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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Molecular line survey of Sagittarius B2(M) from 330 to 355 GHz and comparison with Sagittarius B2(N)

A submillimeter survey of Sgr B2 is described in which sufficient spatial resolution permitted the observation of some of the source structure. The position Sgr B2(M) is examined in relation to the submillimeter emission of Sgr B2(N) and previous millimeter observational data of source (M) at a lower spatial resolution. Because the submillimeter observations are more sensitive to core emission, the molecules SO2 and CH3OH tend to dominate the spectrum. The core emission is found to be similar to that of the Orion molecular cloud, and the submillimeter and millimeter lines have high optical depths. The (N) source has a much higher column density than that of (M) except for SO and SO2, and (N) also appears to have a higher excitation which can indicate a core with a higher density.

Sutton, E. C.↗
NASA NTRS1994

Three millimeter molecular line observations in Sagittarius B2. 1: Full synthesis mapping study of HNO, CCS, and HC(13)CCN

We present the first full synthesis maps of the small molecules HNO, CCS, and HC(13)CCN in Sgr B2. We have observed the 3.8 mm continuum, the HNO J(sub K(sub -1)K(sub 1)) = 1(sub O1)-0(sub OO), the CCS J(sub N) = 7(sub 6)-6(sub 5), and the HC(13)CCN J = 9-8 transitions in the core of the Sgr B2 molecular cloud, using the Berkeley Illinois Maryland Association (BIMA) millimeter array and the NRAO 12 m telescope. We have found that HNO exists in five major gas clumps in the Sgr B2 region, which we have labeled HNO(N), HNO(NW), HNO(E), HNO(M), and HNO(S). Of particular interest is HNO(M), a major molecular gas concentration approximately 15 sec west of Sgr B2(M) in a region of young star formation. HNO is found to be closely associated with the ionized gas and might be depleted around bright H II complexes. In general, the peak intensity of the HNO emission is found to be offset from the peak of the continuum emission. We found evidence for some chemical differentiation among the three species, HNO, CCS, and HC(13)CCN, but the abundance ratios are in fair agreement with theoretical models. Two unidentified lines, U81420 and U81518, were observed, and a previously unknown compact dust source was detected. Our HNO data indicate the presence of a rotating approximately (2.2-4.4) x 10(exp 3)solar mass gas envelope surrounding Sgr B2(N), a possible bipolar gas outflow in HNO(M), and possibly a large (approximately 4.2 x 10(exp 4)solar mass) extended rotating disk associated with HNO(S). In addition, the CCS and HC(13)CCN data approximately outline the extended component of Sgr B2 and clearly show that the southern continuum source Sgr B2(S) is actually a major molecular source as well. Consequently, the kinematics of the Sgr B2 molecular cloud is quite complex, but in moving from the northwest to south, the LSR velocity generally changes from 79 to 46 km/s.

Kuan, Yi-Jehng↗
NASA NTRS1995

Complex molecules in Sagittarius B2(N): The importance of grain chemistry

The complex molecules vinyl cyanide (CH2CHCN), methyl formate (HCOOCH3), and ethyl cyanide (CH3CH2CN) were observed in the Sgr B2 star-forming region with the BIMA millimeter wavelength array. A region with diameter less than 0.1 pc toward the Sgr B2(N) molecular core is found to be the major source of these molecules. Also, this source is coincident with continuum emission from dust and a center of H2O maser activity. Ultracompact (UC) H 11 regions are located within 0.1 pc. Strikingly, none of these molecules is detected toward Sgr B2(M), a core located 1 minute south of Sgr B2(N). The existence of complex molecules, a large mass of dust, high-velocity H2O masers, and UC H 11 regions strongly suggests that the Sgr B2(N) region has just begun to form stars, while the absence of strong dust emission and large molecules suggests Sgr B2(M) is more evolved. The detection of large molecules coincident with continuum emission from dust supports the idea found in current chemical models that grain chemistry is of crucial importance for the formation of these molecules.

