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Sample records for candidate xte j1650-500

  1. Evidence of Spin and Energy Extraction in a Galactic Black Hole Candidate: The XMM-Newton/EPIC-pn Spectrum of XTE J1650-500

    NASA Astrophysics Data System (ADS)

    Miller, J. M.; Fabian, A. C.; Wijnands, R.; Reynolds, C. S.; Ehle, M.; Freyberg, M. J.; van der Klis, M.; Lewin, W. H. G.; Sanchez-Fernandez, C.; Castro-Tirado, A. J.

    2002-05-01

    We observed the Galactic black hole candidate XTE J1650-500 early in its fall of 2001 outburst with the XMM-Newton European Photon Imaging pn Camera (EPIC-pn). The observed spectrum is consistent with the source having been in the ``very high'' state. We find a broad, skewed Fe Kα emission line that suggests the primary in this system may be a Kerr black hole and that indicates a steep disk emissivity profile that is hard to explain in terms of a standard accretion disk model. These results are quantitatively and qualitatively similar to those from an XMM-Newton observation of the Seyfert galaxy MCG -6-30-15. The steep emissivity in MCG -6-30-15 may be explained by the extraction and dissipation of rotational energy from a black hole with nearly maximal angular momentum or from material in the plunging region via magnetic connections to the inner accretion disk. If this process is at work in both sources, an exotic but fundamental general relativistic prediction may be confirmed across a factor of 106 in black hole mass. We discuss these results in terms of the accretion flow geometry in stellar-mass black holes and the variety of enigmatic phenomena often observed in the very high state.

  2. Disentangling the NIR/optical emission of the black hole XTE J1650-500 during outburst

    NASA Astrophysics Data System (ADS)

    Curran, P. A.; Chaty, S.; Zurita Heras, J. A.

    2012-11-01

    Context. While the sources of X-ray and radio emission in the different states of low-mass X-ray binaries are relatively well understood, the origin of the near-infrared (NIR) and optical emission is more often debated. It is likely that the NIR/optical flux originates from an amalgam of different emission regions, because it occurs at the intersecting wavelengths of multiple processes. Aims: We aim to identify the NIR/optical emission region(s) of one such low-mass X-ray binary and black hole candidate, XTE J1650-500, via photometric, timing, and spectral analyses. Methods: We present unique NIR/optical images and spectra, obtained with the ESO-New Technology Telescope, during the peak of the 2001 outburst of XTE J1650-500. Results: The data suggest that the NIR/optical flux is due to a combination of emission mechanisms including a significant contribution from X-ray reprocessing and, at early times in the hard state, a relativistic jet that is NIR/radio dim compared to similar sources. Conclusions: The jet of XTE J1650-500 is relatively weak compared to that of other black hole low-mass X-ray binaries, possibly because we observe as it is being "turned off" or quenched at the state transition. While there are several outliers to the radio-X-ray correlation of the hard state of low-mass X-ray binaries, XTE J1650-500 is the first example of an outlier to the NIR/optical-X-ray correlation. Based on observations made with the European Southern Observatory telescopes obtained from the ESO/ST-ECF Science Archive Facility.

  3. High-Frequency Quasi-Periodic Oscillations in the Black Hole X-Ray Transient XTE J1650-500

    NASA Technical Reports Server (NTRS)

    Holman, Jeroen; Klein-Wolt, Marc; Rossi, Sabrina; Miller, Jon M.; Wijnands, Rudy; Belloni, Tomaso; VanDerKlis, Michiel; Lewin, Walter H. G.

    2003-01-01

    We report the detection of high-frequency variability in the black hole X-ray transient XTE 51650-500. A quasi-periodic oscillation (QPO) was found at 250 Hz during a transition from the hard to the soft state. We also detected less coherent variability around 50 Hz that disappeared when the 250 Hz QPO showed up. There are indications that when the energy spectrum hardened the QPO frequency increased from approx. 110 to approx. 270 Hz, although the observed frequencies are also consistent with being 1 : 2 : 3 harmonics of each other. Interpreting the 250 Hz as the orbital frequency at the innermost stable orbit around a Schwarzschild black hole leads to a mass estimate of 8.2 solar mass. The spectral results by Miller et al., which suggest considerable black hole spin, would imply a higher mass.

  4. Evidence of Spin and Energy Extraction in a Galactic Black Hole Candidate: The XMM-NEWTON/EPIC SPECTRUM of XTE 11650-500

    NASA Technical Reports Server (NTRS)

    Miller, J. M.; Fabian, A. C.; Wunands, R.; Reynolds, C. S.; Ehle, M.; Freyberg, M. J.; VanDerKlis, M.; Lewin, W. H. G.; Sanchez-Fernandez, C.; Castro-Tirado, A. J.

    2002-01-01

    We observed the Galactic black hole candidate XTE J1650-500 early in its fall of 2001 outburst with the XMM-Newton European Photon Imaging pn Camera (EPIC-pn). The observed spectrum is consistent with the source having been in the very high state. We h d a broad, skewed Fe Kar emission line that suggests the primary in this system may be a Kerr black hole and that indicates a steep disk emissivity profile that is hard to explain in terms of a standard accretion disk model. These results are quantitatively and qualitatively similar to those from an XMM-Newton observation of the Seyfert galaxy MCG -6-30-15. The steep emissivity in MCG -6-30-15 may be explained by the extraction and dissipation of rotational energy from a black hole with nearly maximal angular momentum or from material in the plunging region via magnetic connections to the inner accretion disk. If this process is at work in both sources, an exotic but fundamental general relativistic prediction may be confirmed across a factor of l0(exp 6) in black hole mass. We discuss these results in terms of the accretion flow geometry in stellar-mass black holes and the variety of enigmatic phenomena often observed in the very high state.

  5. X-Ray Bursts from the Transient Magnetar Candidate XTE J1810-197

    NASA Technical Reports Server (NTRS)

    Kouveliotou, Chryssa; Woods, Peter M.; Gavriil, Fotis P.; Kaspi, Victoria M.; Roberts, Mallory S. E.; Ibrahim, Alaa; Markwardt, Craig B.; Swank, Jean H.; Finger, Mark H.

    2005-01-01

    We have discovered four X-ray bursts, recorded with the Rossi X-ray Timing Explorer Proportional Counter Array between 2003 September and 2004 April, that we show to originate from the transient magnetar candidate XTE 51810-197. The burst morphologies consist of a short spike or multiple spikes lasting approx. 1 s each followed by extended tails of emission where the pulsed flux from XTE 51810-197 is significantly higher. The burst spikes are likely correlated with the pulse maxima, having a chance probability of a random phase distribution of 0.4%. The burst spectra are best fit to a blackbody with temperatures 4-8 keV, considerably harder than the persistent X-ray emission. During the X-ray tails following these bursts, the temperature rapidly cools as the flux declines, maintaining a constant emitting radius after the initial burst peak. The temporal and spectral characteristics of these bursts closely resemble the bursts seen from 1E 1048.1-5937 and a subset of the bursts detected from 1E 2259+586, thus establishing XTE J1810-197 as a magnetar candidate. The bursts detected from these three objects are sufficiently similar to one another, yet si,g&cantly differe2t from those seen from soft gamma repeaters, that they likely represent a new class of bursts from magnetar candidates exclusive (thus far) to the anomalous X-ray pulsar-like sources.

  6. NIR Imaging of the Candidate Black Hole Transient XTE J1652-453

    NASA Astrophysics Data System (ADS)

    Reynolds, Mark; Callanan, Paul; Nagayama, Takahiro

    2009-07-01

    We obtained a series of 300s exposures in the J, H & K' bands of the field of the candidate black hole transient XTE J1652-453 (ATEL #2107) using the Sirius simultaneous 3 channel NIR imager mounted on the Infrared Survey Facility 1.4m telescope at SAAO. Within the Swift error circle (ATEL #2120), there are at least two objects visible in the K' image (see chart): Star A: 16 52 20.4 -45 20 38.4, K' = 17.0 +/- 0.3 and the other at Star B: 16 52 20.3 -45 20 39.9, K' = 16.9 +/- 0.3 where the positional error is 0.5''.

  7. Multiwavelength Observations of the Black Hole Candidate XTE J1550-564 during the 2000 Outburst

    NASA Astrophysics Data System (ADS)

    Jain, Raj K.; Bailyn, Charles D.; Orosz, Jerome A.; McClintock, Jeffrey E.; Remillard, Ronald A.

    2001-06-01

    We report optical, infrared, and X-ray light curves for the outburst, in 2000, of the black hole candidate XTE J1550-564. We find that the start of the outburst in the H and V bands precedes that seen in the Rossi X-Ray Timing Explorer All-Sky Monitor by 11.5+/-0.9 and 8.8+/-0.6 days, respectively; a similar delay has been observed in two other systems. About 50 days after the primary maxima in the VIH light curves, we find secondary maxima, most prominently in H. This secondary peak is absent in the X-ray light curve but coincides with a transition to the low/hard state. We suggest that this secondary peak may be due to nonthermal emission associated with the formation of a jet.

  8. Long-Term Spectral and Timing Behavior of the Black Hole Candidate XTE J1908+094

    NASA Technical Reports Server (NTRS)

    Gogus, Ersin; Finger, Mark H.; Kouveliotou, Chryssa; Woods, Peter M.; Patel, Sandeep K.; Ruppen, Michael; Swank, Jean H.; Markwardt, Craig B.; VanDerKlis, Michiel

    2004-01-01

    We present the long-term X-ray light curves and detailed spectral and timing analyses of XTE J1908+094 using the Rossi X-Ray Timing Explorer Proportional Counter Array observations covering two outbursts in 2002 and early 2003. At the onset of the first outburst, the source was found in a spectrally low/hard state lasting for approx.40 days, followed by a 3 day long transition to the high/soft state. The source flux (in 2- 10 keV) reached approx.100 mcrab on 2002 April 6, then decayed rapidly. In power spectra, we detect strong band-limited noise and varying low- frequency quasi-periodic oscillations that evolved from approx.0.5 to approx.5 Hz during the initial low/hard state of the source. We find that the second outburst closely resembled the spectral evolution of the first. The X-ray transient s overall outburst characteristics led us to classify XTE J1908+094 as a black hole candidate. Here we also derive precise X-ray position of the source using Chandra observations that were performed during the decay phase of the first outburst and following the second outburst.

  9. Discovery and Monitoring of a New Black Hole Candidate XTE J1752-223 with RXTE: RMS Spectrum Evolution, BH Mass and the Source Distance

    NASA Technical Reports Server (NTRS)

    Shaposhinikov, Nikolai; Markwardt, Craig; Swank, Jean; Krimm, Hans

    2010-01-01

    We report on the discovery and monitoring observations of a new galactic black hole candidate XTE J1752-223 by Rossi X-ray Timing Explorer (RXTE). The new source appeared on the X-ray sky on October 21 2009 and was active for almost 8 months. Phenomenologically, the source exhibited the low-hard/highsoft spectral state bi-modality and the variability evolution during the state transition that matches standard behavior expected from a stellar mass black hole binary. We model the energy spectrum throughout the outburst using a generic Comptonization model assuming that part of the input soft radiation in the form of a black body spectrum gets reprocessed in the Comptonizing medium. We follow the evolution of fractional root-mean-square (RMS) variability in the RXTE/PCA energy band with the source spectral state and conclude that broad band variability is strongly correlated with the source hardness (or Comptonized fraction). We follow changes in the energy distribution of rms variability during the low-hard state and the state transition and find further evidence that variable emission is strongly concentrated in the power-law spectral component. We discuss the implication of our results to the Comptonization regimes during different spectral states. Correlations of spectral and variability properties provide measurements of the BH mass and distance to the source. The spectral-timing correlation scaling technique applied to the RXTE observations during the hardto- soft state transition indicates a mass of the BH in XTE J1752-223 between 8 and 11 solar masses and a distance to the source about 3.5 kiloparsec.

  10. X-ray timing and spectral observations of galactic black hole candidate XTE J1550-564 during outburst

    NASA Astrophysics Data System (ADS)

    Reilly, Kaice Theodore

    2003-09-01

    The timing and spectral properties of the soft X-ray transient (SXT) and microquasar XTE J1550-564 during outburst are studied, emphasizing observations made by the Unconventional Stellar Aspect (USA) Experiment. USA data show a low-frequency quasi-periodic oscillation (LFQPO) with a centroid frequency that tends to increase with increasing flux and a fractional rms amplitude which is correlated with the USA hardness ratio. Several high- frequency quasi-periodic oscillations (HFQPOs) were detected by RXTE, during periods where the LFQPO is seen to be weakening or not detectable at all. The evolution of the USA hardness ratio with time and source flux is examined. The hardness-intensity diagram shows counterclockwise cyclical evolution and possibly indicates the presence of two independent accretion flows: a geometrically thin, optically thick accretion disk and a hot sub-Keplerian flow. A model for production of the LFQPO in XTE J1550-564 is proposed, assuming that the LFQPO is a result of acoustic oscillations in a hot sub-Keplerian transition layer (TL). Under this acoustic oscillation model (AOM), the TL is an acoustic cavity having an outer boundary at RTL, where R TL ≈ Rinner, with Rinner being the radius of the accretion disk inner edge. TL resonance is interpreted as a mechanism for the LFQPO and the eigenfrequencies are associated with the LFQPO frequencies, ν LFQPO. This LFQPO mechanism requires the presence of a TL, capable of inverse-Compton scattering, with RTL regulated by a cool Keplerian accretion disk. Support for the AOM is provided by the correlation of the LFQPO percent rms amplitude with the USA hardness ratio, and other correlations and anti-correlations found in the USA, RXTE and BATSE observations. LFQPO data show increasing rms amplitude with increasing high energy flux and increasing νLFQPO with increasing low energy flux. These observations indicate that ν LFQPO is set by the accretion disk inner edge. The spectrally inferred Rinner

  11. The black hole candidate XTE J1752-223 towards and in quiescence: optical and simultaneous X-ray-radio observations

    NASA Astrophysics Data System (ADS)

    Ratti, E. M.; Jonker, P. G.; Miller-Jones, J. C. A.; Torres, M. A. P.; Homan, J.; Markoff, S.; Tomsick, J. A.; Kaaret, P.; Wijnands, R.; Gallo, E.; Özel, F.; Steeghs, D. T. H.; Fender, R. P.

    2012-07-01

    We present optical, X-ray and radio observations of the black hole transient (BHT) XTE J1752-223 towards and in quiescence. Optical photometry shows that the quiescent magnitude of XTE J1752-223 is fainter than 24.4 mag in the i' band. A comparison with measurements of the source during its 2009-2010 outburst shows that the outburst amplitude is more than 8 mag in the i' band. Known X-ray properties of the source combined with the faintness of the quiescence optical counterpart and the large outburst optical amplitude point towards a short orbital-period system (Porb≲ 6.8 h) with an M type (or later) mass donor, at a distance of 3.5 ≲d≲ 8 kpc. Simultaneous X-ray and radio data were collected with Chandra and the Expanded Very Large Array (EVLA), allowing constraints to be placed on the quiescent X-ray and radio flux of XTE J1752-223. Furthermore, using data covering the final stage of the outburst decay, we investigated the low-luminosity end of the X-ray-radio correlation for this source and compared it with other BHTs. We found that XTE J1752-223 adds to the number of outliers with respect to the 'standard' X-ray-radio luminosity relation. Furthermore, XTE J1752-223 is the second source, after the BHT H1743-322, that shows a transition from the region of the outliers towards the 'standard' correlation at low luminosity. Finally, we report on a faint, variable X-ray source we discovered with Chandra at an angular distance of ˜2.9 arcsec to XTE J1752-223 and at a position angle consistent with that of the radio jets previously observed from the BHT. We discuss the possibility that we detected X-ray emission associated with a jet from XTE J1752-223.

  12. Fermi arc electronic structure and Chern numbers in the type-II Weyl semimetal candidate MoxW1 -xTe2

    NASA Astrophysics Data System (ADS)

    Belopolski, Ilya; Xu, Su-Yang; Ishida, Yukiaki; Pan, Xingchen; Yu, Peng; Sanchez, Daniel S.; Zheng, Hao; Neupane, Madhab; Alidoust, Nasser; Chang, Guoqing; Chang, Tay-Rong; Wu, Yun; Bian, Guang; Huang, Shin-Ming; Lee, Chi-Cheng; Mou, Daixiang; Huang, Lunan; Song, You; Wang, Baigeng; Wang, Guanghou; Yeh, Yao-Wen; Yao, Nan; Rault, Julien E.; Le Fèvre, Patrick; Bertran, François; Jeng, Horng-Tay; Kondo, Takeshi; Kaminski, Adam; Lin, Hsin; Liu, Zheng; Song, Fengqi; Shin, Shik; Hasan, M. Zahid

    2016-08-01

    It has recently been proposed that electronic band structures in crystals can give rise to a previously overlooked type of Weyl fermion, which violates Lorentz invariance and, consequently, is forbidden in particle physics. It was further predicted that MoxW1 -xTe2 may realize such a type-II Weyl fermion. Here, we first show theoretically that it is crucial to access the band structure above the Fermi level ɛF to show a Weyl semimetal in MoxW1 -xTe2 . Then, we study MoxW1 -xTe2 by pump-probe ARPES and we directly access the band structure >0.2 eV above ɛF in experiment. By comparing our results with ab initio calculations, we conclude that we directly observe the surface state containing the topological Fermi arc. We propose that a future study of MoxW1 -xTe2 by pump-probe ARPES may directly pinpoint the Fermi arc. Our work sets the stage for the experimental discovery of the first type-II Weyl semimetal in MoxW1 -xTe2 .

  13. XTE Science Briefing from KSCNF

    NASA Technical Reports Server (NTRS)

    1995-01-01

    The X-ray Timing Explorer (XTE), launched on Dec. 30, 1995, is a Satellite that observes the fast-moving, high-energy worlds of black holes, neutron stars, x-ray pulsars and bursts of X-rays that light up the sky and then disappear forever. This videotape presents a pre-launch science briefing to the press by a few of the scientist and managers associated with the XTE satellite. The moderator for the press briefing is Jim Sahli, from the Public Affairs Office at Goddard Space Flight Center (GSFC). He introduces Alan Bunner, of the High Energy Astrophysics at NASA Headquarters; Fred Lamb, from the University of Illinois; Richard Mashotzky, X Ray Scientist at GSFC; Rick Rothschild, Principal Investigator from the University of California at San Diego; and Dale Schultz, the XTE project manager at GSFC. Dr. Bunner explains the electromagnetic spectrum, the placement of x-rays and the importance of the XTE observations to a better understanding of the Universe. Dr. Lamb, explains the difference between white dwarfs, neutron stars and black holes, and the type of observations that the XTE will give to a further understanding of these phenomena. Dr. Mashotzky expands the viewpoint to beyond the galaxy, and explains the interests of scientists who hope to use XTE to further study Quasars and Active Galactic Nuclei. Dr. Rothschild reviews some of the features of XTE, using a diagram to show the features of interest, such as the X ray Telescopes, and the collecting Proportional Counter Array (PCA.) Mr. Schultz presents a videotape tour of the XTE, in which he shows the scientific instruments and the other features of the satellite. In this tour, the source of each of the instruments is noted. Questions from the members of the press are then fielded. Many of the questions are about the cost of the XTE and any problems that are anticipated in regards to the launch.

  14. XTE J1908+094

    NASA Technical Reports Server (NTRS)

    Woods, P. M.; Kouveliotou, C.; Finger, M. H.; Gogus, E.; Swank, J.; Markwardt, C.; Strohmayer, T.; Six, N. Frank (Technical Monitor)

    2002-01-01

    Goddard Space Flight Center reports the serendipitous discovery of a new x-ray transient, XTE J1908+094, in RXTE (Rossi X-ray Timing Explorer) PCA (Proportional Counter Array) observations of the soft-gamma-ray repeater SGR 1900+14, triggered following the burst activity on Feb. 17-18 (GCN 1253). These observations failed to detect the 5.2-s SGR pulsations, pointing towards a possible new source as the origin of the high x-ray flux. An RXTE PCA scan of the region around SGR 1900+14 on Feb. 21 was consistent with emission only from known sources (and no new sources). However, the scans required SGR 1900+14 to be 20 times brighter than its quiescent flux level (GCN 1256). A Director's Discretionary Time Chandra observation on Mar. 11 showed that the SGR was quiescent and did not reveal any new source within the Chandra ACIS (Advanced CCD (charge coupled device) Imaging Spectrometer) field-of-view. A subsequent RXTE PCA scan on Mar. 17, taken in combination with the first scan, required that a new source be included in the fit. The best-fit position is R.A. 19h 08m 50s, Decl. = +9 22 deg .5 (equinox J2000.0; estimated 2 deg systematic error radius), or approximately 24 deg away from the SGR source. The source spectrum (2-30 kev) can be best fit with a power-law function including photoelectric absorption (column density N_h = 2.3 x 10(exp 22), photon index = 1.55). Iron line emission is present, but may be due to the Galactic ridge. Between Feb. 19 and Mar. 17, the source flux (2-10 keV) has risen from 26 to 64 mCrab. The power spectrum is flat between 1 mHz and 0.1 Hz, falling approximately as 1/f**0.5 up to 1 Hz. At 1 Hz is seen a broad quasiperiodic oscillation peak and a break to a 1/f**2 power law, which continues to 4 Hz. The fractional rms (root mean square) amplitude from 1 mHz to 4 Hz is 43 percent. No coherent pulsations are seen between 0.001 and 1024 Hz. The authors conclude that XTE J1908+094 is a new blackhole candidate.

  15. Doppler Imaging of Black Hole SYSTEMS:XTE J1118+480.

    NASA Astrophysics Data System (ADS)

    Callanan, Paul; Perres-Torres, Manuel; Garcia, Michael

    We present time-resolved spectroscopy of the black-hole candidate XTE J1118+480 obtained during its approach to quiescence. Doppler imaging of the intense Hα line shows persistent emission with an origin in the gas stream/hotspot. In addition the Doppler maps show enhanced emission in the +Vx -Vy quadrant clearing incompatible with a stream/hotspot origin. We favour a non-uniform disk intensity distribution due to tidal effects as the origin of this emission. We compare our map with that of XTE J1118+480 in outburst as well as with those of other transient systems in quiescence

  16. Delta XTE Launch Activities (Scrub #2)

    NASA Technical Reports Server (NTRS)

    1995-01-01

    This NASA Kennedy Space Center video presents Delta XTE (X-Ray Timing Explorer) launch activities on 12/11/95. The launch was rescheduled for next weekend due to out of limit upper level wind conditions.

  17. On the modulation of low-frequency quasi-periodic oscillations in black hole transients

    NASA Astrophysics Data System (ADS)

    Pawar, Devraj D.; Motta, Sara; Shanthi, K.; Bhattacharya, Dipankar; Belloni, Tomaso

    2015-04-01

    We studied the properties of the low-frequency quasi-periodic oscillations detected in a sample of six black hole candidates (XTE J1550-564, H 1743-322, XTE J1859+226, 4U 1630-47, GX 339-4, XTE J1650-500) observed by the Rossi XTE satellite. We analysed the relation between the full width at half-maximum and the frequency of all the narrow peaks detected in power density spectra where a type-C QPO is observed. Our goal was to understand the nature of the modulation of the signal by comparing the properties of different harmonic peaks in the power density spectrum. We find that for the sources in our sample the width of the fundamental and of the first harmonic are compatible with a frequency modulation, while that of the sub-harmonic is independent of frequency, possibly indicating the presence of an additional modulation in amplitude. We compare our results with those obtained earlier from GRS 1915+105 and XTE J1550-564.

  18. Delta XTE Spacecraft Arrives at CCAS Skid Strip

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Footage shows the U.S Air Force Aircraft "Air Mobility Command" approaching, and landing at the Cape Canaveral Air Station Skid Strip (CCAS). The truck carrying the Delta XTE Spacecraft is also shown as it leaves the Air Mobility Command.

  19. Optical observations of XTE J1709-267

    NASA Astrophysics Data System (ADS)

    Wiersema, K.; Higgins, A. B.

    2016-06-01

    The X-ray binary XTE J1709-267 was recently found to be in outburst again by MAXI (Atel #9108). We observed this source using EFOSC2 on the ESO NTT. At 02:33 UT on 23 June 2016, the source was detected at V=17.9 mag. This is several magnitudes brighter than the brightness in quiescence (Jonker et al. 2004, MNRAS 354, 666).

  20. A Pointed RXTE Observation of XTE J1817-330

    NASA Astrophysics Data System (ADS)

    Miller, J. M.; Homan, J.; Steeghs, D.; Torres, M. A. P.; Wijnands, R.

    2006-02-01

    We report on a pointed RXTE observation of XTE J1817-330, obtained on 2006-02-13 at 08:10:40 UT. After standard screening, the net good time for the PCA was 9.6 ksec, and the net good time for the HEXTE (cluster A) was 3.0 ksec. Joint fits were made to the PCU-2 and HEXTE-A spectra on the 2.8-25.0 keV and 20.0-200.0 keV range, respectively, with XSPEC. For a variety of continuum spectral models, a low column density is implied.

  1. A new outburst of XTE J1739-285

    NASA Astrophysics Data System (ADS)

    Maccarone, Thomas J.; Bandyopadhyay, Reba; Kennea, Jamie

    2012-09-01

    With our program of Swift monitoring of the Galactic Bulge region (Atel #4109), we detect renewed activity of the X-ray binary XTE J1739-285. Using the pipeline of Phil Evans (Evans et al. 2007, A&A, 469, 379), we find that the source count rate is about 34 counts/sec in data taken on 4 September from 5:33 to 12:02 UT, with 372 seconds of exposure time on source. We note that the source is heavily piled up, since the data were taken in photon counting mode as part of an imaging survey and hence the count rate should be taken with caution.

  2. Observational Signatures of Black Holes: Spectral and Temporal Features of XTE J1550-564

    NASA Technical Reports Server (NTRS)

    Titarchuk, Lev; Shrader, C. R.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    The theoretical predictions of the converging inflow, or Bulk-Motion Comptonization model are discussed and some predictions are compared to X- and gamma-ray observations of the high-soft state of Galactic black hole candidate XTE J1550+564. The approx. 10(exp 2)-Hz QPO phenomenon tends to be detected in the high-state at times when the bolometric luminosity surges and the hard-powerlaw spectral component is dominant. Furthermore, the power in these features increases with energy. We offer interpretation of this phenomenon, as oscillations of the innermost part of the accretion disk, which in turn supplies the seed photons for the converging inflow where the hard power-law is formed through Bulk Motion Comptonization (BMC). We further argue that the noted lack of coherence between intensity variations of the high-soft-state low and high energy bands is a natural consequence of our model, and that a natural explanation for the observed hard and soft lag phenomenon is offered. In addition, we address some criticisms of the BMC model supporting our claims with observational results.

  3. Delta XTE Spacecraft Solar Panel Deployment, Hangar AO at Cape Canaveral Air Station

    NASA Technical Reports Server (NTRS)

    1995-01-01

    The footage shows technicians in the clean room checking and adjusting the deployment mechanism of the solar panel for XTE spacecraft. Other scenes show several technicians making adjustments to software for deployment of the solar panels.

  4. Relations between X-ray timing features and spectral parameters of Galactic black hole X-ray binaries

    NASA Astrophysics Data System (ADS)

    Stiele, H.; Belloni, T. M.; Kalemci, E.; Motta, S.

    2013-03-01

    We present a study of correlations between spectral and timing parameters for a sample of black hole X-ray binary candidates. Data are taken from GX 339-4, H1743-322 and XTE J1650-500, as the Rossi X-ray Timing Explorer observed complete outbursts of these sources. In our study we investigate outbursts that happened before the end of 2009 to make use of the high-energy coverage of the High Energy X-ray Timing Experiment detector and select observations that show a certain type of quasi-periodic oscillations (QPOs; type-C). The spectral parameters are derived using the empirical convolution model SIMPL to model the Comptonized component of the emission together with a disc blackbody for the emission of the accretion disc. Additional spectral features, namely a reflection component, a high-energy cut-off and excess emission at 6.4 keV, are taken into account. Our investigations confirm the known positive correlation between photon index and centroid frequency of the QPOs and reveal an anticorrelation between the fraction of up-scattered photons and the QPO frequency. We show that both correlations behave as expected in the `sombrero' geometry. Furthermore, we find that during outburst decay the correlation between photon index and QPO frequency follows a general track, independent of individual outbursts.

  5. Swift Detects Likely X-ray Burst from XTE J1701-407

    NASA Astrophysics Data System (ADS)

    Markwardt, C. B.; Cummings, J.; Krimm, H.

    2008-07-01

    XTE J1701-407 was discovered in June 2008 by RXTE PCA scans (Markwardt et al., ATEL #1569) and Swift follow-up observations (Degenaar et al., ATEL #1572). Recently Swift BAT triggered on an X-ray flare from the same source (Barthelmy et al., GCN Circ. #7985). In this telegram we report on BAT results for the XTE J1701-407 flare, which we speculate is a thermonuclear X-ray burst from a neutron star.

  6. Corrected Coordinates for the Possible OC to XTE J1550-56

    NASA Astrophysics Data System (ADS)

    Orosz, Jerome; Bailyn, Charles; Jain, Raj

    1998-09-01

    There was a slight error in the coordinates of the possible optical counterpart to XTE J1550-56 we reported in our previous telegram. The correct J2000 coordinates are RA = 15:50:58.78, DEC = -56:28:35.0. The coordinates printed on the finding chart available at http://www.astro.psu.edu/users/orosz/xte.html has been corrected (the arrow points to the correct object in any case). We regret this error.

  7. Discovery of a Transient Magnetar: XTE J1810-197

    NASA Technical Reports Server (NTRS)

    Ibrahim, Alaa I.; Markwardt, Craig B.; Swank, Jean H.; Ransom, Scott; Roberts, Mallory; Kaspi, Victoria; Woods, Peter M.; Safi-Harb, Samar; Balman, Solen; Parke, William C.

    2004-01-01

    We report the discovery of a new X-ray pulsar, XTE J1810-197, that was serendipitously discovered on 2003 July 15 by the Rossi X-Ray Timing Explorer (RXTE) while observing the soft gamma repeater SGR 1806-20. The pulsar has a 5.54 s spin period, a soft X-ray spectrum (with a photon index of approx. = 4). and is detectable in earlier RXTE observations back to 2003 January but not before. These show that a transient outburst began between 2002 November 17 and 2003 January 23 and that the source's persistent X-ray flux has been declining since then. The pulsar exhibits a high spin-down rate P approx.= l0(exp -11) s/s with no evidence of Doppler shifts due to a binary companion. The rapid spin-down rate and slow spin period imply a supercritical characteristic magnetic field B approx. = 3 x l0(exp 14) G and a young age tau less than or = 7600 yr. Follow-up Chandra observations provided an accurate position of the source. Within its error radius, the 1.5 m Russian-Turkish Optical Telescope found a limiting magnitude R(sub c) = 21.5. All such properties are strikingly similar to those of anomalous X-ray pulsars ad soft gamma repeaters, providing strong evidence that the source is a new magnetar. However, archival ASCA and ROSAT observations found the source nearly 2 orders of magnitude fainter. This transient behavior and the observed long-term flux variability of the source in absence of an observed SGR-like burst activity make it the first confirmed transient magnetar and suggest that other neutron stars that share the properties of XTE 51810- 197 during its inactive phase may be unidentified transient magnetars awaiting detection via a similar activity. This implies a larger population of magnetars than previously surmised and a possible evolutionary connection between magnetars and other neutron star families. Subject headings: pulsars: general -pulsars: individual (XTE 51810- 197) - stars: magnetic fields -

  8. Discovery and Photometric Observation of the Optical Counterpart of a Possible Galactic Halo X-Ray Transient, XTE J1118+480

    NASA Astrophysics Data System (ADS)

    Uemura, Makoto; Kato, Taichi; Matsumoto, Katsura; Yamaoka, Hitoshi; Takamizawa, Kesao; Sano, Yasuo; Haseda, Katsumi; Cook, Lewis M.; Buczynski, Denis; Masi, Gianluca

    2000-08-01

    We discovered an optical counterpart of about 13 mag of a soft X-ray transient, XTE J1118+480 on 2000 March 30. We performed astrometry and provided an accurate position of R.A. = 11h18m10.85s85, Decl. = +48deg02'12.9{' '}. The outbursting object has been identified with a 18.8 mag star in the USNO catalog. Our pre-discovery data shows another outburst during 2000 January, again coinciding with an outburst detected in X-rays. Through CCD time-series photometry, we found the presence of a periodic variation with an amplitude of 0.055 mag and a period of 0.17078 \\pm 0.00004 d$, which we consider to be a promising candidate of the orbital period. Because of the high galactic latitude and faint quiescence magnitude of 18.8, XTE J1118+480 is possibly the first firmly identified black hole candidate X-ray transient in the galactic halo.

