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Radial Velocities (radial + velocity)
Terms modified by Radial Velocities Selected AbstractsIs the sky falling?MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008RAVE surveys, Searching for stellar streams in the local Milky Way disc in the CORAVEL ABSTRACT We have searched for in-falling stellar streams on to the local Milky Way disc in the CORrelation RAdial VELocities (CORAVEL) and RAdial Velocity Experiment (RAVE) surveys. The CORAVEL survey consists of local dwarf stars (Nördstrom et al. Geneva,Copenhagen survey) and local Famaey et al. giant stars. We select RAVE stars with radial velocities that are sensitive to the Galactic vertical space velocity (Galactic latitude b < ,45°). Kuiper statistics have been employed to test the symmetry of the Galactic vertical velocity distribution functions in these samples for evidence of a net vertical flow that could be associated with a (tidal?) stream of stars with vertically coherent kinematics. In contrast to the ,Field of Streams' found in the outer halo, we find that the local volumes of the solar neighbourhood sampled by the CORAVEL dwarfs (complete within ,3 × 10,4 kpc3), CORAVEL giants (complete within ,5 × 10,2 kpc3) and RAVE (5,15 per cent complete within ,8 kpc3) are devoid of any vertically coherent streams containing hundreds of stars. This is sufficiently sensitive to allow our RAVE sample to rule out the passing of the tidal stream of the disrupting Sagittarius (Sgr) dwarf galaxy through the solar neighbourhood. This agrees with the most-recent determinations of its orbit and dissociates it from the Helmi et al. halo stream. Our constraints on the absence of the Sgr stream near the Sun could prove a useful tool for discriminating between Galactic potential models. The lack of a net vertical flow through the solar neighbourhood in the CORAVEL giants and RAVE samples argues against the Virgo overdensity crossing the disc near the Sun. There are no vertical streams in the CORAVEL giants and RAVE samples with stellar densities ,1.6 × 104 and 1.5 × 103 stars kpc,3, respectively, and therefore no evidence for locally enhanced dark matter. [source] Kinematic structure in the Galactic halo at the North Galactic Pole: RR Lyrae and blue horizontal branch stars show different kinematicsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007T. D. Kinman ABSTRACT Radial velocities and proper motions (derived from the GSC-II data base) are given for 38 RR Lyrae (RRL) stars and 79 blue horizontal branch (BHB) stars in a ,200 deg2 area around the North Galactic Pole (NGP). Both heliocentric (UVW) and galactocentric (VR, V,, Vz) space motions are derived for these stars using a homogeneous distance scale consistent with (m,M)0= 18.52 for the Large Magellanic Cloud (LMC). An analysis of the 26 RRL and 52 BHB stars whose height (Z) above the plane is less than 8 kpc shows that this halo sample is not homogeneous. Our BHB sample (like that of Sirko et al.) has a zero galactic rotation (V,) and roughly isotropic velocity dispersions. The RRL sample shows a definite retrograde rotation (V,=,95 ± 29 km s,1) and non-isotropic velocity dispersions. The combined BHB and RRL sample has a retrograde galactic rotation (V) that is similar to that found by Majewski for his sample of subdwarfs in Selected Area (SA) 57. The velocity dispersion of the RRL stars that have a positive W motion is significantly smaller than the dispersion of those ,streaming down' with a negative W. Also, the ratio of RRL to BHB stars is smaller for the sample that has positive W. Our halo sample occupies 10.4 kpc3 at a mean height of 5 kpc above the Galactic plane. In this volume, one component (rich in RRL stars) shows retrograde rotation and the streaming motion that we associate with the accretion process. The other component (traced by the BHB stars) shows essentially no rotation and less evidence of streaming. These two components have horizontal branch (HB) morphologies that suggest that they may be the field star equivalents of the young and old halo globular clusters, respectively. Clearly, it is quite desirable to use more than one tracer in any kinematic analysis of the halo. [source] Radial velocities, dynamics of stars and nebulosities with GAIA and VLT-GIRAFFEASTRONOMISCHE NACHRICHTEN, Issue 9-10 2008C. Martayan Abstract This document is divided in two parts. The first part deals with the radial velocities (RV) distributions for B-type stars and nebulosities observed with the VLT-GIRAFFE in the Large and Small Magellanic Clouds towards the open clusters NGC2004 and NGC330. Thanks to the resolution of GIRAFFE spectra, we found that the RV distribution for the nebulosities in the LMC is bi-modal. This bi-modality can be interpreted, in term of dynamics, by the expansion of the LMC4 super-bubble. The second part deals with the GAIA space mission and the determination of the radial velocities by using Radial Velocity Spectrometer (RVS) spectra. The methods to determine the radial velocities are presented as well as preliminary results on simulated RVS spectra. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] 3D velocity from 3D Doppler radial velocityINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 3 2005J. L. Barron Abstract We present local least squares and regularization frameworks for computing 3D velocity (3D optical flow) from 3D radial velocity measured by a Doppler radar. We demonstrate the performance of our algorithms quantitatively on synthetic radial velocity data and qualitatively on real radial velocity data, obtained from the Doppler radar at Kurnell Radar station, Botany Bay, New South Wales, Australia. Radial velocity can be used to predict the future positions of storms in sequences of Doppler radar datasets.