mid-September of 1999, a multiwavelength campaign was carried out on the coronally active RS Canum Venaticorum binary HR 1099 (K1 IV + G5 V; P = 2.84 days), during commissioning High Energy Transmission Grating Spectrometer (HETGS) Chandra X-ray Observatory (CXO). The coordinated program involved Extreme Ultraviolet Explorer (EUVE), Hubble Space Telescope Imaging Spectrograph (STIS), and Very Large Array (VLA). objective to study system in quiescence, across as much electromagnetic...
We present high-resolution X-ray spectra of the nearby multiple T Tauri star (TTS) system Hen 3-600, obtained with High Energy Transmission Grating Spectrograph (HETGS) aboard Chandra X-Ray Observatory. Both principal binary components 3-600 (A and B, separation 1.4'') were detected in zeroth-order HETGS image. 3-600-A, component a large mid-infrared excess, is factor ~2-3 fainter X-rays than 3-600-B, due to flare at 3-600-B during our observation. The dispersed two primary overlap...
We report initial results from a quasi-simultaneous X-ray/optical observing campaign targeting V4046 Sgr, close, synchronous-rotating classical T Tauri star (CTTS) binary in which both components are actively accreting. Sgr is strong X-ray source, with the X-rays mainly arising high-density (n_e ~ 10^(11-12) cm^(-3)) plasma at temperatures of 3-4 MK. Our multiwavelength aims to simultaneously constrain properties this emitting plasma, large scale magnetic field, and accretion geometry. In...
We present high-resolution X-ray spectra of the multiple (hierarchical quadruple) weak-lined T Tauri star system HD 98800, obtained with High Energy Transmission Grating Spectrograph (HETGS) on board Chandra X-Ray Observatory. In zeroth-order Chandra/HETGS image, both principle binary components 98800 (A and B, separation 08) are detected; component A was observed to flare during observation. The infrared excess (dust disk) component, 98800B, is a factor ~4 fainter in X-rays than apparently...
We observed at very high spectral resolution the prototype Z-source Cyg X-2 twice along its entire X-ray variation pattern. In this preliminary analysis, we find an extended accretion disk corona (ADC) exhibiting Lyα emissions from various H-like ions, as well He-like ions of Fe and Al, Be-like Fe. The brightest lines show a range line broadening: are broad with Doppler velocities between 1100 2700 km s−1, while some others narrower widths few hundred s−1. Line diagnostics allow us for first...
Abstract High-resolution X-ray spectra of π Aqr, a γ Cas-type star, obtained with the Chandra/HETG spectrometer, revealed emission lines H-like ions Mg, Si, S, and Fe; strong, hard continuum; lack He-like ions, indicating presence very hot thermal plasma. The light curve showed significant fluctuations, coherent variability at period about 3400 s in one observation. hardness ratio was relatively constant except for observation which spectrum much harder more absorbed. We interpret as arising...