  9. Looking for black-holes in X-ray binaries with XMM-Newton: XTE J1817-330 and XTE J1856+053

    SciTech Connect

    Sala, Gloria; Greiner, Jochen; Primak, Natalia

    2008-10-08

    The X-ray binary XTE J1817-330 was discovered in outburst on 26 January 2006 with RXTE/ASM. One year later, another X-ray transient discovered in 1996, XTE J1856+053, was detected by RXTE during a new outburst on 28 February 2007. We triggered XMM-Newton target of opportunity observationson these two objects to constrain their parameters and search for a stellar black holes. We summarize the properties of these two X-ray transients and show that the soft X-ray spectra indicate indeed the presence of an accreting stellar black hole in each of the two systems.

  10. EVIDENCE OF LIGHT-BENDING EFFECTS AND ITS IMPLICATION FOR SPECTRAL STATE TRANSITIONS

    SciTech Connect

    Reis, R. C.; Miller, J. M.; Reynolds, M. T.; Fabian, A. C.; Walton, D. J.; Steiner, J. F.; Cackett, E.

    2013-01-20

    It has long been speculated that the nature of the hard X-ray corona may be an important second driver of black hole state transitions, in addition to the mass accretion rate through the disk. However, a clear physical picture of coronal changes has not yet emerged. We present results from a systematic analysis of Rossi X-Ray Timing Explorer observations of the stellar-mass black hole binary XTE J1650-500. All spectra with significant hard X-ray detections were fit using a self-consistent, relativistically blurred disk reflection model suited to high ionization regimes. Importantly, we find evidence that both the spectral and timing properties of black hole states may be partially driven by the height of the X-ray corona above the disk, and related changes in how gravitational light bending affects the corona-disk interaction. Specifically, the evolution of the power-law, thermal disk, and relativistically convolved reflection components in our spectral analysis indicates that: (1) the disk inner radius remains constant at r {sub in} =1.65 {+-} 0.08 GM/c {sup 2} (consistent with values found for the ISCO of XTE J1650-500 in other works) throughout the transition from the brighter phases of the low-hard state to the intermediate states (both the hard-intermediate and soft-intermediate), through to the soft state and back; (2) the ratio between the observed reflected X-ray flux and power-law continuum (the 'reflection fraction', R) increases sharply at the transition between the hard-intermediate and soft-intermediate states ('ballistic' jets are sometimes launched at this transition); (3) both the frequency and coherence of the high-frequency quasi-periodic oscillations observed in XTE J1650-500 increase with R. We discuss our results in terms of black hole states and the nature of black hole accretion flows across the mass scale.

  11. Delta XTE Launch Activities and Scrub (Anomaly) at Cape Canaveral Air Station Complex 17

    NASA Technical Reports Server (NTRS)

    1995-01-01

    This NASA Kennedy Space Center video presents launch activities of the Delta X-ray Timing Explorer and scrub aboard a McDonnell Douglas Delta II rocket from Complex 17. The primary objective of the Delta XTE is to study time variability and broadband spectral phenomena in the X-ray emission from astronomical sources. XTE is designed for a required lifetime of two years with a goal of five years and will be inserted into a low-Earth circular orbit at an altitude of 600 km. The launch was postponed due to unfavorable wind conditions aloft.

  12. LOW-FREQUENCY OSCILLATIONS IN XTE J1550-564

    SciTech Connect

    Rao Fengyun; Belloni, Tomaso; Stella, Luigi; Zhang Shuangnan; Li Tipei E-mail: tomaso.belloni@brera.inaf.i

    2010-05-10

    We present the results of a timing analysis of the low-frequency quasi-periodic oscillation (QPO) in the Rossi X-Ray Timing Explorer data of the black hole binary XTE J1550-564 during its 1998 outburst. The QPO frequency is observed to vary on timescales between {approx}100 s and days, correlated with the count rate contribution from the optically thick accretion disk: we studied this correlation and discuss its influence on the QPO width. In all observations, the quality factors ({nu}{sub 0}/FWHM) of the fundamental and second harmonic peaks were observed to be consistent, suggesting that the quasi-periodic nature of the oscillation is due to frequency modulation. In addition to the QPO and its harmonic peaks, a new 1.5{nu} component was detected in the power spectra. This component is broad, with a quality factor of {approx}0.6. From this, we argue that the peak observed at half the QPO frequency, usually referred to as 'sub-harmonic', could be the fundamental frequency, leading to the sequence 1:2:3:4. We also studied the energy dependence of the timing features and conclude that the two continuum components observed in the power spectrum, although both more intense at high energies, show a different dependence on energy. At low energies, the lowest-frequency component dominates, while at high energies the higher-frequency one has a higher fractional rms. An interplay between these two components was also observed as a function of their characteristic frequency. In this source, the transition between the low/hard state and the hard-intermediate state appears to be a smooth process.

  13. Further comments on segregation during Bridgman growth of Cd(x)Hg(1-x)Te

    NASA Technical Reports Server (NTRS)

    Lehoczky, S. L.; Szofran, F. R.

    1984-01-01

    The authors comment on recent papers published by Capper et al. (1983) and Jones et al. (1983) which report and discuss the variation of composition with axial position in Bridgman-grown Cd(x)Hg(1-x)Te alloys. The validity of a diffusion-controlled model for non-mixing growth conditions is particularly noted.

  14. The 2002 Outburst of the Millisecond Accreting Pulsar XTE J1751-305

    NASA Astrophysics Data System (ADS)

    Markwardt, C. B.; Swank, J. H.

    2002-12-01

    The millisecond accreting pulsar XTE J1751--305 was discovered in the galactic bulge region by the RXTE PCA in early 2002. It is one of only a handful of now-known millisecond pulsars that are presumably spinning up by mass accretion (along with SAX J1808.4--3658 and XTE J0929--314). We will present an analysis of the complete outburst of XTE J1751--305, including spectroscopy and timing. The outburst followed a similar track to the first known millisecond accreting pulsar, SAX J1808.4--3658, with a fast rise, exponential decay (time constant ~ 7 day), and a sudden cut-off. Over the outburst, the energy spectral shape remained essentially constant, and showed no strong line features. Aside from the pulsations, XTE J1751--305 also exhibited lower frequency fluctuations in the power spectrum, which are typical of low mass X-ray binaries. While there appears to be no strong kiloHertz quasiperiodic oscillations, there is some evidence for a weak and broad power spectral excess feature centered on a few hundred Hertz.

  15. Surface photovoltage spectroscopy analyses of Cd{sub 1-x}Zn{sub x}Te

    SciTech Connect

    Cavalcoli, D.; Fraboni, B.; Cavallini, A.

    2008-02-15

    Cd{sub 1-x}Zn{sub x}Te alloys have been studied by surface photovoltage spectroscopy (SPS) and energy dispersive spectroscopy (EDS). The analyses of surface photovoltage spectra have been perfomed at near and above band gap energies. Surface recombination effects on the surface photovoltage have been investigated. SPS analyses of Cd{sub 1-x}Zn{sub x}Te alloys with different surface conditions have shown that the surface recombination velocity significantly affects the SPS determination of the material band gap. Accounting for this and preparing the surfaces accordingly, SPS spectra of Cd{sub 1-x}Zn{sub x}Te samples have allowed an accurate determination of the optical band gap as a function of the Zn concentration, determined via EDS analyses. The local increases in the density of states associated with band structure features in Cd{sub 1-x}Zn{sub x}Te alloys have been investigated by SPS spectra in the above band gap energy range.

  16. Development of the solar array deployment and drive system for the XTE spacecraft

    NASA Technical Reports Server (NTRS)

    Farley, Rodger; Ngo, Son

    1995-01-01

    The X-ray Timing Explorer (XTE) spacecraft is a NASA science low-earth orbit explorer-class satellite to be launched in 1995, and is an in-house Goddard Space Flight Center (GSFC) project. It has two deployable aluminum honeycomb solar array wings with each wing being articulated by a single axis solar array drive assembly. This paper will address the design, the qualification testing, and the development problems as they surfaced of the Solar Array Deployment and Drive System.

  17. XTE J1752-223: Optical spectroscopy and infrared counterpart detection

    NASA Astrophysics Data System (ADS)

    Torres, M. A. P.; Steeghs, D.; Jonker, P. G.; Thompson, I.; Soderberg, A. M.

    2009-10-01

    Prompted by the discovery of its bright optical counterpart and the announcement of increased X-ray activity (ATels #2258, #2259, #2261, #2265, #2263), we have acquired additional observations of XTE J1752-223 at optical and near-infrared wavelengths. OPTICAL SPECTROSCOPY: An optical spectrum covering 3330-9165 Angstrom was obtained with the MIKE echelle spectrograph on the Magellan Clay telescope starting on 2009 Oct 26 UT 23:52.

  18. Discovery of Radio Emission From Transient Anomalous X-Ray Pulsar XTE J1810-197

    SciTech Connect

    Halpern, J P; Gotthelf, E V; Becker, R H; Helfand, D J; White, R L

    2005-10-25

    We report the first detection of radio emission from any anomalous X-ray pulsar (AXP). Data from the Very Large Array (VLA) MAGPIS survey with angular resolution 6'' reveals a point-source of flux density 4.5 {+-} 0.5 mJy at 1.4 GHz at the precise location of the 5.54 s pulsar XTE J1810-197. This is greater than upper limits from all other AXPs and from quiescent states of soft gamma-ray repeaters (SGRs). The detection was made in 2004 January, 1 year after the discovery of XTE J1810-197 during its only known outburst. Additional VLA observations both before and after the outburst yield only upper limits that are comparable to or larger than the single detection, neither supporting nor ruling out a decaying radio afterglow related to the X-ray turn-on. Another hypothesis is that, unlike the other AXPs and SGRs, XTE J1810-197 may power a radio synchrotron nebula by the interaction of its particle wind with a moderately dense environment that was not evacuated by previous activity from this least luminous, in X-rays, of the known magnetars.

  19. Revealing Evidence of Spin in Galactic Black Holes

    NASA Astrophysics Data System (ADS)

    Miller, J. M.; Fabian, A. C.; Reynolds, C. S.; Nowak, M.; Wijnands, R.; Homan, J.; Belloni, T.; van der Klis, M.; Lewin, W. H. G.

    2002-12-01

    Our observations of Galactic black holes with Chandra and XMM-Newton have recently revealed broad, skewed Fe K-alpha emission lines similar to those seen in some AGN. If such lines are produced near the inner edge of the accretion disk, they can serve as an excellent spin diagnostic. Our analysis of the XMM-Newton spectrum of XTE J1650-500 reveals a strong, skewed Fe K-alpha emission line that requires near-maximal spin; with RXTE, we have discovered a 250 Hz QPO in this source which may also be produced near to the black hole. Although many Galactic black holes have been studied extensively, it is extremely rare that spectroscopic and timing studies both reveal features plausibly associated with the inner accretion disk. We will present the results of our XMM-Newton, Chandra, and RXTE observations of XTE J1650-500, as well as the results of our Chandra observations of Cygnus X-1 and preliminary results from our observations of GX 339-4 with XMM-Newton. We will discuss these results within the context of the relativistic Fe K lines reported by our group and others, and comment on the prospects for revealing evidence of spin in future observations. (JMM acknowledges support from the NSF through the Astronomy and Astrophysics Fellowship program.)

  20. Serendipitous Detections of XTE J1906+09 with the Rossi X-Ray Timing Explorer

    NASA Technical Reports Server (NTRS)

    Wilson, Colleen A.; Finger, Mark H.; Gogus, Ersin; Woods, Peter M.; Kouveliotou, Chryssa

    2002-01-01

    The 89 s X-ray pulsar XTE J1906+09 was discovered during Rossi X-Ray Timing Explorer (RXTE) observations of SGR 1900+14 in 1996. Because of monitoring campaigns of SGR 1900+14, XTE J1906+09 was also monitored regularly in 1996 September, 1998 May-June, 1998 August-1999 July, and 2000 March-2001 January. A search for pulsations resulted in detections of only the two previously reported outbursts in 1996 September and 1998 August-September. Pulsed flux upper limits for the rest of the observations show that XTE J1906+09 is a transient X-ray pulsar and likely has a Be star companion. The RXTE all-sky monitor did not reveal XTE J1906+09. Pulse-timing analysis of the second outburst discovered a sinusoidal signature in the pulse frequencies that is likely produced by an orbital periastron passage. Fits to pulse phases using an orbital model and quadratic phase model have chi(exp 2) minima at orbital periods of 26-30 days for fixed mass functions of 5, 10, 15, and 20 solar masses. The pulse shape showed energy- and intensity-dependent variations. Pulse-phase spectroscopy quantified the energy-dependent variations. The phase-averaged spectrum used the pulse minimum spectrum as the background spectrum to eliminate effects from SGR 1900+14 and the Galactic ridge and was well fitted by an absorbed power law with a high-energy cutoff with column density N(sub H) = 6 +/- 1 x 10(exp 22)/sq cm, a photon index of 1.01 +/- 0.08, cutoff energy E(sub cut) = 11 +/- 1 keV, and e-folding energy E(sub fold) = 19 +/- 4 keV. Estimated 2-10 keV peak fluxes, corrected for contributions from the Galactic ridge and SGR 1900+14, are 6 x l0(exp -12) and 1.1 x 10(exp -10) ergs/sq cm/s for the 1996 and 1998 outbursts, respectively. XTE J1906+09 may be part of an unusual class of Be/X-ray binaries that do not lie on the general spin period versus orbital period correlation with the majority of Be/X-ray binaries.

  1. Near-infrared and optical observations of the failed outbursts of black hole binary XTE J1550-564

    NASA Astrophysics Data System (ADS)

    Curran, P. A.; Chaty, S.

    2013-09-01

    Context. A number of low mass X-ray binaries (LMXBs) undergo "failed outbursts" in which, instead of evolving through the canonical states, they remain in a hard state throughout the outburst. While the sources of X-ray and radio emission in the hard state are relatively well understood, the origin of the near-infrared (NIR) and optical emission is more complex though it likely stems from an amalgam of different emission processes, occurring as it does, at the intersecting wavelengths of those processes. Aims: We aim to identify the NIR/optical emission region(s) during a number of failed outbursts of one such LMXB and black hole candidate, XTE J1550-564, in order to confirm or refute their classification as hard-state, failed outbursts. Methods: We present unique NIR/optical images and spectra, obtained with the ESO-New Technology Telescope, during the failed outbursts of 2001 and 2000. We compare the NIR/optical photometric, timing, and spectral properties with those expected for the different emission mechanisms in the various LMXB states. Results: The NIR/optical data are consistent with having come from reprocessing of X-rays in the accretion disk, with no evidence of direct thermal emission from the disk itself. However, the observed variability in high-cadence NIR light curves suggest that the radio jet extends and contributes to the NIR wavelengths. Conclusions: We find that these failed outbursts did not transition to an intermediate state but remained in a true, hard state where there was no sign of jet quenching or deviation from the observed hard state correlations. Based on observations made with the European Southern Observatory telescopes obtained from the ESO/ST-ECF Science Archive Facility.

  2. Serendipitous Detections of XTE J1906+09 with the Rossi X-ray Timing Explorer

    NASA Technical Reports Server (NTRS)

    Wilson, Colleen A.; Finger, Mark H.; Gogus, Ersin; Woods, Peter M.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    In 1996 during Rossi X-ray Timing Explorer (RXTE) observations of SCR 1900+14, the 89-second X-ray pulsar XTE J1906+09 was discovered. As a result of monitoring campaigns of SGR 1900+14, XTE J1906+09 was also monitored regularly in 1996 September, 1998 May-June, 1998 August-1999 July, and 2000 March-2001 January. A frequency grid search of these observations resulted in detections of only the two previously reported outbursts in 1996 September and 1998 August-September. The non-detection of XTE J1906+09 in most observations indicates that it is a transient X-ray pulsar and therefore likely has a Be star companion, Pulse timing analysis of the second outburst revealed a sinusoidal signature in the pulse frequencies that is likely produced by periastron passage in a long period, eccentric, orbit. During the second outburst, the pulse shape changed with increasing intensity, Low intensity pulse profiles from the second outburst are consistent with profiles from the fainter first outburst. Energy dependent pulse shape variations were seen in both outbursts. Pulse phase spectroscopy was used to quantify these variations. The phase averaged spectrum, using the pulse minimum spectrum as the background spectrum to eliminate effects from SGR 1900+14 and the galactic ridge, was well fitted by an absorbed power law with a high energy cutoff with column density N(sub H) = (6 +/- 1) x 10(exp 22) cm(sup -2), photon index = 1.01 +/- 0.08, cutoff energy E(sub cut) = 11 +/- 1 keV, and folding energy E(sub fold) = 19 +/- 4 keV.

  3. The Accretion Rate Independence of Horizontal Branch Oscillation in XTE J1701-462

    NASA Astrophysics Data System (ADS)

    Li, Zhaosheng; Chen, Li; Qu, Jinlu; Bu, Qingcui; Wang, Dehua; Xu, Renxin

    2014-05-01

    We study the temporal and energy spectral properties of the unique neutron star low-mass X-ray binary XTE J1701-462. Assuming the horizontal branch/normal branch (HB/NB) vertex as a reference position of the accretion rate, the horizontal branch oscillation (HBO) of the HB/NB vertex is roughly 50 Hz. It indicates that the HBO is independent of the accretion rate or the source intensity. The spectral analysis shows R_{in}\\propto \\dot{M}_{Disk}^{2.9+/- 0.09} in the HB/NB vertex and R_{in}\\propto \\dot{M}_{Disk}^{1.7+/- 0.06} in the NB/flaring branch (FB) vertex, which implies that different accretion rates may be produced in the HB/NB and NB/FB vertex. The Comptonization component could be fitted by a constrained broken power law or nthComp. Unlike GX 17+2, the frequencies of HBO positively correlate with the inner disk radius, which contradict with the prediction of the Lense-Thirring precession model. XTE J1701-462, both in the Cyg-like phase and in the Sco-like phase, follows a positive correlation between the break frequency of broadband noise and the characteristic frequency of HBO, which is called the W-K relation. An anticorrelation between the frequency of HBO and photon energy is observed. Moreover, the rms of HBO increases with photon energy until ~10 keV. We discuss the possible origin of HBO from the corona in XTE J1701-462.

  4. An XTE Observation of the VELA Pulsar and Inner Region of the VELA SNR

    NASA Astrophysics Data System (ADS)

    Strickman, Mark

    Using three XTE pointing fields in the inner region of the Vela Supernova Remnant, we propose to answer three fundamental questions concerning this most interesting object: 1) What is the spectrum of the Vela Pulsar between 1 keV (ROSAT) and 60 keV (OSSE)? If a cutoff is detected, it may constitute a measurement of the pulsar magnetic field in the production region. 2) Does unpulsed emission recently detected by OSSE actually come from the compact nebula surrounding the pulsar? 3) Is the asymmetry of emission NE and SW of the pulsar as viewed by ROSAT and EINSTEIN reflected at higher energies?

  5. Corrected Name for 5.54 s Pulsar: XTE J1810-197

    NASA Astrophysics Data System (ADS)

    Swank, J. H.; Markwardt, C. B.; Ibrahim, A. I.

    2003-07-01

    In ATEL 167, we reported the position of a new source as R.A. = 18h10.9m, Decl. = -19o42' (equinox 2000.0) , with estimated 99% confidence semi-major axes of 5' in R.A. and 7' in Decl. We designated the new pulsar as XTE J1811-197. The same name appeared in CBET 36. It was brought to our attention by Dr. Marion Schmitz, head of the IAU Working Group on Designations, that the name did not follow the specifications of the IAU, which can be found at: http://cdsweb.u-strasbg.fr/iau-spec.html.

  6. Magnetoreflectivity of Pb{sub 1{minus}x}Eu{sub x}Te epilayers and PbTe/Pb{sub 1{minus}x}Eu{sub x}Te multiple quantum wells

    SciTech Connect

    Yuan, S.; Krenn, H.; Springholz, G.; Ueta, Y.; Bauer, G.; McCann, P.J.

    1997-02-01

    Molecular-beam epitaxy grown n-type Pb{sub 1{minus}x}Eu{sub x}Te epilayers (x{le}0.034) and PbTe/Pb{sub 1{minus}x}Eu{sub x}Te (x{le}0.039) multiple-quantum-well (MQW) samples were studied by magnetoreflectivity in the Faraday configuration (B{parallel}[111]) for magnetic fields up to 6T at 4.2 K. Since the IV-VI lead salt compounds are quite polar semiconductors, resonant electron-longitudinal-optic- (LO-) phonon coupling (Fr{umlt o}hlich coupling) modifies the cyclotron resonance (CR) energies in the Pb{sub 1{minus}x}Eu{sub x}Te single epilayers for the three-dimensional (3D) case. Due to the many-valley band structure {ital two} different Fr{umlt o}hlich coupling constants are relevant. However, the CR energies of quasi-two-dimensional (2D) carriers in PbTe wells [n{sup 2D}=(1.5{minus}3){times}10{sup 11}cm{sup {minus}2}] of PbTe/Pb{sub 1{minus}x}Eu{sub x}Te MQW samples do {ital not} exhibit a significant resonant electron-LO-phonon interaction. This observation is attributed to finite-electron concentration effects, in particular, to a partial filling of the lowest 2D Landau spin level. The static and dynamic screening of the polar interaction are considered as well, but are ruled out as an explanation for the absence of any remarkable polaron correction to the CR energies of electrons in the PbTe quantum wells for the range of carrier concentrations investigated. The magnetoreflectivity spectra of Pb{sub 1{minus}x}Eu{sub x}Te single layers and PbTe/Pb{sub 1{minus}x}Eu{sub x}Te quantum well samples are simulated numerically, using a model for the dielectric response of which also includes the electron-LO-phonon interaction. The transverse and longitudinal masses, and thus also the interband momentum matrix elements are determined for Pb{sub 1{minus}x}Eu{sub x}Te as a function of the composition up to x{lt}0.034. It is found that the transverse mass {ital increases} with Eu content, whereas the longitudinal one nearly stays constant. (Abstract Truncated)

  7. Growth and magnetic properties of IV-VI diluted magnetic semiconductor Ge{sub 1-x}Cr{sub x}Te

    SciTech Connect

    Fukuma, Y.; Taya, T.; Miyawaki, S.; Irisa, T.; Asada, H.; Koyanagi, T.

    2006-04-15

    IV-VI diluted magnetic semiconductor Ge{sub 1-x}Cr{sub x}Te films were grown on BaF{sub 2} substrates by molecular-beam epitaxy. The Ge{sub 1-x}Cr{sub x}Te film up to x=0.103 is single phase as determined by reflection high-energy electron diffraction and x-ray diffraction measurements. The optical band gap decreases with increasing Cr composition. Ferromagnetic order of the Ge{sub 1-x}Cr{sub x}Te films is characterized by direct magnetization and anomalous Hall effect measurements.

  8. Doppler tomography of the X-ray nova XTE J1118+480 in outburst and near quiescence

    NASA Astrophysics Data System (ADS)

    Torres, M. A. P.; Callanan, P. J.; Garcia, M. R.

    2002-01-01

    We present Doppler images of the more intense emission lines in the spectrum of the Black Hole X-ray Nova XTE J1118+480 during the 2000 outburst and near quiescence. Use of MOLLY, DOPPLER and TRAILER routines developed largely by T. R. Marsh is acknowledged.

  9. INTEGRAL Long-Term Monitoring of the Supergiant Fast X-Ray Transient XTE J1739-302

    NASA Technical Reports Server (NTRS)

    Blay, P.; Martinez-Nunez, S.; Negueruela, I.; Pottschmidt, K.; Smith, D. M.; Torrejon, J. M.; Reig, P.; Kretschmar, P.; Kreykenbohm, I.

    2008-01-01

    Context. In the past few years, a new class of High Mass X-Ray Binaries (HMXRB) has been claimed to exist, the Supergiant Fast X-ray Transients (SFXT). These are X-ray binary systems with a compact companion orbiting a supergiant star which show very short and bright outbursts in a series of activity periods overimposed on longer quiescent periods. Only very recently the first attempts to model the behaviour of these sources have been published, some of them within the framework of accretion from clumpy stellar winds. Aims. Our goal is to analyze the properties of XTE J1739-302/IGR J17391-3021 within the context of the clumpy structure of the supergiant wind. Methods. We have used INTEGRAL and RXTE/PCA observations in order to obtain broad band (1 - 200 keV) spectra and light curves of XTE J1739-302 and investigate its X-ray spectrum and temporal variability. Results. We have found that XTE J1739-302 follows a much more complex behaviour than expected. Far from presenting a regular variability pattern, XTE J1739-302 shows periods of high, intermediate, and low flaring activity.

  10. Looking into the Theory of Pulsar Accretion: The Case of XTE J1946+274

    NASA Astrophysics Data System (ADS)

    Marcu, Diana Monica; Pottschmidt, Katja; Kühnel, Matthias; Wolff, Michael Thomas; Becker, Peter A.; Müller, Sebastian; Hemphill, Paul Britton; Caballero, Isabel; Finger, Mark H.; Jenke, Peter; Wilson-Hodge, Colleen; Fuerst, Felix; Grinberg, Victoria; Kreykenbohm, Ingo; Klochkov, Dmitry; Rothschild, Richard E.; Terada, Yukikatsu; Enoto, Teruaki; Iwakiri, Wataru; Nakajima, Motoki; Wilms, Joern

    2014-08-01

    XTE J1946+274 is a transient accreting pulsar with a Be companion and a Cyclotron Resonance Scattering Feature (CRSF). It has been observed during several outbursts, with multiple instruments, and over a large range of luminosities. We extend previous studies to low flux using a Suzaku observation from the end of an outburst. This study focuses on the relationship between the cyclotron line energy and X-ray luminosity, which is believed to be linked to the physical processes occurring in the CRSF forming region. The physics of pulsar accretion, i.e., the process of plasma flow onto the neutron star surface, can be further constrained from its spectral properties. To this end, we discuss a new implementation of the physical continuum model developed by Becker and Wolff (2007, ApJ 654, 435). The model comprises Comptonized black body, bremsstrahlung, and cyclotron emission. We discuss preliminary results of applying the new tool to the test case of XTE J1946+274. We are working towards making this pulsar continuum model available in Xspec.

  11. Phonon Density of States and Heat Capacity of La$_{3-x}$Te$_4$

    SciTech Connect

    Delaire, Olivier A; May, Andrew F.; McGuire, Michael A; Porter, Wallace D; Lucas,; Stone, Matthew B; Abernathy, Douglas L; Snyder, G. J.

    2009-01-01

    The phonon density of states (DOS) of La$_{3-x}$Te$_4$ compounds ($x=0.0, 0.18, 0.32$) was measured at 300, 520, and 780$\\,$K, using inelastic neutron scattering. A significant stiffening of the phonon DOS, and a large broadening of features were observed upon introduction of vacancies on La sites (increasing $x$). Heat capacity measurements were performed at temperatures $~1.85 \\leqslant T \\leqslant 1200 \\,$K, and were analyzed to quantify the contributions of phonons and electrons. The Debye temperature and the electronic coefficient of heat capacity determined from these measurements are consistent with the neutron scattering results, and with previously reported first-principles calculations. Our results indicate that La vacancies in La$_{3-x}$Te$_4$ strongly scatter phonons, and this source of scattering appears to be independent of temperature. The stiffening of the phonon DOS induced by the introduction of vacancies is explained in terms of the electronic structure and the change in bonding. The temperature dependence of the phonon DOS is captured satisfactorily by the quasiharmonic approximation.

  12. Discovery of a Second Millesecond Accreting Pulsar: XTE J1751-305

    NASA Technical Reports Server (NTRS)

    Markwardt, C. B.; Swank, J. H.; Strohmayer, T. E.; intZand, J. J. M.; Marshall, F. E.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We report the discovery by the RXTE PCA of a second transient accreting millisecond pulsar, XTE J1751-305, during regular monitoring observations of the galactic bulge region. The pulsar has a spin frequency of 435 Hz, making it one of the fastest pulsars. The pulsations contain the signature of orbital Doppler modulation, which implies an orbital period of 42 minutes, the shortest orbital period of any known radio or X-ray millisecond pulsar. The mass function, f(sub x) = (1.278 +/- 0.003) x 10 (exp -6) solar mass, yields a minimum mass for the companion of between 0.013 and 0.0017 solar mass depending on the mass of the neutron star. No eclipses were detected. A previous X-ray outburst in June, 1998, was discovered in archival All-Sky Monitor data. Assuming mass transfer in this binary system is driven by gravitational radiation, we constrain the orbital inclination to be in the range 30 deg-85 deg and the companion mass to be 0.013-0.035 solar mass. The companion is most likely a heated helium dwarf. We also present results from the Chandra HRC-S observations which provide the best known position of XTE J1751-305.

  13. The variable spin-down rate of the transient magnetar XTE J1810-197

    NASA Astrophysics Data System (ADS)

    Pintore, Fabio; Bernardini, Federico; Mereghetti, Sandro; Esposito, Paolo; Turolla, Roberto; Rea, Nanda; Coti Zelati, Francesco; Israel, Gian Luca; Tiengo, Andrea; Zane, Silvia

    2016-05-01

    We have analysed XMM-Newton and Chandra observations of the transient magnetar XTE J1810-197 spanning more than 11 yr, from the initial phases of the 2003 outburst to the current quiescent level. We investigated the evolution of the pulsar spin period and we found evidence for two distinct regimes: during the outburst decay, dot{ν } was highly variable in the range -(2-4.5) × 10-13 Hz s-1, while during quiescence the spin-down rate was more stable at an average value of -1 × 10-13 Hz s-1. Only during ˜3000 d (from MJD 54165 to MJD 56908) in the quiescent stage it was possible to find a phase-connected timing solution, with dot{ν }=-4.9× 10^{-14} Hz s-1, and a positive second frequency derivative, ddot{ν }=1.8× 10^{-22} Hz s-2. These results are in agreement with the behaviour expected if the outburst of XTE J1810-197 was due to a strong magnetospheric twist.