© 2005 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 15, 189,198, 2005 [source] Radial velocity and light curves analysis of the eclipsing binary NN VirASTRONOMISCHE NACHRICHTEN, Issue 9 2004R. Pazhouhesh Abstract The eclipsing binary NN Vir is a short period system showing an EW-type light curve. Photometric observations of NN Vir were done by Gomez-Ferrellad & Garcia-Melendo (1997) at Esteve Duran Observatory. We used photometric data of NN Vir for light curve analysis. The available spectroscopic data of NN Vir is new and we also used the first radial velocity data of this system obtained by Rusinski & Lu (1999) for analysis. The radial velocity and light curves analysis was made with the latest version ofWilson program(1998) and the geometric and physical elements of the system are derived. By searching the simultaneous solutions of the system, we have determined the masses and radii of the components : 1.89(M,) and 1.65(R,) for the primary component; 0.93(M,) and 1.23(R,) for the secondary component. We estimated effective temperatures of 7030(K) for the primary and 6977(K) for the secondary component. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Characterization of Taylor vortex flow in a short liquid columnAICHE JOURNAL, Issue 12 2009Rensheng Deng Abstract We present a study on Taylor vortex flow in the annulus between a rotating inner cylinder and a stationary outer cylinder, featured with a wide gap (radius ratio is 0.613) and a short column (aspect ratio is 5.17). A particle image velocimetry (PIV) system was used to determine the position, shape, and velocity distribution of the vortices, by which the flow was also confirmed to lie in the nonwavy Taylor vortex regime for all operating conditions explored in this study. Our results suggest that end boundary effects are important, in which the vortex number decreases with decreasing column length. For a system with an aspect ratio of 5.17, six vortices appear in the gap with their position, size, and shape varying at different Reynolds numbers. The fluid velocities show an asymmetric feature with respect to the vortex centers, while the maximum axial and radial velocities increase almost linearly with the increasing reduced Reynolds number (Re , Rec). In addition, computational fluid dynamics study was employed under the same conditions, and its results agree well with the PIV measurements. Overall, this study provides a quantitative understanding of the formation of Taylor vortices in a constrained space. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Is the sky falling?MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008RAVE surveys, Searching for stellar streams in the local Milky Way disc in the CORAVEL ABSTRACT We have searched for in-falling stellar streams on to the local Milky Way disc in the CORrelation RAdial VELocities (CORAVEL) and RAdial Velocity Experiment (RAVE) surveys. The CORAVEL survey consists of local dwarf stars (Nördstrom et al. Geneva,Copenhagen survey) and local Famaey et al. giant stars. We select RAVE stars with radial velocities that are sensitive to the Galactic vertical space velocity (Galactic latitude b < ,45°). Kuiper statistics have been employed to test the symmetry of the Galactic vertical velocity distribution functions in these samples for evidence of a net vertical flow that could be associated with a (tidal?) stream of stars with vertically coherent kinematics. In contrast to the ,Field of Streams' found in the outer halo, we find that the local volumes of the solar neighbourhood sampled by the CORAVEL dwarfs (complete within ,3 × 10,4 kpc3), CORAVEL giants (complete within ,5 × 10,2 kpc3) and RAVE (5,15 per cent complete within ,8 kpc3) are devoid of any vertically coherent streams containing hundreds of stars. This is sufficiently sensitive to allow our RAVE sample to rule out the passing of the tidal stream of the disrupting Sagittarius (Sgr) dwarf galaxy through the solar neighbourhood. This agrees with the most-recent determinations of its orbit and dissociates it from the Helmi et al. halo stream. Our constraints on the absence of the Sgr stream near the Sun could prove a useful tool for discriminating between Galactic potential models. The lack of a net vertical flow through the solar neighbourhood in the CORAVEL giants and RAVE samples argues against the Virgo overdensity crossing the disc near the Sun. There are no vertical streams in the CORAVEL giants and RAVE samples with stellar densities ,1.6 × 104 and 1.5 × 103 stars kpc,3, respectively, and therefore no evidence for locally enhanced dark matter. [source] Spectroscopic and photometric observations of the selected Algol-type binaries , II.