19 research outputs found
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SORCE and TSIS-1 SIM Comparison: Absolute Irradiance Scale Reconciliation
The Solar Radiation and Climate Experiment (SORCE) and Total and Spectral Irradiance Sensor (TSIS-1) conducted an intercomparison for the two Spectral Irradiance Monitors (SIM) spanning 704 days from 23 March 2018 to 25 February 2020 and permitted 554 time-matched pairs of observations. This comparison was conducted during the extremely quiescent Solar Cycle 24 minimum, so all observed differences and drifts between the two sensors are instrumental in nature. The TSIS-1 SIM benefitted from advanced calibration capabilities based on SI standards that were not available during the preflight calibration time period of SORCE. For this reason, a revision of the SORCE SIM absolute scale is appropriate. As expected, wavelength dependent differences in absolute agreement are a function of detector sensitivity and local changes in spectral slope. At the time of the comparison SORCE SIM has been on-orbit for 17 years while TSIS-1 observations commenced immediately after a 100-day outgassing and commissioning period. Peak-to-peak absolute scale differences are about 12% with a mean fractional difference of 0.7% ± 2.9%. The greatest scale differences occur at the change-over between the UV and visible photodiodes in the 310 nm region, and a systematic disagreement is present in the 850–1,600 nm range. A multiplicative scale correction factor has been developed to reconcile the TSIS-1 and SORCE difference with a wavelength dependent error on the mean typically less than 0.01% derived from every matched pair of observations.
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Metal Depletion and Warm H2 in the Brown Dwarf 2M1207 Accretion Disk
We present new far-ultraviolet observations of the young M8 brown dwarf 2MASS
J12073346-3932539, which is surrounded by an accretion disk. The data were
obtained using the Hubble Space Telescope-Cosmic Origins Spectrograph. Moderate
resolution spectra (R~17,000-18,000) obtained in the 1150-1750 A and 2770-2830
A bandpasses reveal H2 emission excited by HI Ly photons, several
ionization states of carbon (CI - CIV), and hot gas emission lines of HeII and
NV (T ~ 10^4-5 K). Emission from some species that would be found in a typical
thermal plasma at this temperature (SiII, SiIII, SiIV, and MgII) are not
detected. The non-detections indicate that these refractory elements are
depleted into grains, and that accretion shocks dominate the production of the
hot gas observed on 2MASS J12073346-3932539. We use the observed CIV luminosity
to constrain the mass accretion rate in this system. We use the kinematically
broadened H2 profile to confirm that the majority of the molecular emission
arises in the disk, measure the radius of the inner hole of the disk
(R_{hole}~3R_{*}), and constrain the physical conditions of the warm molecular
phase of the disk (T(H2)~2500-4000 K). A second, most likely unresolved H2
component is identified. This feature is either near the stellar surface in the
region of the accretion shock or in a molecular outflow, although the
possibility that this Jovian-like emission arises on the day-side disk of a 6
M_{J} companion (2M1207b) cannot be conclusively ruled out. In general, we find
that this young brown dwarf disk system is a low-mass analog to classical T
Tauri stars that are observed to produce H2 emission from a warm layer in their
disks, such as the well studied TW Hya and DF Tau systems.Comment: ApJ, accepted. 12 pages, 10 figures. 3 tables
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Algorithm Theoretical Basis Document - Post Launch update : Spectral Irradiance Monitor (SIM)
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TSIS-1 SIM V08 Solar Spectral Irradiance
NASA’s Total and Spectral Solar Irradiance Sensor -1 (TSIS-1) operates on the International Space Station. TSIS-1 provides absolute measurements of the total solar irradiance (TSI) and spectral solar irradiance (SSI), important for accurate scientific models of climate change and solar variability. TSIS-1 is comprised of two instruments, the Total Irradiance Monitor (TIM), and the Spectral Irradiance Monitor (SIM).
This repository archives Version 8 (V08) of the TSIS-1 SIM Level 3 (L3) data release, and contains SSI in two cadences, 12-hour and 24-hour. The TSIS-1 SIM L3 V08 data release contains data from 14 March 2018 to 11 November 2022. TSIS-1 SIM data obtained between 19 March 2022 and 19 May 2022 were affected by an anomaly of the sun-pointing sensor (HFSS-B), which offset pointing by ~1 arcminute.The TSIS-1 SIM V08 L3 data release, and later releases, includes a wavelength-dependent correction for this period. See the V08 release notes at https://lasp.colorado.edu/home/tsis/data/ssi-data/sim-ssi-release-notes/ for further details.
Data is archived in ASCII, netCDF, and IDL SAVfile format. See the attached V08 L3 data release notes for further details.
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Multiwavelength Observations of A0620-00 in Quiescence
[Abridged.] We present multiwavelength observations of the black hole binary
system, A0620-00. Using the Cosmic Origins Spectrograph on the Hubble Space
Telescope, we have obtained the first FUV spectrum of A0620-00. The observed
spectrum is flat in the FUV and very faint (with continuum fluxes \simeq 1e -
17 ergs/cm^2/s/A). We compiled the dereddened, broadband spectral energy
distribution of A0620-00 and compared it to previous SEDs as well as
theoretical models. The SEDs show that the source varies at all wavelengths for
which we have multiple samples. Contrary to previous observations, the
optical-UV spectrum does not continue to drop to shorter wavelengths, but
instead shows a recovery and an increasingly blue spectrum in the FUV. We
created an optical-UV spectrum of A0620-00 with the donor star contribution
removed. The non-stellar spectrum peaks at \simeq3000 {\deg}A. The peak can be
fit with a T=10,000 K blackbody with a small emitting area, probably
originating in the hot spot where the accretion stream impacts the outer disk.