  14. The Reawakening of the Sleeping X-ray Pulsar XTE J1946+274

    NASA Technical Reports Server (NTRS)

    Mueller, Sebastian; Mueller, Sebastian; Kuechnel, Matthias; Fuerst, Felix; Kreykenbohm, Ingo; Sagredo, Macarena; Obst, Maria; Wilms, Joern; Caballero, Isabel; Potttschmidt, Katja; Ferrigno, Carlo; Rothschild, Richard E.

    2012-01-01

    We report on a series of outbursts of the high mass X-ray binary XTE 11946+274 in 2010/2011 as observed with INTEGRAL, RXTE, and Swift. We discuss possible mechanisms resulting in the extraordinary outburst behavior of this source. The X-ray spectra can be described by standard phenomenological models, enhanced by an absorption feature of unknown origin at about 10 keV and a narrow iron K alpha fluorescence line at 6.4keV, which are variable in flux and pulse phase. We find possible evidence for the presence of a cyclotron resonance scattering feature at about 25 keV at the 93% level. The presence of a strong cyclotron line at 35 keV seen in data from the source's 1998 outburst and confirmed by a reanalysis of these data can be excluded. This result indicates that the cyclotron line feature in XTE 11946+274 is variable between individual outbursts.

  15. Doppler tomography of XTE J1118+480 revealing chromospheric emission from the secondary star

    NASA Astrophysics Data System (ADS)

    Zurita, C.; González Hernández, J. I.; Escorza, A.; Casares, J.

    2016-08-01

    Doppler tomography of emission lines in low-mass X-ray binaries allows us to investigate the structure and variability of the accretion discs as well as possible activity arising from the secondary stars. We present Doppler maps of the black hole binary XTE J1118+480 from spectra obtained using OSIRIS@GTC during quiescence on four different nights in 2011 and 2012. Doppler imaging of the Hα line shows, for the first time, a narrow component from the secondary star with observed equivalent widths varying in the range 1.2-2.9 Å but not correlated with the veiling of the accretion disc. The Hα flux of the secondary star is too large to be powered by X-ray irradiation, supporting chromospheric activity, possibly induced by rapid rotation, as the most likely origin of this feature in the black hole X-ray binary XTE J1118+480. In addition, we detect variations in the centroid of the Hα line on nightly basis. These are likely caused by a precessing accretion disc, although with a much lower amplitude (˜50 km s-1) than previously observed.

  16. Relativistic Iron Emission and Disk Reflection in Galactic Microquasar XTE J1748-288

    NASA Technical Reports Server (NTRS)

    Miller, J. M.; Fox, D. W.; DiMatteo, T.; Wijnands, R.; Belloni, T.; Pooley, D.; Kouveliotou, C.; Lewin, W. H. G.

    2001-01-01

    We report evidence for an Fe K-alpha fluorescence line feature and disk reflection in the very high, high-, and low-state X-ray spectra of the Galactic microquasar XTE J1748 - 288 during its 1998 June outburst. Spectral analyses are made on data gathered throughout the outburst by the Rossi X-Ray Timing Explorer Proportional Counter Array. Gaussian line, relativistic disk emission line, and ionized disk reflection models are fitted to the data. In the very high state the line profile appears strongly redshifted, consistent with disk emission from the innermost stable orbits around a maximally rotating Kerr black hole. In the high state the line profile is less redshifted and increasingly prominent. The low-state line profile is very strong (approx. 0.5 keV equivalent width) and centered at 6.7 +/- 0.10 keV; disk line emission model fits indicate that the inner edge of the disk fluctuates between approx. 20R(sub g) and - approx. 100R(sub g) in this state. The disk reflection fraction is traced through the outburst; reflection from an ionized disk is preferred in the very high and high states, and reflection from a relatively neutral disk is preferred in the low state. We discuss the implications of our findings for the binary system dynamics and accretion flow geometry in XTE J1748 - 288.

  17. Relativistic Iron Emission and Disk Reflection in Galactic Microquasar XTE J1748-288

    NASA Technical Reports Server (NTRS)

    Miller, J. M.; Fox, D. W.; Matteo, T. DI; Wijnands, R.; Belloni, T.; Pooley, D.; Kouveliotou, C.; Lewin, W. H. G.

    2001-01-01

    We report evidence for an Fe K(alpha) fluorescence line feature and disk reflection in the very high, high-, and low-state X-ray spectra of the Galactic microquasar XTE J1748-288 during its 1998 June outburst. Spectral analyses are made on data gathered throughout the outburst by the Rossi X-Ray Timing Explorer Proportional Counter Array. Gaussian line, relativistic disk emission line, and ionized disk reflection models are fitted to the data. In the very high state the line profile appears strongly redshifted, consistent with disk emission from the innermost stable orbits around a maximally rotating Kerr black hole. In the high state the line profile is less redshifted and increasingly prominent. The low-state line profile is very strong (approx. 0.5 keV equivalent width) and centered at 6.7 +/- 0.10 keV; disk line emission model fits indicate that the inner edge of the disk fluctuates between approx. 20Rg and approx. 100Rg in this state. The disk reflection fraction is traced through the outburst; reflection from an ionized disk is preferred in the very high and high states, and reflection from a relatively neutral disk is preferred in the low state. We discuss the implications of our findings for the binary system dynamics and accretion flow geometry in XTE J1748-288.

  18. Doppler tomography of XTE J1118+480 revealing chromospheric emission from the secondary star

    NASA Astrophysics Data System (ADS)

    Zurita, C.; González Hernández, J. I.; Escorza, A.; Casares, J.

    2016-05-01

    Doppler tomography of emission lines in low-mass X-ray binaries allows us to investigate the structure and variability of the accretion disks as well as possible activity arising from the secondary stars. We present Doppler maps of the black hole binary XTE J1118+480 from spectra obtained using OSIRIS@GTC during quiescence on four different nights in 2011 and 2012. Doppler imaging of the Hα line shows, for the first time, a narrow component from the secondary star with observed equivalent widths varying in the range 1.2-2.9 Å but not correlated with the veiling of the accretion disc. The Hα flux of the secondary star is too large to be powered by X-ray irradiation, supporting chromospheric activity, possibly induced by rapid rotation, as the most likely origin of this feature in the black hole X-ray binary XTE J1118+480. In addition, we detect variations in the centroid of the Hα line on nightly basis. These are likely caused by a precessing accretion disc, although with a much lower amplitude (˜50 km/s) than previously observed.

  19. Black Hole X Ray Nova Outburst with XTE and HST

    NASA Technical Reports Server (NTRS)

    Patterson, Joseph; Haswell, Carole

    1998-01-01

    We obtained multiwavelength coverage of the soft X-ray transient. GRO J1655-40 during its 1996 outburst, using HST (Hubble Space Telescope), RXTE (Rossi X Ray Timing Explorer), CGRO (Compton Gamma Ray Observatory), and ground-based facilities. This outburst was qualitatively different from other SXT (Soft X Ray Telescope) outbursts and from previous outbursts of this source. The onset of hard X-ray activity occurred very slowly, over several months, and was delayed relative to the soft X-ray rise. During this period, the optical fluxes declined steadily. This apparent anticorrelation is not consistent with with the standard disk instability model of SXT outbursts, nor is it expected if the optical output is dominated by reprocessed X-rays, as in persistent low-mass X-ray binaries. Based on the strength of the 2175-A interstellar absorption feature, we constrain the reddening to be E(B - V) = 1.2 plus or minus 0.1, a result which is consistent with the known properties of the source and with the strength of other interstellar absorption lines. After this dereddening we find that the spectra are dominated by a component peaking in the optical, with the expected v (sup l/3) disk spectrum seen only in the ultraviolet. Bowen fluorescence lines of NIII and OIII are also seen, as well as possible P Cyg profiles in the ultraviolet resonance lines. These features suggest an accretion-disk wind. The X-ray spectra broadly resemble the high/soft state commonly seen in black hole candidates, but evolve through two substates.

  20. CORRELATIONS IN HORIZONTAL BRANCH OSCILLATIONS AND BREAK COMPONENTS IN XTE J1701-462 AND GX 17+2

    SciTech Connect

    Bu, Qing-cui; Chen, Li; Zhang, Liang; Li, Zhao-sheng; Qu, Jin-lu; Belloni, T. M. E-mail: chenli@bnu.edu.cn E-mail: tomaso.belloni@brera.inaf.it

    2015-01-20

    We studied the horizontal branch oscillations (HBO) and the band-limited components observed in the power spectra of the transient neutron star low-mass X-ray binary XTE J1701-462 and the persistent ''Sco-like'' Z source GX 17+2. These two components were studied based on the state-resolved spectra. We found that the frequencies of XTE J1701-462 lie on the known correlations (WK and PBK), showing consistency with other types of X-ray binaries (black holes, atoll sources, and millisecond X-ray pulsars). However, GX 17+2 is shifted from the WK correlation like other typical Z sources. We suggest that the WK/PBK main track forms a boundary that separates persistent sources from transient sources. The characteristic frequencies of break and HBO are independent of accretion rate in both sources, though it depends on spectral models. We also report the energy dependence of the HBO and break frequencies in XTE J1701-462 and how the temporal properties change with spectral state in XTE J1701-462 and GX 17+2. We studied the correlation between rms at the break and the HBO frequency. We suggest that HBO and break components for both sources probably arise from a similar physical mechanism: Comptonization emission from the corona. These two components could be caused by the same kind of oscillation in a corona with uneven density, and they could be generated from different areas of the corona. We further suggest that different proportions of the Comptonization component in the total flux cause the different distribution between GX 17+2 and XTE J1701-462 in the rms{sub break}-rms{sub HBO} diagram.

  1. Correlations in Horizontal Branch Oscillations and Break Components in XTE J1701-462 and GX 17+2

    NASA Astrophysics Data System (ADS)

    Bu, Qing-cui; Chen, Li; Li, Zhao-sheng; Qu, Jin-lu; Belloni, T. M.; Zhang, Liang

    2015-01-01

    We studied the horizontal branch oscillations (HBO) and the band-limited components observed in the power spectra of the transient neutron star low-mass X-ray binary XTE J1701-462 and the persistent "Sco-like" Z source GX 17+2. These two components were studied based on the state-resolved spectra. We found that the frequencies of XTE J1701-462 lie on the known correlations (WK and PBK), showing consistency with other types of X-ray binaries (black holes, atoll sources, and millisecond X-ray pulsars). However, GX 17+2 is shifted from the WK correlation like other typical Z sources. We suggest that the WK/PBK main track forms a boundary that separates persistent sources from transient sources. The characteristic frequencies of break and HBO are independent of accretion rate in both sources, though it depends on spectral models. We also report the energy dependence of the HBO and break frequencies in XTE J1701-462 and how the temporal properties change with spectral state in XTE J1701-462 and GX 17+2. We studied the correlation between rms at the break and the HBO frequency. We suggest that HBO and break components for both sources probably arise from a similar physical mechanism: Comptonization emission from the corona. These two components could be caused by the same kind of oscillation in a corona with uneven density, and they could be generated from different areas of the corona. We further suggest that different proportions of the Comptonization component in the total flux cause the different distribution between GX 17+2 and XTE J1701-462 in the rmsbreak-rmsHBO diagram.

  2. Accretion flow behaviour during the evolution of the quasi-periodic oscillation frequency of XTE J1550-564 in 1998 outburst

    NASA Astrophysics Data System (ADS)

    Chakrabarti, Sandip K.; Dutta, Broja G.; Pal, P. S.

    2009-04-01

    Low and intermediate frequency quasi-periodic oscillations (QPOs) are thought to be due to oscillations of Comptonizing regions or hot regions embedded in Keplerian discs. Observational evidence of evolutions of QPOs would therefore be very important as they throw lights on the dynamics of the hotter region. Our aim is to find systems in which there is a well-defined correlation among the frequencies of the QPOs over a range of time so as to understand the physical picture. In this paper, we concentrate on the archival data of XTE J1550-564 obtained during 1998 outburst, and study the systematic drifts during the rising phase from the 1998 September 7 to the 1998 September 19, when the QPO frequency increased monotonically from 81mHz to 13.1Hz. Immediately after that, QPO frequency started to decrease and on the 1998 September 26, the QPO frequency became 2.62Hz. After that, its value remained almost constant. This frequency drift can be modelled satisfactorily with a propagatory oscillating shock solution where the post-shock region behaves as the Comptonized region. Comparing with the nature of a more recent 2005 outburst of another black hole candidate GRO 1655-40, where QPOs disappeared at the end of the rising phase, we conjecture that this so-called `outburst' may not be a full-fledged outburst.

  3. Tuning the composition of ternary Bi2Se3xTe3(1-x) nanoplates and their Raman scattering investigations

    NASA Astrophysics Data System (ADS)

    Wu, Peng; Chen, Haiping; Yang, Chao; Gan, Wei; Muhammad, Zahir; Song, Li

    2016-07-01

    We present the composition engineering and Raman scattering study of Bi2Se3xTe3(1-x) nanoplates that were synthesized by chemical vapor deposition method using different substrates, including fluorophlogopite mica, SiO2/Si. The characterizations revealed high crystallinity and layered-structure in the ternary Bi2Se3xTe3(1-x) products. Raman spectra of Bi2Se3xTe3(1-x) ranging from 80-200 cm-1 as a function of different Se-doping levels shows that intrinsic Raman peaks of Bi2Se3xTe3(1-x) nanoplates shift to higher frequency as the ratio of doped-Se increasing. The discontinuity of Raman peaks was found and discussed.

  4. A versatile 50 ft-lb-sec reaction wheel for TRMM and XTE missions

    NASA Astrophysics Data System (ADS)

    Bialke, Bill

    A 50 ft-lb-sec Reaction Wheel is being manufactured by ITHACO, Inc. for NASA's X-ray Timing Explorer (XTE) and Tropical Rainfall Measuring Mission (TRMM) missions, using the same mechanical assemblies as a similar Reaction Wheel developed by ITHACO for the Air Force's Advanced Research and Global Observation Satellite (ARGOS) (P91-1) mission. The versatile design allows variation in motor torque and speed capability with no mechanical modifications. State of the art ball bearing technology is combined with flight proven materials and conventional fabrication techniques to produce a relaible and manufacturable wheel assembly. An ironless armature brushless DC motor is incorporated for high efficiency and minimum weight. Comprehensive tradeoff analyses from the Reaction Wheel development are discussed for each component, and performance characteristics are presented for design variations from a high torque Reaction Wheel used in a three axis stabilized spacecraft to a low torque Momentum Wheel used in a momentum biased attitude Control System.

  5. Analysis of Cd{sub 1{minus}x}Zn{sub x}Te microstructure

    SciTech Connect

    Heffelfinger, J.R.; Medlin, D.L.; Yoon, H.; James, R.B.

    1997-08-01

    The microstructure and chemical inhomogeneities of commercially available Cd{sub 1{minus}x}Zn{sub x}Te (CZT) have been evaluated using electron microscopy and microanalytical techniques. Since imperfections, such as inclusions, cracks and extended crystallographic defects are known to affect the performance of CZT gamma-ray spectrometers, understanding the nature and origins of such imperfections is vital to the improvement of device performance. CZT that is grown using a high-pressure Bridgeman method has a polycrystalline microstructure that contains numerous grain boundaries, twins and inclusions. In this study, scanning electron microscopy and X-ray energy-dispersive spectroscopy were used to analyze inclusions and cracks inside CZT material. Such analysis found regions of material rich in C, O, Si, Zn and Te. Transmission electron microscopy revealed small subgrains and thin platelets of a second phase material located inside the large-grain CZT matrix. Details of these microstructural features and their possible origins are discussed.

  6. Gamma-ray polarization in accreting black holes: the case of XTE J1118+480

    NASA Astrophysics Data System (ADS)

    Vieyro, Florencia; Chaty, Sylvain; Romero, Gustavo E.

    2016-07-01

    Several black hole binaries (BHBs) present persistent soft gamma-ray emission (up to E ˜MeV). Although different models have been proposed to explain the origin of this component (non-thermal corona, relativistic jets), its nature still remains unknown. The detection of strong polarization at high-energies in the well-studied system Cygnus X-1 provides new constraints on the emitting region of the radiation. In this work we study the case of the BHB XTE J1118+480, a transient source that has been observed during two outbursts. In both cases multiwavelenght observations could be obtained because of the privileged location of the source, which implies low interstellar absorption. We apply a non-thermal lepto-hadronic coronal model to reproduce the X/γ-ray emission of this BHB during its outburts, and study the polarization of high-energy radiation expected for future episodes.

  7. SUBARCSECOND LOCATION OF IGR J17480-2446 WITH ROSSI XTE

    SciTech Connect

    Riggio, A.; Burderi, L.; Egron, E.; Di Salvo, T.; D'Ai, A.; Iaria, R.; Robba, N. R.; Papitto, A.; Belloni, T.; Motta, S.; Floris, M.; Testa, V.; Menna, M. T.

    2012-07-20

    On 2010 October 13, the X-ray astronomical satellite Rossi XTE, during the observation of the newly discovered accretion powered X-ray pulsar IGR J17480-2446, detected a lunar occultation of the source. From knowledge of the lunar topography and Earth, Moon, and spacecraft ephemerides at the epoch of the event, we determined the source position with an accuracy of 40 mas (1{sigma} c.l.), which is interesting, given the very poor imaging capabilities of RXTE ({approx}1 Degree-Sign ). For the first time, using a non-imaging X-ray observatory, the position of an X-ray source with a subarcsecond accuracy is derived, demonstrating the neat capabilities of a technique that can be fruitfully applied to current and future X-ray missions.

  8. Ultrafast Exciton Dynamics in CdxHg(1-x)Te alloy Quantum Dots

    NASA Astrophysics Data System (ADS)

    Leontiadou, Marina A.; Al-Otaify, Ali; Kershaw, Stephen V.; Zhovtiuk, Olga; Kalytchuk, Sergii; Mott, Derrick; Maenosono, Shinya; Rogach, Andrey L.; Binks, David J.

    2016-05-01

    Ultrafast transient absorption spectroscopy is used to investigate sub-nanosecond exciton dynamics in CdxHg(1-x)Te alloy colloidal quantum dots. A bleach was observed at the band gap due to state-filling, the mono-exponential decay of which had a characteristic lifetime of 91 ± 1 ps and was attributed to biexciton recombination; no evidence of surface-related trapping was observed. The rise time of the bleach, which is determined by the rate at which hot electrons cool to the band-edge, ranged between 1 and 5 ps depending on the pump photon energy. Measuring the magnitude of the bleach decay for different pump fluences and wavelengths allowed the quantum yield of multiple exciton generation to be determined, and was 115 ± 1% for pump photons with energy equivalent to 2.6 times the band gap.

  9. Joint BeppoSAX/RossiXTE Observation of Cygnus X-2

    NASA Astrophysics Data System (ADS)

    Piraino, S.; Santangelo, A.; Kaaret, P.

    2001-09-01

    We report on a joint BeppoSAX/RossiXTe observation of the Z-type low mass X-ray binary Cygnus X-2. The source was in the so-called high overall intensity state and in less than 24 hours went through all three branches of the Z-track. The continuum X-ray spectrum could be described by the absorbed sum of a soft thermal component and a Comptonized component. The timing power spectrum showed several components including QPO in the ranges 28-50 Hz while the source was on the horizontal branch (HBO). We found that the HBO frequency was well correlated with the parameters of soft thermal component in the X-ray spectrum.

  10. BLACK HOLE MASS AND SPIN FROM THE 2:3 TWIN-PEAK QPOs IN MICROQUASARS

    SciTech Connect

    Mondal, Soumen

    2010-01-10

    In the Galactic microquasars with double peak kHz quasi-periodic oscillations (QPOs) detected in X-ray fluxes, the ratio of the twin-peak frequencies is exactly, or almost exactly 2:3. This rather strongly supports the fact that they originate a few gravitational radii away from its center due to two modes of accretion disk oscillations. Numerical investigations suggest that post-shock matter, before they settle down in a subsonic branch, execute oscillations in the neighborhood region of 'shock transition'. This shock may excite QPO mechanism. The radial and vertical epicyclic modes of oscillating matter exactly match with these twin-peak QPOs. In fully general relativistic transonic flows, we investigate that shocks may form very close to the horizon around highly spinning Kerr black holes and appear as extremum in the inviscid flows. The extreme shock location provides upper limit of QPOs and hence fixes 'lower cutoff' of the spin. We conclude that the 2:3 ratio exactly occurs for spin parameters a >= 0.87 and almost exactly, for wide range of spin parameter, for example, XTE 1550-564, and GRO 1655-40 a>0.87, GRS 1915+105 a>0.83, XTE J1650-500 a>0.78, and H 1743-322 a>0.68. We also make an effort to measure unknown mass for XTE J1650-500(9.1 approx 14.1 M{sub sun}) and H 1743-322(6.6 approx 11.3 M{sub sun}).

  11. The formation of thermally evaporated stable Schottky barriers on p-ZnxPb(1-x)Te thin films

    NASA Astrophysics Data System (ADS)

    Khairnar, U. P.; Jadhav, S. R.

    2013-06-01

    Metal-semiconductor contacts are drawing increasing attention due to their potential for applications in devices and integrated circuits. Experimentally, lower barrier heights have been reported more often for metallic contacts on p-type semiconductors. Here we report our results regarding barrier heights of Ag/Au on p-ZnxPb(1-x)Te. The barrier heights can be perceived using data on the interface reaction and the phase formation in direct contacts with ZnxPb(1-x)Te. In such contacts which are normally thought to be responsible for the observation of low barrier heights on p-type semiconductor. Thermally stable Ag/Au-contacts with a barrier height of 0.56 eV were produced.

  12. Ion-implantation-induced damage and resonant levels in Pb/sub 1-x/Sn/sub x/Te

    SciTech Connect

    Gresslehner, K.H.; Palmetshofer, L.

    1980-09-01

    The dependence of the carrier concentration on the implantation dose and on the temperature was investigated in ion-implanted thin films of Pb/sub 1-x/Sn/sub x/Te (0< or =x<0.1). By assuming a twofold defect level in the conduction band we are able to fit the experimental results. With increasing tin content the energy of the defect level shifts towards the conduction-band edge. By extending the results to SnTe a general model for the understanding of the electrical properties of ion-implanted Pb/sub 1-x/Sn/sub x/Te (0< or =x< or =1) is suggested.

  13. Chemical analysis of anodic oxide layers based on Hg/sub 1-x/Cd/sub x/Te

    SciTech Connect

    Korsak, T.E.

    1987-02-01

    The goal of this work is to study the application of the photometric method in analyzing the composition of Hg/sub 1-x/Cd/sub x/Te solid solution anodic oxide with high accuracy and without preliminary separation of the elements. In order to determine cadmium content, a photometric measurement on a complex of this element with xylenol orange was used. Mercury concentration was determined using an extraction photometric method based on benzene extraction of chloride complexes of mercury anions with crystal violet. Tellurium content was determined by extraction with dichloroethane of bromide complexes of tellurium with diantipyrylpropylmethane. The authors synthesized diantipyrylpropylmethane as described. They studied single crystal Hg/sub 1-x/Cd/sub x/Te samples of random orientation with x = 0.2 and n-type conductivity.

  14. INTEGRAL measures the hard X-ray spectrum of the Be/X-ray binary XTE J1859+083

    NASA Astrophysics Data System (ADS)

    Malyshev, D.; Gotz, C. Ferrigno D.

    2015-04-01

    During the INTEGRAL observations performed from 2015 April 17, 19:47 to April 19, 20:01 UTC, the IBIS/ISGRI instrument detected a highly significant signal from a transient source, positionally coincident with the Be/X-ray pulsar XTE J1859+083 (ra, dec) = (284.78 ; 8.25) , which is reported to be in outburst since 2015-02-08 (ATeL #7034).

  15. Optical second-harmonic imaging of Pb{sub x}Cd{sub 1-x}Te ternary alloys

    SciTech Connect

    Scheidt, T.; Rohwer, E.G.; Bergmann, H.M. von; Saucedo, E.; Dieguez, E.; Fornaro, L.; Stafast, H.

    2005-05-15

    We employ femtosecond laser pulses (80 fs, 1.59 eV, and 80 MHz) to study the optical second-harmonic (SH) response of Pb{sub x}Cd{sub 1-x}Te ternary alloys (x about 0.2) grown by the vertical Bridgman method. The alloy segregates into a Pb-rich and a Cd-rich phase, the latter dominating the SH response of the ternary alloy by at least two orders of magnitude. Several sample regions show a regular layer-by-layer accommodation of the Pb-rich and Cd-rich phases as seen by a periodic alternation of the alloy's SH response on a {approx}10-{mu}m length scale. Furthermore, we employ polarization-resolved SH imaging as well as SH imaging at different azimuthal angles to obtain spatially resolved mappings of the sample, which are sensitive to the composition as well as the growth orientation of the Pb{sub x}Cd{sub 1-x}Te material system. We observe an azimuthal phase shift of approximately 30 deg. between coherent macroscopic regions (several mm{sup 2}) in the Cd-rich phase of the ternary alloy. We interpret these regions as large area crystalline grains of (111) and (411) crystal orientations and approximately equal composition. Hence, SH imaging is shown to spatially resolve regions of different growth directions within the Pb{sub x}Cd{sub 1-x}Te sample.

  16. Structural and chemical analysis of grain boundaries and tellurium precipitates in commercial Cd{sub 1{minus}x}Zn{sub x}Te

    SciTech Connect

    Heffelfinger, J.R.; Medlin, D.L.; James, R.B.

    1998-06-01

    The structure and chemistry of grain boundaries in commercial Cd{sub 1{minus}x}Zn{sub x}Te, prepared by the high-pressure Bridgman technique, have been analyzed using transmission electron microscopy, scanning electron microscopy, infrared-light microscopy and visible-light microscopy. These analyses show that the grain boundaries inside the Cd{sub 1{minus}x}Zn{sub x}Te materials are decorated with tellurium precipitates. Analysis of a tellurium precipitate at a grain boundary by transmission electron microscopy and selected-area electron diffraction found the precipitate to consist of a single, saucer-shaped grain. Electron diffraction from the precipitate was consistent with the trigonal phase of tellurium (space group P3{sub 1}21), which is the equilibrium phase at room temperature and atmospheric pressure. This precipitate was found to be aligned with one of the adjacent CZT grains such that the tellurium (0{bar 1}11) planes were nearly parallel to the CZT (111) planes. High-resolution transmission electron microscopy of the Te/Cd{sub 1{minus}x}Zn{sub x}Te interface showed no tertiary phase at the interface. The structures of the grain boundaries and the Te/Cd{sub 1{minus}x}Zn{sub x}Te interface are discussed and related to their possible implications on Cd{sub 1{minus}x}Zn{sub x}Te gamma-ray detector performance.

  17. Radio Disappearance of the Magnetar XTE J1810-197 and Continued X-ray Timing

    NASA Astrophysics Data System (ADS)

    Camilo, F.; Ransom, S. M.; Halpern, J. P.; Alford, J. A. J.; Cognard, I.; Reynolds, J. E.; Johnston, S.; Sarkissian, J.; van Straten, W.

    2016-04-01

    We report on timing, flux density, and polarimetric observations of the transient magnetar and 5.54 s radio pulsar XTE J1810-197 using the Green Bank, Nançay, and Parkes radio telescopes beginning in early 2006, until its sudden disappearance as a radio source in late 2008. Repeated observations through 2016 have not detected radio pulsations again. The torque on the neutron star, as inferred from its rotation frequency derivative \\dot{ν }, decreased in an unsteady manner by a factor of three in the first year of radio monitoring, until approximately mid-2007. By contrast, during its final year as a detectable radio source, the torque decreased steadily by only 9%. The period-averaged flux density, after decreasing by a factor of 20 during the first 10 months of radio monitoring, remained relatively steady in the next 22 months, at an average of 0.7 ± 0.3 mJy at 1.4 GHz, while still showing day-to-day fluctuations by factors of a few. There is evidence that during this last phase of radio activity the magnetar had a steep radio spectrum, in contrast to earlier flat-spectrum behavior. No secular decrease presaged its radio demise. During this time, the pulse profile continued to display large variations; polarimetry, including of a new profile component, indicates that the magnetic geometry remained consistent with that of earlier times. We supplement these results with X-ray timing of the pulsar from its outburst in 2003 up to 2014. For the first 4 years, XTE J1810-197 experienced non-monotonic excursions in frequency derivative by at least a factor of eight. But since 2007, its \\dot{ν } has remained relatively stable near its minimum observed value. The only apparent event in the X-ray record that is possibly contemporaneous with the radio shutdown is a decrease of ≈20% in the hot-spot flux in 2008-2009, to a stable, minimum value. However, the permanence of the high-amplitude, thermal X-ray pulse, even after the (unexplained) radio demise, implies

  18. Modification of band gap in surface layer in Cd 1-xZn xTe by YAG:Nd +3 laser radiation

    NASA Astrophysics Data System (ADS)

    Medvid, Artur; Fedorenko, Leonid L.; Korbutjak, Dmytro V.; Kryluk, Sergiy G.; Yusupov, Mikola M.; Mychko, Aleksandr

    2007-02-01

    A mechanism of formation of graded band-gap based on Thermogradient Effect (TGE) is proposed in Cd 1-xZn xTe at irradiation by second harmonic of a Q-switched YAG:Nd laser. According to the effect, the interstitial atoms of Cd (Cd i) in Cd 1-xZn xTe move along the temperature gradient while the Cd vacancies (V Cd) and Zn atoms - in the opposite direction, into the bulk of the semiconductor where temperature is lower. Photoluminescence (PL) spectra studied at 5 K show that concentration of Zn atoms increases due to aggregation of VCd with Zn after laser irradiation. Formation of a graded band-gap in Cd 1-xZn xTe crystal at irradiation by second harmonica of YAG:Nd laser by is shown to be possible.

  19. VLT spectroscopy of XTE J2123-058 during quiescence: the masses of the two components

    NASA Astrophysics Data System (ADS)

    Casares, J.; Dubus, G.; Shahbaz, T.; Zurita, C.; Charles, P. A.

    2002-01-01

    We present Very Large Telescope (VLT) low-resolution spectroscopy of the neutron star X-ray transient XTE J2123-058 during its quiescent state. Our data reveal the presence of a K7V companion which contributes 77 per cent to the total flux at λ6300 and orbits the neutron star at K2=287+/-12kms-1. Contrary to other soft X-ray transients (SXTs), the Hα emission is almost exactly in antiphase with the velocity curve of the optical companion. Using the light-centre technique we obtain K1=140+/-27kms-1 and hence q=K1/K2=M2/M1=0.49+/-0.10. This, combined with a previous determination of the inclination angle (i=73°+/-4°) yields M1=1.55+/-0.31Msolar and M2=0.76+/-0.22Msolar. M2 agrees well with the observed spectral type. Doppler tomography of the Hα emission shows a non-symmetric accretion disc distribution mimicking that seen in SW Sex stars. Although we find a large systemic velocity of - 110+/-8kms-1 this value is consistent with the galactic rotation velocity at the position of J2123-058, and hence a halo origin. The formation scenario of J2123-058 is still unresolved.

  20. On the Nature of XTE J0421+560/CI Cam

    NASA Technical Reports Server (NTRS)

    Belloni, T.; vandenAncker, M.; Dieters, S.; Fender, R.; Fox, D. W.; Kommers, J. M.; Lewin, W. H. G.; VanParadijs, J.

