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Search Results: 1 - 10 of 563333 matches for " E. A. Magnier "
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Supersoft X-Ray Sources in M31
J. Greiner,R. Supper,E. A. Magnier
Physics , 1996, DOI: 10.1007/BFb0102248
Abstract: The nearby Andromeda galaxy (M31) has been observed with the ROSAT PSPC in a mosaic of 6 pointings with 25 ksec each. In the paper describing the results on the total sample of detected sources, Supper et al. (1996) also report the positions for 15 supersoft X-ray sources and the blackbody fit results for the brightest of these sources. We report here in more detail on the X-ray spectral characteristics of all these 15 supersoft X-ray sources. Optical multi-colour photometric data obtained in 1990 at the Michigan- Dartmouth-MIT Observatory at Kitt Peak were used originally in the selection process of the supersoft sources, and are the basis for the finding charts given here for most selected X-ray sources.
Search for and Characterization of Galactic Open Clusters with 2MASS
C. C. Lin,W. P. Chen,E. A. Magnier
Physics , 2011,
Abstract: We have developed a star-counting algorithm and tested it on the 2MASS star catalog to search for density enhancements significantly above the field in Galactic latitude $|b|<50^{\circ}$. Nearly 500 open clusters are "rediscovered", along with 89 globular clusters, 35 galaxies, 55 galaxy clusters, 11 H II regions, and 4 regions contaminated by nearby bright stars. Fifty-two density enhancement regions remain unaccounted for. Here we present one such candidate HDG\,01, $(\ell, b)=(144.9038, 0.4338)$ which has an angular size of 3', a distance of 1.5 kpc, hence a physical size of 3.7 pc. Due to some nebulous shape, this star cluster should be an young-aged ($\le 10$ Myr).
Transitional YSOs: Candidates from Flat-Spectrum IRAS Sources
A. W. Volp,E. A Magnier,M. E. van den Ancker,L. B. F. M. Waters
Physics , 1999,
Abstract: We are searching for Young Stellar Objects (YSOs) near the boundary between protostars and pre-main sequence objects, what we have termed transitional YSOs. We have identified a sample of 125 objects as candidate transitional YSOs on the basis of IRAS colors and optical appearance on DSS images. We find that the majority of our objects are associated with star-forming regions, confirming our expectation that the bulk of these are YSOs. We present optical, near-IR and high-resolution IRAS images of 92 objects accessible from the northern and 62 from the southern hemisphere. The objects have been classified on the basis of their morphology and spectral index. Of the 125 objects, 28 have a variety of characteristics very similar to other transitional YSOs, while another 22 show some of these characteristics, suggesting that these transitional YSOs are not as rare as predicted by theory.
Four Brown Dwarfs in the Taurus Star-Forming Region
E. L. Martin,C. Dougados,E. Magnier,F. Menard,A. Magazzu,J. -C. Cuillandre,X. Delfosse
Physics , 2001, DOI: 10.1086/324754
Abstract: We have identified four brown dwarfs in the Taurus star-forming region. They were first selected from $R$ and $I$ CCD photometry of 2.29 square degrees obtained at the Canada-France-Hawaii Telescope. Subsequently, they were recovered in the 2MASS second incremental data release point source catalog. Low-resolution optical spectra obtained at the William Herschel telescope allow us to derive spectral types in the range M7--M9. One of the brown dwarfs has very strong H$\alpha$ emission (EW=-340 \AA). It also displays Br$\gamma$ emission in an infrared spectrum obtained with IRCS on the Subaru telescope, suggesting that it is accreting matter from a disk. The \ion{K}{1} resonance doublet and the \ion{Na}{1} subordinate doublet at 818.3 and 819.5 nm in these Taurus objects are weaker than in field dwarfs of similar spectral type, consistent with low surface gravities as expected for young brown dwarfs. Two of the objects are cooler and fainter than GG Tau Bb, the lowest mass known member of the Taurus association. We estimate masses of only 0.03 M$_\odot$ for them. The spatial distribution of brown dwarfs in Taurus hints to a possible anticorrelation between the density of stars and the density of brown dwarfs.