However, one or more components in addition to the blackbody are needed to fit
the FUV upturn and the red optical fluxes in the optical-UV spectrum. By
comparing the mass accretion rate determined from the hot spot luminosity to
the mean accretion rate inferred from the outburst history, we find that the
latter is an order of magnitude smaller than the former, indicating that
\sim90% of the accreted mass must be lost from the system if the predictions of
the disk instability model and the estimated interoutburst interval are
correct. The mass accretion rate at the hot spot is 10^5 the accretion rate at
the black hole inferred from the X-ray luminosity. To reconcile these requires
that outflows carry away virtually all of the accreted mass, a very low rate of
mass transfer from the outer cold disk into the inner hot region, and/or
radiatively inefficient accretion.Comment: ApJ, accepte
The Cosmic Origins Spectrograph
The Cosmic Origins Spectrograph (COS) is a moderate-resolution spectrograph
with unprecedented sensitivity that was installed into the Hubble Space
Telescope (HST) in May 2009, during HST Servicing Mission 4 (STS-125). We
present the design philosophy and summarize the key characteristics of the
instrument that will be of interest to potential observers. For faint targets,
with flux F_lambda ~ 1.0E10-14 ergs/s/cm2/Angstrom, COS can achieve comparable
signal to noise (when compared to STIS echelle modes) in 1-2% of the observing
time. This has led to a significant increase in the total data volume and data
quality available to the community. For example, in the first 20 months of
science operation (September 2009 - June 2011) the cumulative redshift
pathlength of extragalactic sight lines sampled by COS is 9 times that sampled
at moderate resolution in 19 previous years of Hubble observations. COS
programs have observed 214 distinct lines of sight suitable for study of the
intergalactic medium as of June 2011. COS has measured, for the first time with
high reliability, broad Lya absorbers and Ne VIII in the intergalactic medium,
and observed the HeII reionization epoch along multiple sightlines. COS has
detected the first CO emission and absorption in the UV spectra of low-mass
circumstellar disks at the epoch of giant planet formation, and detected
multiple ionization states of metals in extra-solar planetary atmospheres. In
the coming years, COS will continue its census of intergalactic gas, probe
galactic and cosmic structure, and explore physics in our solar system and
Galaxy.Comment: 17 pages, 15 figure
Diet of St. Lawrence Estuary Beluga (Delphinapterus leucas) in a changing ecosystem
Ecosystems and community structure fluctuate over time as a result of natural and anthropogenic factors that may affect prey availability and population dynamics. Most of what we know about St. Lawrence Estuary (SLE) Beluga (Delphinapterus leucas) diet comes from stomach contents collected 80 years ago mainly from a hunting site that Beluga no longer use. How reflective these data are of Beluga diet at other sites and at the current time is unknown. In the context of the recent population decline, general information of prey species alone may help identify useful conservation actions for potentially important prey or habitats. Here, we examined the diet of SLE Beluga using digestive tracts collected from carcasses recovered over the past 30 years, in the context of historical diet data and recent changes in the St. Lawrence ecosystem. We showed they have a varied diet composed of fish and invertebrates generally <30 cm in length, and that adult males and females differ in their summer diet in a way that is consistent with the sex segregation observed in this population. Our results also indicate that polychaete worms, squid, and cod are still among the most prevalent prey, and that species such as redfish (Sebastes spp.) might be important prey items. This study shows that Beluga diet has changed since the 1930s, and that prey from digestive tracts identified to species are valuable for making comparisons to the past, and for improving applications of molecular analyses, such as stable isotopes and fatty acids
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TSIS-1 SIM V06 Solar Spectral Irradiance
NASA's Total and Spectral Solar Irradiance Sensor -1 (TSIS-1) operates on the International Space Station. TSIS-1 provides absolute measurements of the total solar irradiance (TSI) and spectral solar irradiance (SSI), important for accurate scientific models of climate change and solar variability. TSIS-1 is comprised of two instruments, the Total Irradiance Monitor (TIM), and the Spectral Irradiance Monitor (SIM).
This repository archives Version 6 (V06) of the TSIS-1 SIM Level 3 (L3) data release, and contains SSI in two cadences, 12-hour and 24-hour.
Data is archived in ASCII, and IDL SAVfile format.
See the attached release notes for further details.
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Multispecies mass mortality of marine fauna linked to a toxic dinoflagellate bloom
<div><p>Following heavy precipitation, we observed an intense algal bloom in the St. Lawrence Estuary (SLE) that coincided with an unusually high mortality of several species of marine fish, birds and mammals, including species designated at risk. The algal species was identified as <i>Alexandrium tamarense</i> and was determined to contain a potent mixture of paralytic shellfish toxins (PST). Significant levels of PST were found in the liver and/or gastrointestinal contents of several carcasses tested as well as in live planktivorous fish, molluscs and plankton samples collected during the bloom. This provided strong evidence for the trophic transfer of PST resulting in mortalities of multiple wildlife species. This conclusion was strengthened by the sequence of mortalities, which followed the drift of the bloom along the coast of the St. Lawrence Estuary. No other cause of mortality was identified in the majority of animals examined at necropsy. Reports of marine fauna presenting signs of neurological dysfunction were also supportive of exposure to these neurotoxins. The event reported here represents the first well-documented case of multispecies mass mortality of marine fish, birds and mammals linked to a PST-producing algal bloom.</p></div