    1999-01-01

    We present the results of the analysis of RXTE, BATSE and optical/IR data of the 1998 outburst of the x-ray transient system XTE J0421+650. The x-ray outburst shows a very fast decay initial e-folding time approximately 0.5 days, slowing down to about 2.3 days). The X ray spectrum in the 2-25 keV band is thermal, softening considerably during decay. Intrinsic absorption is observed, also strongly variable. A strong iron line at around 6.7 keV is observed. No fast time variability is observed (<0.1 rms in the 1-4906 Hz band at peak). The analysis of optical/IR data suggest that the secondary is a b[e] star and place the system at a distance of about 2 kpc. At this distance the 2-25 keV luminosity is about 5 x 10(exp 37) erg/seconds. We compare the properties of this system with those of the Be/NS LMC transient A 0538-66 and suggest that CI cam is of a similar nature. The presence of strong radio emission during outburst indicates that the compact object could be a black hole.

  1. First Principles Calculations of Structural, Electronic, Thermodynamic and Thermal Properties of BaxSr1-xTe Ternary Alloys

    NASA Astrophysics Data System (ADS)

    Chelli, S.; Meradji, H.; Amara Korba, S.; Ghemid, S.; El Haj Hassan, F.

    2014-12-01

    The structural, electronic thermodynamic and thermal properties of BaxSr1-xTe ternary mixed crystals have been studied using the ab initio full-potential linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT). In this approach, the Perdew-Burke-Ernzerhof-generalized gradient approximation (PBE-GGA) was used for the exchange-correlation potential. Moreover, the recently proposed modified Becke Johnson (mBJ) potential approximation, which successfully corrects the band-gap problem was also used for band structure calculations. The ground-state properties are determined for the cubic bulk materials BaTe, SrTe and their mixed crystals at various concentrations (x = 0.25, 0.5 and 0.75). The effect of composition on lattice constant, bulk modulus and band gap was analyzed. Deviation of the lattice constant from Vegard's law and the bulk modulus from linear concentration dependence (LCD) were observed for the ternary BaxSr1-xTe alloys. The microscopic origins of the gap bowing were explained by using the approach of Zunger and co-workers. On the other hand, the thermodynamic stability of these alloys was investigated by calculating the excess enthalpy of mixing, ΔHm as well as the phase diagram. It was shown that these alloys are stable at high temperature. Thermal effects on some macroscopic properties of BaxSr1-xTe alloys were investigated using the quasi-harmonic Debye model, in which the phononic effects are considered.

  2. The neutron star transient XTE J1701-407 has returned to quiescence after a 3-year long outburst

    NASA Astrophysics Data System (ADS)

    Degenaar, N.; Wijnands, R.; Altamirano, D.; Cackett, E.; Linares, M.; Homan, J.; Fridriksson, J.

    2011-08-01

    The neutron star low-mass X-ray binary and long thermonuclear burst source XTE J1701-407 (ATel #1618) has been active ever since its discovery in 2008 June (ATel #1569), displaying a typical 2-10 keV luminosity of ~5E36 erg/s (assuming a distance D=5.0 kpc; ATel #2814). However, routine monitoring of the Galactic bulge with the PCA aboard RXTE (Swank & Markwardt 2001, ASP conference series 251, 94) indicates that the outburst has now ceased: the source intensity has remained below the detection limit of the PCA since 2011 August 9 (see the link provided below).

  3. Non-linear behaviour of XTE J1550-564 during its 1998-1999 outburst, revealed by recurrence analysis

    NASA Astrophysics Data System (ADS)

    Suková, Petra; Janiuk, Agnieszka

    2016-06-01

    We study the X-ray emission of the microquasar XTE J1550-564 and analyze the properties of its light curves using the recurrence analysis method. The indicators for non-linear dynamics of the accretion flow are found in the very high state and soft state of this source. The significance of deterministic variability depends on the energy band. We discuss the non-linear dynamics of the accretion flow in the context of the disc-corona geometry and propagating oscillations in the accretion flow.

  4. Terahertz radiation from Cd{sub x}Hg{sub 1-x}Te photoexcited by femtosecond laser pulses

    SciTech Connect

    Krotkus, A.; Adomavicius, R.; Molis, G.; Urbanowicz, A.; Eusebe, H.

    2004-10-01

    Terahertz radiation from Cd{sub x}Hg{sub 1-x}Te samples excited by femtosecond Ti:sapphire laser pulses were measured by using an ultrafast photoconductive antenna manufactured from low-temperature grown GaAs. Terahertz fields radiated by the samples of all three investigated alloy compositions with x=0, 0.2, and 0.3 were of the same order of magnitude. No azimuthal angle dependence of the radiated signal was detected, which evidences that linear current surge effect is dominating over nonlinear optical rectification.

  5. The multicolour optical monitoring of the High Mass X-ray Binary CI Cam/XTE J0421+560

    NASA Astrophysics Data System (ADS)

    Konstsntinova, T.; Larionov, V.; Kopatskaya, E.; Larionova, E.; Efimova, N.

    2014-07-01

    We analyse the photometric behaviour of the high-mass X-ray binary system CI Cam/XTE J0421+560. Our observations cover the time interval 1999-2014. The source was monitored with 70-cm AZT-8 (CrAO, Ukraine) and 0.4-m LX-200 (St.Petersburg, Russia) telescopes. During the monitoring period, CI Cam displayed two significant increases of brightness in the optical photometric bands. The first one follows the X-ray outburst that occurred in 1998 March. The second one started in 2013 and lasts until January - February of 2014.

  6. Implication of the Observable Spectral Cutoff Energy Evolution in XTE J1550-564

    NASA Technical Reports Server (NTRS)

    Titarchuk, Lev; Shaposhnikov, Nikolai

    2010-01-01

    The physical mechanisms responsible for production of the non-thermal emission in accreting black holes should be imprinted in the observational appearances of the power law tails in the X-ray spectra from these objects. Variety of spectral states observed from galactic black hole binaries by it Rossi X-ray Timing Explorer (RXTE) allow examination of the photon upscattering under different accretion regimes. We revisit of RXTE data collected from the black hole X-ray binary XTE J1550-564 during two periods of X-ray activity in 1998 and 2000 focusing on the behavior of the high energy cutoff of the power law part of the spectrum. For the 1998 outburst the Iran- sition from the low-hard state to the intermediate state was accompanied by a gradual decrease in the cutoff energy which then showed a sharp reversal to a clear increasing trend during the further evolution towards the very high and high-soft states. However, the 2000 outburst showed only the decreasing part of this pattern. Notably, the photon indexes corresponding to the cutoff increase for the 1998 event are much higher than the index values reached during the 2000 rise transition. We attribute this difference in the cutoff' energy behav- for to the different partial contributions of the thermal and non-thermal (bulk motion) Comptonization in photon upscattering. Namely, during the 1998 event the higher accretion rate presumably provided more cooling to the Comptonizing media and thus reducing the effectiveness of the thermal upscattering process. Under these conditions the bulk motion takes a leading role in boosting the input soft photons. Monte Carlo simulations of the The physical mechanisms responsible for production of the non-thermal emission in accreting black holes should be imprinted in the observational apperances of the power law tails in the X-ray spectra from these objects. Variety of spectral states observed from galactic black hole binaries by it Rossi X-ray Timing Explorer (RXTE) allow

  7. Implication of the Observed Spectral Cutoff Energy Evolution in XTE J1550-564

    NASA Astrophysics Data System (ADS)

    Titarchuk, Lev; Shaposhnikov, Nikolai

    2010-12-01

    The physical mechanisms responsible for the production of non-thermal emission in accreting black holes (BHs) should be imprinted in the observational appearances of the power-law tails in the X-ray spectra from these objects. Phenomenology of different spectral states exhibited by galactic BH binaries allows us to establish the physics of the photon upscattering under different accretion regimes. We revisit the data collected by the Rossi X-ray Timing Explorer from the BH X-ray binary XTE J1550-564 during two periods of X-ray activity in 1998 and 2000 focusing on the behavior of the high-energy cutoff of the power-law part of the spectrum. For the 1998 outburst, the transition from the low-hard state to the intermediate state was accompanied by a gradual decrease in the cutoff energy. This was followed by an extended minimum which then showed an abrupt reversal to a clear increasing trend as the source evolved to the very high and high-soft states. The 2000 outburst showed only the decreasing and extended minimum portions of this pattern. We attribute this difference in the cutoff energy behavior to the different partial contributions of the thermal and non-thermal (bulk motion) Comptonization. Namely, during the 1998 event the higher accretion rate presumably provided more cooling to the Comptonizing media and thus reducing the effectiveness of the thermal upscattering process. Under these conditions, the bulk motion takes a leading role in boosting the input soft photons. Recent Monte Carlo simulations by Laurent & Titarchuk strongly support this scenario.

  8. Cd{sub 1−x}Mn{sub x}Te ultrasmall quantum dots growth in a silicate glass matrix by the fusion method

    SciTech Connect

    Dantas, Noelio Oliveira; Lima Fernandes, Guilherme de; Almeida Silva, Anielle Christine; Baffa, Oswaldo; Gómez, Jorge Antônio

    2014-09-29

    In this study, we synthesized Cd{sub 1−x}Mn{sub x}Te ultrasmall quantum dots (USQDs) in SiO{sub 2}-Na{sub 2}CO{sub 3}-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3} glass system using the fusion method. Growth of these Cd{sub 1−x}Mn{sub x}Te USQDs was confirmed by optical absorption, atomic force microscopy (AFM), magnetic force microscopy (MFM), scanning transmission electron microscopy (TEM), and electron paramagnetic resonance (EPR) measurements. The blueshift of absorption transition with increasing manganese concentration gives evidence of incorporation of manganese ions (Mn{sup 2+}) in CdTe USQDs. AFM, TEM, and MFM confirmed, respectively, the formation of high quality Cd{sub 1−x}Mn{sub x}Te USQDs with uniformly distributed size and magnetic phases. Furthermore, EPR spectra showed six lines associated to the S = 5/2 spin half-filled d-state, characteristic of Mn{sup 2+}, and confirmed that Mn{sup 2+} are located in the sites core and surface of the CdTe USQD. Therefore, synthesis of high quality Cd{sub 1−x}Mn{sub x}Te USQDs may allow the control of optical and magnetic properties.

  9. Type I X-ray Bursts from the Neutron-star Transient XTE J1701-462

    NASA Astrophysics Data System (ADS)

    Lin, Dacheng; Altamirano, Diego; Homan, Jeroen; Remillard, Ronald A.; Wijnands, Rudy; Belloni, Tomaso

    2009-07-01

    The neutron-star X-ray transient XTE J1701-462 was observed for ~3 Ms with RXTE during its 2006-2007 outburst. Here we report on the discovery of three type-I X-ray bursts from XTE J1701-462. They occurred as the source was in transition from the typical Z-source behavior to the typical atoll-source behavior, at ~10% of the Eddington luminosity. The first burst was detected in the Z-source flaring branch (FB); the second in the vertex between the FB and normal branches; and the third in the atoll-source soft state. The detection of the burst in the FB cast doubts on earlier speculations that the FB is due to unstable nuclear burning of accreted matter. The last two of the three bursts show photospheric radius expansion, from which we estimate the distance to the source to be 8.8 kpc with a 15% uncertainty. No significant burst oscillations in the range 30-4000 Hz were found during these three bursts.

  10. Prediction of an arc-tunable Weyl Fermion metallic state in MoxW1-xTe2

    NASA Astrophysics Data System (ADS)

    Chang, Tay-Rong; Xu, Su-Yang; Chang, Guoqing; Lee, Chi-Cheng; Huang, Shin-Ming; Wang, Baokai; Bian, Guang; Zheng, Hao; Sanchez, Daniel; Belopolski, Ilya; Alidoust, Nasser; Neupane, Madhab; Bansil, Arun; Jeng, Horng-Tay; Lin, Hsin; Hasan, M. Zahid

    A Weyl semimetal is a new state of matter that hosts Weyl fermions as emergent quasiparticles. The Weyl fermions correspond to isolated points of bulk band degeneracy, Weyl nodes, which are connected only through the crystal's boundary by an exotic Fermi arc surface state. The length of the Fermi arc gives a measure of the topological strength, because the only way to destroy the Weyl nodes is to annihilate them in pairs in k space. To date, Weyl semimetals are only realized in the TaAs class. Here, we propose a tunable Weyl metallic state in MoxW1-xTe2 via our first-principles calculations, where the Fermi arc length can be continuously changed as a function of Mo concentration, thus tuning the topological strength of the system. Our results provide an experimentally feasible route to realizing Weyl physics in the layered compound MoxW1-xTe2 where non-saturating magneto-resistance and pressure driven superconductivity have been observed.

  11. Prediction of an arc-tunable Weyl Fermion metallic state in MoxW1-xTe2

    NASA Astrophysics Data System (ADS)

    Chang, Tay-Rong; Xu, Su-Yang; Chang, Guoqing; Lee, Chi-Cheng; Huang, Shin-Ming; Wang, Baokai; Bian, Guang; Zheng, Hao; Sanchez, Daniel S.; Belopolski, Ilya; Alidoust, Nasser; Neupane, Madhab; Bansil, Arun; Jeng, Horng-Tay; Lin, Hsin; Zahid Hasan, M.

    2016-02-01

    A Weyl semimetal is a new state of matter that hosts Weyl fermions as emergent quasiparticles. The Weyl fermions correspond to isolated points of bulk band degeneracy, Weyl nodes, which are connected only through the crystal's boundary by exotic Fermi arcs. The length of the Fermi arc gives a measure of the topological strength, because the only way to destroy the Weyl nodes is to annihilate them in pairs in the reciprocal space. To date, Weyl semimetals are only realized in the TaAs class. Here, we propose a tunable Weyl state in MoxW1-xTe2 where Weyl nodes are formed by touching points between metallic pockets. We show that the Fermi arc length can be changed as a function of Mo concentration, thus tuning the topological strength. Our results provide an experimentally feasible route to realizing Weyl physics in the layered compound MoxW1-xTe2, where non-saturating magneto-resistance and pressure-driven superconductivity have been observed.

  12. Quantum-interference effects in single- and poly-crystalline topological insulator Bi2-xTe3

    NASA Astrophysics Data System (ADS)

    Chiu, Shao-Pin; Lin, Juhn-Jong

    2014-03-01

    We have studied the carrier transport properties of both single- and poly-crystalline topological insulator (TI) Bi2-xTe3 samples. Single-crystalline microflakes were made by exfoliation from a single-crystalline Bi2Te3 bulk. Polycrystalline samples were made by flash evaporation of 5N purity Bi2Te3 sheets. In single-crystalline Bi2Te3 microflakes, temperature dependent resistances revealed two-dimensional (2D) electron-electron interaction effect. The extracted Coulomb screening parameter is negative, in accord with the situation of strong spin-orbit coupling in the TI materials. Positive magnetoresistances (MRs) originated from 2D weak-antilocalization (WAL) effect were measured in low magnetic fields, and satisfactorily described by a multichannel-conduction model. Especially, as T below 1 K and under high positive backgate voltages, signature of two coherent conduction channels was found. We discuss our results in terms of Dirac fermion states on the bottom surface, in addition to the bulk states. Polycrystalline Bi2-xTe3 thin films were patterned by electron-beam lithography. In low perpendicular magnetic fields, positive MRs due to the 2D WAL effect were observed. In parallel magnetic fields, Aharonov-Bohm oscillations were measured, suggesting the presence of metallic surface states. This work was supported by the Taiwan National Science Council through Grant No. NSC102-2120-M-009-003 (J.J.L.).

  13. Prediction of an arc-tunable Weyl Fermion metallic state in Mo(x)W(1-x)Te2.

    PubMed

    Chang, Tay-Rong; Xu, Su-Yang; Chang, Guoqing; Lee, Chi-Cheng; Huang, Shin-Ming; Wang, BaoKai; Bian, Guang; Zheng, Hao; Sanchez, Daniel S; Belopolski, Ilya; Alidoust, Nasser; Neupane, Madhab; Bansil, Arun; Jeng, Horng-Tay; Lin, Hsin; Zahid Hasan, M

    2016-01-01

    A Weyl semimetal is a new state of matter that hosts Weyl fermions as emergent quasiparticles. The Weyl fermions correspond to isolated points of bulk band degeneracy, Weyl nodes, which are connected only through the crystal's boundary by exotic Fermi arcs. The length of the Fermi arc gives a measure of the topological strength, because the only way to destroy the Weyl nodes is to annihilate them in pairs in the reciprocal space. To date, Weyl semimetals are only realized in the TaAs class. Here, we propose a tunable Weyl state in Mo(x)W(1-x)Te2 where Weyl nodes are formed by touching points between metallic pockets. We show that the Fermi arc length can be changed as a function of Mo concentration, thus tuning the topological strength. Our results provide an experimentally feasible route to realizing Weyl physics in the layered compound Mo(x)W(1-x)Te2, where non-saturating magneto-resistance and pressure-driven superconductivity have been observed. PMID:26875819

  14. Reflection Spectroscopy of the Black Hole Binary XTE J1752-223 in the Bright Hard State

    NASA Astrophysics Data System (ADS)

    Garcia, Javier; Steiner, James F.; Grinberg, Victoria; McClintock, Jeffrey E.; Dauser, Thomas; Remillard, Ronald A.

    2016-04-01

    During its rise to maximum in 2009, XTE J1752-223 stalled for a full month in the bright hard state at about 30% of its peak (Eddington) luminosity. Along this extended period, 60 RXTE pointed observations showed the luminosity and hardness ratio of the source to be extraordinarily stable, resulting in a unique data set of exceptional quality. We combined all these 300 ks of RXTE data into a single PCA (3-45 keV) spectrum with 82 million counts and a single HEXTE spectrum (20-250 keV) with 10.4 million counts. Using our calibration tools PCACORR and HEXBCORR, we greatly enhanced the sensitivity of the detectors to faint spectral features, such as the Fe line and edge. Fitting the PCA+HEXTE spectrum using an advanced version of our reflection code, which includes a physical model of Comptonization, we constrained: the spin of the black hole (or alternatively the inner radius of the accretion disk); the inclination of the system; the ionization state and Fe abundance of the disk's atmosphere; and the temperature and optical depth of the corona. We compare these results with similar ones we reported earlier for GX 339-4 in the bright hard state. XTE J1752-223 and GX 339-4 are the first two of 29 black hole binaries we propose to study using recalibrated RXTE archival data and our reflection models.

  15. Ferromagnetism in Ge{sub 1-x}Cr{sub x}Te epilayers grown by molecular beam epitaxy

    SciTech Connect

    Fukuma, Y.; Asada, H.; Taya, T.; Irisa, T.; Koyanagi, T.

    2006-10-09

    IV-VI ferromagnetic semiconductor Ge{sub 1-x}Cr{sub x}Te has been grown on BaF{sub 2} (111) by molecular beam epitaxy. The ferromagnetism was clearly established by direct magnetization and Hall measurements. The experimental correlation between the anomalous Hall resistivity {rho}{sub xy} and the resistivity {rho}{sub xx}, {rho}{sub xy}{proportional_to}{rho}{sub xx}{sup 1.76}, is understood from the semiclassical nature of the charge carrier dynamics, suggesting that the ferromagnetism gives rise to p-d exchange interaction. The Curie temperature increases systematically from the substrate temperature T{sub S} of 300 to 250 to 200 deg. C and with increasing the Cr composition along with each T{sub S}.

  16. IV-VI diluted magnetic semiconductor Ge{sub 1-x}Mn{sub x}Te epilayer grown by molecular beam epitaxy

    SciTech Connect

    Fukuma, Y.; Goto, K.; Senba, S.; Miyawaki, S.; Asada, H.; Koyanagi, T.; Sato, H.

    2008-03-01

    Growth of the IV-VI diluted magnetic semiconductor Ge{sub 1-x}Mn{sub x}Te by molecular beam epitaxy is reported. The epitaxial growth of Ge{sub 1-x}Mn{sub x}Te (x=0.13) on BaF{sub 2} (111) with a GeTe buffer layer is confirmed by x-ray diffraction and reflection high-energy electron diffraction. The ferromagnetic order is clearly established by the magnetization and magnetotransport measurements. The Curie temperature of 100 K is obtained for the hole concentration of 7.86x10{sup 20} cm{sup -3}. The existence of the strong p-d exchange which gives rise to the ferromagnetic order is revealed by the hard x-ray photoemission measurements.

  17. Photovoltaic performances of Cu2-xTe sensitizer based on undoped and indium(3+)-doped TiO2 photoelectrodes and assembled counter electrodes.

    PubMed

    Srathongluan, Pornpimol; Kuhamaneechot, Rattanakorn; Sukthao, Prapatsawan; Vailikhit, Veeramol; Choopun, Supab; Tubtimtae, Auttasit

    2016-02-01

    Novel binary Cu2-xTe nanoparticles based on undoped and indium-doped TiO2 photoelectrodes were synthesized using a successive ionic layer adsorption and reaction (SILAR) technique as a sensitizer for liquid-junction solar cells. A larger diameter of TiO2 promoted a narrower energy band gap after indium doping, attributing to yield a broader absorption range of nanoparticle sensitizer due to the increasing amount of Cu2-xTe NPs on TiO2 surface. The atomic percentages showed the stoichiometric formation of Cu2Te incorporated in a Cu2-xTe structure. The best photovoltaic performance with the lower SILAR cycle, i.e., n=13 was performed after indium doping in both of carbon and Cu2S CEs and revealed that the efficiency of 0.73% under the radiant 100mW/cm(2) (AM 1.5G). The electrochemical impedance spectroscopy (EIS) was used to investigate the electrical properties via effect of material doping and counter electrodes with a lower charge-transfer resistance (Rct) and it was also found that the electron lifetime was improved after the sample doped with indium and assembled with carbon CE. PMID:26524258

  18. Charge Mediated Reversible Metal-Insulator Transition in Monolayer MoTe2 and WxMo1-xTe2 Alloy.

    PubMed

    Zhang, Chenxi; Kc, Santosh; Nie, Yifan; Liang, Chaoping; Vandenberghe, William G; Longo, Roberto C; Zheng, Yongping; Kong, Fantai; Hong, Suklyun; Wallace, Robert M; Cho, Kyeongjae

    2016-08-23

    Metal-insulator transitions in low-dimensional materials under ambient conditions are rare and worth pursuing due to their intriguing physics and rich device applications. Monolayer MoTe2 and WTe2 are distinguished from other TMDs by the existence of an exceptional semimetallic distorted octahedral structure (T') with a quite small energy difference from the semiconducting H phase. In the process of transition metal alloying, an equal stability point of the H and the T' phase is observed in the formation energy diagram of monolayer WxMo1-xTe2. This thermodynamically driven phase transition enables a controlled synthesis of the desired phase (H or T') of monolayer WxMo1-xTe2 using a growth method such as chemical vapor deposition (CVD) and molecular beam epitaxy (MBE). Furthermore, charge mediation, as a more feasible method, is found to make the T' phase more stable than the H phase and induce a phase transition from the H phase (semiconducting) to the T' phase (semimetallic) in monolayer WxMo1-xTe2 alloy. This suggests that a dynamic metal-insulator phase transition can be induced, which can be exploited for rich phase transition applications in two-dimensional nanoelectronics. PMID:27415610

  19. Detection of a large Be circumstellar disk during X-ray quiescence of XTE J1946+274

    NASA Astrophysics Data System (ADS)

    Özbey Arabacı, M.; Camero-Arranz, A.; Zurita, C.; Gutiérrez-Soto, J.; Nespoli, E.; Suso, J.; Kiaeerad, F.; García-Rojas, J.; Kızıloǧlu, Ü.

    2015-10-01

    Aims: We present a multiwavelength study of the Be/X-ray binary system XTE J1946+274 with the main goal of better characterizing its behavior during X-ray quiescence. We also aim to shed light on the possible mechanisms which trigger the X-ray activity for this source. Methods: XTE J1946+274 was observed by Chandra-ACIS during quiescence in 2013 March 12. In addition, this source has been monitored from the ground-based astronomical observatories of El Teide (Tenerife, Spain), Roque de los Muchachos (La Palma, Spain) and Sierra Nevada (Granada, Spain) since 2011 September, and from the TÜBİTAK National Observatory (Antalya, Turkey) since 2005 April. We have performed spectral and photometric temporal analyses in order to investigate the quiescent state and transient behavior of this binary system. Results: Our optical study revealed that a long mass ejection event from the Be star took place in 2006, lasting for about seven years, and another one is currently ongoing. We also found that a large Be circumstellar disk is present during quiescence, although major X-ray activity is not observed. We made an attempt to explain this by assuming the permanently presence of a tilted (sometimes warped) Be decretion disk. The 0.3-10 keV X-ray spectrum of the neutron star during quiescence was well fitted with either an absorbed black-body or an absorbed power-law models. The main parameters obtained for these models were kT = 1.43 ± 0.17 and Γ = 0.9 ± 0.4 (with NH ~ 2-7 × 1022 cm-2). The 0.3-10 keV flux of the source was ~0.8-1 × 10-12 erg-1 cm-2 s-1. Pulsations were found with Ppulse = 15.757(1) s (epoch MJD 56 363.115) and an rms pulse fraction of 32.1(3)%. The observed X-ray luminosity during quiescent periods was close to that of expected in supersonic propeller regimen.

  20. Teaching "Candide": A Debate.

    ERIC Educational Resources Information Center

    Braun, Theodore E. D.; And Others

    1988-01-01

    Two different approaches to teaching Voltaire's "Candide", one deriving meaning from the textual fabric or "inside" of the story and the other focusing on the author's "external" intent in writing the story, are presented and compared. (MSE)

  1. Excitation of a non-radial mode in a millisecond X-ray pulsar XTE J1751-305

    NASA Astrophysics Data System (ADS)

    Lee, Umin

    2014-08-01

    We discuss non-radial modes in mass-accreting and rapidly rotating neutron stars for the coherent frequency detected in a millisecond X-ray pulsar XTE J1751-305. The spin frequency of the pulsar is νspin ≅ 435 Hz and the identified frequency is νosc = 0.572 7595 × νspin. Assuming that the frequency detected is that in the corotating frame of the star, we examine r and g modes in the surface layer of accreting matter composed mostly of helium, inertial and r modes in the fluid core, and toroidal modes in the solid crust. We find that the r modes of l' = m = 1 and 2 excited by ɛ-mechanism in the surface layer can give the ratio κ = νosc/νspin ≃ 0.57 at νspin = 435 Hz, where m and l' are the azimuthal wavenumber and the harmonic degree of the modes. We also suggest a toroidal crust mode and a core r mode destabilized by gravitational wave emission for the observed ratio κ. We find that the amplitude of the core r mode of l' = m = 2 can be amplified at the surface layer by a large factor famp ˜ 102 at νspin = 435 Hz for a M = 1.4 M⊙ neutron-star model. This amplification, however, may not be large enough for the r-mode amplitude to be consistent with an estimation by Mahmoodifar & Strohmayer (2013).

  2. ACCRETION TORQUES AND MOTION OF THE HOT SPOT ON THE ACCRETING MILLISECOND PULSAR XTE J1807-294

    SciTech Connect

    Patruno, Alessandro; Wijnands, R.; Van der Klis, Michiel; Hartman, Jacob M.; Chakrabarty, Deepto

    2010-07-10

    We present a coherent timing analysis of the 2003 outburst of the accreting millisecond pulsar (AMXP) XTE J1807-294. We find a 95% confidence interval for the pulse frequency derivative of (+0.7, + 4.7) x 10{sup -14} Hz s{sup -1} and (-0.6, + 3.8) x 10{sup -14} Hz s{sup -1} for the fundamental and second harmonics, respectively. The sinusoidal fractional amplitudes of the pulsations are the highest observed among AMXPs and can reach values of up to 27% (2.5-30 keV). The pulse arrival time residuals of the fundamental frequency follow a linear anti-correlation with the fractional amplitudes that suggests hot spot motion both in longitude and latitude over the surface of the neutron star. An anti-correlation between residuals and X-ray flux suggests an influence of the accretion rate on pulse phase and casts doubts on the interpretation of pulse frequency derivatives in terms of changes of spin rates and torques on the neutron star.

  3. Optical properties of Ge xSb 20- xTe 80 thin films and their changes by light illumination

    NASA Astrophysics Data System (ADS)

    Pamukchieva, V.; Szekeres, A.

    2008-03-01

    The influence of light illumination on the optical constants of chalcogenide thin films with non-stoichiometric Ge xSb 20- xTe 80 ( x = 15, 17, 19) composition is studied by spectral ellipsometry in the visible range of light. The films were deposited onto glass substrates by vacuum thermal evaporation of parent glasses and were subjected to an 1-h illumination with a 500 W HBO mercury lamp. It has been established that illumination of the films leads to a decrease of the refractive index, n, in the whole spectral region studied and to an increase of the extinction coefficient, k, in the range of 600-800 nm. The optical bandgap energy Eg values are within 0.55-0.76 eV with a tendency to increase with increasing the Ge content. Illumination resulted in a sharp decrease of the Eg values indicating structural change in the films. Leaving the films at atmospheric conditions the optical parameters values change toward their initial values of unilluminated state.

  4. Candidate CDTI procedures study

    NASA Technical Reports Server (NTRS)

    Ace, R. E.

    1981-01-01

    A concept with potential for increasing airspace capacity by involving the pilot in the separation control loop is discussed. Some candidate options are presented. Both enroute and terminal area procedures are considered and, in many cases, a technologically advanced Air Traffic Control structure is assumed. Minimum display characteristics recommended for each of the described procedures are presented. Recommended sequencing of the operational testing of each of the candidate procedures is presented.

  5. Deposition and characterization of Cd{sub 1−x}Mg{sub x}Te thin films grown by a novel cosublimation method

    SciTech Connect

    Kobyakov, Pavel S. Swanson, Drew E.; Sampath, Walajabad S.; Moore, Andrew; Raguse, John M.

    2014-03-15

    Photovoltaic cells utilizing the CdS/CdTe structure have improved substantially in the past few years. Despite the recent advances, the efficiency of CdS/CdTe cells is still significantly below their Shockley–Queisser limit. CdTe based ternary alloy thin films, such as Cd{sub 1−x}Mg{sub x}Te (CMT), could be used to improve efficiency of CdS/CdTe photovoltaic cells. Higher band gap Cd{sub 1−x}Mg{sub x}Te films can be the absorber in top cells of a tandem structure or an electron reflector layer in CdS/CdTe cells. A novel cosublimation method to deposit CMT thin films has been developed. This method can deposit CMT films of band gaps ranging from 1.5 to 2.3 eV. The cosublimation method is fast, repeatable, and scalable for large areas, making it suitable for implementing into large-scale manufacturing. Characterization of as-deposited CMT films, with x varying from 0 to 0.35, reveals a linear relationship between Mg content measured by energy dispersive x-ray spectroscopy and the optical band gap. Glancing angle x-ray diffraction (GAXRD) measurements of Cd{sub 1−x}Mg{sub x}Te films show a zinc-blende structure similar to CdTe. Furthermore, increasing Mg content decreases the lattice parameter and the grain size. GAXRD shows the films are under mild tension after deposition.

  6. MAXI/GSC detection of renewed X-ray activity of the neutron star X-ray binary XTE J1709-267

    NASA Astrophysics Data System (ADS)

    Nakahira, S.; Matsuoka, T. Mihara M.; Negoro, H.; Ueno, S.; Tomida, H.; Ishikawa, M.; Nakagawa, Y. E.; Sugawara, Y.; Sugizaki, M.; Serino, M.; Iwakiri, W.; Shidatsu, M.; Sugimoto, J.; Takagi, T.; Kawai, N.; Isobe, N.; Sugita, S.; Yoshii, T.; Tachibana, Y.; Ono, Y.; Fujiwara, T.; Yoshida, A.; Sakamoto, T.; Kawakubo, Y.; Kitaoka, Y.; Tsunemi, H.; Shomura, R.; Nakajima, M.; Tanaka, K.; Masumitsu, T.; Kawase, T.; Ueda, Y.; Kawamuro, T.; Hori, T.; Tanimoto, A.; Tsuboi, Y.; Nakamura, Y.; Sasaki, R.; Yamauchi, M.; Furuya, K.; Yamaoka, K.

