6 research outputs found
Feasibility-study for space-based transit photometry using mid-sized nanosatellites
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 85-88).The photometric precision needed to measure a transit of small planets cannot be achieved by taking observations from the ground, so observations must be made from space. Mid-sized nanosatellites can provide a low-cost option for building an optical system to take these observations. The potential of using nanosatellites of varying sizes to perform transit measurements was evaluated using a theoretical noise budget, simulated exoplanet-transit data, and case studies to determine the expected results of a radial velocity followup mission and transit survey mission. Optical systems on larger mid-sized nanosatellites (such as ESPA satellites) have greater potential than smaller mid-sized nanosatellites (such as CubeSats) to detect smaller planets, detect planets around dimmer stars, and discover more transits in RV followup missions.by Rachel Bowens-Rubin.S.M
Surveying Nearby Brown Dwarfs with HGCA: Direct Imaging Discovery of a Faint, High-Mass Brown Dwarf Orbiting HD 176535 A
Brown dwarfs with well-measured masses, ages and luminosities provide direct
benchmark tests of substellar formation and evolutionary models. We report the
first results from a direct imaging survey aiming to find and characterize
substellar companions to nearby accelerating stars with the assistance of the
Hipparcos-Gaia Catalog of Accelerations (HGCA). In this paper, we present a
joint high-contrast imaging and astrometric discovery of a substellar companion
to HD 176535 A, a K3.5V main-sequence star aged approximately
Gyrs at a distance of pc. In advance of
our high-contrast imaging observations, we combined precision HARPS RVs and
HGCA astrometry to predict the potential companion's location and mass. We
thereafter acquired two nights of KeckAO/NIRC2 direct imaging observations in
the band, which revealed a companion with a contrast of mag at a projected separation of 0.\!\!''35
(13 AU) from the host star. We revise our orbital fit by incorporating
our dual-epoch relative astrometry using the open-source MCMC orbit fitting
code . HD 176535 B is a new benchmark dwarf useful for constraining
the evolutionary and atmospheric models of high-mass brown dwarfs. We found a
luminosity of and a model-dependent
effective temperature of K for HD 176535 B. Our dynamical mass
suggests that some substellar evolutionary models may be underestimating
luminosity for high-mass T dwarfs. Given its angular separation and luminosity,
HD 176535 B would make a promising candidate for Aperture Masking
Interferometry with JWST and GRAVITY/KPIC, and further spectroscopic
characterization with instruments like the CHARIS/SCExAO/Subaru integral field
spectrograph
Paleomagnetism conglomerate test on Archean conglomerate rock from Jack Hills, Australia
Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (pages 59-60).A paleomagnetism study known as a conglomerate test was run on an Archean sandstone conglomerate rock to determine if the sample contained a remnant magnetization from the time of its formation. Twenty-nine clasts from a thin section of the sample were thermally demagnetized up to a temperature of 395°C. The heating revealed two components of magnetization which were unblocked at low and mid temperatures, revealing a magnetic mineralogy of Pyrrhotite.Eight matrix samples were heated to a temperature of 650°C which revealed two components of magnetization at mid and high temperatures, providing evidence for a magnetic mineralogy of Hematite.The direction of measured magnetic moment of the clasts were statistically similar, indicating that the rock failed the conglomerate test and was remagnetized after the rock formed.by Rachel Bowens-Rubin.S.B
Developing adaptive secondary mirror concepts for the APF and W.M. Keck Observatory based on HVR technology
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Improved Constraints on Cosmology and Foregrounds from BICEP2 and Keck Array Cosmic Microwave Background Data with Inclusion of 95Â GHz Band
We present results from an analysis of all data taken by the BICEP2 and Keck Array cosmic microwave background (CMB) polarization experiments up to and including the 2014 observing season. This includes the first Keck Array observations at 95 GHz. The maps reach a depth of 50 nK deg in Stokes Q and U in the 150 GHz band and 127 nK deg in the 95 GHz band. We take auto- and cross-spectra between these maps and publicly available maps from WMAP and Planck at frequencies from 23 to 353 GHz. An excess over lensed ΛCDM is detected at modest significance in the 95 × 150 BB spectrum, and is consistent with the dust contribution expected from our previous work. No significant evidence for synchrotron emission is found in spectra such as 23 × 95, or for correlation between the dust and synchrotron sky patterns in spectra such as 23 × 353. We take the likelihood of all the spectra for a multicomponent model including lensed ΛCDM, dust, synchrotron, and a possible contribution from inflationary gravitational waves (as parametrized by the tensor-to-scalar ratio r) using priors on the frequency spectral behaviors of dust and synchrotron emission from previous analyses of WMAP and Planck data in other regions of the sky. This analysis yields an upper limit r0.05 < 0.09 at 95% confidence, which is robust to variations explored in analysis and priors. Combining these B-mode results with the (more model-dependent) constraints from Planck analysis of CMB temperature plus baryon acoustic oscillations and other data yields a combined limit r0.05 < 0.07 at 95% confidence. These are the strongest constraints to date on inflationary gravitational waves.AstronomyPhysic
Design and performance of wide-band corrugated walls for the BICEP Array detector modules at 30/40 GHz
BICEP Array is a degree-scale Cosmic Microwave Background (CMB) experiment that will search for primordial B-mode polarization while constraining Galactic foregrounds. BICEP Array will be comprised of four receivers to cover a broad frequency range with channels at 30/40, 95, 150 and 220/270 GHz. The first low-frequency receiver will map synchrotron emission at 30 and 40 GHz and will deploy to the South Pole at the end of 2019. In this paper, we give an overview of the BICEP Array science and instrument, with a focus on the detector module. We designed corrugations in the metal frame of the module to suppress unwanted interactions with the antenna-coupled detectors that would otherwise deform the beams of edge pixels. This design reduces the residual beam systematics and temperature-to-polarization leakage due to beam steering and shape mismatch between polarized beam pairs. We report on the simulated performance of single- and wide-band corrugations designed to minimize these effects. Our optimized design alleviates beam differential ellipticity caused by the metal frame to about 7% over 57% bandwidth (25 to 45 GHz), which is close to the level due the bare antenna itself without a metal frame. Initial laboratory measurements are also presented