Spectral Sciences Incorporated

About: Spectral Sciences Incorporated is a company organization based out in Burlington, Massachusetts, United States. It is known for research contribution in the topics: Hyperspectral imaging & Radiance. The organization has 114 authors who have published 342 publications receiving 10875 citations.

Space telescope and optical reverberation mapping project. II. Swift and HST reverberation mapping of the accretion disk of NGC 5548

Abstract: Recent intensive Swift monitoring of the Seyfert 1 galaxy NGC 5548 yielded 282 usable epochs over 125 days across six UV/optical bands and the X-rays. This is the densest extended active galactic nucleus (AGN) UV/optical continuum sampling ever obtained, with a mean sampling rate <0.5 day. Approximately daily Hubble Space Telescope UV sampling was also obtained. The UV/optical light curves show strong correlations (r max =0.57-0.90) and the clearest measurement to date of interband lags. These lags are well-fit by a τ ∝ λ4/3 wavelength dependence, with a normalization that indicates an unexpectedly large disk radius of ∼0.35 ± 0.05 lt-day at 1367 A, assuming a simple face-on model. The U band shows a marginally larger lag than expected from the fit and surrounding bands, which could be due to Balmer continuum emission from the broad-line region as suggested by Korista and Goad. The UV/X-ray correlation is weaker (rm < 0.45) and less consistent over time. This indicates that while Swift is beginning to measure UV/optical lags in general agreement with accretion disk theory (although the derived size is larger than predicted), the relationship with X-ray variability is less well understood. Combining this accretion disk size estimate with those from quasar microlensing studies suggests that AGN disk sizes scale approximately linearly with central black hole mass over a wide range of masses.

The Changing Face of the Extrasolar Giant Planet HD 209458b

Abstract: High-resolution atmospheric flow simulations of the tidally locked extrasolar giant planet HD 209458b show large-scale spatio-temporal variability. This is in contrast to the simple, permanent day/night (i.e., hot/cold) picture. The planet's global circulation is characterized by a polar vortex in motion around each pole and a banded structure corresponding to approximately three broad zonal (east-west) jets. For very strong jets, the circulation-induced temperature difference between moving hot and cold regions can reach up to ~1000 K, suggesting that atmospheric variability could be observed in the planet's spectral and photometric signatures.

Quick atmospheric correction code: algorithm description and recent upgrades

Abstract: The quick atmospheric correction (QUAC) code performs atmospheric correction on multi- and hyperspectral imagery spanning all or part of the visible and near infrared-short wave infrared spectral range, ∼ 400−2500 nm. It utilizes an in-scene approach, requiring only approximate specification of sensor band locations (i.e., central wavelengths) and their radiometric calibration; no additional metadata is required. Because QUAC does not involve first principles radiative-transfer calculations, it is significantly faster than physics-based methods; however, it is also more approximate. We present a detailed description of the QUAC algorithm, highlighting recent accuracy improvements. Example results for several multi-and hyperspectral data sets are presented, and comparisons are made to more rigorous correction approaches.

Space Telescope and Optical Reverberation Mapping Project. II. Swift and HST Reverberation Mapping of the Accretion Disk of NGC 5548

Abstract: Recent intensive Swift monitoring of the Seyfert 1 galaxy NGC 5548 yielded 282 usable epochs over 125 days across six UV/optical bands and the X-rays. This is the densest extended AGN UV/optical continuum sampling ever obtained, with a mean sampling rate <0.5 day. Approximately daily HST UV sampling was also obtained. The UV/optical light curves show strong correlations (r_max = 0.57 - 0.90) and the clearest measurement to date of interband lags. These lags are well-fit by a \tau propto \lambda^4/3 wavelength dependence, with a normalization that indicates an unexpectedly large disk radius of 0.35 +/- 0.05 lt-day at 1367 A, assuming a simple face-on model. The U-band shows a marginally larger lag than expected from the fit and surrounding bands, which could be due to Balmer continuum emission from the broad-line region as suggested by Korista and Goad. The UV/X-ray correlation is weaker (r_max < 0.45) and less consistent over time. This indicates that while Swift is beginning to measure UV/optical lags in general agreement with accretion disk theory (although the derived size is larger than predicted), the relationship with X-ray variability is less well understood. Combining this accretion disk size estimate with those from quasar microlensing studies suggests that AGN disk sizes scale approximately linearly with central black hole mass over a wide range of masses.