    2016-06-01

    We report on a detection of X-ray outburst from XTE J1709-267 triggered by the MAXI/GSC nova alert system at 12:25 on 2016 May 31. The MAXI/GSC 2-6 keV X-ray flux on May 31 is 210 mCrab, which is brighter than the peak flux of the previous outburst in July 2012 (160 mCrab in 2-6 keV; Atel #5319, Asai, K. et al, PASJ 67, 92, 2015).

  7. Formation of acceptor centers under the action of redox media on the surface of Cd{sub x}Hg{sub 1-x}Te films

    SciTech Connect

    Varavin, V. S.; Sidorov, G. Yu.

    2009-12-15

    The effect of redox media on the formation of acceptor centers in the Cd{sub x}Hg{sub 1-x}Te films grown by molecular beam epitaxy on the GaAs (301) substrates is studied. When tested for long-term stability, the untreated n-type films do not change their parameters, whereas the treated films exhibit a decrease in the conductivity and the mobility of charge carriers by nearly two orders of magnitude. It is shown that, on the treatments, a source of acceptors is formed at the surface, and the acceptors are most likely mercury vacancies.

  8. Analysis of variability in the burst oscillations of the accreting millisecond pulsar XTE J1814-338

    NASA Technical Reports Server (NTRS)

    Watts, Anna L.; Strohmayer, Tod E.; Markwardt, Craig B.

    2005-01-01

    The accreting millisecond pulsar XTE J1814-338 exhibits oscillations at the known spin frequency during Type I X-ray bursts. The properties of the burst oscillations reflect the nature of the thermal asymmetry on the stellar surface. We present an analysis of the variability of the burst oscillations of this source, focusing on three characteristics: fractional amplitude, harmonic content and frequency. Fractional amplitude and harmonic content constrain the size, shape and position of the emitting region, whilst variations in frequency indicate motion of the emitting region on the neutron star surface. We examine both long-term variability over the course of the outburst, and short-term variability during the bursts. For most of the bursts, fractional amplitude is consistent with that of the accretion pulsations, implying a low degree of fuel spread. There is however a population of bursts whose fractional amplitudes are substantially lower, implying a higher degree of fuel spread, possibly forced by the explosive burning front of a precursor burst. For the first harmonic, substantial differences between the burst and accretion pulsations suggest that hotspot geometry is not the only mechanism giving rise to harmonic content in the latter. Fractional amplitude variability during the bursts is low; we can only rule out the hypothesis that the fractional amplitude remains constant at the l(sigma) level for bursts that do not exhibit photospheric radius expansion (PRE). There are no significant variations in frequency in any of the bursts except for the one burst that exhibits PRE. This burst exhibits a highly significant but small (= 0.1Hz) drop in frequency in the burst rise. The timescale of the frequency shift is slower than simple burning layer expansion models predict, suggesting that other mechanisms may be at work.

  9. ALA Candidates: Presidential Timbre

    ERIC Educational Resources Information Center

    Berry, John N., III

    2010-01-01

    This article presents an interview with two effective spokespeople, notable school librarian Sara Kelly Johns and retired public library administrator Molly Raphael, who compete to be American Library Association (ALA) president. One of them will be elected president of ALA for a year's term beginning in July 2011. Each candidate comes from a…

  10. Growth and characterization of CdTe single quantum wells confined by Cd 1- xZn xTe alloy and short period CdTe/ZnTe superlattice

    NASA Astrophysics Data System (ADS)

    Magnea, N.; Lentz, G.; Mariette, H.; Feuillet, G.; Dal'bo, F.; Tuffigo, H.

    1989-02-01

    A comparative study of structural and optical properties of CdTe single quantum wells has been performed. Very efficient CdTe-Cd 1-xZn xTe (x Zn ≤ 0.2) wells have been grown and short period superlattices appear as a promising substitute of the alloy.

  11. The Transient Accreting X-Ray Pulsar XTE J1946+274: Stability of X-Ray Properties at Low Flux and Updated Orbital Solution

    NASA Astrophysics Data System (ADS)

    Marcu-Cheatham, Diana M.; Pottschmidt, Katja; Kühnel, Matthias; Müller, Sebastian; Falkner, Sebastian; Caballero, Isabel; Finger, Mark H.; Jenke, Peter J.; Wilson-Hodge, Colleen A.; Fürst, Felix; Grinberg, Victoria; Hemphill, Paul B.; Kreykenbohm, Ingo; Klochkov, Dmitry; Rothschild, Richard E.; Terada, Yukikatsu; Enoto, Teruaki; Iwakiri, Wataru; Wolff, Michael T.; Becker, Peter A.; Wood, Kent S.; Wilms, Jörn

    2015-12-01

    We present a timing and spectral analysis of the X-ray pulsar XTE J1946+274 observed with Suzaku during an outburst decline in 2010 October and compare with previous results. XTE J1946+274 is a transient X-ray binary consisting of a Be-type star and a neutron star with a 15.75 s pulse period in a 172 days orbit with 2-3 outbursts per orbit during phases of activity. We improve the orbital solution using data from multiple instruments. The X-ray spectrum can be described by an absorbed Fermi-Dirac cut-off power-law model along with a narrow Fe Kα line at 6.4 keV and a weak Cyclotron Resonance Scattering Feature (CRSF) at ˜35 keV. The Suzaku data are consistent with the previously observed continuum flux versus iron line flux correlation expected from fluorescence emission along the line of sight. However, the observed iron line flux is slightly higher, indicating the possibility of a higher iron abundance or the presence of non-uniform material. We argue that the source most likely has only been observed in the subcritical (non-radiation dominated) state since its pulse profile is stable over all observed luminosities and the energy of the CRSF is approximately the same at the highest (˜5 × 1037 erg s-1) and lowest (˜5 × 1036 erg s-1) observed 3-60 keV luminosities.

  12. Conduction mechanisms in p-type Pb{sub 1-x}Eu{sub x}Te alloys in the insulator regime

    SciTech Connect

    Peres, M. L.; Rubinger, R. M.; Ribeiro, L. H.; Rubinger, C. P. L.; Ribeiro, G. M.; Chitta, V. A.; Rappl, P. H. O.; Abramof, E.

    2012-06-15

    Electrical resistivity measurements were performed on p-type Pb{sub 1-x}Eu{sub x}Te films with Eu content x = 4%, 5%, 6%, 8%, and 9%. The well-known metal-insulator transition that occurs around 5% at room temperature due to the introduction of Eu is observed, and we used the differential activation energy method to study the conduction mechanisms present in these samples. In the insulator regime (x > 6%), we found that band conduction is the dominating conduction mechanism for high temperatures with carriers excitation between the valence band and the 4f levels originated from the Eu atoms. We also verified that mix conduction dominates the low temperatures region. Samples with x = 4% and 5% present a temperature dependent metal insulator transition and we found that this dependence can be related to the relation between the thermal energy k{sub B}T and the activation energy {Delta}{epsilon}{sub a}. The physical description obtained through the activation energy analysis gives a new insight about the conduction mechanisms in insulating p-type Pb{sub 1-x}Eu{sub x}Te films and also shed some light over the influence of the 4f levels on the transport process in the insulator region.

  13. Erratum: "Photoionization Modeling of Oxygen K Absorption in the Interstellar Medium, the Chandra Grating Spectra of XTE J1817-330" (2013, Apj, 768, 60)

    NASA Technical Reports Server (NTRS)

    Gatuzz, E.; Garcia, J.; Mendoza, C.; Kallman, Timothy R.; Witthoeft, Michael C.; Lohfink, A.; Bautista, M. A.; Palmeri, P.; Quinet, P.

    2013-01-01

    In the published version of this paper, there are some minor inaccuracies in the absorption-line wavelengths listed in Table 4 as a result of a faulty reduction procedure of the Obs6615 spectrum. The shifts have been detected in a comparison with the wavelengths listed for this spectrum in the Chandra Transmission Grating Catalog and Archive (TGCat8). They are due to incorrect centroid positions of the zero-order image in both reductions as determined by the tgdetect utility which, when disentangled, yield the improved line positions of the amended Table 4 given below. It must also be pointed out that other quantitative findings of the original paper: 1. Table 5, p. 9: the column density (NH), ionization parameter, oxygen abundance of the warmabs model and the normalization and photon index of the power-law model; 2. Table 6, p. 9: the hydrogen column density of the warmabs fit; 3. Table 7, p. 9: the present oxygen equivalent widths of XTE J1817-330; and 4. Table 8, p. 10: the present oxygen column densities of XTE J1817-330 derived from both the curve of growth and warmabs model fit have been revised in the new light and are, within the estimated uncertainty ranges, in good accord with the new rendering.

  14. A new approach to the crystal growth of Hg 1- xMn xTe by the cold travelling heater method (CTHM)

    NASA Astrophysics Data System (ADS)

    Reig, C.; Gómez-García, C. J.; Muñoz, V.

    2001-03-01

    In order to obtain crystals with a homogeneous composition and to reduce the Hg high pressure related to the temperature synthesis reaction between the components in elemental form, Hg 1- xMn xTe bulk crystals were produced by the cold travelling heater method (CTHM). Following the technique initially proposed for the growth of CdHgTe by the Triboulet group, the feed material was a split ingot of two segments, one of HgTe and the other of MnTe, with cross-sectional areas chosen to establish the desired final composition. The growth was carried out at a temperature of 600°C and a rate of 2 mm/h. The Hg 1- xMn xTe crystals have been characterised by scanning electron microscopy, including energy dispersive X-ray analysis and backscattered mode, powder X-ray diffractometry, Fourier transformed infrared spectroscopy, and SQUID magnetic susceptibility measurements. The crystals, with standard magnetic properties, show an excellent axial and radial composition uniformity throughout most of the total ingot length.

  15. Modeling the polarization of high-energy radiation from accreting black holes. A case study of XTE J1118+480

    NASA Astrophysics Data System (ADS)

    Vieyro, F. L.; Romero, G. E.; Chaty, S.

    2016-03-01

    Context. The high-energy emission (400 keV-2 MeV) of Cygnus X-1, which is the best-studied Galactic black hole, was recently found to be strongly polarized. The origin of this radiation is still unknown. Aims: We suggest that the emission is the result of non-thermal processes in the hot corona around the accreting compact object and study the polarization of high-energy radiation that is expected for black hole binaries. Methods: Two contributions to the total magnetic field were taken into account in our study: a small-scale random component related to the corona, and an ordered magnetic field associated with the accretion disk. The degree of polarization of gamma-ray emission for this particular geometry was estimated together with the angle of the polarization vector. Results: We obtain that the configuration of corona plus disk can account for the high degree of polarization of gamma-rays that are detected in galactic black holes and does not need to invoke a relativistic jet. We make specific predictions for sources in a low-hard state. In particular, the model is applied to the transient source XTE J1118+480. We show that if a new outburst of XTE J1118+480 is observed, then its gamma-ray polarization should be measurable by future instruments, such as ASTRO-H or the proposed ASTROGAM.

  16. Dark matter candidates

    SciTech Connect

    Turner, M.S.

    1989-01-01

    One of the simplest, yet most profound, questions we can ask about the Universe is, how much stuff is in it, and further what is that stuff composed of. Needless to say, the answer to this question has very important implications for the evolution of the Universe, determining both the ultimate fate and the course of structure formation. Remarkably, at this late date in the history of the Universe we still do not have a definitive answer to this simplest of questions---although we have some very intriguing clues. It is known with certainty that most of the material in the Universe is dark, and we have the strong suspicion that the dominant component of material in the Cosmos is not baryons, but rather is exotic relic elementary particles left over from the earliest, very hot epoch of the Universe. If true, the Dark Matter question is a most fundamental one facing both particle physics and cosmology. The leading particle dark matter candidates are: the axion, the neutralino, and a light neutrino species. All three candidates are accessible to experimental tests, and experiments are now in progress. In addition, there are several dark horse, long shot, candidates, including the superheavy magnetic monopole and soliton stars. 13 refs.

  17. Photoionization Modeling of Oxygen K Absorption in the Interstellar Medium: The Chandra Grating Spectra of XTE J1817-330

    NASA Technical Reports Server (NTRS)

    Gatuzz, E.; Garcia, J.; Menodza, C.; Kallman, T. R.; Witthoeft, M.; Lohfink, A.; Bautista, M. A.; Palmeri, P.; Quinet, P.

    2013-01-01

    We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra towards the X-ray low-mass binary XTE J1817-330. The 11-25 A broadband is described with a simple absorption model that takes into account the pileup effect and results in an estimate of the hydrogen column density. The oxygen K-edge region (21-25 A) is fitted with the physical warmabs model, which is based on a photoionization model grid generated with the XSTAR code with the most up-to-date atomic database. This approach allows a benchmark of the atomic data which involves wavelength shifts of both the K lines and photoionization cross sections in order to fit the observed spectra accurately. As a result we obtain: a column density of N(sub H) = 1.38 +/- 0.01 x 10(exp 21) cm(exp -2); ionization parameter of log xi = .2.70 +/- 0.023; oxygen abundance of A(sub O) = 0.689(exp +0.015./-0.010); and ionization fractions of O I/O = 0.911, O II/O = 0.077, and O III/O = 0.012 that are in good agreement with previous studies. Since the oxygen abundance in warmabs is given relative to the solar standard of Grevesse and Sauval (1998), a rescaling with the revision by Asplund et al. (2009) yields A(sub O) = 0.952(exp +0.020/-0.013, a value close to solar that reinforces the new standard. We identify several atomic absorption lines.K-alpha , K-beta, and K-gamma in O I and O II; and K-alpha in O III, O VI, and O VII--last two probably residing in the neighborhood of the source rather than in the ISM. This is the first firm detection of oxygen K resonances with principal quantum numbers n greater than 2 associated to ISM cold absorption.

  18. Photoionization Modeling of Oxygen K Absorption in the Interstellar Medium:. [The Chandra Grating Spectra of XTE J1817-330

    NASA Technical Reports Server (NTRS)

    Gatuzz, E.; Garcia, J.; Mendoza, C.; Kallman, T. R.; Witthoeft, M.; Lohfink, A.; Bautista, M. A.; Palmeri, P.; Quinet, P.

    2013-01-01

    We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra toward the X-ray low-mass binary XTE J1817-330. The 11-25 Angstrom broadband is described with a simple absorption model that takes into account the pile-up effect and results in an estimate of the hydrogen column density. The oxygen K-edge region (21-25 Angstroms) is fitted with the physical warmabs model, which is based on a photoionization model grid generated with the xstar code with the most up-to-date atomic database. This approach allows a benchmark of the atomic data which involves wavelength shifts of both the K lines and photoionization cross sections in order to fit the observed spectra accurately. As a result we obtain a column density of N(sub H) = 1.38 +/- 0.01 × 10(exp 21) cm(exp -2); an ionization parameter of log xi = -2.70 +/- 0.023; an oxygen abundance of A(sub O) = 0.689 (+0.015/-0.010); and ionization fractions of O(sub I)/O = 0.911, O(sub II)/O = 0.077, and O(sub III)/O = 0.012 that are in good agreement with results from previous studies. Since the oxygen abundance in warmabs is given relative to the solar standard of Grevesse & Sauval, a rescaling with the revision by Asplund et al. yields A(sub O) = 0.952(+0.020/-0.013), a value close to solar that reinforces the new standard.We identify several atomic absorption lines-K(alpha), K(beta), and K(gamma) in O(sub I) and O(sub II) and K(alpha) in O(sub III), O(sub VI), and O(sub VII)-the last two probably residing in the neighborhood of the source rather than in the ISM. This is the first firm detection of oxygen K resonances with principal quantum numbers n greater than 2 associated with ISM cold absorption.

  19. PHOTOIONIZATION MODELING OF OXYGEN K ABSORPTION IN THE INTERSTELLAR MEDIUM: THE CHANDRA GRATING SPECTRA OF XTE J1817-330

    SciTech Connect

    Gatuzz, E.; Mendoza, C.; Garcia, J.; Lohfink, A.; Kallman, T. R.; Witthoeft, M.; Bautista, M. A.; Palmeri, P.; Quinet, P. E-mail: claudio@ivic.gob.ve E-mail: alohfink@astro.umd.edu E-mail: michael.c.witthoeft@nasa.gov E-mail: palmeri@umons.ac.be

    2013-05-01

    We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra toward the X-ray low-mass binary XTE J1817-330. The 11-25 A broadband is described with a simple absorption model that takes into account the pile-up effect and results in an estimate of the hydrogen column density. The oxygen K-edge region (21-25 A) is fitted with the physical warmabs model, which is based on a photoionization model grid generated with the XSTAR code with the most up-to-date atomic database. This approach allows a benchmark of the atomic data which involves wavelength shifts of both the K lines and photoionization cross sections in order to fit the observed spectra accurately. As a result we obtain a column density of N{sub H} = 1.38 {+-} 0.01 Multiplication-Sign 10{sup 21} cm{sup -2}; an ionization parameter of log {xi} = -2.70 {+-} 0.023; an oxygen abundance of A{sub O}= 0.689{sup +0.015}{sub -0.010}; and ionization fractions of O I/O = 0.911, O II/O = 0.077, and O III/O = 0.012 that are in good agreement with results from previous studies. Since the oxygen abundance in warmabs is given relative to the solar standard of Grevesse and Sauval, a rescaling with the revision by Asplund et al. yields A{sub O}=0.952{sup +0.020}{sub -0.013}, a value close to solar that reinforces the new standard. We identify several atomic absorption lines-K{alpha}, K{beta}, and K{gamma} in O I and O II and K{alpha} in O III, O VI, and O VII-the last two probably residing in the neighborhood of the source rather than in the ISM. This is the first firm detection of oxygen K resonances with principal quantum numbers n > 2 associated with ISM cold absorption.

  20. The Internal-Candidate Syndrome

    ERIC Educational Resources Information Center

    Barden, Dennis M.

    2008-01-01

    In this article, the author explains the complications involved when an internal candidate is included in an open search for a leadership position in an academic institution. Internal-candidate syndrome is a dilemma faced by institutions when they have to choose between an internal candidate and an external one. There are two reasons why…

  1. Candidate Assembly Statistical Evaluation

    Energy Science and Technology Software Center (ESTSC)

    1998-07-15

    The Savannah River Site (SRS) receives aluminum clad spent Material Test Reactor (MTR) fuel from all over the world for storage and eventual reprocessing. There are hundreds of different kinds of MTR fuels and these fuels will continue to be received at SRS for approximately ten more years. SRS''s current criticality evaluation methodology requires the modeling of all MTR fuels utilizing Monte Carlo codes, which is extremely time consuming and resource intensive. Now that amore » significant number of MTR calculations have been conducted it is feasible to consider building statistical models that will provide reasonable estimations of MTR behavior. These statistical models can be incorporated into a standardized model homogenization spreadsheet package to provide analysts with a means of performing routine MTR fuel analyses with a minimal commitment of time and resources. This became the purpose for development of the Candidate Assembly Statistical Evaluation (CASE) program at SRS.« less

  2. Hg-loss compensation and wiping-off of source liquid on slider liquid phase epitaxy of Hg 1- xCd xTe

    NASA Astrophysics Data System (ADS)

    Shinohara, Motoya; Nugraha; Noda, Yasutoshi; Furukawa, Yoshitaka

    1994-08-01

    Hg loss measurement and wiping the liquid source on Hg 1- xCd xTe (MCT) layer growth were performed using a slider liquid phase epitaxy (LPE) boat with a HgTe reservoir. The optimum conditions to compensate Hg loss were revealed, where an increased amount of HgTe in the reservoir was effective to stabilize the weight change of source liquid due to Hg evaporation. The wiping was effectively made on equilibrium cooling from the melting point, where thin MCT layers (2-4 μm) resulted and the surface was slightly terraced. Thick layers (30-40 μm) resulted from the supercooling and step cooling with a supercooling of 15 K. The composition of the grown layers was x = 0.25-0.42.

  3. Abundancias químicas de la compañera visible del agujero negro binario V4641 Sgr (XTE J1819-254)

    NASA Astrophysics Data System (ADS)

    Cúneo, V. A.; Jofré, E.; Pintado, O. I.; Gómez, M. N.

    2015-08-01

    In this work we expose an analysis of the chemical abundances of the optical companion of the confirmed black hole binary V4641 Sgr (XTE J1819-254) from GMOS spectra obtained with the Gemini North telescope. This analysis allowed to observe an enhancement of N, O, Mg and Si, attributed to the contamination of heavy elements generated during the supernova explosion that gave birth to the black hole. It was also observed that Cr and Fe were subabundant. The aim of this study is to test the formation scenario of a binary system containing a black hole as remnant of the supernova explosion of a massive star, and to provide information to better understand the final stages in the evolution of massive stars and black hole progenitors.

  4. The reaction kinetics of Cu with the CdTe(111)-B surface: Formation of metastable Cu{sub x}Te (x{approx}2)

    SciTech Connect

    Teeter, Glenn

    2005-11-08

    In the present study, elemental Cu is deposited on the clean CdTe(111)-B surface and annealed in vacuum. Surface-composition maps generated by scanning Auger microcopy provide evidence that a reaction occurs between Cu and the CdTe(111)-B substrate that results in the formation of a metastable copper telluride phase Cu{sub x}Te (x{approx}2) at the surface. In situ thermal-desorption mass spectrometry measurements show that elemental Cd is released during the reaction and desorbs from the surface. Desorption of Te from the substrate is suppressed during the reaction. Analysis of Cd desorption traces demonstrates that the Cu+CdTe(111)-B reaction proceeds via zero-order kinetics, with an activation energy of 180{+-}5 kJ mol{sup -1}.

  5. Influence of samarium on the thermoelectric figure of merit of Sm{sub x}Pb{sub 1-x}Te alloys

    SciTech Connect

    Aliev, F. F. Hasanov, H. A.

    2012-03-15

    The temperature and concentration dependences of the electrical (conductivity {sigma}, the Hall coefficient R), thermoelectric (thermovoltage {alpha}), and thermal (thermal conductivity K{sub tot}) characteristics of Sm{sub x}Pb{sub 1-x}Te alloys (x = 0, 0.02, 0.04, 0.08) are studied in the temperature range 100-500 K. Using the data for {sigma}, {alpha}, and K{sub tot}, the thermoelectric power {alpha}{sup 2}{sigma}, figure of merit Z, and efficiency {delta} are calculated. It is established that at room-temperature {alpha}{sup 2}{sigma} and Z peak at the hole concentration p Almost-Equal-To 1.2 Multiplication-Sign 10{sup 18} cm{sup -3}.

  6. Mechanisms of recombination of nonequilibrium charge carriers in epitaxial Cd{sub x}Hg{sub 1-x}Te (x = 0.20-0.23) layers

    SciTech Connect

    Ikusov, D. G.; Sizov, F. F.; Staryi, S. V. Teterkin, V. V.

    2007-02-15

    The experimental temperature dependences of the photosensitivity and the data on the lifetime of nonequilibrium charge carriers in epitaxial Cd{sub x}Hg{sub 1-x}Te layers with x = 0.20-0.23 were used to show that, in the region of intrinsic and extrinsic conductivity in n-type films grown by molecular beam epitaxy, CHCC Auger recombination is the prevailing recombination mechanism. At the same time, in p-type films grown by liquid-or vapor-phase epitaxy, it is observed that, in the region of extrinsic conductivity, CHLH Auger recombination competes with Shockley-Read recombination. The n-type films grown by molecular beam epitaxy contain a much lower concentration of recombination centers than the p-type films grown by liquid-or gasphase epitaxy.

  7. Phase separation and exchange biasing in the ferromagnetic IV-VI semiconductor Ge{sub 1-x}Mn{sub x}Te

    SciTech Connect

    Lechner, R. T.; Springholz, G.; Hassan, M.; Groiss, H.; Kirchschlager, R.; Stangl, J.; Hrauda, N.; Bauer, G.

    2010-07-12

    Ferromagnetic Ge{sub 1-x}Mn{sub x}Te grown by molecular beam epitaxy with Mn content of x{sub Mn}approx =0.5 is shown to exhibit a strong tendency for phase separation. At higher growth temperatures apart from the cubic Ge{sub 0.5}Mn{sub 0.5}Te, a hexagonal MnTe and a rhombohedral distorted Ge{sub 0.83}Mn{sub 0.17}Te phase is formed. This coexistence of antiferromagnetic MnTe and ferromagnetic Ge{sub 0.5}Mn{sub 0.5}Te results in magnetic exchange-bias effects.

  8. Constraints on braneworld gravity models from a kinematic limit on the age of the black hole XTE J1118+480.

    PubMed

    Psaltis, Dimitrios

    2007-05-01

    In braneworld gravity models with a finite anti-de Sitter space (AdS) curvature in the extra dimension, the AdS/conformal field theory correspondence leads to a prediction for the lifetime of astrophysical black holes that is significantly smaller than the Hubble time, for asymptotic curvatures that are consistent with current experiments. Using the recent measurements of the position, three-dimensional spatial velocity, and mass of the black hole XTE J1118+480, I calculate a lower limit on its kinematic age of > or =11 Myr (95% confidence). This translates into an upper limit for the asymptotic AdS curvature in the extra dimensions of <0.08 mm, which significantly improves the limit obtained by table top experiments of sub mm gravity. PMID:17501556

  9. Optimal bandgap variants of Cd 1- xZn xTe for high-resolution X-ray and gamma-ray spectroscopy

    NASA Astrophysics Data System (ADS)

    Toney, J. E.; Schlesinger, T. E.; James, R. B.

    1999-06-01

    We show that the trade-off between noise and charge generation statistics in Cd 1- xZn xTe leads to an optimal band gap of approximately 2.0 eV at room temperature. This implies a ZnTe fraction of approximately 0.7-0.8. We show that for X-rays and relatively low energy gamma-rays Cd 0.2Zn 0.8Te theoretically offers a significant potential improvement in energy resolution over Cd 0.9Zn 0.1Te even if compensation of shallow levels is less complete and carrier lifetimes are an order of magnitude lower for the higher x variant. We also show that these calculations are consistent with observed detector performance reported by many workers over a large period of time.

  10. Spin-glass behavior and anomalous magnetoresistance in ferromagnetic Ge{sub 1-x}Fe{sub x}Te epilayer

    SciTech Connect

    Liu, Jindong; Cheng, Xiaomin Tong, Fei; Miao, Xiangshui

    2014-07-28

    We report that the Ge{sub 1-x}Fe{sub x}Te thin film exhibits spin-glass behavior when the Fe concentration increases to 0.08. A large bifurcation between the zero-field cooling and field cooling temperature-dependent magnetization was observed. The hysteresis loops after zero-field cooling and field cooling show an exchange bias effect. A time-dependent thermoremanent magnetization follows power-law decay, which confirms the existence of spin glass. The anomalous magnetotranport properties present a further evidence for spin-glass behavior and give a freezing temperature T{sub g} ∼ 5 K in the Ge{sub 0.92}Fe{sub 0.08}Te thin film.

  11. Evolution of a Low Luminosity Outburst of the Black Hole Candidate H1743-322

    NASA Technical Reports Server (NTRS)

    Swank, J.; Markwardt, C.; Rupen, M.; Mioduszewski, A.; Dhawa, V.

    2005-01-01

    The black hole candidate X-ray transient H1743-322 = IGR J1746-3213 = XTE J17464-3213 had a bright outburst starting in March 2003, which reached a peak flux around 1.3 Crab and lasted nearly 2/3 of a year. After a similar period in apparent quiescence (below approx. 1 mCrab), the source began another outburst in July 2004, this time rising only to about 1/4 Crab and decaying in about 4.5 months. It appeared with an optically thick disk and a steep power law component (number index approx. 3), and began a steady increase, with mild spectral change. After 50 days, a hard power-law component appeared, along with low frequency quasiperiodic oscillations. Gradual decay of both components began, but after another month the soft component dropped faster and left the source in a harder state to continue the decay. The Very Large Array found no radio activity during the first month, but a 2 mJy radio source appeared during the X-ray rise. Evidence for jet ejection corresponding to changes in the X-ray source will be discussed in connection with interpretation of the system.

  12. ON THE NATURE OF QUASI-PERIODIC OSCILLATION PHASE LAGS IN BLACK HOLE CANDIDATES

    SciTech Connect

    Shaposhnikov, Nikolai E-mail: lev@milkyway.gsfc.nasa.gov

    2012-06-20

    Observations of quasi-periodic oscillations (QPOs) in X-ray binaries hold a key to understanding many aspects of these enigmatic systems. Complex appearance of the Fourier phase lags related to QPOs is one of the most puzzling observational effects in accreting black holes (BHs). In this Letter we show that QPO properties, including phase lags, can be explained in a framework of a simple scenario, where the oscillating media provide feedback on the emerging spectrum. We demonstrate that the QPO waveform is presented by the product of a perturbation and time-delayed response factors, where the response is energy dependent. The essential property of this effect is its nonlinear and multiplicative nature. Our multiplicative reverberation model successfully describes the QPO components in energy-dependent power spectra as well as the appearance of the phase lags between signals in different energy bands. We apply our model to QPOs observed by the Rossi X-Ray Timing Explorer in BH candidate XTE J1550-564. We briefly discuss the implications of the observed energy dependence of the QPO reverberation times and amplitudes on the nature of the power-law spectral component and its variability.

  13. On the Nature of QPO Phase Lags in Black Hole Candidates

    NASA Technical Reports Server (NTRS)

    Shaposhnikov, Nikolai

    2012-01-01

    Observations of quasi-periodic oscillations (QPOs) in X-ray binaries hold a key to understanding many aspects of these enigmatic systems. Complex appearance of the Fourier phase lags related to QPOs is one of the most puzzling observational effects in accreting black holes. In this Letter we show that QPO properties, including phase lags, can be explained in a framework of a simple scenario, where the oscillating media provides a feedback on the emerging spectrum. We demonstrate that the QPO waveform is presented by the product of a perturbation and a time delayed response factors, where the response is energy dependent. The essential property of this effect is its non-linear and multiplicative nature. Our multiplicative reverberation model successfully describes the QPO components in energy dependent power spectra as well as the appearance of the phase lags between signal in different energy bands. We apply our model to QPOs observed by Rossi X-ray Timing Explorer in BH candidate XTE J1550-564. We briefly discuss the implications of the observed energy dependence of the QPO reverberation times and amplitudes to the nature of the power law spectral component and its variability.

  14. A SPECTRAL STUDY OF THE RAPID TRANSITIONS OF TYPE-B QUASI-PERIODIC OSCILLATIONS IN THE BLACK HOLE TRANSIENT XTE J1859+226

    SciTech Connect

    Sriram, K.; Choi, C. S.; Rao, A. R.

