The molecular spectrum of sunspots
Sunspot molecular lines and rotational temperatures of MgH, CaH and TiO using model umbral atmospheres and photographic spectrograms
Webber, J. C.↗
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Scanner observations of selected cool stars
Photoelectric spectral scans at 30-A resolution of 9 dwarfs, 10 giants and 6 supergiants with spectral types GO to M5 were presented. All stars were observed every 4 A from wavelength 3300 to wavelength 7000. Absorption features at this resolution coincide with: strong atomic lines of Fe 1,11, Ca 1,11, Mg 1, and Na 1; vibrational bands of the electronic transitions of TiO, MgH, CaH, SiH, AlH, Cn, Ch, C2, OH, and NH. The dependence of the wavelength 3740 Fe 1 blend and the wavelength 3440 depression on temperature is discussed.
Fay, T. D., Jr.↗
Scanner observations of selected cool stars
Photoelectric spectral scans at 30 A resolution of nine dwarfs, ten giants, and six supergiants with spectral types G0 to M5 are presented. (All stars were observed every 4 A from 3300 to 7000 A.) Absorption features observed at this resolution coincide with: strong atomic lines of Fe I, Fe II, Ca I, Ca II, Mg I, and Na I; vibrational bands of the electronic transitions of TiO, MgH, CaH, SiH, AlH, CN, CH, C2, OH, and NH. The dependences of the 3740-A Fe I blend and the 3440-A depression on temperature are discussed.
Fay, T. D., Jr.↗
Further observations of BL Lacertae
Spectrophotometric observations of BL Lac have been obtained under conditions of fair to excellent seeing with BL Lac near the zenith. The nucleus was faint for all observations. Four absorption features identified as the Mg I and MgH band, the 4410-A band, the G-band, and H and K of Ca II, are observed. The redshift is approximately 0.070, in agreement with results in a previous paper. When the effects of the radiation from the central bright source are removed as well as possible, the residual spectral energy distribution is found to be very similar to that of a standard giant elliptical galaxy redshifted by 0.070 and reddened by a factor corresponding to a color excess of 0.28 to 0.40. The absolute visual magnitude of the underlying galaxy is -22.6 if the Hubble constant is 60 km/s per Mpc and the color excess is 0.28.
Thuan, T. X.↗
Model atmospheres for M (sub)dwarf stars. 1: The base model grid
We have calculated a grid of more than 700 model atmospheres valid for a wide range of parameters encompassing the coolest known M dwarfs, M subdwarfs, and brown dwarf candidates: 1500 less than or equal to T(sub eff) less than or equal to 4000 K, 3.5 less than or equal to log g less than or equal to 5.5, and -4.0 less than or equal to (M/H) less than or equal to +0.5. Our equation of state includes 105 molecules and up to 27 ionization stages of 39 elements. In the calculations of the base grid of model atmospheres presented here, we include over 300 molecular bands of four molecules (TiO, VO, CaH, FeH) in the JOLA approximation, the water opacity of Ludwig (1971), collision-induced opacities, b-f and f-f atomic processes, as well as about 2 million spectral lines selected from a list with more than 42 million atomic and 24 million molecular (H2, CH, NH, OH, MgH, SiH, C2, CN, CO, SiO) lines. High-resolution synthetic spectra are obtained using an opacity sampling method. The model atmospheres and spectra are calculated with the generalized stellar atmosphere code PHOENIX, assuming LTE, plane-parallel geometry, energy (radiative plus convective) conservation, and hydrostatic equilibrium. The model spectra give close agreement with observations of M dwarfs across a wide spectral range from the blue to the near-IR, with one notable exception: the fit to the water bands. We discuss several practical applications of our model grid, e.g., broadband colors derived from the synthetic spectra. In light of current efforts to identify genuine brown dwarfs, we also show how low-resolution spectra of cool dwarfs vary with surface gravity, and how the high-regulation line profile of the Li I resonance doublet depends on the Li abundance.
