650 research outputs found
The Physical Parameters of the Micro-quasar S26 in the Sculptor Group Galaxy NGC 7793
NGC 7793 - S26 is an extended source (350 pc 185 pc) previously
studied in the radio, optical and x-ray domains. It has been identified as a
micro-quasar which has inflated a super bubble. We used Integral Field Spectra
from the Wide Field Spectrograph on the ANU 2.3 m telescope to analyse spectra
between 3600--7000 \AA. This allowed us to derive fluxes and line ratios for
selected nebular lines. Applying radiative shock model diagnostics, we estimate
shock velocities, densities, radiative ages and pressures across the object. We
show that S26 is just entering its radiative phase, and that the northern and
western regions are dominated by partially-radiative shocks due to a lower
density ISM in these directions. We determine a velocity of expansion along the
jet of 330 km s, and a velocity of expansion of the bubble in the minor
axis direction of 132 km s. We determine the age of the structure to be
yr, and the jet energy flux to be erg
s The jet appears to be collimated within deg, and to undergo
very little precession. If the relativistic , then some 4
M of relativistic matter has already been processed through the jet.
We conclude that the central object in S26 is probably a Black Hole with a mass
typical of the ultra-luminous X-ray source population which is currently
consuming a fairly massive companion through Roche Lobe accretion.Comment: Accepted for publication in MNRAS; 12 pages, 7 figures and 3 table
The structure of Herbig-Haro object 43 and Orion dark cloud extinction
New ultraviolet and optical observations of Herbig-Haro Object No. 43 are reported. Continuum and emission line fluxes in the range 1250 A equal to or less than lambda equal to less than 7350A have been measured. The continuum fluxes are best matched by an enhanced H two photon component added to H free bound emission, assuming theta Ori extinction curve with E(B-V) = 0.2, R = 5. The strucutre and dynamics of three components within the object are discussed. The object has a radiative output of equal to or greater than 0.23 infrared luminosity in ultraviolet and optical radiation combined. The energy requirements are discussed in terms of the production of shock waves by a collimated, supersonic mass outflow from a nearby infrared source
The physics and kinematics of the evolved, interacting planetary nebula PN G342.0-01.7
Here we aim to study the physical and kinematical characteristics of the
unstudied old planetary nebula (PN) PN G342.0-01.7, which shows evidence of
interaction with its surrounding interstellar medium. We used Integral Field
Spectra from the Wide Field Spectrograph on the ANU 2.3 m telescope to provide
spectroscopy across the whole object covering the spectral range 3400-7000
{\AA}. We formed narrow-band images to investigate the excitation structure.
The spectral analysis shows that the object is a distant Peimbert Type I PN of
low excitation, formally of excitation class of 0.5. The low electron density,
high dynamical age, and low surface brightness of the object confirm that it is
observed fairly late in its evolution. It shows clear evidence for dredge-up of
CN-processed material characteristic of its class. In addition, the low
peculiar velocity of 7 km s shows it to be a member of the young disk
component of our Galaxy. We built a self-consistent photoionisation model for
the PNe matching the observed spectrum, the H luminosity, and the
diameter. On the basis of this we derive an effective temperature and luminosity . The temperature is much
higher than might have been expected using the excitation class, proving that
this can be misleading in classifying evolved PNe. PN G342.0-01.7 is in
interaction with its surrounding interstellar medium through which the object
is moving in the south-west direction. This interaction drives a slow shock
into the outer PN ejecta. A shock model suggests that it only accounts for
about 10\% of the total luminosity, but has an important effect on the global
spectrum of the PN.Comment: 15 pages, 6 figures, A&A accepted 201
[Fe XIV] and [Fe XI] reveal the forward shock in SNR 1E0102.2-7219
Aims. We study the forward shock in the oxygen-rich young supernova remnant
(SNR) 1E0102.2-7219 (1E0102 in short) via optical coronal emission from [Fe
XIV] and [Fe XI]: emission lines which offer an alternative method to X-rays to
do so.
Methods. We have used the Multi-Unit Spectroscopic Explorer (MUSE) optical
integral field spectrograph at the Very Large Telescope (VLT) on Cerro Paranal
to obtain deep observations of SNR 1E0102 in the Small Magellanic Cloud. Our
observations cover the entire extent of the remnant with a seeing limited
spatial resolution of 0.7" = 0.2 pc at the distance of 1E 0102.
Results. Our MUSE observations unambiguously reveal the presence of [Fe XIV]
and [Fe XI] emission in 1E0102. The emission largely arises from a thin,
partial ring of filaments surrounding the fast moving O-rich ejecta in the
system. The brightest [Fe XIV] and [Fe XI] emission is found along the eastern
and north-western sides of 1E0102, where shocks are driven into denser ISM
material, while fainter emission along the northern edge reveals the location
of the forward shock in lower density gas, possibly the relic stellar wind
cavity. Modeling of the eastern shocks and the photoionization precursor
surrounding 1E0102, we derive a pre-shock density = (7.4 +-1.5)
cm, and a shock velocity 330 km/s < < 350 km/s.Comment: 4 pages, 4 figures, accepted for publications in A&A as a Letter to
the Edito
- …