    2013-09-20

    The fast transitions of type-B and type-A quasi-periodic oscillations (QPOs) are rarely found, and they are observed at the peak of the outburst in black hole transient (BHT) sources. The associated spectral variations during such events are crucial to understand the origin and location of such QPOs in the accretion disk. During the 1999 outburst of XTE J1859+226, on four occasions a rapid transition of type-B/A QPOs was noted. We performed broadband spectral analysis on these four observations to unveil the responsible spectral parameter causing the rapid transitions. After invoking simple spectral models, it was observed that disk parameters were consistently varying along with disk and power-law fluxes, and almost no change was noted in the power-law index parameter. Though using a complex physical model showed consistent results, the spectral parameter variations across the transitions were not significant. It was observed that the type-B QPO was always associated with an inner disk front which is closer to the BH. In one observation, a type-A QPO appeared as the source count rate suddenly dropped, and the power-law index as well as disk normalization parameter considerably changed during this transition. The spectral changes in this particular observation were similar to the changes observed in XTE J1817-330, indicating a common underlying mechanism. We have also examined a similar observation of BHT source GX 339-4, where a sudden transition of a type-A/B QPO was noted. Similar spectral study again revealed that the disk parameters were changing. We discuss the results in the framework of a truncated disk model and conclude that the movement of the coupled inner disk-corona region is responsible for such rapid transitions of type-B QPOs.

  15. 2009 Elections: The Candidates Statements

    ERIC Educational Resources Information Center

    TechTrends: Linking Research and Practice to Improve Learning, 2009

    2009-01-01

    This article presents the candidates for the 2009 Association for Educational Communications and Technology (AECT) election and their statements. The candidates are: (1) Andy Gibbons (President-Elect); (2) Barbara B. Lockee (President-Elect); (3) Mary Jean Bishop (At-Large Representative); and (4) Deepak Subramony (At-Large Representative). In…

  16. Determination of Black Hole Masses in Galactic Black Hole Binaries Using Scaling of Spectral and Variability Characteristics

    NASA Astrophysics Data System (ADS)

    Shaposhnikov, Nickolai; Titarchuk, Lev

    2009-07-01

    We present a study of correlations between X-ray spectral and timing properties observed from a number of Galactic black hole (BH) binaries during hard-soft state spectral evolution. We analyze 17 transition episodes from eight BH sources observed with Rossi X-Ray Timing Explorer. Our scaling technique for BH mass determination uses a correlation between the spectral index and quasi-periodic oscillation (QPO) frequency. In addition, we use a correlation between the index and the normalization of the disk "seed" component to cross-check the BH mass determination and estimate the distance to the source. While the index-QPO correlations for two given sources contain information on the ratio of the BH masses in those sources, the index-normalization correlations depend on the ratio of the BH masses and the distance square ratio. In fact, the index-normalization correlation also discloses the index-mass accretion rate saturation effect given that the normalization of disk "seed" photon supply is proportional to the disk mass accretion rate. We present arguments that this observationally established index saturation effect is a signature of the bulk motion (converging) flow onto a BH, which was early predicted by the dynamical Comptonization theory. We use GRO J1655 - 40 as a primary reference source for which the BH mass, distance, and inclination angle are evaluated by dynamical measurements with unprecedented precision among other Galactic BH sources. We apply our scaling technique to determine BH masses and distances for Cygnus X-1, GX 339 - 4, 4U 1543 - 47, XTE J1550 - 564, XTE J1650 - 500, H 1743 - 322, and XTE J1859 - 226. A good agreement of our results for sources with known values of BH masses and distance provides independent verification for our scaling technique.

  17. Imaging X-Ray, Optical, and Infrared Observations of the Transient Anomalous X-Ray Pulsar XTE J1810-197

    NASA Astrophysics Data System (ADS)

    Gotthelf, E. V.; Halpern, J. P.; Buxton, M.; Bailyn, C.

    2004-04-01

    We report X-ray imaging, timing, and spectral studies of XTE J1810-197, a 5.54 s pulsar discovered by Ibrahim and coworkers in recent Rossi X-Ray Timing Explorer (RXTE) observations. In a set of short exposures with the High Resolution Camera on board the Chandra X-Ray Observatory, we detect a strongly modulated signal (55%+/-4% pulsed fraction) with the expected period located at (J2000) 18h09m51s08, -19deg43'51.7", with a uncertainty radius of 0.6" (90% confidence level). Spectra obtained with XMM-Newton are well fitted by a two-component model that typically describes anomalous X-ray pulsars (AXPs), an absorbed blackbody plus power law with parameters kT=0.67+/-0.01 keV, Γ=3.7+/-0.2, NH=(1.05+/-0.05)×1022 cm-2, and FX(0.5-10keV)=3.98×10-11 ergs cm-2 s-1. Alternatively, a two-temperature blackbody fit is just as acceptable. The location of CXOU J180951.0-194351 is consistent with a point source seen in archival Einstein, ROSAT, and ASCA images, when its flux was nearly 2 orders of magnitude fainter, and from which no pulsations are found. The spectrum changed dramatically between the ``quiescent'' and ``active'' states; the former can be modeled as a softer blackbody. Using XMM-Newton timing data, we place an upper limit of 0.03 lt-s on any orbital motion in the period range 10 minutes-8 hr. Optical and infrared images obtained on the SMARTS 1.3 m telescope at the Cerro Tololo Inter-American Observatory (CTIO) show no object in the Chandra error circle to limits V=22.5, I=21.3, J=18.9, and K=17.5. Together, these results argue that CXOU J180951.0-194351 is an isolated neutron star, one most similar to the transient AXP AX J1844.8-0256. Continuing study of XTE J1810-197 in various states of luminosity is important for understanding and possibly unifying a growing class of isolated, young neutron stars that are not powered by rotation.

  18. Superconductivity in the orthorhombic phase of thermoelectric CsPbxBi4-xTe6 with 0.3≤x≤1.0

    NASA Astrophysics Data System (ADS)

    Zhang, R. X.; Yang, H. X.; Tian, H. F.; Chen, G. F.; Wu, S. L.; Wei, L. L.; Li, J. Q.

    2015-12-01

    Experimental measurements clearly reveal the presence of bulk superconductivity in the CsPbxBi4-xTe6 (0.3≤x≤1.0) materials, i.e. the first member of the thermoelectric series of Cs[PbmBi3Te5+m], these materials have the layered orthorhombic structure containing infinite anionic [PbBi3Te6]- slabs separated with Cs+ cations. Temperature dependences of electrical resistivity, magnetic susceptibility, and specific heat have consistently demonstrated that the superconducting transition in Cs0.96Pb0.25Bi3.75Te6.04 occurs at Tc=3.1 K, with a superconducting volume fraction close to 100% at 1.8 K. Structural study using aberration-corrected STEM/TEM reveals a rich variety of microstructural phenomena in correlation with the Pb-ordering and chemical inhomogeneity. The superconducting material Cs0.96Pb0.25Bi3.75Te6.04 with the highest Tc shows a clear ordered structure with a modulation wave vector of q≈a*/2+c*/1.35 on the a-c plane. Our study evidently demonstrates that superconductivity deriving upon doping of narrow-gap semiconductor is a viable approach for exploration of novel superconductors.

  19. The use of pulse processing techniques to improve the performance of Cd{sub 1{minus}x}Zn{sub x}Te gamma-ray spectrometers

    SciTech Connect

    Lund, J.C.; Olsen, R.; Van Scyoc, J.M.; James, R.B.

    1996-06-01

    Cd{sub 1{minus}x}Zn{sub x}Te (CZT) has recently shown great promise for use as a room temperature gamma-ray detector material. The availability of large volume (>1 cm{sup 3}) high resistivity CZT crystals has allowed the demonstration of detectors much larger than can be built with the similar material CdTe. However, CZT--like many other room-temperature materials--suffers from the poor transport properties of holes. The poor hole drift properties of CZT cause the characteristic hole tailing in gamma-ray pulse height spectra. The authors have applied pulse processing methods to reduce the hole tailing effects and improve the energy resolution of CZT detectors. They have used two signal processing methods to reduce hole tailing in CZT detectors: digital rise-time compensation and dual time-constant sampling. They discuss the implementation of these techniques, demonstrate results obtained in the laboratory, and compare the performance obtained with other detector systems.

  20. Jet-dominated quiescent state in black hole X-ray binaries: the cases of A0620-00 and XTE J1118+480

    NASA Astrophysics Data System (ADS)

    Yang, Qi-Xiang

    2016-04-01

    The radiative mechanism of black hole X-ray transients (BHXTs) in their quiescent states (defined as the 2-10 keV X-ray luminosity ≲ 1034 erg s-1) remains unclear. In this work, we investigate the quasi-simultaneous quiescent state spectrum (including radio, infrared, optical, ultraviolet and X-ray) of two BHXTs, A0620-00 and XTE J1118+480. We find that these two sources can be well described by a coupled accretion - jet model. More specifically, most of the emission (radio up to infrared, and the X-ray waveband) comes from the collimated relativistic jet. Emission from hot accretion flow is totally insignificant, and it can only be observed in mid-infrared (the synchrotron peak). Emission from the outer cold disk is only evident in the UV band. These results are consistent with our previous investigation on the quiescent state of V404 Cyg and confirm that the quiescent state is jet-dominated.

  1. ON THE NATURE OF THE FIRST TRANSIENT Z SOURCE XTE J1701-462: ITS ACCRETION DISK STRUCTURE, NEUTRON STAR MAGNETIC FIELD STRENGTH, AND HARD TAIL

    SciTech Connect

    Ding, G. Q.; Wang, N.; Yan, S. P.; Zhang, S. N.; Qu, J. L. E-mail: dinggq@gmail.com

    2011-08-15

    Using data from the Rossi X-Ray Timing Explorer, we investigate the spectral evolution along a 'Z' track and a '{nu}' track on the hardness-intensity diagrams of the first transient Z source XTE J1701-462. The spectral analyses suggest that the inner disk radius depends on the mass accretion rate, in agreement with the model prediction, R{sub in}{proportional_to}M-dot{sup 2/7}{sub disk}, for a radiation-pressure-dominated accretion disk interacting with the magnetosphere of a neutron star (NS). The changes in the disk mass accretion rate M-dot{sub disk} are responsible for the evolution of the 'Z' or '{nu}' track. Radiation pressure thickens the disk considerably and also produces significant outflows. The NS surface magnetic field strength, derived from the interaction between the magnetosphere and the radiation-pressure-dominated accretion disk, is {approx}(1-3) x 10{sup 9} G, which is possibly between normal atoll and Z sources. A significant hard tail is detected in the horizontal branches and we discuss several possible origins of the hard tail.

  2. 76 FR 4896 - Call for Candidates

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-27

    ... From the Federal Register Online via the Government Publishing Office FEDERAL ACCOUNTING STANDARDS ADVISORY BOARD Call for Candidates AGENCY: Federal Accounting Standards Advisory Board. ACTION: Notice... Federal Accounting Standards Advisory Board (FASAB) is currently seeking candidates (candidates must...

  3. Quasar candidates near 1057 + 01

    SciTech Connect

    Crampton, D.; Cartledge, S.; Cowley, A.P.; Hartwick, F.D.A. Arizona State Univ., Tempe Victoria Univ. )

    1991-04-01

    Positions and magnitudes are given for 143 quasar candidates and three white dwarf candidates discovered with the CFHT blue grens in a 2.7 square degree area in the direction 1057 + 01. The goal of this survey is to provide complete samples of quasars to study the large scale distribution of matter at moderate to high (z less than 3.4) redshifts. Part of the region surveyed in this paper was previously studied by Crampton and Parmar (1983), allowing a comparison of the search and measurements accuracies. Redshifts, derived from MMT spectroscopy, for 27 of the candidates are also presented. One quasar, 1058.1 + 0052, displays strong broad absorption lines characteristic of BAL quasars. 5 refs.

  4. Dependence of the electrical parameters of MBE-grown Cd{sub x}Hg{sub 1} {sub -} {sub x}Te films on the level of doping with indium

    SciTech Connect

    Varavin, V. S. Dvoretskii, S. A.; Ikusov, D. G.; Mikhailov, N. N.; Sidorov, Yu. G.; Sidorov, G. Yu.; Yakushev, M. V.

    2008-06-15

    Dependences of the minority-carrier lifetime and electron mobility in Cd{sub x}Hg{sub 1-x}Te films on their indium-doping level are studied. Films with x {approx} 0.22 grown by molecular-beam epitaxy on GaAs substrates were in situ doped with indium across their entire thickness. The temperature dependences of the lifetime were studied in the temperature range 77-300 K. The decrease in the lifetime, observed as the doping level increases, is governed by the mechanism of Auger recombination. As the doping level becomes higher, the mobility decreases in qualitative agreement with theoretical calculations.

  5. Candidate cave entrances on Mars

    USGS Publications Warehouse

    Cushing, Glen E.

    2012-01-01

    This paper presents newly discovered candidate cave entrances into Martian near-surface lava tubes, volcano-tectonic fracture systems, and pit craters and describes their characteristics and exploration possibilities. These candidates are all collapse features that occur either intermittently along laterally continuous trench-like depressions or in the floors of sheer-walled atypical pit craters. As viewed from orbit, locations of most candidates are visibly consistent with known terrestrial features such as tube-fed lava flows, volcano-tectonic fractures, and pit craters, each of which forms by mechanisms that can produce caves. Although we cannot determine subsurface extents of the Martian features discussed here, some may continue unimpeded for many kilometers if terrestrial examples are indeed analogous. The features presented here were identified in images acquired by the Mars Odyssey's Thermal Emission Imaging System visible-wavelength camera, and by the Mars Reconnaissance Orbiter's Context Camera. Select candidates have since been targeted by the High-Resolution Imaging Science Experiment. Martian caves are promising potential sites for future human habitation and astrobiology investigations; understanding their characteristics is critical for long-term mission planning and for developing the necessary exploration technologies.

  6. Interviewing Teacher-Librarian Candidates

    ERIC Educational Resources Information Center

    Yucht, Alice

    2004-01-01

    When recently asked by an administrator for some realistic questions and "recommended" responses to expect while interviewing candidates for school library positions, the author grouped the questions into three categories: library management, information skills and teaching skills. In this article are the questions she suggested, along with topics…

  7. Candidate gene prioritization with Endeavour.

    PubMed

    Tranchevent, Léon-Charles; Ardeshirdavani, Amin; ElShal, Sarah; Alcaide, Daniel; Aerts, Jan; Auboeuf, Didier; Moreau, Yves

    2016-07-01

    Genomic studies and high-throughput experiments often produce large lists of candidate genes among which only a small fraction are truly relevant to the disease, phenotype or biological process of interest. Gene prioritization tackles this problem by ranking candidate genes by profiling candidates across multiple genomic data sources and integrating this heterogeneous information into a global ranking. We describe an extended version of our gene prioritization method, Endeavour, now available for six species and integrating 75 data sources. The performance (Area Under the Curve) of Endeavour on cross-validation benchmarks using 'gold standard' gene sets varies from 88% (for human phenotypes) to 95% (for worm gene function). In addition, we have also validated our approach using a time-stamped benchmark derived from the Human Phenotype Ontology, which provides a setting close to prospective validation. With this benchmark, using 3854 novel gene-phenotype associations, we observe a performance of 82%. Altogether, our results indicate that this extended version of Endeavour efficiently prioritizes candidate genes. The Endeavour web server is freely available at https://endeavour.esat.kuleuven.be/. PMID:27131783

  8. Candidate Exercise Technologies and Prescriptions

    NASA Technical Reports Server (NTRS)

    Loerch, Linda H.

    2010-01-01

    This slide presentation reviews potential exercise technologies to counter the effects of space flight. It includes a overview of the exercise countermeasures project, a review of some of the candidate exercise technologies being considered and a few of the analog exercise hardware devices, and a review of new studies that are designed to optimize the current and future exercise protocols.

  9. Empathy Development in Teacher Candidates

    ERIC Educational Resources Information Center

    Boyer, Wanda

    2010-01-01

    Using a grounded theory research design, the author examined 180 reflective essays of teacher candidates who participated in a "Learning Process Project," in which they were asked to synthesize and document their discoveries about the learning process over the course of a completely new learning experience as naive learners. This study explored…

  10. SAO RAS SN candidates classifications

    NASA Astrophysics Data System (ADS)

    Fatkhullin, T. A.; Moskvitin, A. S.

    2016-08-01

    We observed SN candidates (AT 2016eow, AT 2016enu and AT 2016enf) with the BTA/Scorpio-I on August, 4. Direct images in the R band and long-slit spectra in the range of 3600-7600AA (resolution FWHM = 10A) were obtained.

  11. XTE J1701-462 AND ITS IMPLICATIONS FOR THE NATURE OF SUBCLASSES IN LOW-MAGNETIC-FIELD NEUTRON STAR LOW-MASS X-RAY BINARIES

    SciTech Connect

    Homan, Jeroen; Fridriksson, Joel K.; Remillard, Ronald A.; Lewin, Walter H. G.; Van der Klis, Michiel; Wijnands, Rudy; Altamirano, Diego; Mendez, Mariano; Lin Dacheng; Casella, Piergiorgio; Belloni, Tomaso M.

    2010-08-10

    We report on an analysis of Rossi X-Ray Timing Explorer data of the transient neutron star low-mass X-ray binary (NS-LMXB) XTE J1701-462, obtained during its 2006-2007 outburst. The X-ray properties of the source changed between those of various types of NS-LMXB subclasses. At high luminosities, the source switched between two types of Z source behavior and at low luminosities we observed a transition from Z source to atoll source behavior. These transitions between subclasses primarily manifest themselves as changes in the shapes of the tracks in X-ray color-color (CD) and hardness-intensity diagrams (HID), but they are accompanied by changes in the kHz quasi-periodic oscillations, broadband variability, burst behavior, and/or X-ray spectra. We find that for most of the outburst the low-energy X-ray flux is a good parameter to track the gradual evolution of the tracks in CD and HID, allowing us to resolve the evolution of the source in greater detail than before and relate the observed properties to other NS-LMXBs. We further find that during the transition from Z to atoll, characteristic behavior known as the atoll upper banana can equivalently be described as the final stage of a weakening Z source flaring branch, thereby blurring the line between the two subclasses. Our findings strongly suggest that the wide variety in behavior observed in NS-LXMBs with different luminosities can be linked through changes in a single variable parameter, namely the mass accretion rate, without the need for additional differences in the neutron star parameters or viewing angle. We briefly discuss the implications of our findings for the spectral changes observed in NS-LMXBs and suggest that, contrary to what is often assumed, the position along the color-color tracks of Z sources is not determined by the instantaneous mass accretion rate.

  12. Modeling of electron energy spectra and mobilities in semi-metallic Hg{sub 1−x}Cd{sub x}Te quantum wells

    SciTech Connect

    Melezhik, E. O. Gumenjuk-Sichevska, J. V.; Sizov, F. F.

    2015-11-21

    Electron mobility, energy spectra, and intrinsic carrier concentrations in the n-type Hg{sub 0.32}Cd{sub 0.68}Te/Hg{sub 1−x}Cd{sub x}Te/Hg{sub 0.32}Cd{sub 0.68}Te quantum well (QW) in semi-metallic state are numerically modeled. Energy spectra and wave functions were calculated in the framework of the 8-band k-p Hamiltonian. In our model, electron scattering on longitudinal optical phonons, charged impurities, and holes has been taken into account, and the mobility has been calculated by an iterative solution of the Boltzmann transport equation. Our results show that the increase of the electron concentration in the well enhances the screening of the 2D electron gas, decreases the hole concentration, and can ultimately lead to a high electron mobility at liquid nitrogen temperatures. The increase of the electron concentration in the QW could be achieved in situ by delta-doping of barriers or by applying the top-gate potential. Our modeling has shown that for low molar composition x the concentration of holes in the well is high in a wide range of electron concentrations; in this case, the purity of samples does not significantly influence the electron mobility. These results are important in the context of establishing optimal parameters for the fabrication of high-mobility Hg{sub 1−x}Cd{sub x}Te quantum wells able to operate at liquid nitrogen temperature and thus suitable for applications in terahertz detectors.

  13. Characterization of CdTe substrates and MOCVD Cd 1- xZn xTe epilayers by Raman, photoluminescence and X-ray diffraction techniques

    NASA Astrophysics Data System (ADS)

    Levy, M.; Amir, N.; Khanin, E.; Muranevich, A.; Nemirovsky, Y.; Beserman, R.

    1998-05-01

    CdTe substrates and the quality of the Cd 1- xZn xTe ( x⩽0.1) epilayers grown by metalorganic chemical vapor deposition (MOCVD) on CdTe substrates, are characterized by Raman scattering and photoluminescence (PL) as well as by X-ray double-crystal rocking curve (DCRC). At a low temperature the intensity of LO phonon is enhanced wherever there is a structural defect. The defect-induced enhancement is due to a large momentum transfer which enhances the intraband Frolich interaction. In addition, the bound exciton peak intensity measured by PL decreases wherever the LO phonon scattering efficiency increases confirming that the defect is the origin of the above Raman enhancement. The quantitative measure of the structural perfection is related to the ratio between the defect band and excitonic peaks in the PL spectra, and correlates with the X-ray full-width at half-maximum (FWHM) of the layer peak. It is shown that in addition to these parameters, the FWHM of the PL defect band is a useful parameter to determine the quality of the epilayer, and a good correlation is obtained between the different parameters. The effect of growth parameters such as zinc partial pressure in the reactor during growth and the reactor design are studied. The results indicate that crystalline imperfection is caused by lattice mismatch between the CdTe substrate and the CdZnTe epilayer and by the nonuniformity of the zinc composition throughout the layers. The quality of the layers is independent of the reactor volume.

  14. OPTOPUS observations of quasar candidates.

    NASA Astrophysics Data System (ADS)

    Cristiani, S.

    1987-06-01

    OPTOPUS is a fiber-optic instrument for multiple-object spectroscopy with the Boiler & Chivens spectrograph and a CCD detector at the 3.6-m telescope. The system has been described in detail by the Optical Instrumentation Group (1985, The Messenger 41,25). Its application for observing Halley's comet has been reported by Lund and Surdej (1986, The Messenger 43, 1). Here another "classical" use of multiple-object spectroscopy is presented: followup observations of quasar candidates.

  15. Metal Nitrides Grown from Ca/Li Flux: Ca6Te3N2 and New Nitridoferrate(I) Ca6(LixFe1-x)Te2N3.

    PubMed

    Dickman, Matthew J; Latturner, Susan E

    2016-08-24

    Two new tellurium-containing nitrides were grown from reactions in molten calcium and lithium. The compound Ca6Te3N2 crystallizes in space group R3̅c (a = 12.000(3)Å, c = 13.147(4)Å; Z = 6); its structure is an anti-type of rinneite (K3NaFeCl6) and 2H perovskite related oxides such as Sr3Co2O6. The compound Ca6(LixFe1-x)Te2N3 where x ≈ 0.48 forms in space group P42/m (a = 8.718(3)Å, c = 6.719(2)Å; Z = 2) with a new stuffed anti-type variant of the Tl3BiCl6 structure. Band structure calculations and easily observable red/green dichroic behavior indicate that Ca6Te3N2 is a highly anisotropic direct band gap semiconductor (Eg = 2.5 eV). Ca6(LixFe1-x)Te2N3 features isolated linear N-Fe-N units with iron in the rare Fe(1+) state. The magnetic behavior of the iron site was characterized by magnetic susceptibility measurements, which indicate a very high magnetic moment (5.16μB) likely due to a high degree of spin-orbit coupling. Inherent disorder at the Fe/Li mixed site frustrates long-range communication between magnetic centers. PMID:27479366

  16. 1998 astronaut candidates tour KSC

    NASA Technical Reports Server (NTRS)

    1999-01-01

    At the Apollo/Saturn V Center, some of the 1998 astronaut candidate class (group 17) take a close look at the Saturn V rocket on display. The U.S. candidates include Clayton C. Anderson, Lee J. Archambault, Tracy E. Caldwell (Ph.D.), Gregory E. Chamitoff (Ph.D.), Timothy J. Creamer, Christopher J. Ferguson, Michael J. Foreman, Michael E. Fossum, Kenneth T. Ham, Patricia C. Hilliard (M.D.), Gregory C. Johnson, Gregory H. Johnson, Stanley G. Love (Ph.D.), Leland D. Melvin, Barbara R. Morgan, William A. Oefelein, John D. Olivas (Ph.D.), Nicholas J.M. Patrick (Ph.D.), Alan G. Poindexter, Garrett E. Reisman (Ph.D.), Steven R. Swanson, Douglas H. Wheelock, Sunita L. Williams, Neil W. Woodward III, George D. Zamka; and international candidates Leopold Eyharts, Paolo Nespoli, Hans Schlegel, Roberto Vittori, Bjarni V. Tryggvason, and Marcos Pontes. The class is at KSC for training activities, including fire training and a flight awareness program, plus touring the OPF, SSME Processing Facility, VAB, SSPF, launch pads, SLF, Apollo/Saturn V Center and the crew headquarters.

  17. 1998 astronaut candidates tour KSC

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Some of the 1998 astronaut candidate class (group 17) take a close look at displays in the Apollo/Saturn V Center at KSC. The U.S. candidates include Clayton C. Anderson, Lee J. Archambault, Tracy E. Caldwell (Ph.D.), Gregory E. Chamitoff (Ph.D.), Timothy J. Creamer, Christopher J. Ferguson, Michael J. Foreman, Michael E. Fossum, Kenneth T. Ham, Patricia C. Hilliard (M.D.), Gregory C. Johnson, Gregory H. Johnson, Stanley G. Love (Ph.D.), Leland D. Melvin, Barbara R. Morgan, William A. Oefelein, John D. Olivas (Ph.D.), Nicholas J.M. Patrick (Ph.D.), Alan G. Poindexter, Garrett E. Reisman (Ph.D.), Steven R. Swanson, Douglas H. Wheelock, Sunita L. Williams, Neil W. Woodward III, George D. Zamka; and international candidates Leopold Eyharts, Paolo Nespoli, Hans Schlegel, Roberto Vittori, Bjarni V. Tryggvason, and Marcos Pontes. The class is at KSC for training activities, including fire training and a flight awareness program, plus touring the OPF, SSME Processing Facility, VAB, SSPF, launch pads, SLF, Apollo/Saturn V Center and the crew headquarters.

  18. 1998 astronaut candidates tour KSC

    NASA Technical Reports Server (NTRS)

    1999-01-01

    At the Apollo/Saturn V Center, some of the 1998 astronaut candidate class (group 17) line up for a photo while standing under the engines of the Saturn V rocket on display. The U.S. candidates include Clayton C. Anderson, Lee J. Archambault, Tracy E. Caldwell (Ph.D.), Gregory E. Chamitoff (Ph.D.), Timothy J. Creamer, Christopher J. Ferguson, Michael J. Foreman, Michael E. Fossum, Kenneth T. Ham, Patricia C. Hilliard (M.D.), Gregory C. Johnson, Gregory H. Johnson, Stanley G. Love (Ph.D.), Leland D. Melvin, Barbara R. Morgan, William A. Oefelein, John D. Olivas (Ph.D.), Nicholas J.M. Patrick (Ph.D.), Alan G. Poindexter, Garrett E. Reisman (Ph.D.), Steven R. Swanson, Douglas H. Wheelock, Sunita L. Williams, Neil W. Woodward III, George D. Zamka; and international candidates Leopold Eyharts, Paolo Nespoli, Hans Schlegel, Roberto Vittori, Bjarni V. Tryggvason, and Marcos Pontes. The class is at KSC for training activities, including fire training and a flight awareness program, plus touring the OPF, SSME Processing Facility, VAB, SSPF, launch pads, SLF, Apollo/Saturn V Center and the crew headquarters.

  19. 1998 astronaut candidates tour KSC

    NASA Technical Reports Server (NTRS)

    1999-01-01

    At the Apollo/Saturn V Center, some of the 1998 astronaut candidate class (group 17) line up for a photo during a tour of facilities at KSC. The U.S. candidates include Clayton C. Anderson, Lee J. Archambault, Tracy E. Caldwell (Ph.D.), Gregory E. Chamitoff (Ph.D.), Timothy J. Creamer, Christopher J. Ferguson, Michael J. Foreman, Michael E. Fossum, Kenneth T. Ham, Patricia C. Hilliard (M.D.), Gregory C. Johnson, Gregory H. Johnson, Stanley G. Love (Ph.D.), Leland D. Melvin, Barbara R. Morgan, William A. Oefelein, John D. Olivas (Ph.D.), Nicholas J.M. Patrick (Ph.D.), Alan G. Poindexter, Garrett E. Reisman (Ph.D.), Steven R. Swanson, Douglas H. Wheelock, Sunita L. Williams, Neil W. Woodward III, George D. Zamka; and international candidates Leopold Eyharts, Paolo Nespoli, Hans Schlegel, Roberto Vittori, Bjarni V. Tryggvason, and Marcos Pontes. The class is at KSC for training activities, including fire training and a flight awareness program, plus touring the OPF, SSME Processing Facility, VAB, SSPF, launch pads, SLF and the crew headquarters.

  20. Wasson's alternative candidates for soma.

    PubMed

    Riedlinger, T J

    1993-01-01

    Citing recently published challenges to R. Gordon Wasson's identification of Vedic soma as the psychoactive mushroom Amanita muscaria (fly-agaric), this article reviews unpublished letters by Wasson in which he considered and rejected other psychoactive plants as candidates, including the mint Lagochilus inebrians, Convolvulaceae (morning glory) seeds, the fungal parasite Claviceps purpurea (ergot), and especially the psilocybin mushroom Stropharia cubensis, known also as Psilocybe cubensis. Apart from their historical interest, these letters--from the Tina and Gordon Wasson Ethnomycological Collection at the Harvard Botanical Museum--demonstrate that Wasson remained open to refinements of his theory. PMID:8377083

  1. Environmentally friendly lubricating oil candidate.

    PubMed

    Ozgülsün, A; Karaosmanoğlu, F

    1999-01-01

    Synthetic lubricating oils based on renewable sources, excluding petroleum, have a great importance among all of the lubricating oil alternatives that are included in the research field about clean and environmentally friendly lubricating oil technologies. One of the environmentally friendly lubricating oils is a vegetable oil-based product. In this study, the esterification product of oleic acid with a fraction of molasses fusel oil as a lubricating oil candidate was determined according to the American Society for Testing and Materials (ASTM) standard tests. The results indicate that the ester product can be used as an environmental friendly lubricating oil or lubricating oil additive. PMID:10399269

  2. Four Republican Presidential Candidates Debate Educational Issues.

    ERIC Educational Resources Information Center

    Equity and Excellence, 1988

    1988-01-01

    Provides the transcript of a September 1987 debate on educational issues between Republican presidential candidates Jack Kemp and Pierre du Pont. Interspersed throughout the transcript are written responses to questions submitted to additional candidates Robert Dole and George Bush. (BJV)

  3. Kepler Discovers Earth-size Planet Candidates

    NASA Video Gallery

    NASA's Kepler mission has discovered its first Earth-size planet candidates and its first candidates in the habitable zone, a region where liquid water could exist on a planet's surface. Five of th...

  4. A DIRECT MEASUREMENT OF THE HEAT RELEASE IN THE OUTER CRUST OF THE TRANSIENTLY ACCRETING NEUTRON STAR XTE J1709-267

    SciTech Connect

    Degenaar, N.; Miller, J. M.; Wijnands, R.

