Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “EXCEPTIONS”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Understanding the Nature of an Unusual Post-starburst Quasar with Exceptionally Strong Ne v Emission

We present a z = 0.94 quasar, SDSS J004846.45-004611.9, discovered in the Sloan Digital Sky Survey III (SDSS-III) BOSS survey. A visual analysis of this spectrum reveals highly broadened and blueshifted narrow emission lines, in particular, [Ne v] λ3426 and [O III ] λ5007, with outflow velocities of 4000 km s -1 , along with unusually large [Ne v] λ3426/[Ne III ] λ3869 ratios. The gas shows higher ionization at higher outflow velocities, indicating a connection between the powerful outflow and the unusual strength of the high ionization lines. The spectral energy distribution and the i – W3 color of the source reveal that it is likely a core extremely red quasar (ERQ); a candidate population of young active galactic nuclei (AGN) that are violently blowing out gas and dust from their centers. The dominance of host galaxy light in its spectrum and its fortuitous position in the SDSS S82 region allows us to measure its star formation history and investigate variability for the first time in an ERQ. Our analysis indicates that SDSS J004846.45-004611.9 underwent a short-lived starburst phase 400 Myr ago and was subsequently quenched, possibly indicating a time lag between star formation quenching and the onset of AGN activity. We also find that the strong extinction can be uniquely attributed to the AGN and does not persist in the host galaxy, contradicting a scenario where the source has recently transitioned from being a dusty submillimeter galaxy. In our relatively shallow photometric data, the source does not appear to be variable at 0.24–2.4 μm in the rest frame, most likely due to the dominant contribution of host galaxy starlight at these wavelengths.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

An Exceptionally Powerful, Radiatively Driven Ultrafast Outflow in the Rapidly Accreting AGN RE J1034+396

We report the analysis of ∼1 Ms of XMM-Newton observations of the rapidly accreting active galactic nucleus RE J1034+396. The 0.3–9 keV EPIC-pn spectra are well described by a model consisting of steep continuum emission from the corona accompanied by relativistically blurred reflection from a highly ionized accretion disk. The source is known to exhibit strong excess soft X-ray emission, which we show is well represented by thermal disk photons Comptonized by a warm plasma spanning the inner accretion flow. Additionally, the EPIC-pn data provide compelling evidence (ΔC ∼ 60 for four additional parameters) for the presence of an ultrafast outflow (UFO) with a line-of-sight velocity v/c = 0.307$^{+0.001}_{-0.005}$, and an emission signature consistent with reflection of the corona from modestly ionized, outflowing gas. The simultaneous 0.5–2.5 keV RGS spectra show clear absorption lines. Modelling of these data confirms the presence of the UFO and constrains its equivalent hydrogen column density, log N H /(atom cm −2 ) = 21.7$^{+0.1}_{-0.2}$. The RGS data also reveal at least two warm absorber components with a modest outflow velocity (1680$^{+40}_{-50}$ km s -1 ). The measured properties and time evolution of the UFO in RE J1034+396 suggest that it is formed from collisionally ionized plasma, launched from the disk surface and accelerated by radiation pressure. The high terminal velocity and substantial absorbing column density imply that the outflow carries sufficient momentum and energy to transform its environment, being capable of driving out essentially all dust and gas it interacts with along the line of sight, even if the AGN were initially surrounded by a Compton-thick absorber.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

GRB 221009A: Discovery of an Exceptionally Rare Nearby and Energetic Gamma-Ray Burst

We report the discovery of the unusually bright long-duration gamma-ray burst (GRB), GRB 221009A, as observed by the Neil Gehrels Swift Observatory (Swift), Monitor of All-sky X-ray Image, and Neutron Star Interior Composition Explorer Mission. This energetic GRB was located relatively nearby (z = 0.151), allowing for sustained observations of the afterglow. The large X-ray luminosity and low Galactic latitude (b = 4$^°_.$3) make GRB 221009A a powerful probe of dust in the Milky Way. Using echo tomography, we map the line-of-sight dust distribution and find evidence for significant column densities at large distances (≳10 kpc). We present analysis of the light curves and spectra at X-ray and UV–optical wavelengths, and find that the X-ray afterglow of GRB 221009A is more than an order of magnitude brighter at T 0 + 4.5 ks than that from any previous GRB observed by Swift. In its rest frame, GRB 221009A is at the high end of the afterglow luminosity distribution, but not uniquely so. In a simulation of randomly generated bursts, only 1 in 10 4 long GRBs were as energetic as GRB 221009A; such a large E γ,iso implies a narrow jet structure, but the afterglow light curve is inconsistent with simple top-hat jet models. Using the sample of Swift GRBs with redshifts, we estimate that GRBs as energetic and nearby as GRB 221009A occur at a rate of ≲1 per 1000 yr—making this a truly remarkable opportunity unlikely to be repeated in our lifetime.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1983