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008V2080 Cygni, V2365 Ophiuchi ABSTRACT This paper is the second in the planned series of investigations. We present new radial velocities and photometric observations of V2080 Cyg and V2365 Oph. New UBV photometric data and radial velocities were analysed for the systems' parameters. While V2080 Cyg consists of two nearly equal F-type main-sequence stars, V2365 Oph has two different components, namely an early A-type primary and a G-type secondary star. New ephemerides are calculated for both systems. The masses of the component stars have been derived as 1.19 ± 0.02 and 1.16 ± 0.02 M, for V2080 Cyg and 1.97 ± 0.02 and 1.06 ± 0.01 M, for V2365 Oph. The effective temperatures and reddening of the systems have been estimated from Johnson wide-band UBV photometric calibrations. The radii have been measured by simultaneous fitting the UBV light curves using Wilson,Devinney code and are 1.60 ± 0.01 R, for both components of V2080 Cyg and 2.19 ± 0.01 and 0.934 ± 0.004 R, for V2365 Oph. The absolute parameters of the stars in both systems lie within the same ranges in the mass,radius, mass,effective temperature, mass,luminosity and luminosity,effective temperature planes as in detached Algol systems. A comparison between the properties of the systems of interest and the predictions of theoretical evolutionary models is undertaken in the log g,logTeff, log R, log M and radius,log age diagrams. The model predictions match the measured properties of V2080 Cyg for an age of about 5.6 Gyr and a ,solar' metal abundance (Z= 0.019), indicating the components near the end of their core hydrogen-burning phases. However, the position of the components of V2365 Oph on the Hertzsprung,Russell (HR) diagram is best reproduced with evolutionary models for somewhat metal-deficient (Z= 0.004) stars. We found an age of about 700 Myr, with the primary component slightly evolved off the zero-age main-sequence and the secondary one still very close to it. From the basic stellar parameters we have also redetermined the distances to V2080 Cyg and V2365 Oph as 78 ± 1 and 251 ± 8 pc, which are in agreement with, and more accurate than, Hipparcos values. The observations show that at least one of the components of V2365 Oph is an intrinsic variable with a period and peak-to-peak amplitude of 0.07 d and 0.05 mag, respectively. In accordance with its position in the HR diagram, the primary component should be considered as a , Scuti star and it is believed to be the variable star in the system. [source] Observational studies of early-type binary stars: VV OrionisMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2007Dirk Terrell ABSTRACT New and previously published observations of the bright eclipsing binary VV Orionis are analyzed. We present new radial velocities and interstellar reddening measurements from high-resolution spectra of this detached, short-period (P= 1.48 d) binary. We discuss the validity of prior claims for the existence of a third body and show that our new velocities and light-curve solution cast doubt on them. The components of VV Ori are shown to be a B1 V primary with a mass M1= 10.9 ± 0.1 M, and a radius R1= 4.98 ± 0.02 R, and a B4.5 V secondary with a mass M2= 4.09 ± 0.05 M, and a radius R2= 2.41 ± 0.01 R,. [source] Gemini near-infrared integral field spectroscopy of the narrow-line region of ESO 428,G14: kinematics, excitation and the role of the radio jetMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2006Rogemar A. Riffel ABSTRACT We present two-dimensional (2D) gas kinematics and excitation of the inner 300 pc of the Seyfert galaxy ESO 428,G14 at a sampling of 14 pc2, from near-infrared spectroscopic observations at R, 6000 obtained with the Integral Field Unit (IFU) of the Gemini Near-Infrared Spectrograph. From measurements of fluxes and profiles of the emission lines [Fe ii],1.257 ,m, Pa,, H2, 2.121 ,m and Br,, we construct 2D maps of line intensities and ratios, radial velocities and velocity dispersions. Emission line ,tomography' is provided by velocity slices obtained across the line profiles, a unique capability of IFUs, which allows the mapping of not only the peak velocities but including also the wings. We compare these maps with a previously published high spatial resolution radio map and find a tight relation between the radio structure and the emission-line flux distributions and kinematics, revealing that the radio jet plays a fundamental role not only in shaping the narrow-line region but also in the imprint of its kinematics. Blueshifts of up to 400 km s,1 and velocity dispersions of up to 150 km s,1 are observed in association with the radio jet at a position angle (PA) = 129°, which is also the PA of the photometric major axis of the galaxy. We conclude that the radio jet is launched at a small angle relative to the galactic plane, with the north-western side slightly oriented towards us. This angle is small enough for the radio jet to shock and compress the gas in the plane of the galaxy, and for the nuclear continuum to ionize and heat it. The distinct kinematics and flux distributions observed for the different emission lines suggest different origins for their emission. The [Fe ii] shows the largest blueshifts and velocity dispersions and its flux distribution is concentrated along the jet, while the H2 shows the lowest velocity dispersions and has additional flux contribution from regions beyond the jet. Both X-rays emitted by the active galactic nucleus and shocks produced by the radio jet can excite the H2 and [Fe ii] emission lines. We use the 2D velocity dispersion maps to estimate upper limits to the contribution of the radio jet to the excitation of [Fe ii] and H2 which may reach 90 per cent for [Fe ii] and 80 per cent for H2 in the jet region. The [Fe ii]/Pa, emission-line ratios and the association of the [Fe ii] flux distribution and kinematics