    2013-04-20

    The heating and cooling of transiently accreting neutron stars provides a powerful probe of the structure and composition of their crust. Observations of superbursts and cooling of accretion-heated neutron stars require more heat release than is accounted for in current models. Obtaining firm constraints on the depth and magnitude of this extra heat is challenging and therefore its origin remains uncertain. We report on Swift and XMM-Newton observations of the transient neutron star low-mass X-ray binary XTE J1709-267, which were made in 2012 September-October when it transitioned to quiescence after a {approx_equal}10 week long accretion outburst. The source is detected with XMM-Newton at a 0.5-10 keV luminosity of L{sub X} {approx_equal} 2 Multiplication-Sign 10{sup 34}(D/8.5 kpc){sup 2} erg s{sup -1}. The X-ray spectrum consists of a thermal component that fits to a neutron star atmosphere model and a non-thermal emission tail, each of which contribute {approx_equal}50% to the total flux. The neutron star temperature decreases from {approx_equal}158 to {approx_equal}152 eV during the {approx_equal}8 hr long observation. This can be interpreted as cooling of a crustal layer located at a column density of y {approx_equal} 5 Multiplication-Sign 10{sup 12} g cm{sup -2} ({approx_equal}50 m inside the neutron star), which is just below the ignition depth of superbursts. The required heat generation in the layers on top would be {approx_equal}0.06-0.13 MeV per accreted nucleon. The magnitude and depth rule out electron captures and nuclear fusion reactions as the heat source, but it may be accounted for by chemical separation of light and heavy nuclei. Low-level accretion offers an alternative explanation for the observed variability.

  5. Teacher Candidate Dispositions: Perspectives of Professional Expectations

    ERIC Educational Resources Information Center

    Wake, Donna; Bunn, Gary

    2016-01-01

    This study describes a programmatic effort to examine dispositions perceptions of teacher candidates entering the profession. Study participants included 114 master's level teaching candidates in their first semester of a nontraditional teacher education program. Teacher candidates scored themselves on a department disposition rubric designed to…

  6. 11 CFR 110.13 - Candidate debates.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... parties may stage candidate debates in accordance with this section and 11 CFR 114.4(f). (2) Broadcasters... periodical publications may stage candidate debates in accordance with this section and 11 CFR 114.4(f... candidate debates in accordance with 11 CFR part 100, subparts B and C and part 100, subparts D and E....

  7. 11 CFR 9002.2 - Candidate.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 11 Federal Elections 1 2010-01-01 2010-01-01 false Candidate. 9002.2 Section 9002.2 Federal Elections FEDERAL ELECTION COMMISSION PRESIDENTIAL ELECTION CAMPAIGN FUND: GENERAL ELECTION FINANCING DEFINITIONS § 9002.2 Candidate. (a) For the purposes of this subchapter, candidate means with respect to any presidential election, an individual who—...

  8. Lutetium +: A better clock candidate

    NASA Astrophysics Data System (ADS)

    Arnold, Kyle; Paez, Eduardo; Haciyev, Elnur; Arifin, Arifin; Cazan, Radu; Barrett, Murray

    2015-05-01

    With the extreme precision now reached by optical clocks it is reasonable to consider redefinition of the frequency standard. In doing so it is important to look beyond the current best-case efforts and have an eye on future possibilities. We will argue that singly ionized Lutetium is a strong candidate for the next generation of optical frequency standards. Lu + has a particularly narrow optical transition in combination with several advantageous properties for managing systematic uncertainties compared to the other atomic species. We summarize these properties and our specific strategies for managing the uncertainties due to external perturbations. Finally, we present the status of our ongoing experiments with trapped Lu +, including the results of precision measurements of its atomic structure.

  9. Photometric monitoring of polar candidates

    NASA Astrophysics Data System (ADS)

    Gabdeev, M. M.

    2015-10-01

    We present photometric observations of two polar candidates, IPHAS J052832.69+283837.6 and 1RXS J073346.0+261933. Both objects reveal brightness variations related to the orbital period with an amplitude of about 1m, and about 0ṃ5 on the long-termscale. The object IPHASJ052832.69+283837.6 also exhibits variations of color indices and light curve shape. Long-term observations allowed us to determine the orbital period of the first system and refine the orbital period of the second system, which proved to be {P_{ord}} = 0_.^d055593(4) and {P_{ord}} = 0_.^d139095(2) respectively. The photometric data analysis proves that these systems are polars.

  10. Asteroid candidates for mass determination

    NASA Astrophysics Data System (ADS)

    Galád, A.

    2001-04-01

    The first 9511 numbered asteroids are studied in terms of their mutual closest approaches and encounter velocities during the period from November 6, 1967, to September 13, 2023. Several large asteroids (diameter 200 km and above) were (will be) encountered by smaller counterparts within a distance of 0.0200 AU. Thus, they are possible candidates for mass determination by the astrometrical method. Similarly, the search for effective perturbers is extended to even smaller asteroids for the much closer separation distance of 0.0020 AU and below. Only the simplified method for evaluation of observable effects on a perturbed body is used. Asteroid masses alone are not computed here. But a stronger criterion to reveal pairs for this purpose in comparison to some specially devoted papers should compensate for the difference and act as a reliable test. The best candidates for mass determination at present are asteroids (1), (2), (4), (10), (11), (24), (52) and (65). This list may be extended by at least (29) in the next 5 years and by many others in the next two decades. Several other strong perturbers from the last three decades are not included in the list, while there is still only a limited number of (or no) precise and reliable observations of perturbed asteroids before a close encounter. It seems that a perturbation by (10) is at least as effective as that by (2) and could be included in asteroid orbit determination in the future. Except for their bulk density determinations (knowing the size), the masses of perturbers could occasionally be used to improve the precision of the computed orbit for perturbed large-numbered and unnumbered asteroids as well.

  11. Phase Diagram of HgTe -ZnTe Pseudobinary and Density, Heat Capacity, and Enthalphy of Mixing of Hg(sub 1-x)Zn(sub x)Te Pseudobinary Melts

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Sha, Yi-Gao; Mazuruk, K.; Lehoczky, S. L.

    1996-01-01

    In this article, the solidus temperatures of the Hg(sub 1-x) Zn(sub x)Te pseudobinary phase diagram for several compositions in the low x region were measured by differential thermal analysis and the HgTe-ZnTe pseudobinary phase diagram was constructed. The densities of two HgZnTe melts, x = 0.10 and 0.16, were determined by an in situ pycnometric technique in a transparent furnace over, respectively, 110 and 50 C ranges of temperature. The thermodynamic properties of the melts, such as the heat capacity and enthalpy of mixing, were calculated for temperatures between the liquidus and 1500 C by assuming an associated solution model for the liquid phase.

  12. Defect structure of Cd{sub x}Hg{sub 1-x}Te films grown by liquid-phase epitaxy, studied by means of low-energy ion treatment

    SciTech Connect

    Izhnin, I. I. Izhnin, A. I.; Fitsych, E. I.; Smirnova, N. A.; Denisov, I. A.; Pociask, M.; Mynbaev, K. D.

    2011-09-15

    Treatment with low-energy ions and measurements of electrical parameters of samples have been used to study the defect structure of Cd{sub x}Hg{sub 1-x}Te films grown by liquid-phase epitaxy. The films contain neutral defects supposedly associated with tellurium nanoinclusions. Ion treatment electrically activates these defects, with a high concentration of donor centers ({approx}10{sup 17} cm{sup -3}) created in the films. These defects decompose in {approx}10{sup 3} min of aging at room temperature. Then the properties of the material are determined by the concentration of residual donors, which is found to be very low (down to {approx}10{sup 14} cm{sup -3}) for the films under study.

  13. Homo- and heterovalent substitutions in the new clathrates I Si30P16Te(8-x)Se(x) and Si(30+x)P(16-x)Te(8-x)Br(x): synthesis, crystal structure, and thermoelectric properties.

    PubMed

    Abramchuk, Nikolay S; Carrillo-Cabrera, Wilder; Veremchuk, Igor; Oeschler, Niels; Olenev, Andrei V; Prots, Yurii; Burkhardt, Ulrich; Dikarev, Evgeny V; Grin, Juri; Shevelkov, Andrei V

    2012-11-01

    The new cationic clathrates I Si(30)P(16)Te(8-x)Se(x) and Si(30+x)P(16-x)Te(8-x)Br(x) were synthesized by the standard ampule technique. The Si(30)P(16)Te(8-x)Se(x) (x = 0-2.3) clathrates crystallize in the cubic space group Pm3̅n with the unit cell parameter a ranging from 9.9382(2) to 9.9696(1) Å. In the case of the Si(30+x)P(16-x)Te(8-x)Br(x) (x = 1-6.4) clathrates, the lattice parameter varies from 9.9720(8) to 10.0405(1) Å; at lower Si/P ratios (x = 1-3) the ordering of bromine atoms induces the splitting of the guest positions and causes the transformation from the space group Pm3n to Pm3. Irrespective of the structure peculiarities, the normal temperature motion of the guest atoms inside the oversized cages of the framework is observed. The title clathrates possess very low thermal expansion coefficients ranging from 6.6 × 10(-6) to 1.0 × 10(-5) K(-1) in the temperature range of 298-1100 K. The characteristic Debye temperature is about 490 K. Measurements of the electrical resistivity and thermopower showed typical behavior of p-type thermally activated semiconductors, whereas the temperature behavior of the thermal conductivity is glasslike and in general consistent with the PGEC concept. The highest value of the thermoelectric figure of merit (ZT = 0.1) was achieved for the Br-bearing clathrate Si(32.1(2))P(13.9(2))Te(6.6(2))Br(1.0(1)) at 750 K. PMID:23072375

  14. Special Education Teacher Candidate Assessment: A Review

    ERIC Educational Resources Information Center

    McCall, Zach; McHatton, Patricia Alvarez; Shealey, Monika Williams

    2014-01-01

    Teacher preparation has been under intense scrutiny in recent years. In order for preparation of special education teacher candidates to remain viable, candidate assessment practices must apply practices identified in the extant literature base, while special education teacher education researchers must extend this base with rigorous efforts to…

  15. 47 CFR 76.206 - Candidate rates.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Candidate rates. 76.206 Section 76.206 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Cablecasting § 76.206 Candidate rates. (a) Charges for use of cable...

  16. 47 CFR 76.206 - Candidate rates.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Candidate rates. 76.206 Section 76.206 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Cablecasting § 76.206 Candidate rates. (a) Charges for use of cable...

  17. 47 CFR 76.206 - Candidate rates.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Candidate rates. 76.206 Section 76.206 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Cablecasting § 76.206 Candidate rates. (a) Charges for use of cable...

  18. 47 CFR 76.206 - Candidate rates.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Candidate rates. 76.206 Section 76.206 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Cablecasting § 76.206 Candidate rates. (a) Charges for use of cable...

  19. Portfolio Development for Teacher Candidates. ERIC Digest.

    ERIC Educational Resources Information Center

    Takona, James P.

    This Digest is intended to help teacher candidates systematically gauge their progress toward the teaching profession by developing a portfolio. Portfolios are one way to assess teacher candidates, and they are a major requirement for experienced teachers seeking board certification from the National Board for Professional Teaching Standards. The…

  20. 11 CFR 110.13 - Candidate debates.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... political parties may stage candidate debates in accordance with this section and 11 CFR 114.4(f). (2... CFR 114.4(f), provided that they are not owned or controlled by a political party, political committee... also cover or carry candidate debates in accordance with 11 CFR part 100, subparts B and C and part...

  1. 11 CFR 110.13 - Candidate debates.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... political parties may stage candidate debates in accordance with this section and 11 CFR 114.4(f). (2... CFR 114.4(f), provided that they are not owned or controlled by a political party, political committee... also cover or carry candidate debates in accordance with 11 CFR part 100, subparts B and C and part...

  2. 11 CFR 110.13 - Candidate debates.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... political parties may stage candidate debates in accordance with this section and 11 CFR 114.4(f). (2... CFR 114.4(f), provided that they are not owned or controlled by a political party, political committee... also cover or carry candidate debates in accordance with 11 CFR part 100, subparts B and C and part...

  3. 11 CFR 110.13 - Candidate debates.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 11 Federal Elections 1 2010-01-01 2010-01-01 false Candidate debates. 110.13 Section 110.13 Federal Elections FEDERAL ELECTION COMMISSION GENERAL CONTRIBUTION AND EXPENDITURE LIMITATIONS AND PROHIBITIONS § 110.13 Candidate debates. (a) Staging organizations. (1) Nonprofit organizations described in 26 U.S.C. 501 (c)(3) or (c)(4) and which do...

  4. 47 CFR 73.1942 - Candidate rates.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Candidate rates. 73.1942 Section 73.1942 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Rules Applicable to All Broadcast Stations § 73.1942 Candidate rates. (a) Charges for use of...

  5. 47 CFR 76.206 - Candidate rates.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Candidate rates. 76.206 Section 76.206 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Cablecasting § 76.206 Candidate rates. (a) Charges for use of cable...

  6. Critical Thinking Tendencies among Teacher Candidates

    ERIC Educational Resources Information Center

    Genc, Salih Zeki

    2008-01-01

    The study aims to determine critical thinking tendencies among teacher candidates. 720 students from primary school teaching department (Primary School Teaching Programme, Science Teaching Programme and Pre-School Teaching Programme) form the sample of the study. When the gender and age distributions were investigated, 253 candidates are males and…

  7. New supernova remnant candidates in M 31.

    NASA Astrophysics Data System (ADS)

    Magnier, E. A.; Prins, S.; van Paradijs, J.; Lewin, W. H. G.; Supper, R.; Hasinger, G.; Pietsch, W.; Truemper, J.

    1995-12-01

    We have performed a CCD Hα, [SII], V survey of ~1.0 square degree of the disk of M 31 to search for new supernova remnant (SNR) candidates. We have identified candidates based on a combination of criteria: optical line-flux ratios, the presence or absence of ionizing blue stars, and optical morphology. We have identified a total of 178 candidate SNRs, divided into three confidence categories: 13 with the highest confidence, 54 with moderate confidence, and 111 with the lowest confidence. We have also identified 14 large structures with the characteristics of the superbubbles seen in the Galaxy and Magellanic Clouds. Of our 178 candidates, 15 have been identified in previous searches (Braun & Walterbos 1993; Blair et al. 1981; D'Odorico et al. 1980). We present finding charts of all candidate SNRs and the superbubbles we have noted. We also present a detailed discussion of SNR searches in the Local Group.

  8. Undercover Stars Among Exoplanet Candidates

    NASA Astrophysics Data System (ADS)

    2005-03-01

    events by monitoring the brightness of a very large number of stars over extended time intervals. During the past years, it has also included a search for periodic, very shallow "dips" in the brightness of stars, caused by the regular transit of small orbiting objects (small stars, brown dwarfs [2] or Jupiter-size planets). The OGLE team has since announced 177 "planetary transit candidates" from their survey of several hundred thousand stars in three southern sky fields, one in the direction of the Galactic Centre, another within the Carina constellation and the third within the Centaurus/Musca constellations. The nature of the transiting object can however only be established by subsequent radial-velocity observations of the parent star. The size of the velocity variations (the amplitude) is directly related to the mass of the companion object and therefore allows discrimination between stars and planets as the cause of the observed brightness "dip". A Bonanza of Low-Mass Stars An international team of astronomers [3] has made use of the 8.2-m VLT Kueyen telescope for this work. Profiting from the multiplex capacity of the FLAMES/UVES facility that permits to obtain high-resolution spectra of up to 8 objects simultaneously, they have looked at 60 OGLE transit candidate stars, measuring their radial velocities with an accuracy of about 50 m/s [4]. This ambitious programme has so far resulted in the discovery of five new transiting exoplanets (see, e.g., ESO PR 11/04 for the announcement of two of those). Most of the other transit candidates identified by OGLE have turned out to be eclipsing binaries, that is, in most cases common, small and low-mass stars passing in front of a solar-like star. This additional wealth of data on small and light stars is a real bonanza for the astronomers. Constraining the Relation Between Mass and Radius Low-mass stars are exceptionally interesting objects, also because the physical conditions in their interiors have much in common with

  9. SALT Classification of DES Supernova Candidates

    NASA Astrophysics Data System (ADS)

    Kasai, E.; Bassett, B.; Crawford, S.; Smith, M.; Gupta, R.; Kovacs, E.; Kuhlmann, S.; Spinka, H.; Ahn, E.; Finley, D. A.; Frieman, J.; Marriner, J.; Wester, W.; Aldering, G.; Kim, A. G.; Thomas, R. C.; Barbary, K.; Bloom, J. S.; Goldstein, D.; Nugent, P.; Perlmutter, S.; Foley, R. J.; Castander, F. J.; Desai, S.; Paech, K.; Smith, R. C.; Schubnell, M.; Kessler, R.; Scolnic, D.; Covarrubias, R. A.; Brout, D. J.; Fischer, J. A.; Gladney, L.; March, M.; Sako, M.; Wolf, R. C.; Brown, P. J.; Krisciunas, K.; Suntzeff, N.; D'Andrea, C.; Nichol, R.; Papadopoulos, A.; Sullivan, M.; Maartens, R.

    2015-02-01

    We report optical spectroscopy of a supernova candidates discovered by the Dark Energy Survey. The spectra (400-850 nm) were obtained using the Robert Stobie Spectrograph (RSS) on the Southern African Large Telescope (SALT).

  10. Seven Democratic Presidential Candidates Debate Educational Issues.

    ERIC Educational Resources Information Center

    Equity and Excellence, 1988

    1988-01-01

    Provides the transcript of a debate on educational issues among Democratic presidential candidates Paul Simon, Albert Gore, Joseph Biden, Jesse Jackson, Bruce Babbitt, Richard Gephart, and Michael Dukakis. (BJV)

  11. Triton stellar occultation candidates - 1992-1994

    NASA Technical Reports Server (NTRS)

    Mcdonald, S. W.; Elliot, J. T.

    1992-01-01

    A search for Triton stellar occultation candidates for the period 1992-1994 has been completed with CCD strip-scanning observations. The search reached an R magnitude of about 17.4 and found 129 candidates within 1.5 arcsec of Triton's ephemeris during this period. Of these events, around 30 occultations are expected to be visible from the earth, indicating that a number of Triton occultation events should be visible from major observatories. Even the faintest of the present candidate events could produce useful occultation data if observed with a large enough telescope. The present astrometric accuracy is inadequate to identify which of these appulse events will produce occultations on the earth; further astrometry is needed to refine the predictions for positive occultation identification. To aid in selecting candidates for additional astrometric and photometric studies, finder charts and earth-based visibility charts for each event are included.

  12. 29 CFR 452.28 - Unopposed candidates.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... officers or delegates that would otherwise be required by the Act to be held by secret ballot need not be held by secret ballot when all candidates are unopposed and the following conditions are met: (a)...

  13. Updated candidate list for engineered barrier materials

    SciTech Connect

    McCright, R.D.

    1995-10-01

    This report describes candidate materials to be evaluated over the next several years during advanced design phases for the waste package to be used for the underground disposal of high-level radioactive wastes at the Yucca Mountain facility.

  14. Towards Treating Chemistry Teacher Candidates as Human

    NASA Astrophysics Data System (ADS)

    Lewthwaite, Brian Ellis

    2008-05-01

    This research inquiry investigates the factors influencing chemistry teacher candidates’ development during their extended practica in the second and final year of an After-Degree Bachelor of Education at a university in central Canada. A variety of data sources are used to identify the risk and protective factors impeding and contributing to the achievement of their chemistry pedagogical aspirations. Two theoretical frameworks, both having their origins in the pioneering work of Kurt Lewin, are used to conceptualize how a complex amalgam of personal attribute and environmental factors and the interplay among these factors influence teacher candidate developmental trajectories. The tenets of both Bronfenbrenner’s bioecological model and Learning Environment research provide insights into how the factors influencing teacher candidate development can be understood and systematically documented to provide a template for reflective consideration of the practicum experience for both teacher candidates and those involved in fostering the development of chemistry teacher candidates.

  15. Candidate preferences and expectations of election outcomes

    PubMed Central

    Delavande, Adeline; Manski, Charles F.

    2012-01-01

    Analysis of data from the American Life Panel shows that in the presidential election of 2008 and in multiple statewide elections in 2010, citizens exhibited large differences in their expectations of election outcomes. Expectations were strongly positively associated with candidate preferences, persons tending to believe that their preferred candidate is more likely to win the election. Committed supporters of opposing candidates regularly differed by 20–30% in their assessments of the likelihood that each candidate would win. These findings contribute evidence on the false consensus effect, the empirical regularity that own preferences tend to be positively associated with perceptions of social preferences. We used unique measures of preferences and perceptions that enabled respondents to express uncertainty flexibly. We studied a setting that would a priori seem inhospitable to false consensus—one where persons have little private information on social preferences but substantial common knowledge provided by media reports of election polls. PMID:22355121

  16. Candidates for GRL North American coeditor sought

    NASA Astrophysics Data System (ADS)

    Geophysical Research Letters (GRL), AGU's all-Union primary research journal, is seeking candidates and nominations for candidates to succeed Rob Van der Voo, whose term as North American Coeditor ends December 31, 1986. The successful candidate will be challenged to seek out interesting papers at the forefront of the geophysical sciences and to attempt to strike a balance in the publication of that science that is of interest to the entire AGU membership. While complementing the interests of Editor in Chief Alex Dessler, the successful candidate will also be challenged to maintain rapid publication time and minimize the publication of research that is routine. The North American Coeditor should be prepared to welcome controversial research papers that challenge conventional wisdom in all fields of interest to AGU. The individual selected for this prestigious position will have a vital role in making GRL an even more important and more exciting journal that readers look forward to receiving each month.

  17. Vaccine candidates for malaria: what's new?

    PubMed

    Takashima, Eizo; Morita, Masayuki; Tsuboi, Takafumi

    2016-01-01

    Although it is more than a decade since the parasite genome information was obtained, standardized novel genome-wide selection/prioritization strategies for candidacy of malaria vaccine antigens are still sought. In the quest to systematically identify candidates, it is impossible to overemphasize the usefulness of wheat germ cell-free technology in expressing quality proteins for the post-genome vaccine candidate discovery. PMID:26559316

  18. A New Way to Confirm Planet Candidates

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-05-01

    What was the big deal behind the Kepler news conference yesterday? Its not just that the number of confirmed planets found by Kepler has more than doubled (though thats certainly exciting news!). Whats especially interesting is the way in which these new planets were confirmed.Number of planet discoveries by year since 1995, including previous non-Kepler discoveries (blue), previous Kepler discoveries (light blue) and the newly validated Kepler planets (orange). [NASA Ames/W. Stenzel; Princeton University/T. Morton]No Need for Follow-UpBefore Kepler, the way we confirmed planet candidates was with follow-up observations. The candidate could be validated either by directly imaging (which is rare) or obtaining a large number radial-velocity measurements of the wobble of the planets host star due to the planets orbit. But once Kepler started producing planet candidates, these approaches to validation became less feasible. A lot of Kepler candidates are small and orbit faint stars, making follow-up observations difficult or impossible.This problem is what inspired the development of whats known as probabilistic validation, an analysis technique that involves assessing the likelihood that the candidates signal is caused by various false-positive scenarios. Using this technique allows astronomers to estimate the likelihood of a candidate signal being a true planet detection; if that likelihood is high enough, the planet candidate can be confirmed without the need for follow-up observations.A breakdown of the catalog of Kepler Objects of Interest. Just over half had previously been identified as false positives or confirmed as candidates. 1284 are newly validated, and another 455 have FPP of1090%. [Morton et al. 2016]Probabilistic validation has been used in the past to confirm individual planet candidates in Kepler data, but now Timothy Morton (Princeton University) and collaborators have taken this to a new level: they developed the first code thats designed to do fully

  19. Spectroscopy of Kepler Candidate Exoplanet Host Stars

    NASA Astrophysics Data System (ADS)

    Everett, Mark E.; Howell, Steve B.; Silva, David R.; Szkody, Paula

    2014-02-01

    Currently the NASA Kepler Mission has identified 3449 exoplanet candidates, one third with estimated radii R_p<2.5R_oplus and orbiting faint (m_Kep>14.5) host stars. The NASA sponsored Kepler Follow-up Program is focusing on small exoplanet candidates (R_p<2.5R_oplus) and those in habitable zone orbits. Planet radii estimates depend on estimates of host star radii. Based on spectra previously obtained at the KPNO Mayall 4-m for 220 stars with candidate exoplanets, Everett et al. (2013) have shown that many host stars are larger than originally assumed (up to factor of 2). Therefore, the exoplanet candidates they host must be larger than originally assumed, which conversely reduces the number of known Earth- sized exoplanet candidates. Determination of the frequency of such Earth-sized planets is a cornerstone Kepler mission objective and of keen general interest. These Mayall spectra were also used to confirm the Buchhave et al. (2012) result that exoplanet candidates larger than 4R_oplus in short-period orbits are preferentially associated with host stars with solar or higher metallicity, using a fainter and larger sample of stars than Buchhave et al. In short, followup Mayall optical spectroscopy is critical to confirming the detection of Earth-sized exoplanets, a Kepler cornerstone goal, as well as characterizing the relationship between host star properties and planetary system properties. Here, we propose to continue our reconnaissance survey with a focus on the smallest (most rare) exoplanet candidates orbiting the faintest Kepler host stars.

  20. Jellyfish Galaxy Candidates at Low Redshift

    NASA Astrophysics Data System (ADS)

    Poggianti, B. M.; Fasano, G.; Omizzolo, A.; Gullieuszik, M.; Bettoni, D.; Moretti, A.; Paccagnella, A.; Jaffé, Y. L.; Vulcani, B.; Fritz, J.; Couch, W.; D'Onofrio, M.

    2016-03-01

    Galaxies that are being stripped of their gas can sometimes be recognized from their optical appearance. Extreme examples of stripped galaxies are the so-called “jellyfish galaxies” that exhibit tentacles of debris material with a characteristic jellyfish morphology. We have conducted the first systematic search for galaxies that are being stripped of their gas at low-z (z = 0.04-0.07) in different environments, selecting galaxies with varying degrees of morphological evidence for stripping. We have visually inspected B- and V-band images and identified 344 candidates in 71 galaxy clusters of the OMEGAWINGS+WINGS sample and 75 candidates in groups and lower mass structures in the PM2GC sample. We present the atlas of stripping candidates and a first analysis of their environment and their basic properties, such as morphologies, star formation rates and galaxy stellar masses. Candidates are found in all clusters and at all clustercentric radii, and their number does not correlate with the cluster velocity dispersion σ or X-ray luminosity LX. Interestingly, convincing cases of candidates are also found in groups and lower mass halos (1011-1014M⊙), although the physical mechanism at work needs to be securely identified. All the candidates are disky, have stellar masses ranging from log M/M⊙ < 9 to > 11.5 and the majority of them form stars at a rate that is on average a factor of 2 higher (2.5σ) compared to non-stripped galaxies of similar mass. The few post-starburst and passive candidates have weak stripping evidence. We conclude that disturbed morphologies suggestive of stripping phenomena are ubiquitous in clusters and could be present even in groups and low mass halos. Further studies will reveal the physics of the gas stripping and clarify the mechanisms at work.

  1. CANDID: A flexible method for prioritizing candidate genes for complex human traits

    PubMed Central

    Hutz, Janna E.; Kraja, Aldi T.; McLeod, Howard L.; Province, Michael A.

    2015-01-01

    Genomewide studies and localized candidate gene approaches have become everyday study designs for identifying polymorphisms in genes that influence complex human traits. Yet, in general, the number of significant findings and the need to focus in smaller regions require a prioritization of genes for further study. Some candidate gene identification algorithms have been proposed in recent years to attempt to streamline this prioritization, but many suffer from limitations imposed by the source data or are difficult to use and understand. CANDID is a prioritization algorithm designed to produce impartial, accurate rankings of candidate genes that influence complex human traits. CANDID can use information from publications, protein domain descriptions, cross-species conservation measures, gene expression profiles, and protein-protein interactions in its analysis. Additionally, users may supplement these data sources with results from linkage, association and other studies. CANDID was tested on well-known complex trait genes using data from the Online Mendelian Inheritance in Man (OMIM) database. Additionally, CANDID was evaluated in a modeled gene discovery environment, where it ranked genes whose trait associations were published after CANDID’s databases were compiled. In all settings, CANDID exhibited high sensitivity and specificity, indicating an improvement upon previously published algorithms. Its accuracy and ease of use make CANDID a highly useful tool in study design and analysis for complex human traits. PMID:18613097

  2. A PROPELLER-EFFECT INTERPRETATION OF MAXI/GSC LIGHT CURVES OF 4U 1608-52 AND Aql X-1 AND APPLICATION TO XTE J1701-462

    SciTech Connect

    Asai, K.; Matsuoka, M.; Mihara, T.; Sugizaki, M.; Serino, M.; Nakahira, S.; Negoro, H.; Ueda, Y.; Yamaoka, K.

    2013-08-20

    We present the luminosity dwell-time distributions during the hard states of two low-mass X-ray binaries containing a neutron star (NS), 4U 1608-52 and Aql X-1, observed with MAXI/GSC. The luminosity distributions show a steep cutoff on the low-luminosity side at {approx}1.0 Multiplication-Sign 10{sup 36} erg s{sup -1} in both sources. The cutoff implies a rapid luminosity decrease in their outburst decay phases and this decrease can be interpreted as being due to the propeller effect. We estimate the surface magnetic field of 4U 1608-52 to be (0.5-1.6) Multiplication-Sign 10{sup 8} G and Aql X-1 to be (0.6-1.9) Multiplication-Sign 10{sup 8} G from the cutoff luminosity and apply the same propeller mechanism to the similar rapid luminosity decrease observed in the transient Z source, XTE J1701-462, with RXTE/ASM. Assuming that the spin period of the NS is on the order of milliseconds, the observed cutoff luminosity implies a surface magnetic field on the order of 10{sup 9} G.

  3. A Propeller-effect Interpretation of MAXI/GSC Light Curves of 4U 1608-52 and Aql X-1 and Application to XTE J1701-462

    NASA Astrophysics Data System (ADS)

    Asai, K.; Matsuoka, M.; Mihara, T.; Sugizaki, M.; Serino, M.; Nakahira, S.; Negoro, H.; Ueda, Y.; Yamaoka, K.

    2013-08-01

    We present the luminosity dwell-time distributions during the hard states of two low-mass X-ray binaries containing a neutron star (NS), 4U 1608-52 and Aql X-1, observed with MAXI/GSC. The luminosity distributions show a steep cutoff on the low-luminosity side at ~1.0 × 1036 erg s-1 in both sources. The cutoff implies a rapid luminosity decrease in their outburst decay phases and this decrease can be interpreted as being due to the propeller effect. We estimate the surface magnetic field of 4U 1608-52 to be (0.5-1.6) × 108 G and Aql X-1 to be (0.6-1.9) × 108 G from the cutoff luminosity and apply the same propeller mechanism to the similar rapid luminosity decrease observed in the transient Z source, XTE J1701-462, with RXTE/ASM. Assuming that the spin period of the NS is on the order of milliseconds, the observed cutoff luminosity implies a surface magnetic field on the order of 109 G.