Allard, France↗
Evidence of Circumstellar Matter Surrounding the Hercules X-1 System
We analyze data from two eclipse ingresses of Her X-1 observed with Ginga on 1989 April 30 and May 19. These observations occur, respectively, during the MAIN HIGH and SHORT HIGH states in the 35 day modulation of Her X-1 intensity. We find significant residual X-ray flux during eclipse, with a gradual decrease in flux following the occultation of the neutron star by the atmosphere of HZ Her. During the central part of the eclipse the count rate becomes nearly constant, at 0.5 mcrab in the energy range 1.7-36.8 keV. From a spec- tral analysis of the residual emission during the total eclipse of the central source in the MAIN MGH state, we determine the energy spectral index, alpha = 0.8, similar to that before eclipse. A remarkable feature of the eclipse spectrum is that it does not show a significant iron line feature in contrast to massive wind-fed pulsars, such as Vela X-1 and Cen X-3. From a timing analysis of the same eclipse data, we show that there are no pulses. These results imply that the emission comes from the scattering of continuum X-rays by material in a region considerably larger than the companion star. An extended accretion disk corona may be responsible for this scattering. However, partial eclipse of an extended accretion disk corona is insufficient to account for the count rates in mid-eclipse, when known parameters of the binary system are used. Based on the present results, we suggest that scattering occurs not only in the accretion disk corona but also in the circumstellar matter surrounding the system of Her X-1/HZ Her.
Choi, C. S.↗
Molecular Line and Continuum Opacities for Modeling of Extrasolar Giant Planet and Cool Stellar Atmospheres
The molecular line and continuum opacities are investigated in the atmospheres of cool stars and Extrasolar Giant Planets (EGPs). Using a combination of ab inito and experimentally derived potential curves and dipole transition moments, accurate data have been calculated for rovibrationally-resolved oscillator strengths and photodissociation cross sections in the B' (sup 2)Sigma+ (left arrow) X (sup 2)Sigma+ and A (sup 2)Pi (left arrow) X (sup 2)Sigma+ band systems in MgH. We also report our progress on the study of the electronic structure of LiCl and FeH.
Weck, P. F.↗
Single-Event Effect Testing of the Vishay Si7414DN n-Type TrenchFET(Registered Trademark) Power MOSFET
This study was being undertaken to determine the single event effect susceptibility of the commercial Vishay 60-V TrenchFET power MOSFET. Heavy-ion testing was conducted at the Texas AM University Cyclotron Single Event Effects Test Facility (TAMU) and the Lawrence Berkeley National Laboratory BASE Cyclotron Facility (LBNL). In addition, initial 200-MeV proton testing was conducted at Massachusetts General Hospital (MGH) Francis H. Burr Proton Beam Therapy Center. Testing was performed to evaluate this device for single-event effects from lower-LET, lighter ions relevant to higher risk tolerant space missions.
proton testing↗
Proton Testing of nVidia Jetson TX1
Single-Event Effects (SEE) testing was conducted on the nVidia Jetson TX1 System on Chip (SOC); herein referred to as device under test (DUT). Testing was conducted at Massachusetts General Hospitals (MGH) Francis H. Burr Proton Therapy Center on October 16th, 2016 using 200MeV protons. This testing trip was purposed to provide a baseline assessment of the radiation susceptibility of the DUT as no previous testing had been conducted on this component.
Proton testing↗
Proton Testing of nVidia GTX 1050 GPU
Single-Event Effects (SEE) testing was conducted on the nVidia GTX 1050 Graphics Processor Unit (GPU); herein referred to as device under test (DUT). Testing was conducted at Massachusetts General Hospitals (MGH) Francis H. Burr Proton Therapy Center on April 9th, 2017 using 200-MeV protons. This testing trip was purposed to provide a baseline assessment of the radiation susceptibility of the DUT as no previous testing had been conducted on this component.