with the radio structure support a stronger contribution of the radio jet to the [Fe ii] excitation than that of H2. In the regions beyond the jet, the observations favour X-ray excitation. [source] Elemental abundance survey of the Galactic thick discMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006Bacham E. Reddy ABSTRACT We have performed an abundance analysis for F- and G- dwarfs of the Galactic thick-disc component. A sample of 176 nearby (d, 150 pc) thick-disc candidate stars was chosen from the Hipparcos catalogue and subjected to a high-resolution spectroscopic analysis. Using accurate radial velocities combined with the Hipparcos astrometry, kinematics (U, V and W) and Galactic orbital parameters were computed. We estimate the probability for a star to belong to the thin disc, the thick disc or the halo. With a probability P, 70 per cent taken as certain membership, we assigned 95 stars to the thick disc, 13 to the thin disc, and 20 to the halo. The remaining 48 stars in the sample cannot be assigned with reasonable certainty to one of the three components. Abundances of C, O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Ba, Ce, Nd and Eu have been obtained. The abundances for the thick-disc stars are compared with those for the thin-disc members from Reddy et al. The ratios of ,-elements (O, Mg, Si, Ca and Ti) to iron for thick-disc stars show a clear enhancement compared to thin-disc members in the range ,0.3 < [Fe/H] < ,1.2. There are also other elements , Al, Sc, V, Co, and possibly Zn , which show enhanced ratios to iron in the thick disc relative to the thin disc. The abundances of Na, Cr, Mn, Ni and Cu (relative to Fe) are very similar for thin- and thick-disc stars. The dispersion in abundance ratios [X/Fe] at given [Fe/H] for thick-disc stars is consistent with the expected scatter due to measurement errors, suggesting a lack of ,cosmic' scatter. A few stars classified as members of the thick disc by our kinematic criteria show thin-disc abundances. These stars, which appear older than most thin-disc stars, are also, on average, younger than the thick-disc population. They may have originated early in the thin-disc history, and been subsequently scattered to hotter orbits by collisions. The thick disc may not include stars with [Fe/H] > ,0.3. The observed compositions of the thin and thick discs seem to be consistent with the models of galaxy formation by hierarchical clustering in a Lambda cold dark matter (,CDM) universe. [source] Spectroscopic study of the long-period dust-producing WC7pd+O9 binary HD 192641MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2005L. Lefèvre ABSTRACT We present the results of an optical spectroscopic study of the massive Wolf,Rayet (WR) binary HD 192641 = WR 137. These 1986,2000 data cover the dust-formation maximum in 1997. Combining all available measurements of radial velocities, we derive, for the first time, a spectroscopic orbit with period 4766 ± 66 d (13.05 ± 0.18 yr). The resulting masses, adopting i= 67 °, are MO= 20 ± 2 M, for the O component and MWR= 4.4 ± 1.5 M, for the WR component. These appear, respectively, approximately normal and on the low side for the given spectral types. Analysis of the intense multisite spectroscopic monitoring in 1999 shows that the C iii,5696 and C iv,,5802/12 lines have the highest intrinsic variability levels. The periodogram analysis yields a small-amplitude modulation in the absorption troughs of the C iv,,5802/12 and He i,5876 lines with a period of 0.83 d, which could be related either to pulsations or large-scale rotating structures as seen in the WN4 star EZ Canis Majoris (WR 6). Wavelet analysis of the strong emission lines of C iii,5696 and C iv,,5802/12 enabled us to isolate and follow for several hours small structures (emission subpeaks) associated with density enhancements within the wind of the Wolf,Rayet star. Cross-correlating the variability patterns seen in different lines, we find a weak but significant correlation between the variability in emission lines with different ionization potentials, i.e. in lines formed at different distances from the WR stellar core. Adopting a , wind-velocity law, from the motion of individual subpeaks we find ,, 5, which is significantly larger than the canonical value ,, 1 found in O star winds. [source] Eclipsing binaries in open clusters , III.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2004Persei, V621 Per in ABSTRACT V621 Persei is a detached eclipsing binary in the open cluster , Persei, which is composed of an early B-type giant star and a main-sequence secondary component. From high-resolution spectroscopic observations and radial velocities from the literature, we determine the orbital period to be 25.5 d and the primary velocity semi-amplitude to be K= 64.5 ± 0.4 km s,1. No trace of the secondary star has been found in the spectrum. We solve the discovery light curves of this totally eclipsing binary and find that the surface gravity of the secondary star is log gB= 4.244 ± 0.054. We compare the absolute masses and radii of the two stars in the mass,radius diagram, for different possible values of the primary surface gravity, with the predictions of stellar models. We find that log gA, 3.55, in agreement with values found from fitting Balmer lines with synthetic profiles. The expected masses of the two stars are 12 and 6 M, and the expected radii are 10 and 3 R,. The primary component is near the blue loop stage