Jayadev Rajagopal

The near-infrared size-luminosity relations for Herbig Ae/Be disks

We report the results of a sensitive K-band survey of Herbig Ae/Be disk sizes using the 85 m baseline Keck Interferometer. Targets were chosen to span the maximum range of stellar properties to probe the disk size dependenceonluminosityandeffectivetemperature.Formosttargets,themeasurednear-infraredsizes(rangingfrom0.2to 4AU)supportasimple diskmodelpossessingacentralopticallythin(dust-free) cavity,ringedbyhotdustemitting at theexpected sublimation temperatures (Ts � 1000–1500 K).Furthermore, wefindatightcorrelation of disksizewith source luminosity R / L 1 =2 for Ae and late Be systems (valid over more than two decades in luminosity), confirming earlier suggestions based on lower quality data. Interestingly, the inferred dust-free inner cavities of the highest luminosity sources (Herbig B0–B3 stars) are undersized compared to predictions of the ‘‘optically thin cavity’’ model, likely because of optically thick gas within the inner AU. Subject headingg accretion, accretion disks — circumstellar matter — instrumentation: interferometers — radiative transfer — stars: formation — stars: pre–main-sequence

The Asymmetric Dust Environment of IK Tauri

Mid-infrared observations of IK Tau have been made at 11.15 μm with the three-telescope Infrared Spatial Interferometer on Mount Wilson and also using individual segments of the Keck telescope for multiple-aperture interferometry on the Keck telescope at 10.7 μm. Both experiments provided closure phase and show temporal variations and asymmetries in the surrounding dust, with a difference of about 15% in intensity between two sides of the star. Asymmetries have been previously observed in the distribution of SiO masers closely surrounding the star. Comparison with earlier interferometric measurements shows substantial reduction in dust surrounding the star over the last decade. Several asymmetric dust models are investigated and simple images constructed.

Mid-Infrared Interferometry of Dust around Massive Evolved Stars

We report long-baseline interferometric measurements of circumstellar dust around massive evolved stars with the MIDI instrument on the Very Large Telescope Interferometer and provide spectrally dispersed visibilities in the 8-13 mu m wavelength band. We also present diffraction-limited observations at 10.7 mu m on the Keck Telescope with baselines up to 8.7 m, which explore larger scale structure. We have resolved the dust shells around the late-type WC stars WR 106 and WR 95 and the enigmatic NaSt1 ( formerly WR 122), suspected to have recently evolved from a luminous blue variable (LBV) stage. For AG Car, the prototypical LBV in our sample, we marginally resolve structure close to the star, distinct from the well-studied detached nebula. The dust shells around the two WC stars show fairly constant size in the 8-13 mu m MIDI band, with Gaussian half-widths of similar to 25 to 40 mas, and the Keck observations reveal an additional extended structure around WR 106. The visibility profiles for NaSt 1 obtained from two MIDI baselines indicate a compact source embedded in an extended structure. The compact dust we detect around NaSt 1 and AG Car favors recent or ongoing dust formation. Using the measured visibilities, we build spherically symmetric radiative transfer models of the WC dust shells, which enable detailed comparison with existing SED-based models. Our results indicate that the inner radii of the shells are within a few tens of AU from the stars. In addition, our models favor grain size distributions with large (similar to 1 mu m) dust grains. This proximity of the inner dust to the hot central star emphasizes the difficulty faced by current theories in forming dust in the hostile environment around WR stars. Although we detect no direct evidence for binarity for these objects, dust production in a colliding-wind interface in a binary system is a feasible mechanism in WR systems under these conditions.

ODI - Portal, Pipeline, and Archive (ODI-PPA): a web-based astronomical compute archive, visualization, and analysis service

The One Degree Imager-Portal, Pipeline, and Archive (ODI-PPA) is a web science gateway that provides astronomers a modern web interface that acts as a single point of access to their data, and rich computational and visualization capabilities. Its goal is to support scientists in handling complex data sets, and to enhance WIYN Observatorys scientific productivity beyond data acquisition on its 3.5m telescope. ODI-PPA is designed, with periodic user feedback, to be a compute archive that has built-in frameworks including: (1) Collections that allow an astronomer to create logical collations of data products intended for publication, further research, instructional purposes, or to execute data processing tasks (2) Image Explorer and Source Explorer, which together enable real-time interactive visual analysis of massive astronomical data products within an HTML5 capable web browser, and overlaid standard catalog and Source Extractor-generated source markers (3) Workflow framework which enables rapid integration of data processing pipelines on an associated compute cluster and users to request such pipelines to be executed on their data via custom user interfaces. ODI-PPA is made up of several light-weight services connected by a message bus; the web portal built using Twitter/Bootstrap, AngularJS and jQuery JavaScript libraries, and backend services written in PHP (using the Zend framework) and Python; it leverages supercomputing and storage resources at Indiana University. ODI-PPA is designed to be reconfigurable for use in other science domains with large and complex datasets, including an ongoing offshoot project for electron microscopy data.

Scientific rationale for exoplanet characterization from 3-8 microns: the FKSI mission

During the last few years, considerable effort has been directed towards large-scale (>

Cost estimate for the Kilometric Optical Interferometer (KOI)

1 Billion) missions to detect and characterize earth-like planets around nearby stars, such as the Terrestrial Planet Finder Interferometer and Darwin missions. However, technological issues such as formation flying, cryocooling, obtaining sufficient null depth for broadband signals, and control of systematic noise sources will likely prevent these missions from entering Phase A until at least the end of the present decade. Futhermore, a large mission like TPF-I will also need the endorsement of the next Astronomical Decadal Survey to obtain a Phase A start in the next decade. Thus, given the present circumstances, we can expect TPF-I to launch no earlier than about 2020 or even as late as 2025. Presently more than 168 planets have been discovered by precision radial velocity survey techniques, and little is known about the majority of them. A simplified nulling interferometer operating in the near- to mid-infrared (e.g. ~ 3-8 microns), like the Fourier Kelvin Stellar Interferometer (FKSI), can characterize the atmospheres of a large sample of the known planets. Many other scientific problems can be addressed with a system like FKSI, including the imaging of debris disks, active galactic nuclei, and low mass companions around nearby stars. We discuss the rationale, both scientific and technological, for a competed mission in the

LuSci, a lunar scintillometer to study ground layer turbulence

450-600 Million range, of which FKSI is an example. Such a mission is essential to develop our community and keep the larger community, including young scientists, engaged in the long-term effort towards the detection of Earth-like planets.

Adaptive optics and aperture masking: a comparison

We present a parametric cost estimate for the Kilometric Optical Interferometer (KOI) in a classical array configuration: 24 telescopes, 4-meter primary mirror, up to 1 km baseline. The parametric cost estimate is based on available cost information from the Magdalena Ridge Observatory (MRO) Interferometer at New Mexico Tech. A Kilometric Optical Interferometer based on a classical array concept has an estimated construction cost between

The Fourier-Kelvin Stellar Interferometer: a practical interferometer for the detection and characterization of extrasolar giant planets

1B and

The Fourier-Kelvin Stellar Interferometer: a low-complexity low-cost space mission for high-resolution astronomy and direct exoplanet detection

3B if it would be built today (2008 dollars and technology). The implication of the estimated construction cost is that cost reductions are critical in the planning phase to bring the cost within a reasonable envelope. Hence we propose to set a budget ceiling that seems feasible given the support to be expected from the scientific community and funding agencies. Given a budget ceiling, a design-to-cost process should be followed. We propose to set a construction phase budget cap of