Miao, Yanti↗
NASA NTRS1989

Dust emission in the Sagittarius B2 molecular cloud core

A model is presented for the dust emission from the Sagittarius B2 molecular cloud core which reproduces the observed spectrum between 30 and 1300 micron, as well as the distribution of the emission at 1300 micron. The model is based on the assumption that Sgr B2(N) continuum source is located behind the dust cloud associated with Sgr B2(M) continuum source. The fact that Sgr B2(N) is stronger at 1300 micron can be attributed to a local column density maximum at the position of this source. Absence of a 53 micron emission peak at the position of Sgr B2(N) suggests that the luminosity of the north source is lower than that of the middle source.

Lis, Dariusz C.↗
NASA NTRS2013

Effect of Temperature on the Deformation Behavior of B2 Austenite in a Polycrystalline Ni49.9Ti50.1 (at.Percent) Shape Memory Alloy

Superelasticity in austenitic B2-NiTi is of great technical interest and has been studied in the past by several researchers [1]. However, investigation of temperature dependent deformation in B2-NiTi is equally important since competing mechanisms of stress-induced martensite (SIM), retained martensite, plastic and deformation twinning can lead to unusual mechanical behaviors. Identification of the role of various mechanisms contributing to the overall deformation response of B2-NiTi is imperative to understanding and maturing SMA-enabled technologies. Thus, the objective of this work was to study the deformation of polycrystalline Ni49.9Ti50.1 (at. %) above A(sub f) (105 C) in the B2 state at temperatures between 165-440 C, and generate a B2 deformation map showing active deformation mechanisms in different temperature-stress regimes.

Garg, A.↗
NASA NTRS1991

Theoretical study of the spectroscopy of B2

A study is made of the singlet, triplet, and quintet states of B2 below 45,000/cm at the multireference configuration-interaction level. The stronger bonding in B2, as compared with Al2, manifests itself in the potential energy curves. In B2, five of the six states dissociating to the ground state atoms are bound, compared with only two for Al2. Radiative lifetimes are reported for the lowest vibrational level of many of the bound triplet states of B2.

Langhoff, Stephen R.↗
NASA NTRS2001

SHARP-B2: Flight Test Objectives, Project Implementation and Initial Results

On September 28, 2000 the SHARP-B2 flight experiment was launched from Vandenberg Air Force Base, California. SHARP-B2 is the 2nd Ballistic flight test in the SHARP (Slender Hypervelocity Aerothermodynamic Research Probes) program which develops and tests new thermal protection materials and sharp body concepts. The flight tested Ultra-High Temperature Ceramics (UHTCs), which may radically change the design and performance of future aerospace vehicles. The new designs may overturn an age-old tenet of aerodynamics: that blunt-body aerospace vehicles, but not those with sharp leading edges, can survive the searing temperatures created as the vehicles tear through the atmosphere. Sharp leading edges offer numerous advantages over the blunt-body design currently in use. They could allow a space shuttle or crew return vehicle to maneuver in space more like an airplane and potentially allow astronauts to return to Earth from anywhere on orbit. They may allow improved astronaut safety by decreasing the risk of aborting into the ocean. They may reduce the electromagnetic interference that causes the communications blackouts that plague reentering blunt-body space vehicles. Reducing the amount of drag could lead to a reduction in propulsion requirements. Planetary probes could make use of sharp-body technology for aerobraking and to maximize their maneuvering capability. SHARP-B2 was a joint effort among NASA Ames, Sandia National Laboratories, the U.S. Air Force and the U.S. Army. It was funded by the Pathfinder Program at NASA's Marshall Space Flight Center. The SHARP-B2 payload was carried aboard a U.S. Air Force Minuteman III missile carrying a modified Mk 12A reentry vehicle (RV), which blasted off from Vandenberg Air Force Base near Lompoc, CA, at 3:01 a.m. PDT on Sept. 28. The RV was equipped with four 5. 1 inch-long strakes, or sharp leading edges. Each strake contained three UHTCs: ZrB2/SiC/C; ZrB2/SiC; and HfB2/SiC. Once it reached an altitude of about 400 nautical miles, the RV was released, returning through Earth's atmosphere at speeds exceeding Mach 22. One pair of strakes was designed to retract just before reaching temperatures high enough to cause the material to begin ablating. The other pair was designed to retract shortly after ablation began, at an expected temperature of nearly 5,100 degrees Fahrenheit. Sensors in the strakes measured how closely performance matched pre-flight calculations, and data was successfully collected throughout the 23-minute flight. A parachute was deployed (but not fully inflated) and the RV splashed down in a lagoon at the Kwajalein missile range in the Pacific Ocean. Within 3 hours radar track analysis showed ocean entry to be precisely at the latitude/longitude coordinates estimated during pre-flight simulation. An hour later a ship was deployed by the Army to recover the reentry vehicle, which was recovered in 165 feet of water, just 500 feet from its planned splash-down point. This is the first RV recovery in over a decade.