in its evolution. [source] Monitoring lensed starlight emitted close to the Galactic centreMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2004Adi Nusser ABSTRACT We describe the feasibility of detecting the gravitational deflection of light emitted by stars moving around the massive object at the Galactic centre. Light reaching us from an orbiting star can pass closer to the large central mass than the star itself, so the central potential is in principle constrained to a smaller radius by lensing rather than by orbit fitting. A mass of 4.3 × 106 M, causes a 0.1,2 mas deflection in the apparent position of orbiting stars in a cone of diameter 10° as seen from the central mass. The distance to the centre of the Galaxy is uniquely constrained from such measurements because lensing deflections depend on the ratio rg/R0 of the Schwarzschild radius to the distance to the black hole, R0, whereas the ratio rg/R30 is obtained by fitting the shapes of the orbits. Deflection measurements are complimentary to observations of radial velocities of stars which constrain the ratio rg/R0 in the framework of Newtonian gravity. [source] Spectroscopy of globular cluster candidates in the Sculptor group galaxies NGC 253 and 55MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2000M. A. Beasley We have obtained spectra for 103 published globular cluster candidates in the Sculptor group galaxies NGC 253 and 55. On the basis of radial velocities and digitized plate images, 14 globular clusters are identified in NGC 253 and one probable globular cluster is identified in NGC 55. The majority of the objects in the sample appear to be background galaxies. We have obtained and analysed COSMOS plate scans of NGC 253 and 55 and use these along with the spectroscopically identified clusters to define new samples of globular cluster candidates in the two galaxies which should have reduced contamination. [source] Are Complex A and the Orphan stream related?MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2007Shoko Jin ABSTRACT We consider the possibility that the Galactic neutral hydrogen stream Complex A and the stellar Orphan stream are related, and use this hypothesis to determine possible distances to Complex A and the Orphan stream, and line-of-sight velocities for the latter. The method presented uses our current knowledge of the projected positions of the streams, as well as line-of-sight velocities for Complex A, and we show that a solution exists in which the two streams share the same orbit. If Complex A and the Orphan stream are on this orbit, our calculations suggest the Orphan stream to be at an average distance of 9 kpc, with heliocentric radial velocities of approximately ,95 km s,1. Complex A would be ahead of the Orphan stream in the same wrap of the orbit, with an average distance of 4 kpc, which is consistent with the distance constraints determined through interstellar absorption line techniques. [source] Spatial and velocity clumping in a Sloan Digital Sky Survey blue horizontal branch star catalogueMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2006L. Clewley ABSTRACT We present evidence for eight new clumps of blue horizontal branch stars discovered in a catalogue of these stars compiled from the Sloan Digital Sky Survey by Sirko et al. and published in 2004. Clumps are identified by selecting pairs of stars separated by distances ,2 kpc and with differences in galactocentric radial velocities <25 km s,1. Each clump contains four or more stars. Four of the clumps have supporting evidence: two of them also contain overdensities of RR Lyrae stars which makes their reality very likely. At least one of the clumps is likely to be associated with the tidal debris of the Sagittarius dwarf spheroidal galaxy. We emphasize that more accurate observations of the radial velocities or proper motions of the stars in the clumps, as well as the identification of other halo stars in these regions, are required to establish the reality of the remaining clumps. [source] The Cygnus X region: XXIII.ASTRONOMISCHE NACHRICHTEN, Issue 4 2010Is 18P87 galactic or extragalactic? Abstract The radio source 18P87, previously thought to be a point source, has been serendipitously found to be resolved into a core-jet geometry in VLA maps. H I absorption of continuum emission (in data from the Canadian Galactic Plane Survey) appears in gas with radial velocities >+2 km/s but not in brightly emitting gas at lower radial velocity. Examination of further archival observations at radio, infrared and optical wavelengths suggests that the "obvious" interpretation as a radio galaxy requires a rather unusual object of this kind and a highly unusual local line of sight. We argue that 18P87 may be a Galactic object, a local astrophysical jet. If this is correct it could have arisen from outbursts of a microquasar (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Swift observations of CSS081007:030559+054715ASTRONOMISCHE NACHRICHTEN, Issue 2 2010A.P. Beardmore Abstract CSS081007:030559+054715 was discovered by the Catalina Real-time Transient Survey. Optical spectroscopy revealed a multi-peaked H, emission line profile with radial velocities exceeding 1500 km/s, as well as strong Ne emission, suggestive of a neon nova. We monitored the source extensively with the Swift satellite, obtaining a unique dataset spanning 270 days in the soft X-ray and UV bands. The data reveal a soft, blackbody-like spectrum with a temperature