A compact hydrogen maser with exceptional long-term stability

A passive hydrogen maser employing a smaller microwave cavity than previous masers is described. The volume of the entire resonator package, including a conventional source, hexapole state selector, and four magnetic shields, is estimated at 20 liters. The techniques for constructing the ceramic cavity, coating it with FEP, and attaching the endcaps to achieve a stable container (to allow its use as a single vacuum system) are described in detail. Frequency stability measurements were made of four such masers, against an NBS-4 cesium primary standard, against each other, and against eight commercial cesium clocks; frequency stability level is reported as 1.7 x 10 to the -12th tau exp -1/2 from 1 to 100,000 sec, and no drift above 1 x 10 to the -15th/day was found. Pressure and temperature effects on frequency stability were found at the 1 x 10 to the -14th level. Noise behavior beyond 200,000 sec is characterized as random walk. The potential use of a compact stable maser as a clock is suggested.

Howe, D. A.↗
NASA NTRS1987

Forecast of an exceptionally large even-numbered solar cycle

Using the 'dynamo theory' method to predict solar activity, an accurate prediction was made for solar cycle 21 by Schatten et al. (1978). Using the same dynamo technique for solar cycle 22, a value for the smoothed sunspot number of 170 + or - 25 is obtained. This large sunspot number is expected to peak in 1990 + or - 1 year. The F(10.7) radio flux is expected to reach a smoothed value of 210 + or - 25 flux units. Since this value is larger than values obtained with prediction schemes based upon 'statistical' and 'periodicity' methods, it provides a useful test for the current methodology, based upon the strength of the sun's polar field near solar minimum. The predicted degree of solar activity is expected to enhance the density and temperature of the earth's thermosphere to values somewhat larger than those found in solar cycle 21. This will have an impact on the orbital lifetime of low altitude satellites.

Schatten, Kenneth H.↗
NASA NTRS1987

Preliminary experimental results of gas recycling subsystems except carbon dioxide concentration

Oxygen concentration and separation is an essential factor for air recycling in a controlled ecological life support system (CELSS). Furthermore, if the value of the plant assimilatory quotient is not coincident with that of the animal respiratory quotient, the recovery of oxygen from the concentrated CO2 through chemical methods will become necessary to balance the gas contents in a CELSS. Therefore, oxygen concentration and separation equipment using Salcomine and O2 recovery equipment, such as Sabatier and Bosch reactors, were experimentally developed and tested.

Otsuji, K.↗
NASA NTRS1988

An exceptionally bright, compact starburst nucleus

Observations are reported of a remarkably bright (V about 13) starburst nucleus, 0833 + 652, which has been detected at radio, infrared, optical, ultraviolet, and X-ray wavelengths. Despite an observed flux at each of these wavelengths which is comparable to that of NGC 7714, often considered the 'prototypical' example of the starburst phenomenon, 0833 + 652 appears to be a previously uncataloged object. Its ease of detectability throughout the electromagnetic spectrum should make it useful for a variety of problems in the study of compact emission-line galaxies.

Margon, Bruce↗
NASA NTRS1989

Iptycene synthesis: A new method for attaching a 2,3-anthracene moiety to the 9,10-positions of another anthracene moiety - Exceptional conditions for a Lewis acid catalyzed Diels-Alder reaction

An efficient three-step method for appending a 2,3-anthracene moiety to the 9,10-positions of an existing anthracene moiety is described. The first step uses excess 1,4-anthraquinone (3 equiv) and aluminum chloride (6 equiv) to obtain the anthracene-quinone cycloadduct (omission of the AlCl3 resulted in no adduct). The resulting diketone was reduced to the corresponding diol (excess LiAlH4), which was dehydrated to the arene with phosphorus oxychloride and pyridine. Specific examples include the preparation of heptipycene 8 from pentiptycene 6 (66 percent overall yield) and a similar conversion of 8 to the noniptycene 13 (75 percent overall yield). The methodology led to a markedly improved synthesis of tritriptycene 9 and the first synthesis of undecaiptycene 14.