Millimetric and sub-millimetric observations of IRAS 05327+3404 "Holoea" in M36
O. Morata,Y. J. Kuan,P. T. P. Ho,H. C. Huang,E. A. Magnier,R. Zhao-Geisler
Physics , 2013, DOI: 10.1088/0004-6256/146/3/49
Abstract: The transition between the proto-star, Class I, and the pre-main sequence star, Class II, phases is still one of the most uncertain, and important, stages in the knowledge of the process of formation of an individual star, because it is the stage that determines the final mass of the star. We observed the YSO "Holoea", associated with IRAS 05327+3404, which was classified as an object in transition between the Class I and Class II phases with several unusual properties, and appears to be surrounded by large amounts of circumstellar material. We used the SMA and BIMA telescopes at millimeter and sub-millimeter wavelengths to observe the dust continuum emission and the CO (1-0) and (2-1), HCO+ (1-0) and (3-2), and HCN (1-0) transitions in the region around IRAS 05327+3404. We detected two continuum emission peaks at 1.1-mm: SMM 1, the sub-mm counterpart of IRAS 05327+3404, and SMM 2, ~6 arcsec to the West. The emissions of the three molecules show marked differences. The CO emission near the systemic velocity is filtered out by the telescopes, and CO mostly traces the high-velocity gas. The HCO+ and HCN emissions are more centrally concentrated around the central parts of the region, and show several intensity peaks coincident with the sub-mm continuum peaks. We identify two main molecular outflows: a bipolar outflow in an E-W direction that would be powered by SMM 1 and another one in a NE direction, which we associate with SMM 2. We propose that the SMM sources are probably Class I objects, with SMM 1 in an earlier evolutionary stage.
First optical identification of a suprsoft X-ray source in M31
P. Nedialkov,M. Orio,K. Birkle,C. Conselice,M. Della Valle,J. Greiner,E. Magnier,N. A. Tikhonov
Physics , 2002, DOI: 10.1051/0004-6361:20020575
Abstract: We propose the first association of an optical counterpart with a luminous supersoft X-ray source in M31, RX J0044.0+4118, observed with ROSAT in July 1991. The PSPC position is at 1.6" angular distance from a candidate nova in outburst in September of 1990. This is interesting because the incidence of classical novae among supersoft X-ray sources is an open question. The proposed optical counterpart was measured at R~17.7 in September of 1990, and it had faded to R>19.2 when it was observed again after 70 days. The light curve was too sparsely monitored for definite conclusions on the speed class of the nova. No other variable objects with V<23.5 were found in the ROSAT spatial error box. We evaluate that the probability that a classical or recurrent nova was in outburst in the ROSAT error box in the few years preceding the observation is very small, so the proposed identification is meaningful. We also show evidence that the associated supersoft X-ray source turned off in the third year after the outburst.
Nature of the Supercritical Mesophase  [PDF]
Hamza J. Magnier, Robin A. Curtis, Leslie V. Woodcock
Natural Science (NS) , 2014, DOI: 10.4236/ns.2014.610078
Abstract: It has been reported that at temperatures above the critical there is no “continuity of liquid and gas”, as originally hypothesized by van der Waals [1]. Rather, both gas and liquid phases, with characteristic properties as such, extend to supercritical temperatures [2]-[4]. Each phase is bounded by the locus of a percolation transition, i.e. a higher-order thermodynamic phase change associated with percolation of gas clusters in a large void, or liquid interstitial vacancies in a large cluster. Between these two-phase bounds, it is reported there exists a mesophase that resembles an otherwise homogeneous dispersion of gas micro-bubbles in liquid (foam) and a dispersion of liquid micro-droplets in gas (mist). Such a colloidal-like state of a pure one-component fluid represents a hitherto unchartered equilibrium state of matter besides pure solid, liquid or gas. Here we provide compelling evidence, from molecular dynamics (MD) simulations, for the existence of this supercritical mesophase and its colloidal nature. We report preliminary results of computer simulations for a model fluid using a simplistic representation of atoms or molecules, i.e. a hard-core repulsion with an attraction so short that the atoms are referred to as “adhesive spheres”. Molecular clusters, and hence percolation transitions, are unambiguously defined. Graphics of color-coded clusters show colloidal characteristics of the supercritical mesophase. We append this Letter to Natural Science with a debate on the scientific merits of its content courtesy of correspondence with Nature (Appendix).