around 55 eV (though dependent on the modelling), variable X-ray and UV light curves with a 1.77 day period in both the X-ray and UV bands, a longer timescale modulation of , 50 days, followed by a slowly declining trend in the soft X-ray and UV flux. We highlight the Swift observations and their implications for the SSS nature of this object (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The chromospherically active binary star EI Eridani: I. Absolute dimensionsASTRONOMISCHE NACHRICHTEN, Issue 1 2009A. Washuettl Abstract We present a detailed determination of the astrophysical parameters of the chromospherically active binary star EI Eridani. Our new radial velocities allow to improve the set of orbital elements and reveal long-term variations of the barycentric velocity. A possible third-body orbit with a period of ,19 years is presented. Absolute parameters are determined in combination with the Hipparcos parallax. EI Eri's inclination angle of the rotational axis is confined to 56°.0 ± 4°.5, ist luminosity class IV is confirmed by its radius of 2.37 ± 0.12 R,. A comparison to theoretical stellar evolutionary tracks suggests a mass of 1.09 ± 0.05 M, and an age of , 6.15 Gyr. The present investigation is the basis of our long-term Doppler imaging study of its stellar surface (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Radial velocities, dynamics of stars and nebulosities with GAIA and VLT-GIRAFFEASTRONOMISCHE NACHRICHTEN, Issue 9-10 2008C. Martayan Abstract This document is divided in two parts. The first part deals with the radial velocities (RV) distributions for B-type stars and nebulosities observed with the VLT-GIRAFFE in the Large and Small Magellanic Clouds towards the open clusters NGC2004 and NGC330. Thanks to the resolution of GIRAFFE spectra, we found that the RV distribution for the nebulosities in the LMC is bi-modal. This bi-modality can be interpreted, in term of dynamics, by the expansion of the LMC4 super-bubble. The second part deals with the GAIA space mission and the determination of the radial velocities by using Radial Velocity Spectrometer (RVS) spectra. The methods to determine the radial velocities are presented as well as preliminary results on simulated RVS spectra. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] SiO Maser Sources within 30 pc of the Galactic CenterASTRONOMISCHE NACHRICHTEN, Issue S1 2003Shuji Deguchi Abstract Using the Nobeyama 45-m radio telescope, we have observed 314 large amplitude variables within 30 pc of the Galactic center in SiO maser lines. Resulting detections give the radial velocities of 174 stars; light-variation periods have been known for all of these stars. The SiO detection rate increases sharply with the period and it is about twice of the OH maser detection rate. The radial-velocity data show slow and rapid rotations of the outer and inner circumnuclear-disk stars, respectively. Five high-velocity stars were found only at the negative-longitude side of the Galactic center. Estimation of the ages of high velocity stars suggests that these stars must be be accelerated to high velocities within 108 years. [source] Numerical simulation of turbulent impinging jet on a rotating diskINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2007A. Abdel-Fattah, Article first published online: 25 OCT 200 Abstract The calculations of quasi-three-dimensional momentum equations were carried out to study the influence of wall rotation on the characteristics of an impinging jet. The pressure coefficient, the mean velocity distributions and the components of Reynolds stress are calculated. The flow is assumed to be steady, incompressible and turbulent. The finite volume scheme is used to solve the continuity equation, momentum equations and k,, model equations. The flow characteristics were studied by varying rotation speed , for 0,,,167.6 rad/s, the distance from nozzle to disk (H/d) was (3, 5, 8 and 10) and the Reynolds number Re base on VJ and d was 1.45 × 104. The results showed that, the radial velocity and turbulence intensity increase by increasing the rotation speed and decrease in the impingement zone as nozzle to disk spacing increases. When the centrifugal force increases, the radial normal stresses and shear stresses increase. The location of maximum radial velocity decreases as the local velocity ratio (,) increases. The pressure coefficient depends on the centrifugal force and it decreases as the distance from nozzle to plate increases. In impingement zone and radial wall jet, the spread of flow increases as the angular velocity decreases The numerical results give good agreement with the experiment data of Minagawa and Obi (Int. J. of Heat and Fluid Flow 2004; 25:759,766). Copyright © 2006 John Wiley & Sons, Ltd. [source] 3D velocity from 3D Doppler radial velocityINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 3 2005J. L. Barron Abstract We present local least squares and regularization frameworks for computing 3D velocity (3D optical flow) from 3D radial velocity measured by a Doppler radar. We demonstrate the performance of our algorithms quantitatively on synthetic radial velocity data and qualitatively on real radial velocity data, obtained from the Doppler radar at Kurnell Radar station, Botany Bay, New South Wales, Australia. Radial velocity can be used to predict the future positions of storms in sequences of Doppler radar datasets.