Salute, Joan↗
NASA NTRS1980

Optical and infrared variability of B2 1308+326

Optical and infrared polarimetric and photometric observations of the BL Lacertae object B2 1308+326 during its high-luminosity outburst in the spring of 1978 are reported. The energy distribution, polarization at 0.6 and 2.2 microns, flux and polarization variability and position angle and strength of polarization variations of B2 1308+326, which has a luminosity greater than 10 to the 48th ergs/sec, are observed to be similar to those of BL Lac objects of much lower luminosity, suggesting the same emission process. Models of BL Lac object emission accounting for the high luminosity of B2 1308+326 are examined, and the isotropic synchrotron model is found to be more applicable to the optical and infrared emission of BL Lac objects than a model invoking relativistically enhanced emission.

Moore, R. L.↗
NASA NTRS1982

The nature and origin of type B1 and B2 Ca-Al-rich inclusions in the Allende meteorite

The Type B Ca-Al-rich inclusions in the Allende carbonaceous chondrite form a continuous range from the mineralogically concentrically zoned B1 subtype to the unzoned B2 subtype. These subtypes differ in (1) structure, texture, grain size and shape, (2) mineralogical proportions and compositions, (3) accessory mineralogy, (4) relative abundance of spinel framboids, (5) rim layering, (6) major element chemistry, and (7) degree of secondary alteration. These differences, together with observations on the crystallization of synthetic melts, suggest that the B1 inclusions crystallized relatively rapidly from molten parental material while B2 types crystallized relatively slowly close to the solidus from material that had not been completely melted. The same data are used to construct an evaporative residue model for the origin of the parental Type B materials. In the model, dust in the protosolar nebula was heated with removal of more volatile elements, leaving completely melted (Type B1) residues at the highest temperatures and incompletely melted, less highly evaporated (Type B2) residues at lower temperatures.

Wark, D. A.↗
NASA NTRS1983

The kinetic temperature and CH3CCH column density profiles in SGR B2, Orion, and Dr 21

Kinetic temperatures, T(kin), are presently estimated by means of a technique employing the intensities of the adjacent rotational transitions of symmetric top molecules, under the assumptions that the metastable levels are thermalized, and that the excitation temperature connecting the upper level of the observed transition to the lowest level in the K ladder is the same for the both adjacent transitions. The method is applied to observations of the J = 5-4 and J = 6-5 transitions of CH3CCH obtained at 1-arcmin intervals along a NS-EW cross that centered on Orion KL, Sgr B2, and Dr 21. The technique's application to CH3CN lines from the central positions of Sgr B2 and Orion produces T(kin) values that are in good agreement with other determinations. The fact that these lines are broader than those of CH3CCH is interpreted in terms of a model in which CH3CN emission is confined to small and warm core region while CH3CCH emission is dominated by a more extensive, almost isothermal and cooler halo region in Orion KL and Sgr B2.