Composite reverberation mapping
S. Fine,T. Shanks,S. M. Croom,P. Green,B. C. Kelly,E. Berge,R. Chornock,W. S. Burgett,E. A. Magnier,P. A. Price
Physics , 2012, DOI: 10.1111/j.1365-2966.2012.21248.x
Abstract: Reverberation mapping offers one of the best techniques for studying the inner regions of QSOs. It is based on cross-correlating continuum and emission-line light curves. New time-resolved optical surveys will produce well sampled light curves for many thousands of QSOs. We explore the potential of stacking samples to produce composite cross-correlations for groups of objects that have well sampled continuum light curves, but only a few (~2) emission-line measurements. This technique exploits current and future wide-field optical monitoring surveys (e.g. Pan-STARRS, LSST) and the multiplexing capability of multi-object spectrographs (e.g. 2dF, Hectospec) to significantly reduce the observational expense of reverberation mapping, in particular at high redshift (0.5 to 2.5). We demonstrate the technique using simulated QSO light curves and explore the biases involved when stacking cross-correlations in some simplified situations. We show that stacked cross correlations have smaller amplitude peaks compared to well sampled correlation functions as the mean flux of the emission light curve is poorly constrained. However, the position of the peak remains intact. We find there can be `kinks' in stacked correlation functions due to different measurements contributing to different parts of the correlation function. Using the Pan-STARRS Medium-Deep Survey (MDS) as a template we show that cross-correlation lags should be measurable in a sample size of 500 QSOs that have weekly photometric monitoring and two spectroscopic observations. Finally we apply the technique to a small sample (42) of QSOs that have light curves from the MDS. We find no indication of a peak in the stacked cross-correlation. A larger spectroscopic sample is required to produce robust reverberation lags.
The second ROSAT PSPC survey of M31 and the complete ROSAT PSPC source list
R. Supper,G. Hasinger,W. H. G. Lewin,E. A. Magnier,J. van Paradijs,W. Pietsch,A. M. Read,J. Truemper
Physics , 2001, DOI: 10.1051/0004-6361:20010495
Abstract: This paper reports the results of the analysis of the second ROSAT PSPC survey of M31 performed in summer 1992. We compare our results with those of the first survey. Within the ~10.7 deg^2 field of view, 396 individual X-ray sources are detected in the second survey data, of which 164 are new detections. When combined with the first survey, this result in a total of 560 X-ray sources in the field of M31. Their (0.1 keV - 2.0 keV) fluxes range from 7 x 10^-15 to 7.6 x 10^-12 erg cm^-2 s^-1, and of these 560 sources, 55 are tentatively identified with foreground stars, 33 with globular clusters, 16 with supernova remnants, and 10 with radio sources and galaxies (including M32). A comparison with the results of the Einstein M31 survey reveals 491 newly detected sources, 11 long term variable sources, and 7 possible transient sources. Comparing the two ROSAT surveys, we come up with 34 long term variable sources and 8 transient candidates. For the M31 sources, the observed luminosities range from 4 x 10^35 to 4 x 10^38 erg s^-1. The total (0.1 keV - 2.0 keV) luminosity of M31 is (3.4+-0.3) x 10^39 erg s^-1, distributed approximately equally between the bulge and disk. Within the bulge region, the luminosity of a possible diffuse component combined with faint sources below the detection threshold is (2.0+-0.5) x 10^38 erg s^-1. An explanation in terms of hot gaseous emission leads to a maximum total gas mass of (1.0+-0.3) x 10^6 M_sun.
NEWS : a new spherical gas detector for very low mass WIMP detection
G. Gerbier,I. Giomataris,P. Magnier,A. Dastgheibi,M. Gros,D. Jourde,E. Bougamont,X. F. Navick,T. Papaevangelou,J. Galan,J. Derre,I. Savvidis,G. Tsiledakis
Physics , 2014,
Abstract: The main characteristics of a new concept of spherical gaseous detectors, with some details on its operation are first given. The very low energy threshold of such detector has led to investigations of its potential performance for dark matter particle searches, in particular low mass WIMP's : original methods for energy and fiducial volume calibration and background rejection are described and preliminary results obtained with a low radioactivity prototype operated in Laboratoire Souterrain de Modane ("Frejus" lab) are presented. Typical expected sensitivities in cross section for low mass WIMP's are also shown, and other applications briefly discussed.
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