  4. Evaluating historical candidate genes for schizophrenia.

    PubMed

    Farrell, M S; Werge, T; Sklar, P; Owen, M J; Ophoff, R A; O'Donovan, M C; Corvin, A; Cichon, S; Sullivan, P F

    2015-05-01

    Prior to the genome-wide association era, candidate gene studies were a major approach in schizophrenia genetics. In this invited review, we consider the current status of 25 historical candidate genes for schizophrenia (for example, COMT, DISC1, DTNBP1 and NRG1). The initial study for 24 of these genes explicitly evaluated common variant hypotheses about schizophrenia. Our evaluation included a meta-analysis of the candidate gene literature, incorporation of the results of the largest genomic study yet published for schizophrenia, ratings from informed researchers who have published on these genes, and ratings from 24 schizophrenia geneticists. On the basis of current empirical evidence and mostly consensual assessments of informed opinion, it appears that the historical candidate gene literature did not yield clear insights into the genetic basis of schizophrenia. A likely reason why historical candidate gene studies did not achieve their primary aims is inadequate statistical power. However, the considerable efforts embodied in these early studies unquestionably set the stage for current successes in genomic approaches to schizophrenia. PMID:25754081

  5. Phenoscape: Identifying Candidate Genes for Evolutionary Phenotypes.

    PubMed

    Edmunds, Richard C; Su, Baofeng; Balhoff, James P; Eames, B Frank; Dahdul, Wasila M; Lapp, Hilmar; Lundberg, John G; Vision, Todd J; Dunham, Rex A; Mabee, Paula M; Westerfield, Monte

    2016-01-01

    Phenotypes resulting from mutations in genetic model organisms can help reveal candidate genes for evolutionarily important phenotypic changes in related taxa. Although testing candidate gene hypotheses experimentally in nonmodel organisms is typically difficult, ontology-driven information systems can help generate testable hypotheses about developmental processes in experimentally tractable organisms. Here, we tested candidate gene hypotheses suggested by expert use of the Phenoscape Knowledgebase, specifically looking for genes that are candidates responsible for evolutionarily interesting phenotypes in the ostariophysan fishes that bear resemblance to mutant phenotypes in zebrafish. For this, we searched ZFIN for genetic perturbations that result in either loss of basihyal element or loss of scales phenotypes, because these are the ancestral phenotypes observed in catfishes (Siluriformes). We tested the identified candidate genes by examining their endogenous expression patterns in the channel catfish, Ictalurus punctatus. The experimental results were consistent with the hypotheses that these features evolved through disruption in developmental pathways at, or upstream of, brpf1 and eda/edar for the ancestral losses of basihyal element and scales, respectively. These results demonstrate that ontological annotations of the phenotypic effects of genetic alterations in model organisms, when aggregated within a knowledgebase, can be used effectively to generate testable, and useful, hypotheses about evolutionary changes in morphology. PMID:26500251

  6. Phenoscape: Identifying Candidate Genes for Evolutionary Phenotypes

    PubMed Central

    Edmunds, Richard C.; Su, Baofeng; Balhoff, James P.; Eames, B. Frank; Dahdul, Wasila M.; Lapp, Hilmar; Lundberg, John G.; Vision, Todd J.; Dunham, Rex A.; Mabee, Paula M.; Westerfield, Monte

    2016-01-01

    Phenotypes resulting from mutations in genetic model organisms can help reveal candidate genes for evolutionarily important phenotypic changes in related taxa. Although testing candidate gene hypotheses experimentally in nonmodel organisms is typically difficult, ontology-driven information systems can help generate testable hypotheses about developmental processes in experimentally tractable organisms. Here, we tested candidate gene hypotheses suggested by expert use of the Phenoscape Knowledgebase, specifically looking for genes that are candidates responsible for evolutionarily interesting phenotypes in the ostariophysan fishes that bear resemblance to mutant phenotypes in zebrafish. For this, we searched ZFIN for genetic perturbations that result in either loss of basihyal element or loss of scales phenotypes, because these are the ancestral phenotypes observed in catfishes (Siluriformes). We tested the identified candidate genes by examining their endogenous expression patterns in the channel catfish, Ictalurus punctatus. The experimental results were consistent with the hypotheses that these features evolved through disruption in developmental pathways at, or upstream of, brpf1 and eda/edar for the ancestral losses of basihyal element and scales, respectively. These results demonstrate that ontological annotations of the phenotypic effects of genetic alterations in model organisms, when aggregated within a knowledgebase, can be used effectively to generate testable, and useful, hypotheses about evolutionary changes in morphology. PMID:26500251

  7. Evaluating Historical Candidate Genes for Schizophrenia

    PubMed Central

    Farrell, Martilias; Werge, Thomas; Sklar, Pamela; Owen, Michael J.; Ophoff, Roel; O’Donovan, Michael; Corvin, Aiden; Cichon, Sven; Sullivan, Patrick F

    2015-01-01

    Prior to the genome-wide association era, candidate gene studies were a major approach in schizophrenia genetics. In this invited review, we consider the current status of 25 historical candidate genes for schizophrenia (e.g., COMT, DISC1, DTNBP1, and NRG1). The initial study for 24 of these genes explicitly evaluated common variant hypotheses about schizophrenia. Our evaluation included a meta-analysis of the candidate gene literature, incorporation of the results of the largest genomic study yet published for schizophrenia, ratings from informed researchers who have published on these genes, and ratings from 24 schizophrenia geneticists. On the basis of current empirical evidence and mostly consensual assessments of informed opinion, it appears that the historical candidate gene literature did not yield clear insights into the genetic basis of schizophrenia. A likely reason why historical candidate gene studies did not achieve their primary aims is inadequate statistical power. However, the considerable efforts embodied in these early studies unquestionably set the stage for current successes in genomic approaches to schizophrenia. PMID:25754081

  8. Developing Potential Candidates of Preclinical Preeclampsia

    PubMed Central

    Founds, Sandra; Zeng, Xuemei; Lykins, David; Roberts, James M.

    2015-01-01

    The potential for developing molecules of interest in preclinical preeclampsia from candidate genes that were discovered on gene expression microarray analysis has been challenged by limited access to additional first trimester trophoblast and decidual tissues. The question of whether these candidates encode secreted proteins that may be detected in maternal circulation early in pregnancy has been investigated using various proteomic methods. Pilot studies utilizing mass spectrometry based proteomic assays, along with enzyme linked immunosorbent assays (ELISAs), and Western immunoblotting in first trimester samples are reported. The novel targeted mass spectrometry methods led to robust multiple reaction monitoring assays. Despite detection of several candidates in early gestation, challenges persist. Future antibody-based studies may lead to a novel multiplex protein panel for screening or detection to prevent or mitigate preeclampsia. PMID:26580600

  9. SOPHIE velocimetry of Kepler transit candidates

    NASA Astrophysics Data System (ADS)

    Santerne, A.; Moutou, C.; Bouchy, F.; Hébrard, G.; Deleuil, M.; Díaz, R. F.; Bonomo, A. S.; Almenara, J.-M.

    2011-10-01

    As CoRoT, the Kepler space mission found a large amount of planetary transit candidates for which radial velocity follow-up is necessary in order to establish the planetary nature and then, to characterize the mass of the transiting companion. We are following up some interesting Kepler candidates with the SOPHIE spectrograph mounted at the 1.93-m telescope in Observatoire de Haute Provence (France). More than one year after the first Kepler release, we will present the strategy used to select the most promising Kepler candidates, within reach of a detection with SOPHIE, using the experience of more than 4 years of CoRoT, SWASP and HAT radial velocity follow-up. We will also highlight the results of the first year of observations that led to the discovery of several new transiting exoplanets and help the understanding of the false positive rate of the Kepler mission.

  10. The Angstrom Project: a new microlensing candidate

    NASA Astrophysics Data System (ADS)

    Kerins, E.; Darnley, M. J.; Newsam, A. M.; Duke, J. P.; Gould, A.; Street, C. Han B.-G. Park R. A.

    2008-12-01

    We report the discovery of a new microlensing candidate in M31 by the Angstrom Project M31 bulge microlensing survey using the Liverpool Telescope (La Palma). The candidate was discovered using difference imaging techniques by the Angstrom Project Alert System (APAS) in a series of Sloan i'-band images of the bulge of M31.

  11. Measuring Credential Candidates' Impact on Student Achievement

    ERIC Educational Resources Information Center

    Hagans, Kristi S.; Powers, Kristin

    2015-01-01

    The Council for the Accreditation of Educator Preparation (CAEP) requires faculty from educator preparation programs to provide evidence of credential candidates' impact on K-12 student learning. However, there is a paucity of information on preparation programs' use of direct assessments of student learning to gauge credential candidate…

  12. Automatic Classification of Kepler Planetary Transit Candidates

    NASA Astrophysics Data System (ADS)

    McCauliff, Sean D.; Jenkins, Jon M.; Catanzarite, Joseph; Burke, Christopher J.; Coughlin, Jeffrey L.; Twicken, Joseph D.; Tenenbaum, Peter; Seader, Shawn; Li, Jie; Cote, Miles

    2015-06-01

    In the first three years of operation, the Kepler mission found 3697 planet candidates (PCs) from a set of 18,406 transit-like features detected on more than 200,000 distinct stars. Vetting candidate signals manually by inspecting light curves and other diagnostic information is a labor intensive effort. Additionally, this classification methodology does not yield any information about the quality of PCs; all candidates are as credible as any other. The torrent of exoplanet discoveries will continue after Kepler, because a number of exoplanet surveys will have an even broader search area. This paper presents the application of machine-learning techniques to the classification of the exoplanet transit-like signals present in the Kepler light curve data. Transit-like detections are transformed into a uniform set of real-numbered attributes, the most important of which are described in this paper. Each of the known transit-like detections is assigned a class of PC; astrophysical false positive; or systematic, instrumental noise. We use a random forest algorithm to learn the mapping from attributes to classes on this training set. The random forest algorithm has been used previously to classify variable stars; this is the first time it has been used for exoplanet classification. We are able to achieve an overall error rate of 5.85% and an error rate for classifying exoplanets candidates of 2.81%.

  13. The Responsibility Education of Teacher Candidates

    ERIC Educational Resources Information Center

    Toremen, Fatih

    2011-01-01

    In this study, it was aimed to take the views and suggestions of academicians working at the faculty of education on what can be done about teacher candidates' responsibility education. This study was designed on the basis of qualitative research approach and purposive sampling method was used. Data were collected by unstructured interview method…

  14. Modeling Collaboration for ESL Teacher Candidates

    ERIC Educational Resources Information Center

    DelliCarpini, Margo

    2014-01-01

    This article reports on a semester-long project where a TESOL professor and English Education professor modeled collaborative teaching and explicitly taught collaboration skills to a coscheduled teaching methods class consisting of TESOL and Secondary English teacher candidates. Data were collected in the form of pre- and postsemester surveys. In…

  15. Promoting Team Leadership Skills in Doctoral Candidates

    ERIC Educational Resources Information Center

    Suleiman, Mahmoud; Whetton, Danny

    2014-01-01

    Doctoral programs can serve as an optimal opportunity for candidates to engage in tasks and activities to transform them and their schools. The paradigm shifts in such preparation involve moving from sitting and getting to making and taking. Most importantly, it requires building leadership skills and styles necessary to bring about desired change…

  16. Towards Treating Chemistry Teacher Candidates as Human

    ERIC Educational Resources Information Center

    Lewthwaite, Brian Ellis

    2008-01-01

    This research inquiry investigates the factors influencing chemistry teacher candidates' development during their extended practica in the second and final year of an After-Degree Bachelor of Education at a university in central Canada. A variety of data sources are used to identify the risk and protective factors impeding and contributing to the…

  17. Gallium-67 imaging in candidal esophagitis

    SciTech Connect

    Rundback, J.H.; Goldfarb, C.R.; Ongseng, F. )

    1990-01-01

    Ga-67 scanning has been used to evaluate esophageal carcinoma. It has demonstrated candidal infection in other body sites and, in one previous case, in the esophagus. The authors present a case of diffuse esophageal uptake of Ga-67 in esophageal candidiasis.

  18. Evaluating Constructivist Beliefs of Teacher Candidates

    ERIC Educational Resources Information Center

    Aldrich, Jennifer E.; Thomas, Kelli R.

    2005-01-01

    Teacher education programs that want their future teachers to embrace and employee constructivist principles must strive to provide opportunities for teacher candidates to develop an understanding of constructivism. The paper presents a structure for embedding constructivist principles into early childhood and elementary teacher education courses…

  19. Illustrations of Engagement Styles: Four Teacher Candidates

    ERIC Educational Resources Information Center

    Guerra, Norma S.

    2009-01-01

    The inherent complexity of preparing future teachers and the associated high stakes upon graduation continue to motivate educators to examine how best to engage teacher candidates as students so that they will be skilled and adaptable once they become teachers. To this end, a new conceptualization of engagement styles is presented and illustrated…

  20. Emotional Intelligence and Beginning Teacher Candidates

    ERIC Educational Resources Information Center

    Justice, Madeline; Espinoza, Sue

    2007-01-01

    According to the Bureau of Labor Statistics, Texas will need over 82,000 new teachers by 2008. Many teachers are leaving the profession within 5 years of being employed. Closing a revolving door, teacher preparation programs are discussing this phenomenon. One hundred sixty beginning teacher candidates were surveyed using the Emotional Skills…

  1. 1998 astronaut candidates tour KSC facilities

    NASA Technical Reports Server (NTRS)

    1999-01-01

    On the grounds of the Kennedy Space Center, members of the 1998 astronaut candidate class (Group 17) watch as candidate Clayton C. Anderson practices using firefighting equipment during fire training. The class is at KSC for training activities, including a flight awareness program, plus touring the OPF, VAB, SSPF, SSME Processing Facility, launch pads, SLF, Apollo/Saturn V Center, and the crew quarters. The other U.S. candidates in the '98 class are Lee J. Archambault, Tracy E. Caldwell (Ph.D.), Gregory E. Chamitoff (Ph.D.), Timothy J. Creamer, Christopher J. Ferguson, Michael J. Foreman, Michael E. Fossum, Kenneth T. Ham, Patricia C. Hilliard (M.D.), Gregory C. Johnson, Gregory H. Johnson, Stanley G. Love (Ph.D.), Leland D. Melvin, Barbara R. Morgan, William A. Oefelein, John D. Olivas (Ph.D.), Nicholas J.M. Patrick (Ph.D.), Alan G. Poindexter, Garrett E. Reisman (Ph.D.), Steven R. Swanson, Douglas H. Wheelock, Sunita L. Williams, Neil W. Woodward III, George D. Zamka; and the international candidates are Leopold Eyharts, Paolo Nespoli, Hans Schlegel, Roberto Vittori, Bjarni V. Tryggvason, and Marcos Pontes.

  2. 1998 astronaut candidates tour KSC facilities

    NASA Technical Reports Server (NTRS)

    1999-01-01

    On the grounds of the Kennedy Space Center, members of the 1998 astronaut candidate class (Group 17) watch as candidate Tracy E. Caldwell (Ph.D.) practices using firefighting equipment during fire training. The class is at KSC for training activities, including a flight awareness program, plus touring the OPF, VAB, SSPF, SSME Processing Facility, launch pads, SLF, Apollo/Saturn V Center, and the crew quarters. The other U.S. candidates in the '98 class are Clayton C. Anderson, Lee J. Archambault, Gregory E. Chamitoff (Ph.D.), Timothy J. Creamer, Christopher J. Ferguson, Michael J. Foreman, Michael E. Fossum, Kenneth T. Ham, Patricia C. Hilliard (M.D.), Gregory C. Johnson, Gregory H. Johnson, Stanley G. Love (Ph.D.), Leland D. Melvin, Barbara R. Morgan, William A. Oefelein, John D. Olivas (Ph.D.), Nicholas J.M. Patrick (Ph.D.), Alan G. Poindexter, Garrett E. Reisman (Ph.D.), Steven R. Swanson, Douglas H. Wheelock, Sunita L. Williams, Neil W. Woodward III, George D. Zamka; and the international candidates are Leopold Eyharts, Paolo Nespoli, Hans Schlegel, Roberto Vittori, Bjarni V. Tryggvason, and Marcos Pontes.

  3. 1998 astronaut candidates tour KSC facilities

    NASA Technical Reports Server (NTRS)

    1999-01-01

    On the grounds of the Kennedy Space Center, members of the 1998 astronaut candidate class (Group 17) watch as candidate Sunita L. Williams practices using firefighting equipment during fire training. The class is at KSC for training activities, including a flight awareness program, plus touring the OPF, VAB, SSPF, SSME Processing Facility, launch pads, SLF, Apollo/Saturn V Center, and the crew quarters. The other U.S. candidates in the '98 class are Clayton C. Anderson, Lee J. Archambault, Tracy E. Caldwell (Ph.D.), Gregory E. Chamitoff (Ph.D.), Timothy J. Creamer, Christopher J. Ferguson, Michael J. Foreman, Michael E. Fossum, Kenneth T. Ham, Patricia C. Hilliard (M.D.), Gregory C. Johnson, Gregory H. Johnson, Stanley G. Love (Ph.D.), Leland D. Melvin, Barbara R. Morgan, William A. Oefelein, John D. Olivas (Ph.D.), Nicholas J.M. Patrick (Ph.D.), Alan G. Poindexter, Garrett E. Reisman (Ph.D.), Steven R. Swanson, Douglas H. Wheelock, Neil W. Woodward III, George D. Zamka; and the international candidates are Leopold Eyharts, Paolo Nespoli, Hans Schlegel, Roberto Vittori, Bjarni V. Tryggvason, and Marcos Pontes.

  4. 1998 astronaut candidates tour KSC facilities

    NASA Technical Reports Server (NTRS)

    1999-01-01

    On the grounds of the Kennedy Space Center, members of the 1998 astronaut candidate class (Group 17) watch as candidate Patricia C. Hilliard (M.D.) practices using firefighting equipment during fire training. The class is at KSC for training activities, including a flight awareness program, plus touring the OPF, VAB, SSPF, SSME Processing Facility, launch pads, SLF, Apollo/Saturn V Center, and the crew quarters. The other U.S. candidates in the '98 class are Clayton C. Anderson, Lee J. Archambault, Tracy E. Caldwell (Ph.D.), Gregory E. Chamitoff (Ph.D.), Timothy J. Creamer, Christopher J. Ferguson, Michael J. Foreman, Michael E. Fossum, Kenneth T. Ham, Gregory C. Johnson, Gregory H. Johnson, Stanley G. Love (Ph.D.), Leland D. Melvin, Barbara R. Morgan, William A. Oefelein, John D. Olivas (Ph.D.), Nicholas J.M. Patrick (Ph.D.), Alan G. Poindexter, Garrett E. Reisman (Ph.D.), Steven R. Swanson, Douglas H. Wheelock, Sunita L. Williams, Neil W. Woodward III, George D. Zamka; and the international candidates are Leopold Eyharts, Paolo Nespoli, Hans Schlegel, Roberto Vittori, Bjarni V. Tryggvason, and Marcos Pontes.

  5. 1998 astronaut candidates tour KSC facilities

    NASA Technical Reports Server (NTRS)

    1999-01-01

    On the grounds of the Kennedy Space Center, members of the 1998 astronaut candidate class (Group 17) watch as candidate Alan G. Poindexter practices using firefighting equipment during fire training. The class is at KSC for training activities, including a flight awareness program, plus touring the OPF, VAB, SSPF, SSME Processing Facility, launch pads, SLF, Apollo/Saturn V Center, and the crew quarters. The other U.S. candidates in the '98 class are Clayton C. Anderson, Lee J. Archambault, Tracy E. Caldwell (Ph.D.), Gregory E. Chamitoff (Ph.D.), Timothy J. Creamer, Christopher J. Ferguson, Michael J. Foreman, Michael E. Fossum, Kenneth T. Ham, Patricia C. Hilliard (M.D.), Gregory C. Johnson, Gregory H. Johnson, Stanley G. Love (Ph.D.), Leland D. Melvin, Barbara R. Morgan, William A. Oefelein, John D. Olivas (Ph.D.), Nicholas J.M. Patrick (Ph.D.), Garrett E. Reisman (Ph.D.), Steven R. Swanson, Douglas H. Wheelock, Sunita L. Williams, Neil W. Woodward III, George D. Zamka; and the international candidates are Leopold Eyharts, Paolo Nespoli, Hans Schlegel, Roberto Vittori, Bjarni V. Tryggvason, and Marcos Pontes.

  6. Social Justice Perceptions of Teacher Candidates

    ERIC Educational Resources Information Center

    Turhan, Muhammed

    2010-01-01

    This study aims to determine the social justice perceptions of teacher candidates being trained in an education faculty. For this purpose, national and international literature was reviewed by the researcher and a 32-item questionnaire was developed and implemented on 237 senior year education faculty students. Data from the questionnaires were…

  7. Electronic Portfolio Adoption for Teacher Education Candidates

    ERIC Educational Resources Information Center

    Ledoux, Michael W.; McHenry, Nadine

    2006-01-01

    Programs of professional development for preservice teachers of young children in the United States attempt to align their program goals and candidate performances to The National Association for the Education of Young Children (NAEYC), Association of Childhood Education International (ACEI), and their particular state standards. In addition they…

  8. 76 FR 36130 - Call for Candidates

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-21

    ... From the Federal Register Online via the Government Publishing Office FEDERAL ACCOUNTING STANDARDS ADVISORY BOARD Call for Candidates AGENCY: Federal Accounting Standards Advisory Board. ACTION: Request for... Accounting Standards Advisory Board (FASAB or the Board) with the requested materials in response to...

  9. FAME's Search for Extrasolar Planet Candidates

    NASA Astrophysics Data System (ADS)

    Johnston, K.

    FAME is a five year survey mission to observe the positions, proper motions, and parallaxes of 40,000,000 stars down to 15th magnitude with accuracies of 50 microarcseconds at 9th magnitude. In addition to producing an astrometric and photometric catalog unparalleled for its accuracy and size, the survey will provide significant astrophysics results and search for extrasolar planet candidates.

  10. Query by image example: The CANDID approach

    SciTech Connect

    Kelly, P.M.; Cannon, M.; Hush, D.R.

    1995-02-01

    CANDID (Comparison Algorithm for Navigating Digital Image Databases) was developed to enable content-based retrieval of digital imagery from large databases using a query-by-example methodology. A user provides an example image to the system, and images in the database that are similar to that example are retrieved. The development of CANDID was inspired by the N-gram approach to document fingerprinting, where a ``global signature`` is computed for every document in a database and these signatures are compared to one another to determine the similarity between any two documents. CANDID computes a global signature for every image in a database, where the signature is derived from various image features such as localized texture, shape, or color information. A distance between probability density functions of feature vectors is then used to compare signatures. In this paper, the authors present CANDID and highlight two results from their current research: subtracting a ``background`` signature from every signature in a database in an attempt to improve system performance when using inner-product similarity measures, and visualizing the contribution of individual pixels in the matching process. These ideas are applicable to any histogram-based comparison technique.

  11. 47 CFR 73.1942 - Candidate rates.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ..., or election, to such office shall not exceed: (1) During the 45 days preceding the date of a primary or primary runoff election and during the 60 days preceding the date of a general or special election... advertising, shall be provided to candidates prior to election day if a station has provided a...

  12. Enhancing Advocacy Skills of Teacher Candidates

    ERIC Educational Resources Information Center

    Holmes, Melissa A.; Herrera, Socorro G.

    2009-01-01

    This case study explores the dynamics of enhancing the capacities of teacher candidates in the Bilingual/Bicultural Education Students Interacting to Obtain Success (BESITOS) recruitment and retention program to advocate for culturally and linguistically diverse (CLD) students. Herrera and Murry's advocacy framework provides the theoretical…

  13. Secondary Teacher Candidates' Lesson Planning Learning

    ERIC Educational Resources Information Center

    Santoyo, Christina; Zhang, Shaoan

    2016-01-01

    Teacher candidates (TCs) use clinical experiences to enact concepts taught in their university courses; therefore field experiences may be the most important component of teacher preparation (Hammerness et al., 2005). TCs require support and guidance as they learn to adapt curriculum materials for effective use in the classroom (Davis, 2006). They…

  14. Collaboration with Community Partners: Engaging Teacher Candidates

    ERIC Educational Resources Information Center

    Gandy, S. Kay; Pierce, Judy; Smith, Alicia Brooke

    2009-01-01

    Two social studies methods instructors created an assignment that places teacher candidates in leadership roles in partnerships with community organizations to plan and implement projects to increase student learning. This article outlines the project requirements, past project results, and student reflections on the collaborative effort. It…

  15. GTC Classification of DES Supernova Candidates

    NASA Astrophysics Data System (ADS)

    Castander, F. J.; Casas, R.; Garcia-Alvarez, D.; Perez-Valladares, D.; Miquel, R.; Smith, M.; Ahn, E.; Finley, D. A.; Frieman, J.; Marriner, J.; Wester, W.; Aldering, G.; Kim, A. G.; Thomas, R. C.; Barbary, K.; Bloom, J. S.; Goldstein, D.; Nugent, P.; Perlmutter, S.; Foley, R. J.; Castander, F. J.; Desai, S.; Paech, K.; Smith, R. C.; Schubnell, M.; Kessler, R.; Scolnic, D.; Covarrubias, R. A.; Brout, D. J.; Fischer, J. A.; Gladney, L.; March, M.; Sako, M.; Wolf, R. C.; Brown, P. J.; Krisciunas, K.; Suntzeff, N.; D'Andrea, C.; Nichol, R.; Papadopoulos, A.; Sullivan, M.; Maartens, R.; Gupta, R.; Kovacs, E.; Kuhlmann, S.; Spinka, H.

    2015-03-01

    We report optical spectroscopy and classification of 3 SN candidates discovered by the Dark Energy Survey. The spectra (490-920 nm) were obtained using OSIRIS on the Gran Telescopio CANARIAS (GTC), and classification was performed using SuperFit (Howell et al. 2005, Ap.J. 634, 1190) and SNID (Blondin & Tonry, 2007, Ap.J., 666, 1024).

  16. ESL Teacher-Candidates' Beliefs about Language

    ERIC Educational Resources Information Center

    Fleming, Douglas; Bangou, Francis; Fellus, Osnat

    2011-01-01

    How do ESL teacher-candidates grapple with beliefs about language during their professional training? In this article, we present the findings of a qualitative research study conducted in a large eastern Canadian university Bachelor of Education program. As Johnson (2010) has recently noted, despite extensive research and theoretical work that…

  17. 11 CFR 9003.2 - Candidate certifications.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... eligible to receive payments under 11 CFR part 9005, each Presidential and Vice Presidential candidate of a... excess of the aggregate payments to which they will be entitled under 11 CFR part 9004. (2) That no... established under 11 CFR 9003.3(a); or except to the extent necessary to make up any deficiency in...

  18. 11 CFR 9003.2 - Candidate certifications.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... eligible to receive payments under 11 CFR part 9005, each Presidential and Vice Presidential candidate of a... excess of the aggregate payments to which they will be entitled under 11 CFR part 9004. (2) That no... established under 11 CFR 9003.3(a); or except to the extent necessary to make up any deficiency in...

  19. 11 CFR 9003.2 - Candidate certifications.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... eligible to receive payments under 11 CFR part 9005, each Presidential and Vice Presidential candidate of a... excess of the aggregate payments to which they will be entitled under 11 CFR part 9004. (2) That no... established under 11 CFR 9003.3(a); or except to the extent necessary to make up any deficiency in...

  20. 11 CFR 9003.2 - Candidate certifications.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... eligible to receive payments under 11 CFR part 9005, each Presidential and Vice Presidential candidate of a... excess of the aggregate payments to which they will be entitled under 11 CFR part 9004. (2) That no... established under 11 CFR 9003.3(a); or except to the extent necessary to make up any deficiency in...

  1. Computer Teacher Candidates' Metaphors about the Internet

    ERIC Educational Resources Information Center

    Saban, Aslihan

    2010-01-01

    The purpose of this study was to examine the metaphors of exit-level Turkish computer teacher candidates about the concept of "internet". Participants included 45 seniors (23 boys and 22 girls) majoring in the Department of Computer and Instructional Technologies at Selcuk University, Ahmet Kelesoglu Faculty of Education. They were asked to…

  2. 22 CFR 11.8 - Travel expenses of candidates.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Travel expenses of candidates. 11.8 Section 11... Travel expenses of candidates. The travel and other personal expenses of candidates incurred in... Department may issue round-trip invitational travel orders to bring candidates to Washington at...

  3. 32 CFR 901.6 - Candidate fitness test requirement.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 32 National Defense 6 2010-07-01 2010-07-01 false Candidate fitness test requirement. 901.6... Requirements § 901.6 Candidate fitness test requirement. Before being offered an appointment, candidates must take a Candidate Fitness Test (CFT) which consists of exercises designed to measure muscular...

  4. 32 CFR 901.6 - Candidate fitness test requirement.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 32 National Defense 6 2011-07-01 2011-07-01 false Candidate fitness test requirement. 901.6... Requirements § 901.6 Candidate fitness test requirement. Before being offered an appointment, candidates must take a Candidate Fitness Test (CFT) which consists of exercises designed to measure muscular...

  5. 32 CFR 901.6 - Candidate fitness test requirement.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 32 National Defense 6 2014-07-01 2014-07-01 false Candidate fitness test requirement. 901.6... Requirements § 901.6 Candidate fitness test requirement. Before being offered an appointment, candidates must take a Candidate Fitness Test (CFT) which consists of exercises designed to measure muscular...

  6. 32 CFR 901.6 - Candidate fitness test requirement.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 32 National Defense 6 2012-07-01 2012-07-01 false Candidate fitness test requirement. 901.6... Requirements § 901.6 Candidate fitness test requirement. Before being offered an appointment, candidates must take a Candidate Fitness Test (CFT) which consists of exercises designed to measure muscular...

  7. 32 CFR 901.6 - Candidate fitness test requirement.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 32 National Defense 6 2013-07-01 2013-07-01 false Candidate fitness test requirement. 901.6... Requirements § 901.6 Candidate fitness test requirement. Before being offered an appointment, candidates must take a Candidate Fitness Test (CFT) which consists of exercises designed to measure muscular...

  8. Candidate marketing takes the guessing game out of choosing employers.

    PubMed

    Russell, Judith; Havel, Stacey

    2010-01-01

    Candidate marketing builds a foundation for relationships between employers and potential employees. Additionally, candidate marketing differentiates organizations in the marketplace. Organizations using candidate marketing to communicate the employer brand can expect a higher quality of candidates, and new employees are better prepared for the work environment and culture. Today, organizations can use a variety of integrated tools and techniques to communicate and build relationships with candidates. Candidate marketing demonstrates an organization's willingness towards transparency, and ability to invite open conversations between candidates and members of the organizations. PMID:20672542

  9. Optical Nova Candidate in M 31

    NASA Astrophysics Data System (ADS)

    Henze, M.; Burwitz, V.; Pietsch, W.; Updike, A.; Milne, P.; Williams, G.; Hartmann, D. H.

    2008-05-01

    We report the discovery of an optical nova candidate in M 31 on two 8x60s stacked R filter CCD images obtained with the robotic 60cm telescope with an E2V CCD (2kx2k) of the Livermore Optical Transient Imaging System (Super-LOTIS, located at Steward Observatory, Kitt Peak, Arizona, USA). The object was first detected on 2008 May 26.45 and 27.45 UT with respective magnitudes of 17.0 and 17.5. The position for the nova candidate is RA = 00h43m12.08s, Dec = +41d19'15.8" (J2000, accuracy of 0.3"), which is 5'13" east and 3'6" north of the core of M 31.

  10. Optical Nova Candidate in M 31

    NASA Astrophysics Data System (ADS)

    Burwitz, V.; Henze, M.; Pietsch, W.; Updike, A.; Hartmann, D.; Milne, P.; Williams, G.

    2008-01-01

    We report the discovery of an optical nova candidate in M 31 on two 12*60sec stacked R filter CCD images obtained with the robotic 60cm telescope with an E2V CCD (2kx2k) Livermore Optical Transient Imaging System (Super-LOTIS, located at Steward Observatory, Kitt Peak, Arizona, USA). The object was first detected on 2008 Jan 20.21 and 21.21 with respective magnitudes of 17.2 and 17.9. The position for the nova candidate is RA = 00h42m58.54s, Dec = 41d14'44.1" (J2000, accuracy of 0.3"), which is 2'41" west and 1'25 south of the core of M 31.