Chen, Yong-Shing↗
NASA NTRS1989

A comparison of two exceptional snowstorms during the early 20th century

Two East-Coast snowstorms of the early twentieth century, which generated massive accumulations over portions of the Atlantic coastal plain, are described. The 'Christmas Storm' of December 25-26, 1909 produced snowfalls of greater than 25 cm over most of the Northeast Corridor from Maryland to southern New England, while the 'Knickerbocker Storm' of January 27-29, 1922 produced a total of 71 cm at Washington, DC. The storms are examined by constructing surface-weather analyses based on original data; surface observations for the continental United States at 0100 and 1300 UTC are obtained from the National Climatic Data Center (NCDC), ship reports from American vessels are taken from the NCDC archives, and the 1300 UTC data is supplemented by Canadian observations and European ship reports. In spite of the vast differences in the evolutions of the storms, it is found that both produced similarly massive snowfalls, therefore, it is concluded that a wide range of synoptic conditions can give rise to major snowstorms along the East Coast.

Weiss, Alan D.↗
NASA NTRS1991

Supernova 1987 A - Prototype of low metallicity type III supernovae or peculiar exception?

New stellar evolution calculations for the SN 1987 A progenitor, including a small but appropriate amount of semiconvection and mixing induced by differential rotation, yield good agreement with many observational constraints, as the HRD position of the progenitor star, a previous red supergiant phase, and CNO surface abundances close to the values obtained with the IUE satellite. The HRD track and surface abundances in different evolutionary stages are found to reflect many general properties of massive stars in the LMC. The results indicate that the SN 1987 A progenitor may have been an average massive star in the LMC, and that blue supergiants may be common SN II progenitors in low metallicity galaxies.

Langer, N.↗
NASA NTRS1993

Two new hot white dwarfs in a region of exceptionally low hi density

We report the discovery of two hot white dwarfs which have the lowest line-of-sight neutral hydrogen column densities yet measured. The stars were found independently by the ROSAT EUV, Montreal-Cambridge-Tololo, and Edinburgh-Cape surveys. Follow-up observations made using the Voyager 2 ultraviolet spectrometer reveal strong continua shortward of the 912A Lyman limit from which we deduce that the neutral hydrogen column densities are 1.3 x 10(exp 17) and 2.0 x 10(exp 17) atoms/sq cm.

Barstow, M. A.↗
NASA NTRS1998

Magnetic Field Configuration of Active Region NOAA 6555 at the Time of a Long Duration Flare on 23 March 1991: An Exception to Standard Flare Reconnection Model

The high-resolution H(sub alpha) images observed during the decay phase of a long duration flare on 23 March 1991 are used to study the three-dimensional magnetic field configuration of the active region NOAA 6555. Whereas, all the large flares in NOAA 6555 occurred at the location of high magnetic shear and flux emergence, this long duration flare was observed in the region of low magnetic shear at the photosphere. The H(sub alpha) loop activity started soon after the maximum phase of the flare. There were few long loop at the initial phase of the activity. Some of these were sheared in the chromosphere at an angle of about 45 deg with the east-west axis. Gradually, increasing number of shorter loops, oriented along the east-west axis, started appearing. The chromospheric Dopplergrams show blue-shifts at the end points of the loops. By using different magnetic field models, we have extrapolated the photospheric magnetograms to the chromospheric heights. The magnetic field lines computed by using the potential field model correspond to most of the observed H(sub alpha) loops. The height of the H(sub alpha) loops were derived by comparing them with the computed field lines. From the temporal evolution of the H(sub alpha) loop activity, we derive the negative rate of appearance of H(sub alpha) features as a function of height. It is found that the field lines oriented along one of the neutral lines was sheared and low lying. The higher field lines were mostly potential. The paper also outlines a possible scenario for describing the post-flare stage of the observed long duration flare.

Choudhary, Debi Prasad↗
NASA NTRS2005

Spectral Monitoring Observations of Two Exceptionally Luminous ULXS

The purpose of this proposal was to monitor the spectral variability of two luminous ULXs. One was awarded for study, in the galaxy NGC1365. The ULX NGC1365 X-1 is one of the few reported reaching X-ray luminosities near 10(exp 40) erg/s, and as such is a good IMBH candidate. The ULX was seen to vary in the ROSAT data. We now have 6 new observations: 1 archival Chandra observation and 5 observations we have obtained with XMM, including this proposal and a follow up XMM-Newton observation of NGC1365, aimed at studying the variable nuclear AGN. With this data set, we are studying in detail the spectral variability properties of this source. We observe a factor 4 variability among the XMM observation, with a peak luminosity approx.9 x 10(exp 39) ergs/s. There is also evidence of variability in the X-ray colors and spectral parameters. The last two XMM exposure of 60 ks each demonstrate that a simple power-law spectrum is not a good fit to the data, suggesting in both instances soft excesses, with possibly different temperatures.

Fabbiano, G.↗