Proton testing↗
Proton Testing of nVidia GTX 1050 GPU, Part 2
Single-Event Effects (SEE) testing was conducted on the nVidia GTX 1050 Graphics Processor Unit (GPU); herein referred to as device under test (DUT). Testing was conducted at Massachusetts General Hospital's (MGH) Francis H. Burr Proton Therapy Center on April 28th, 2018 using 200-MeV protons. This testing trip was purposed to provide additional radiation susceptibility data from payloads compiled in Q3FY18. While not all radiation-induced errors are critical, the effects on the application need to be considered. More so, failure of the device and an inability to reset itself should be considered detrimental to the application. Radiation effects on electronic components are a significant reliability issue for systems intended for space.
Single-Event Effects (SEE)↗
Proton Testing of AMD Ryzen 3 1200 Microprocessors
Single-Event Effects (SEE) testing was conducted on the AMD Ryzen 3 1200 microprocessor. Testing was conducted at Massachusetts General Hospital's (MGH) Francis H. Burr Proton Therapy Center on June 2nd, 2019.
single event functional interrupt (SEFI)↗
Proton Testing of AMD Ryzen 3 2200G Microprocessors
Single-Event Effects (SEE) testing was conducted on the AMD Ryzen 3 2200G microprocessor with integrated graphics. Testing was conducted at Massachusetts General Hospital's (MGH) Francis H. Burr Proton Therapy Center on June 2nd, 2019.
radiation tesing↗
Proton Testing of AMD e9173 GPU
Single-Event Effects (SEE) testing was conducted on the AMD e9173 Graphics Processor Unit (GPU). Testing was conducted at Massachusetts General Hospital's (MGH) Francis H. Burr Proton Therapy Center.
Single-Event Effects (SEE)↗
Proton Testing of nVidia Jetson TX2
Single-Event Effects (SEE) testing was conducted on the nVidia Jetson TX2 System on Chip (SOC). Testing was conducted at Massachusetts General Hospital's (MGH) Francis H. Burr Proton Therapy Center on June 2nd, 2019.
System on Chip (SOC)↗
Proton Testing of AMD v1202b System on Chip
Single-Event Effects (SEE) testing was previously conducted on the AMD v1200 System on Chip (SoC) at Massachusetts General Hospital’s (MGH) Francis H. Burr Proton Therapy Center on May 28, 2022, using 200-MeV protons.
Edward J Wyrwas↗
Modeling suggests SARS-CoV-2 rebound after nirmatrelvir-ritonavir treatment is driven by target cell preservation coupled with incomplete viral clearance
In a subset of SARS-CoV-2-infected individuals treated with the antiviral nirmatrelvir-ritonavir, the virus rebounds following treatment. The mechanisms driving this rebound are not well understood. We used a mathematical model to describe the longitudinal viral load dynamics of 51 individuals treated with nirmatrelvir-ritonavir, 20 of whom rebounded. Target cell preservation, either by a robust innate immune response or initiation of N-R near the time of symptom onset, coupled with incomplete viral clearance, appears to be the main factor leading to viral rebound. Moreover, the occurrence of viral rebound is likely influenced by the time of treatment initiation relative to the progression of the infection, with earlier treatments leading to a higher chance of rebound. A comparison with an untreated cohort suggests that early treatments with nirmatrelvir-ritonavir may be associated with a delay in the onset of an adaptive immune response. Nevertheless, our model demonstrates that extending the course of nirmatrelvir-ritonavir treatment to a 10-day regimen may greatly diminish the chance of rebound in people with mild-to-moderate COVID-19 and who are at high risk of progression to severe disease. Altogether, our results suggest that in some individuals, a standard 5-day course of nirmatrelvir-ritonavir starting around the time of symptom onset may not completely eliminate the virus. Thus, after treatment ends, the virus can rebound if an effective adaptive immune response has not fully developed. These findings on the role of target cell preservation and incomplete viral clearance also offer a possible explanation for viral rebounds following other antiviral treatments for SARS-CoV-2.
60 APPLIED LIFE SCIENCES↗