861 research outputs found
Preliminary orbital elements of six visual binary stars
International audiencePreliminary new orbital elements were computed for the visual binary stars A 1 - ADS 1345, A 2629 - ADS 3610, BU 560 - ADS 4371, STF 3115 - ADS 4376, STF 1426 AB - ADS 7730 and STF 2437 - ADS 11956. Using Straizys and Kuriliene's data, we derived new formulae for computing dynamical parallaxes for luminosity classes IV and V. The values found for those systems are in agreement with the {Hipparcos} parallaxes and the corresponding systemic masses are consistent with the spectral types
Locating the ‘radical’ in 'Shoot the Messenger'
This is the author's accepted manuscript. The final published article is available from the link below, copyright 2013 @ Edinburgh University Press.The 2006 BBC drama Shoot the Messenger is based on the psychological journey of a Black schoolteacher, Joe Pascale, accused of assaulting a Black male pupil. The allegation triggers Joe's mental breakdown which is articulated, through Joe's first-person narration, as a vindictive loathing of Black people. In turn, a range of common stereotypical characterisations and discourses based on a Black culture of hypocrisy, blame and entitlement is presented. The text is therefore laid wide open to a critique of its neo-conservatism and hegemonic narratives of Black Britishness. However, the drama's presentation of Black mental illness suggests that Shoot the Messenger may also be interpreted as a critique of social inequality and the destabilising effects of living with ethnicised social categories. Through an analysis of issues of representation, the article reclaims this controversial text as a radical drama and examines its implications for and within a critical cultural politics of ‘race’ and representation
Correction:Canine Mammary Cancer Stem Cells Are Radio- and Chemo- Resistant and Exhibit an Epithelial-Mesenchymal Transition Phenotype.
In the original article [...
Chandra Observations of NGC 4438: An Environmentally Damaged Galaxy in the Virgo Cluster
We present results from a 25 ksec CHANDRA ACIS-S observation of galaxies
NGC4438 and NGC4435 in the Virgo Cluster. X-ray emission in NGC4438 is observed
in a ~700 pc nuclear region, a 2.3 kpc spherical bulge, and a network of
filaments extending 4-10 kpc to the W and SW of the galaxy. The X-ray emission
in all 3 regions is highly correlated to similar features observed in Halpha.
Spectra of the filaments and bulge are well represented by a 0.4 keV MEKAL
model with combined 0.3-2 keV intrinsic luminosity of 1.24x10^{40}erg/s,
electron densities ~ 0.02-0.04 cm^{-3}, cooling times of 400-700 Myr and X-ray
gas mass <~ 3.7x10^8 Msolar. In the nuclear region of NGC4438 X-ray emission is
seen from the nucleus and from two outflow bubbles extending 360(730) pc to the
NW(SE) of the nucleus. The spectrum of the NW outflow bubble plus nucleus is
well fitted by an absorbed (n_H=1.9x10^{21} cm^{-2}) 0.58 keV MEKAL plasma
model plus a heavily absorbed (n_H = 2.9 x10^{22} cm^{-2}) Gamma = 2, power law
component. The electron density, cooling time, and X-ray gas mass in the NW
outflow are ~0.5 cm^{-3}, 30 Myr and 3.5x10^6 Msolar. Weak X-ray emission is
observed in the central region of NGC4435 with the peak of the hard emission
coincident with the galaxy's optical center; while the peak of the soft X-ray
emission is displaced 316 pc to the NE. The spectrum of NGC 4435 is well fitted
by a non-thermal power law plus a thermal component from 0.2-0.3 keV diffuse
ISM gas. We argue that the X-ray properties of gas outside the nuclear region
in NGC4438 and in NGC4435 favor a high velocity, off-center collision between
these galaxies ~ 100 Myr ago; while the nuclear X-ray emitting outflow gas in
NGC4438 has been heated only recently (within ~ 1-2 Myr) by shocks (v_s ~ 600
kms^{-1}) possibly powered by a central AGN.Comment: 40 pages, 7 figures; minor changes to conform to published version,
improved spectral fits to NGC 4435, improved figures 3,5; new figures 6b,
Speckle observations with PISCO in Merate - II. Astrometric measurements of visual binaries in 2004
International audienceWe present relative astrometric measurements of visual binaries taken during the second semester of 2004 with the Pupil Interferometry Speckle camera and Coronagraph (PISCO) at the 1-m Zeiss telescope of the Brera Astronomical Observatory, in Merate, Italy. We performed 207 new observations of 194 objects with angular separations in the range 0.1-4.0 arcsec and an accuracy better than ~0.01 arcsec. Our sample contains orbital couples as well as binaries whose motion is still uncertain. Our purpose is to improve the accuracy of the orbits and constrain the masses of the components. Those measurements show that the orbit of ADS 15115 needs to be revised; we propose a new orbit for this object
Speckle observations with PISCO in Merate - III. Astrometric measurements of visual binaries in 2005 and scale calibration with a grating mask