Churchwell, E.↗
NASA NTRS2001

Atomic Oxygen Abundance in Molecular Clouds: Absorption Toward Sagittarius B2

We have obtained high-resolution (approximately 35 km/s) spectra toward the molecular cloud Sgr B2 at 63 micrometers, the wavelength of the ground-state fine-structure line of atomic oxygen (O(I)), using the ISO-LWS instrument. Four separate velocity components are seen in the deconvolved spectrum, in absorption against the dust continuum emission of Sgr B2. Three of these components, corresponding to foreground clouds, are used to study the O(I) content of the cool molecular gas along the line of sight. In principle, the atomic oxygen that produces a particular velocity component could exist in any, or all, of three physically distinct regions: inside a dense molecular cloud, in the UV illuminated surface layer (PDR) of a cloud, and in an atomic (H(I)) gas halo. For each of the three foreground clouds, we estimate, and subtract from the observed O(I) column density, the oxygen content of the H(I) halo gas, by scaling from a published high-resolution 21 cm spectrum. We find that the remaining O(I) column density is correlated with the observed (13)CO column density. From the slope of this correlation, an average [O(I)]/[(13)CO] ratio of 270 +/- 120 (3-sigma) is derived, which corresponds to [O(I)]/[(13)CO] = 9 for a CO to (13)CO abundance ratio of 30. Assuming a (13)CO abundance of 1x10(exp -6) with respect to H nuclei, we derive an atomic oxygen abundance of 2.7x10(exp -4) in the dense gas phase, corresponding to a 15% oxygen depletion compared to the diffuse ISM in our Galactic neighborhood. The presence of multiple, spectrally resolved velocity components in the Sgr B2 absorption spectrum allows, for the first time, a direct determination of the PDR contribution to the O(I) column density. The PDR regions should contain O(I) but not (13)CO, and would thus be expected to produce an offset in the O(I)-(13)CO correlation. Our data do not show such an offset, suggesting that within our beam O(I) is spatially coexistent with the molecular gas, as traced by (13)CO. This may be a result of the inhomogeneous nature of the clouds.

Lis, D. C.↗
NASA NTRS2013

NuSTAR Detection of the Blazar B2 1023+25 at Redshift 5.3

B2 1023+25 is an extremely radio-loud quasar at zeta = 5.3 that was first identified as a likely high-redshift blazar candidate in the SDSS+FIRST quasar catalog. Here, we use the Nuclear Spectroscopic Telescope Array (NuSTAR) to investigate its non-thermal jet emission, whose high-energy component we detected in the hard X-ray energy band. The X-ray flux is approximately 5.5 × 10 (exp −14) erg cm(exp −2) s(exp −1) (5-10 keV) and the photon spectral index is Gamma(x) approx. =1.3-1.6. Modeling the full spectral energy distribution, we find that the jet is oriented close to the line of sight, with a viewing angle of approximately 3deg, and has significant Doppler boosting, with a large bulk Lorentz factor approximately 13, which confirms the identification of B2 1023+25 as a blazar. B2 1023+25 is the first object at redshift larger than 5 detected by NuSTAR, demonstrating the ability of NuSTAR to investigate the early X-ray universe and to study extremely active supermassive black holes located at very high redshift.

X-rays: general↗
NASA NTRS2018

Validation & Verification of Electrical Components B2 Test Facility

The research focus of this project is to assist in the closure of Measurement, Monitoring and Control System (MMCS) and other electrical requirements in support of the B2 Space Launch System (SLS) Core Stage Green Run Test Project. Alongside this goal I am to understand project management tools to analyze and control activities/tasks associated with those items. The project I am working on will assist electrical engineers in developing and or identifying closure rationale for the MMCS and electrical requirements. Also as serving the role of a training project manager, I am to develop and maintain a method for tracking progress with estimate completion dates specifically identifying those items during this performance window. The methods I used in order to perform the research consisted of worddocuments, excel sheets, and pdf documents needed for review. For example, documents consisted of: a SLS Core Stage Green Run Facility Requirement Document (FRD) identifying the SSC MMCS and electrical requirements, a Stage Controller to SSC Interface Control Document (ICD) identifying the SSC requirements, and the B2 SLS Core Stage Green Run Test project System Requirements Document (SRD) which identifies the MMCS and electrical requirements. The files were sent to me by both mentors, Mr. Barry Robinson and Ms. Dawn Davis. Overall, the review process for the word documents and excel spreadsheets proved to be successful. The data for the electrical components were accurate and were consistent with the original recorded data. However, the consistency with the pdf documents did not follow up all the way. Attention to this mistake was made and further revisions were done in order for the data to agree with each other. Furthermore, an itinerary was designed using Microsoft Outlook in order to track progress with estimated completion dates. This project contributes to NASA/Center Missions and Goals through the Waterfall Model. The Waterfall Model is a linear system used for engineering design. In the Waterfall Model, the fourth step is Verification and Validation. This involves installation, testing, and debugging of the B2 SLS Core Stage electrical components. For the SLS Core Stage Green Run Test Project, each requirement contained in this approved requirements set will have at least one Verification Item (VI) assigned to it. During the design phase, VIs will mostly consist of Analysis or Inspection types. Design phase VIs and closure information will be documented in Dynamics Data Management System (DDMS) in the form of analysis reports and design documentation.

