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

Optical Spectroscopy of the environment of a ULX in NGC 7331

Optical photometric and spectroscopic data are presented that show an association of an ultraluminous X-ray source in NGC 7331 with a young star cluster of mass 1.1e5 solar masses and age 4.25 Myr. If the ULX is part of the bright stellar cluster, then the mass of the progenitor of the compact accretor must have been greater than about 40-50 solar masses in order to already have evolved through the supernova stage to a compact object. The companion star is also likely an evolved massive star. The emission line spectrum of the nebula surrounding the cluster can be interpreted as a result of photoionization by the cluster OB stars with an additional source of shock excitation producing strong [SII], [OI] and NII lines. This additional source appears to be as much as five times more powerful than the supernovae and stellar winds in the cluster can provide. Additional mechanical energy input associated with the ULX itself can help explain the residual shock excited line luminosities of the emission region.Comment: 17 pages, accepted to Ap

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,

POTENTIAL OF ASTROGRAPHIC PLATES FOR STELLAR FLARE DETECTION

A set of four test regions covering a total celestial area of 520 deg2 at low galactic latitude is investigated on a set of 130 century-old astrographic plates. About 8% of the 2 × 105 stars with apparent B magnitude 10–14 and with total proper-motion component larger than 002 yr-1 show a significant flickering greater than 0.4 mag in B over a timescale shorter than 20 minutes. About 25% of these stellar flare candidates concern stars with B-V ~ 0.2 (spectral type A7). A procedure to select pre–main-sequence stellar candidates from the distance-limited sample of 16 × 103 disk dwarfs with detected flickering in B magnitude ≥0.4 is presented in view of a mass loss of 10-8 M☉ yr-1, derived from the analysis of the angular momentum distribution of stellar orbits. Follow-up UBV photoelectric photometry at the present epoch of 200 nearby stellar flares along the Vulpecula Rift shows an effect of reddening in B-V and of blueing in U-B for about 10% of the targets. The detection of optically thin or thick disks around the selected targets is suggested. The success rate in detecting optical flares in nearby stars of ~1.5 M☉ with as much as 5 × 10-6 M☉ dumped onto the central star during the past 100 years, from deep astrographic plates coupled with 1 m–class telescope is estimated to 10% with a kinematical bias that can be dealt with

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

Remnant of a "Wet" Merger: NGC 34 and Its Young Massive Clusters, Young Stellar Disk, and Strong Gaseous Outflow

This paper presents new images and spectroscopy of NGC 34 (Mrk 938) obtained with the du Pont 2.5-m and Baade 6.5-m telescopes at Las Campanas, plus photometry of an HST archival V image. This Mv = -21.6 galaxy has often been classified as a Seyfert 2, yet recently published infrared spectra suggest a dominant central starburst. We find that the galaxy features a single nucleus, a main spheroid containing a blue central disk, and tidal tails indicative of two former disk galaxies. These galaxies appear to have completed merging. The remnant shows three clear optical signs that the merger was gas-rich ("wet") and accompanied by a starburst: (1) It sports a rich system of young star clusters, of which 87 have absolute magnitudes -10.0 > Mv > -15.4. Five clusters with available spectra have ages in the range 0.1-1.0 Gyr, photometric masses between 2x10^6 and 2x10^7 Msun, and are gravitationally bound young globulars. (2) The blue central disk appears to be young. It is exponential, can be traced to >10 kpc radius, and has a smooth structure and colors suggest- ing a dominant, ~400 Myr old poststarburst population. And (3), the center of NGC 34 drives a strong outflow of cool, neutral gas, as revealed by broad blueshifted Na I D lines. The mean outflow velocity of this gas is -620 km/s, while the maximum velocity reaches -1050 km/s. We suggest that NGC 34 stems from two recently merged gas-rich disk galaxies with an estimated mass ratio between 1/3 and 2/3. The remnant seems to have first experienced a galaxy-wide starburst that then shrank to its current central and obscured state. The strong gaseous outflow came last. (Abridged

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

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