International audienceWe present relative astrometric measurements of visual binaries made during the first semester of 2005, with the Pupil Interferometry Speckle Camera and Coronagraph (PISCO) at the 102-cm Zeiss telescope of the Brera Astronomical Observatory, in Merate. We performed 214 new observations of 192 objects, with angular separations in the range 0.2-4.3arcsec, and with an average accuracy of 0.01arcsec. Most of the position angles could be determined without the usual 180° ambiguity, and their mean error is . Our sample contains orbital couples as well as binaries whose motion is still uncertain. The purpose of this long-term programme is to improve the accuracy of the orbits and constrain the masses of the components. For the first time with PISCO, the astrometric calibration was made with a grating mask mounted at the entrance of the telescope. The advantage of this procedure is to provide a reliable and fully independent scale determination. We have found two possible new triple systems: ADS 7871 and KUI 15. We propose a preliminary orbit for ADS 4208
The Central Engines of 19 LINERs as Viewed by Chandra
Using archival Chandra observations of 19 LINERs we explore the X-ray
properties of their inner kiloparsec to determine the origin of their nuclear
X-ray emission, to investigate the presence of an AGN, and to identify the
power source of the optical emission lines. The relative numbers of LINER types
in our sample are similar to those in optical spectroscopic surveys. We find
that diffuse, thermal emission is very common and is concentrated within the
central few hundred parsec. The average spectra of the hot gas in spirals and
ellipticals are very similar to those of normal galaxies. They can be fitted
with a thermal plasma (kT~0.5 keV) plus a power law (photon index of 1.3-1.5)
model. There are on average 3 detected point sources in their inner kiloparsec
with L(0.5-10 keV)~10^37-10^40 erg/s. The average cumulative luminosity
functions for sources in spirals and ellipticals are identical to those of
normal galaxies. In the innermost circle of 2.5" radius in each galaxy we find
an AGN in 12 of the 19 galaxies. The AGNs contribute a median of 60% of the
0.5-10 keV luminosity of the central 2.5" region, they have luminosities of
10^37-10^39 erg/s (Eddington ratios 10^-8 to 10^-5). The ionizing luminosity of
the AGNs is not enough to power the observed optical emission lines in this
particular sample. Thus, we suggest that the lines are powered either by the
mechanical interaction of an AGN jet (or wind) with the circumnuclear gas, or
by stellar processes, e.g. photoionization by post-AGB stars or young stars.Comment: Accepted by Ap.J. 23 pages, 8 figures, emulatepj format, images of
fig 1 not included, for complete PDF preprint see
http://www.astro.psu.edu/users/mce/preprints
Speckle observations of the binary asteroid (22) Kalliope with C2PU/PISCO
We present new speckle measurements of the position of Linus, the satellite
of the asteroid (22) Kalliope, obtained at the 1m C2PU-Epsilon telescope on the
Plateau de Calern, France. Observations were made in the visible domain with
the speckle camera PISCO. We obtained 122 measurements in February-March 2022
and April 2023, with a mean uncertainty close to 10 milli-arcseconds on the
angular separation
Sustaining entrepreneurial business: a complexity perspective on processes that produce emergent practice
This article examines the management practices in an entrepreneurial small firm which sustain the business. Using a longitudinal qualitative case study, four general processes are identified (experimentation, reflexivity, organising and sensing), that together provide a mechanism to sustain the enterprise. The analysis draws on concepts from entrepreneurship and complexity science. We suggest that an entrepreneur’s awareness of the role of these parallel processes will facilitate their approaches to sustaining and developing enterprises. We also suggest that these processes operate in parallel at multiple levels, including the self, the business and inter-firm networks. This finding contributes to a general theory of entrepreneurship. A number of areas for further research are discussed arising from this result
RXTE Discovery of Multiple Cyclotron Lines during the 2004 December Outburst of V0332+53
We present an analysis of the 2-150 keV spectrum of the transient X-ray
pulsar V0332+53 taken with the Rossi X-Ray Timing Explorer (RXTE) in 2004
December. We report on the detection of three cyclotron resonance features at
27, 51, and 74 keV in the phase-averaged data, corresponding to a polar
magnetic field of 2.7 x 10^12 G. After 4U0115+63, this makes V0332+53 the
second accreting neutron star in which more than two cyclotron lines have been
detected; this has now also been confirmed by INTEGRAL. Pulse-phase
spectroscopy reveals remarkably little variability of the cyclotron line
through the 4.4 s X-ray pulse.Comment: 4 pages, 3 figures, accepted for publication in ApJ Letter
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