© 2005 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 15, 189,198, 2005 [source] Test of flow field on the annular meridian plane in a tubular membrane separator with rotary tangential flowJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2004Cheng Duan Wang Abstract Enhancement of membrane microfiltration by rotary tangential flow is a new technique, which is based on the hydrocyclone mechanism. It improved the structure of the general membrane separator and the form of the liquid suspension flowing into the separator, so as to increase membrane fluxes and decrease membrane fouling. In our research, a tubular membrane separator with rotary tangential flow was designed for the first time. The flow field characteristics of polypropylene tubular membrane microfiltration in this tubular separator were studied systematically by means of the Particle Image Velocimetry (PIV) test. Streamlines and velocity distributions of the meridian plane of the separator under different operating parameters were obtained. The velocity distribution characteristics of rotary circular tangential flow were analyzed quantitatively with the following conclusions being obtained: (1)In the non-vortex area, no matter how the operating parameters (flux, entry pressure) change, the velocity near the rotary tangential flow entrance is higher than the velocity far from the entrance at the same radial coordinates. In the vortex area, generally the flow velocity of the inner vortex is lower than that of the outer vortex. At the vortex center, the velocity is the lowest, the radial velocity being generally equal to zero. In the vortex zone, the radial velocity is less than the axial velocity. (2)Under test conditions, the radial velocity and the axial velocity of the vortexes' borders are 1,2 times the average axial velocity in the annular gap of the membrane module. The maximum radial velocity and axial velocity of Taylor vortexes are 2,5 times the average axial velocity in the annular gap of the membrane module. (3)In the vortexes that formed on the meridian plane, it was found that mass transfer occurred between the inner and outer parts of the fluid. Much fluid moved from the outer vortexes into the inner ones, which was able to prevent particles blocking the membrane tube. Copyright © 2004 Society of Chemical Industry [source] Orbital and physical parameters of eclipsing binaries from the All-Sky Automated Survey catalogue , I. A sample of systems with components' masses between 1 and 2 M,MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2009K. G. He, miniak ABSTRACT We derive the absolute physical and orbital parameters for a sample of 18 detached eclipsing binaries from the All-Sky Automated Survey (ASAS) data base based on the available photometry and our own radial velocity (RV) measurements. The RVs are computed using spectra we collected with the 3.9-m Anglo-Australian Telescope (AAT) and its University College London Echelle Spectrograph (UCLES), and the 1.9-m Radcliffe telescope and its Grating Instrument for Radiation Analysis with a Fibre-Fed Echelle (GIRAFFE) at the South African Astronomical Observatory (SAAO). In order to obtain as precise RVs as possible, most of the systems were observed with an iodine cell available at the AAT/UCLES and/or analysed using the two-dimensional cross-correlation technique (TODCOR). The RVs were measured with TODCOR using synthetic template spectra as references. However, for two objects we used our own approach to the tomographic disentangling of the binary spectra to provide observed template spectra for the RV measurements and to improve the RV precision even more. For one of these binaries, AI Phe, we were able to the obtain an orbital solution with an RV rms of 62 and 24 m s,1 for the primary and secondary, respectively. For this system, the precision in M sin3i is 0.08 per cent. For the analysis, we used the photometry available in the ASAS data base. We combined the RV and light curves using phoebe and jktebop codes to obtain the absolute physical parameters of the systems. Having precise RVs, we were able to reach ,0.2 per cent precision (or better) in masses in several cases but in radii, due to the limited precision of the ASAS photometry, we were able to reach a precision of only 1 per cent in one case and 3,5 per cent in a few more cases. For the majority of our objects, the orbital and physical analysis is presented for the first time. [source] H, long-term monitoring of the Be star , Cephei AaMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2008G. Catanzaro ABSTRACT Papers published in recent years have contributed to resolve the enigma of the hypothetical Be nature of the hot pulsating star , Cephei. This star shows variable emission in the H, line, typical for Be stars, but its projected rotational velocity is very much lower than the critical limit, contrary to what is expected for a typical Be star. The emission has been attributed to the secondary component of the , Cephei spectroscopic binary system. In this paper, using both our and archived spectra, we attempt to recover the H, profile of the secondary component and to analyse its behaviour with time for a long period. To accomplish this task, we first derive the atmospheric parameters of the primary, Teff= 24 000 ± 250 K and log g= 3.91 ± 0.10, and then we use these values to compute its synthetic H, profile, and finally we reconstruct the secondary's profile disentangling the observed one. The secondary's H, profile shows the typical