Bastian, Tyler↗
NASA NTRS1977

On the infrared emission from SGR B2

Results are reported for 2.2-micron observations of a 3.5 by 4 arcmin region centered on Sgr B2. More than 30 discrete sources stronger than 10 magnitudes (60 mJy) were found, but no extended emission stronger than about 80 mJy was seen with the 15-arcsec beam. All the emission objects are shown to have colors typical of stars reddened by 10 to 35 magnitudes, and it is postulated that they are all unrelated field stars at unknown distances along the line of sight to the H II region. It is concluded that there is no evidence for a statistical excess of 2.2-micron sources in the direction of Sgr B2. A previously reported observation of extended emission in the same region is attributed to source confusion and the limited number of scans made.

Becklin, E. E.↗
NASA NTRS1979

Detection of HC/O-18//plus/ in Sagittarius B2

Line emission at 85.1 GHz attributed to the J equals 1-0 rotational transition of the formyl ion HC(O-18)(plus) has been detected in Sgr B2 (OH). The double isotopic ratio (O-16/O-18)/(C-12/C-13) in the formyl ion in Sgr B2 is estimated to be in the range 5-10, hence within a factor 2 of the terrestrial value of 5.5. This determination implies that the C-13/C-12 ratio near the galactic center does not differ greatly from that in local molecular clouds.

Guelin, M.↗
NASA NTRS1983

The kinetic temperature and density of the Sagittarius B2 molecular cloud from observations of methyl cyanide

Observations of the K components of the CH3CN J = 4-to-3 rotational transition at 73.6 GHz, the 6-to-5 transition at 110.4 GHz, and the 7-to-6 transition at 128.7 GHz, yield a mean kinetic temperature value of 85 + or - 10 K and a mean H2 density of 110,000 + or - 50,000/cu cm for the central 2.0 arcmin of the Sgr B2 molecular cloud. Within the K = zero-to-4 ladders of CH3CN in Sgr B2, the populations of the radiatively coupled J levels are relaxed and exhibit a rotational temperature of about 16 K, which is similar to that of several linear molecules.

Cummins, S. E.↗
NASA NTRS1984

The B2 aluminides as alternative materials

The potential of the B2 aluminides as structural material alternatives for the strategic element containing superalloys currently used in gas turbine engines is being explored with emphasis on the equiatomic Fe and Ni aluminides. Although Co is a strategic material, the equiatomic Co aluminide is also being studied to gain a more complete understanding of these fourth period intermetallics. Research focuses on initial processing techniques such as ingot melting, power metallurgy, and rapid solidification with and without additional thermomechanical processing; high temperature deformation - primarily compressive creep; compositional effects within the binary B2 aluminides; third-element alloying addition effects on high temperature strength and oxidation resistance, and near room temperature ductility as influenced by processing, alloying, and grain size. Various programs now underway are reviewed and some highlights of research results are presented.

Stephens, J. R.↗
NASA NTRS1985

The B2 aluminides as alternative materials

The potential of the B2 aluminides as structural material alternatives for the strategic element containing superalloys currently used in gas turbine engines is being explored with emphasis on the equiatomic Fe and Ni aluminides. Although Co is a strategic material, the equiatomic Co aluminide is also being studied to gain a more complete understanding of these fourth period intermetallics. Research focuses on initial processing techniques such as ingot melting, power metallurgy, and rapid solidification with and without additional thermomechanical processing; high temperature deformation primarily compressive creep; compositional effects within the binary B2 aluminides; third-element alloying addition effects on high temperature strength and oxidation resistance, and near room temperature ductility as influenced by processing, alloying, and grain size. Various programs now underway are reviewed and some highlights of research results are presented.

Stephens, J. R.↗