278 research outputs found
Balmer-Dominated Shocks Exclude Hot Progenitors for Many Type Ia Supernovae
The evolutionary mechanism underlying Type Ia supernova explosions remains
unknown. Recent efforts to constrain progenitor models based on the influence
that their high energy emission would have on the interstellar medium (ISM) of
galaxies have proven successful. For individual remnants, Balmer-dominated
shocks reveal the ionization state of hydrogen in the immediately surrounding
gas. Here we report deep upper limits on the temperature and luminosity of the
progenitors of four Type Ia remnants with associated Balmer filaments: SN 1006,
0509-67.5, 0519-69.0, and DEM L71. For SN 1006, existing observations of helium
line emission in the diffuse emission ahead of the shock provide an additional
constraint on the helium ionization state in the vicinity of the remnant. Using
the photoionization code Cloudy, we show that these constraints exclude any
hot, luminous progenitor for SN 1006, including stably hydrogen or helium
nuclear-burning white dwarfs, as well as any Chandrasekhar-mass white dwarf
accreting matter at yr via a disk. For
0509-67.5, the Balmer emission alone rules out any such white dwarf accreting
yr. For 0519-69.0 and DEM L71, the inferred
ambient ionization state of hydrogen is only weakly in tension with a recently
hot, luminous progenitor, and cannot be distinguished from e.g., a relatively
higher local Lyman continuum background, without additional line measurements.
Future deep spectroscopic observations will resolve this ambiguity, and can
either detect the influence of any luminous progenitor or rule out the same for
all resolved SN Ia remnants.Comment: 9 pages, 3 figures, 1 table. Accepted for publication in Ap
No hot and luminous progenitor for Tycho's supernova
Type Ia supernovae have proven vital to our understanding of cosmology, both
as standard candles and for their role in galactic chemical evolution; however,
their origin remains uncertain. The canonical accretion model implies a hot and
luminous progenitor which would ionize the surrounding gas out to a radius of
10--100 parsecs for 100,000 years after the explosion. Here we
report stringent upper limits on the temperature and luminosity of the
progenitor of Tycho's supernova (SN 1572), determined using the remnant itself
as a probe of its environment. Hot, luminous progenitors that would have
produced a greater hydrogen ionization fraction than that measured at the
radius of the present remnant (3 parsecs) can thus be excluded. This
conclusively rules out steadily nuclear-burning white dwarfs (supersoft X-ray
sources), as well as disk emission from a Chandrasekhar-mass white dwarf
accreting yr (recurrent novae). The lack of a
surrounding Str\"omgren sphere is consistent with the merger of a double white
dwarf binary, although other more exotic scenarios may be possible.Comment: 17 pages, 2 figures, including supplementary information. Original
accepted manuscript (before copyediting/formatting by Nature Astronomy
[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
Spitzer Imaging and Spectral Mapping of the Oxygen-Rich Supernova Remnant G292.0+1.8
We present mid-infrared continuum and emission line images of the Galactic
oxygen-rich supernova remnant (SNR) G292.0+1.8, acquired using the MIPS and IRS
instruments on the Spitzer Space Telescope. The MIPS 24 micron and 70 micron
images of G292.0+1.8 are dominated by continuum emission from a network of
filaments encircling the SNR. The morphology of the SNR, as seen in the
mid-infrared, resembles that seen in X-rays with the Chandra X-ray Observatory.
Most of the mid-infrared emission in the MIPS images is produced by
circumstellar dust heated in the non-radiative shocks around G292.0+1.8,
confirming the results of earlier mid-IR observations with AKARI. In addition
to emission from hot dust, we have also mapped atomic line emission between 14
micron and 36 micron using IRS spectral maps. The line emission is primarily
associated with the bright oxygen-rich optical knots, but is also detected from
fast-moving knots of ejecta. We confirm our earlier detection of 15-25 micron
emission characteristic of magnesium silicate dust in spectra of the
radiatively shocked ejecta. We do not detect silicon line emission from any of
the radiatively shocked ejecta in the southeast of the SNR, possibly because
that the reverse shock has not yet penetrated most of the Si-rich ejecta in
that region. This may indicate that G292.0+1.8 is less evolved in the southeast
than the rest of the SNR, and may be further evidence in favor of an asymmetric
SN explosion as proposed in recent X-ray studies of G292.0+1.8.Comment: 16 pages, 1 table, 7 figures, accepted for publication in Ap
Dust in a Type Ia Supernova Progenitor: Spitzer Spectroscopy of Kepler's Supernova Remnant
Characterization of the relatively poorly-understood progenitor systems of
Type Ia supernovae is of great importance in astrophysics, particularly given
the important cosmological role that these supernovae play. Kepler's Supernova
Remnant, the result of a Type Ia supernova, shows evidence for an interaction
with a dense circumstellar medium (CSM), suggesting a single-degenerate
progenitor system. We present 7.5-38 m infrared (IR) spectra of the
remnant, obtained with the {\it Spitzer Space Telescope}, dominated by emission
from warm dust. Broad spectral features at 10 and 18 m, consistent with
various silicate particles, are seen throughout. These silicates were likely
formed in the stellar outflow from the progenitor system during the AGB stage
of evolution, and imply an oxygen-rich chemistry. In addition to silicate dust,
a second component, possibly carbonaceous dust, is necessary to account for the
short-wavelength IRS and IRAC data. This could imply a mixed chemistry in the
atmosphere of the progenitor system. However, non-spherical metallic iron
inclusions within silicate grains provide an alternative solution. Models of
collisionally-heated dust emission from fast shocks ( 1000 km s)
propagating into the CSM can reproduce the majority of the emission associated
with non-radiative filaments, where dust temperatures are K, but
fail to account for the highest temperatures detected, in excess of 150 K. We
find that slower shocks (a few hundred km s) into moderate density
material ( cm) are the only viable source of heating
for this hottest dust. We confirm the finding of an overall density gradient,
with densities in the north being an order of magnitude greater than those in
the south.Comment: Accepted by ApJ. 11 pages, 5 figures, 1 table. Produced using
emulateapj forma
The Outer Shock of the Oxygen-Rich Supernova Remnant G292.0+1.8: Evidence for the Interaction with the Stellar Winds from its Massive Progenitor
We study the outer-shock structure of the oxygen-rich supernova remnant
G292.0+1.8, using a deep observation with the Chandra X-ray Observatory. We
measure radial variations of the electron temperature and emission measure that
we identify as the outer shock propagating into a medium with a radially
decreasing density profile. The inferred ambient density structure is
consistent with models for the circumstellar wind of a massive progenitor star
rather than for a uniform interstellar medium. The estimated wind density n_H =
0.1 ~ 0.3 cm^-3) at the current outer radius (~7.7 pc) of the remnant is
consistent with a slow wind from a red supergiant (RSG) star. The total mass of
the wind is estimated to be ~ 15 - 40 solar mass (depending on the estimated
density range), assuming that the wind extended down to near the surface of the
progenitor. The overall kinematics of G292.0+1.8 are consistent with the
remnant expanding through the RSG wind.Comment: 9 pages (2-column), 5 figures, accepted for Ap
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