232 research outputs found
High Resolution Spectroscopy of Balmer-Dominated Shocks in the RCW 86, Kepler and SN 1006 Supernova Remnants
We report results from high resolution optical spectroscopy of three
non-radiative galactic supernova remnants, RCW 86, Kepler's supernova remnant
and SN 1006. We have measured the narrow component H-alpha line widths in
Balmer-dominated filaments in RCW 86 and SN 1006, as well as the narrow
component width in a Balmer-dominated knot in Kepler's SNR. The narrow
component line widths measured in RCW 86 and Kepler's SNR show FWHM of 30-40
km/s, similar to what has been seen in other Balmer-dominated remnants. Of the
remnants in our sample, SN 1006 is the fastest shock (~3000 km/s). The narrow
component H-alpha and H-beta lines in this remnant have a FWHM of merely 21
km/s. Comparing the narrow component widths measured in our sample with those
measured in other remnants shows that the width of the narrow component does
not correlate in a simple way with the shock velocity. The implications for the
pre-heating mechanism responsible for the observed line widths are discussed.Comment: Accepted by A&
[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
Proper Motions of H-alpha filaments in the Supernova Remnant RCW 86
We present a proper motion study of the eastern shock-region of the supernova
remnant RCW 86 (MSH 14-63, G315.4-2.3), based on optical observations carried
out with VLT/FORS2 in 2007 and 2010. For both the northeastern and southeastern
regions, we measure an average proper motion of H-alpha filaments of 0.10 +/-
0.02 arcsec/yr, corresponding to 1200 +/- 200 km/s at 2.5kpc. There is
substantial variation in the derived proper motions, indicating shock
velocities ranging from just below 700 km/s to above 2200 km/s.
The optical proper motion is lower than the previously measured X-ray proper
motion of northeastern region. The new measurements are consistent with the
previously measured proton temperature of 2.3 +/- 0.3 keV, assuming no
cosmic-ray acceleration. However, within the uncertainties, moderately
efficient (< 27 per cent) shock acceleration is still possible. The combination
of optical proper motion and proton temperature rule out the possibility that
RCW 86 has a distance less than 1.5kpc.
The similarity of the proper motions in the northeast and southeast is
peculiar, given the different densities and X-ray emission properties of the
regions. The northeastern region has lower densities and the X-ray emission is
synchrotron dominated, suggesting that the shock velocities should be higher
than in the southeastern, thermal X-ray dominated, region. A possible solution
is that the H-alpha emitting filaments are biased toward denser regions, with
lower shock velocities. Alternatively, in the northeast the shock velocity may
have decreased rapidly during the past 200yr, and the X-ray synchrotron
emission is an afterglow from a period when the shock velocity was higher.Comment: Accepted for publication in MNRA
The pre-shock gas of SN1006 from HST/ACS observations
We derive the pre-shock density and scale length along the line of sight for
the collisionless shock from a deep HST image that resolves the H alpha
filament in SN1006 and updated model calculations. The very deep ACS
high-resolution image of the Balmer line filament in the northwest (NW)
quadrant shows that 0.25 < n_0 < le$ 0.4 cm-3 and that the scale along the line
of sight is about 2 x 10^{18} cm, while bright features within the filament
correspond to ripples with radii of curvature less than 1/10 that size. The
derived densities are within the broad range of earlier density estimates, and
they agree well with the ionization time scale derived from the Chandra X-ray
spectrum of a region just behind the optical filament. This provides a test for
widely used models of the X-ray emission from SNR shocks. The scale and
amplitude of the ripples are consistent with expectations for a shock
propagating though interstellar gas with ~ 20% density fluctuations on parsec
scales as expected from studies of interstellar turbulence. One bulge in the
filament corresponds to a knot of ejecta overtaking the blast wave, however.
The interaction results from the rapid deceleration of the blast wave as it
encounters an interstellar cloud.Comment: 16 pages, 6 figures, to appear in Ap
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