two-peak emission of a Be star with a strong variability. We also analysed the behaviour versus time of some linewidth parameters: equivalent width, ratio of blue to red peak intensities, full width at half-maximum, peak separation and radial velocity of the central depression. The projected rotational velocity (v sin i) of the secondary and the dimension of the equatorial surrounding disc have also been estimated. [source] A photometric,spectroscopic analysis and the evolutionary status of the Algol-type binary U Coronae BorealisMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2003S. K. Yerli ABSTRACT The prime purposes of this study are to obtain reliable orbital parameters for the Algol-type binary U Coronae Borealis (U CrB) and to explain the evolutionary status of this system. All observations of the primary star's radial velocity are consistent with the value K1= 58.6 ± 2.0 km s,1. Measurements of the radial velocity of the secondary component give K2 = 185.2 ± 5.0 km s,1. Using the photometrically determined inclination of 78.7 ± 0.3, the masses of the two stars are therefore deduced to be 4.74 ± 0.28 and 1.46 ± 0.06 M, for the primary and secondary components, respectively. Using all available observations, we discuss the origin and evolution of the close binary system U CrB. We derive the restrictions concerning masses and period from a general network of calculations of medium mass close binary evolution. Detailed models are calculated within the derived ranges, giving the most likely initial system parameters as and Pi= 1.4 d. It turns out that the interactive evolution up to the present stage has been non-conservative. During its evolution, U CrB has lost about 14 per cent of its initial total mass (,M, 1 M,) and around 18 per cent of its initial total angular momentum. We also examine the possibility of probing dynamo action in the mass-losing component of U CrB. We point out that, in order to maintain the evolution of U CrB in its later stages, which is presumably driven by stellar ,magnetic braking', an efficient mechanism for producing large-scale surface magnetic fields in the donor star is required. We suggest that observed X-ray activity in U CrB may be a good indicator of its evolutionary status and the internal structure of the mass-losing component. [source] Kinematic structure in the young , Orionis associationMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2006R. D. Jeffries ABSTRACT We have used precise radial velocity measurements for a large number of candidate low-mass stars and brown dwarfs to show that the young , Ori ,cluster' consists of two spatially superimposed components which are kinematically separated by 7 km s,1 in radial velocity, and which have different mean ages. We examine the relationship of these two kinematic groups to other populations in the Orion OB1 association, and briefly discuss the consequence of mixed age samples for ongoing investigations of the formation and evolution of low-mass objects in this much-observed region. [source] The exceptional Herbig Ae star HD 101412: The first detection of resolved magnetically split lines and the presence of chemical spots in a Herbig star,ASTRONOMISCHE NACHRICHTEN, Issue 4 2010S. Hubrig Abstract In our previous search for magnetic fields in Herbig Ae stars, we pointed out that HD 101412 possesses the strongest magnetic field among the Herbig Ae stars and hence is of special interest for follow-up studies of magnetism among young pre-main-sequence stars. We obtained high-resolution, high signal-to-noise UVES and a few lower quality HARPS spectra revealing the presence of resolved magnetically split lines. HD 101412 is the first Herbig Ae star for which the rotational Doppler effect was found to be small in comparison to the magnetic splitting and several spectral lines observed in unpolarized light at high dispersion are resolved into magnetically split components. The measured mean magnetic field modulus varies from 2.5 to 3.5kG, while the mean quadratic field was found to vary in the range of 3.5 to 4.8 kG. To determine the period of variations, we used radial velocity, equivalent width, line width, and line asymmetry measurements of variable spectral lines of several elements, as well as magnetic field measurements. The period determination was done using the Lomb-Scargle method. The most pronounced variability was detected for spectral lines of He I and the iron peak elements, whereas the spectral lines of CNO elements are only slightly variable. From spectral variations and magnetic field measurements we derived a potential rotation period Prot = 13.86 d, which has to be proven in future studies with a larger number of observations. It is the first time that the presence of element spots is detected on the surface of a Herbig Ae/Be star. Our previous study of Herbig Ae stars revealed a trend towards stronger magnetic fields for younger Herbig Ae stars, confirmed by statistical tests. This is in contrast to a few other (non-statistical) studies claiming that magnetic Herbig Ae stars are progenitors of the magnetic Ap stars. New developments in MHD theory show that the measured magnetic field strengths are compatible with a current-driven instability of toroidal fields generated by differential rotation in the stellar interior. This explanation for magnetic intermediate-mass stars could be an alternative to a frozen-in fossil field (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||