275 research outputs found
HST Images and Spectra of the Remnant of SN 1885 in M31
Near UV HST images of the remnant of SN 1885 (S And) in M31 show a 0"70 +-
0"05 diameter absorption disk silhouetted against M31's central bulge, at SN
1885's historically reported position. The disk's size corresponds to a linear
diameter of 2.5 +- 0.4 pc at a distance of 725 +- 70 kpc, implying an average
expansion velocity of 11000 +- 2000 km/s over 110 years. Low-dispersion FOS
spectra over 3200-4800 A; reveal that the absorption arises principally from Ca
II H & K (equivalent width ~215 A;) with weaker absorption features of Ca I
4227 A; and Fe I 3720 A;. The flux at Ca II line center indicates a foreground
starlight fraction of 0.21, which places SNR 1885 some 64 pc to the near side
of the midpoint of the M31 bulge, comparable to its projected 55 pc distance
from the nucleus. The absorption line profiles suggest an approximately
spherically symmetric, bell-shaped density distribution of supernova ejecta
freely expanding at up to 13100 +- 1500 km/s. We estimate Ca I, Ca II, and Fe I
masses of 2.9(+2.4,-0.6) x 10^-4 M_o, 0.005(+0.016,-0.002) M_o, and
0.013(+0.010,-0.005) M_o respectively. If the ionization state of iron is
similar to the observed ionization state of calcium, M_CaII/M_CaI = 16(+42,-5),
then the mass of Fe II is 0.21(+0.74,-0.08) M_o, consistent with that expected
for either normal or subluminous SN Ia.Comment: 8 pages, including 4 embedded EPS figures, emulateapj.sty style file.
Color image at http://casa.colorado.edu/~mcl/sand.shtml . Submitted to Ap
Detection of CO and Dust Emission in Near-Infrared Spectra of SN 1998S
Near-infrared spectra (0.95 -- 2.4 micron) of the peculiar Type IIn supernova
1998S in NGC 3877 from 95 to 355 days after maximum light are presented. K-band
data taken at days 95 and 225 show the presence of the first overtone of CO
emission near 2.3 micron, which is gone by day 355. An apparent extended blue
wing on the CO profile in the day 95 spectrum could indicate a large CO
expansion velocity (~2000 -- 3000 km/s). This is the third detection of
infrared CO emission in nearly as many Type II supernovae studied, implying
that molecule formation may be fairly common in Type II events, and that the
early formation of molecules in SN 1987A may be typical rather than
exceptional. Multi-peak hydrogen and helium lines suggest that SN 1998S is
interacting with a circumstellar disk, and the fading of the red side of this
profile with time is suggestive of dust formation in the ejecta, perhaps
induced by CO cooling. Continuum emission that rises towards longer wavelengths
(J -> K) is seen after day 225 with an estimated near-infrared luminosity >~
10^40 erg/s. This may be related to the near-infrared excesses seen in a number
of other supernovae. If this continuum is due to free-free emission, it
requires an exceptionally shallow density profile. On the other hand, the shape
of the continuum is well fit by a 1200 +- 150 K blackbody spectrum possibly due
to thermal emission from dust. Interestingly, we observe a similar 1200 K
blackbody-like, near-infrared continuum in SN 1997ab, another Type IIn
supernova at an even later post-maximum epoch (day 1064+). A number of dust
emission scenarios are discussed, and we conclude that the NIR dust continuum
is likely powered by the interaction of SN 1998S with the circumstellar medium.Comment: 38 Pages, 12 Figures, Submitted to The Astronomical Journa
Hubble Space Telescope WFPC2 Imaging of Cassiopeia A
The young galactic supernova remnant Cassiopeia A was imaged with Wide Field Planetary Camera 2 (WFPC2) aboard the Hubble Space Telescope through filters selected to capture the complete velocity range of the remnant\u27s main shell in several emission lines. The primary lines detected, along with the specific WFPC2 filters used, were [O III] λλ4959, 5007 (F450W), [N II] λ6583 (F658N), [S II] λλ6716, 6731 + [O II] λλ7319, 7330 + [O I] λλ6300, 6364 (F675W), and [S III] λλ9069, 9532 (F850LP). About three-quarters of the remnant\u27s 4\u27 diameter main shell was imaged with all four filters in three WFPC2 pointings, with most remaining shell regions imaged in just the F675W filter via three additional pointings. Considerable detail is observed in the reverse-shocked ejecta with typical knot scale lengths of 02â04 (1â2 Ă 1016 cm). Both bright and faint emission features appear highly clumped with little in the way of a smooth, diffuse emission component detected. Strong differences in [S III] and [O III] line intensities, indicating chemical abundance differences, are also seen, particularly in knots located along the bright northern limb and near the base of the northeastern jet. A line of curved overlapping filaments in the remnant\u27s northwestern rim appears to mark the location of the remnant\u27s reverse shock front in this region. The morphology of some finger-like ejecta structures elsewhere suggest cases in which the reverse shock front is encountering the remnant\u27s clumped ejecta. Large velocity shears (1000 km s-1), possibly associated with the formation of these Rayleigh-Taylorâlike features, are found in the line profiles of several emission lines (e.g., [S III] λλ9069, 9532 and [Cl II] λ8679) in ground-based, optical spectra of knots near the remnant\u27s center. The [N II] images of the remnant\u27s circumstellar knots (QSFs) reveal them to be 01â06 thick knots and filaments, often with diffuse edges facing away from the center of expansion. Three-color composite images of the whole remnant and certain sections, along with individual filter enlargements of selected regions of the bright optical shell, are presented and discussed
Carbon Monoxide in the Cassiopeia A Supernova Remnant
We report the likely detection of near-infrared 2.29 m first overtone
Carbon Monoxide (CO) emission from the young supernova remnant Cassiopeia A
(Cas A). The continuum-subtracted CO filter map reveals CO knots within the
ejecta-rich reverse shock. We compare the first overtone CO emission with that
found in the well-studied supernova, SN 1987A and find 30 times less CO
in Cas A. The presence of CO suggests that molecule mixing is small in the SN
ejecta and that astrochemical processes and molecule formation may continue at
least ~300 years after the initial explosion.Comment: Accepted for the publication in ApJ Lette
Carbon Monoxide in type II supernovae
Infrared spectra of two type II supernovae 6 months after explosion are
presented. The spectra exhibit a strong similarity to the observations of SN
1987A and other type II SNe at comparable epochs. The continuum can be fitted
with a cool black body and the hydrogen lines have emissivities that are
approximately those of a Case B recombination spectrum. The data extend far
enough into the thermal region to detect emission by the first overtone of
carbon monoxide. The molecular emission is modeled and compared with that in
the spectra of SN 1987A. It is found that the flux in the CO first overtone is
comparable to that found in SN 1987A. We argue that Carbon Monoxide forms in
the ejecta of all type II SNe during the first year after explosion.Comment: 6 pages, 6 figures, accepted for publications in A&
Developing an advocacy agenda for increasing access to opioid substitution therapy as part of comprehensive services for people who use drugs in South Africa
Hubble Space Telescope Images and Spectra of the Remnant of SN 1885 in M31
Near-UV Hubble Space Telescope images of the remnant of SN 1885 (S And) in M31 show a 070±005 diameter absorption disk silhouetted against M31\u27s central bulge, at SN 1885\u27s historically reported position. The disk\u27s size corresponds to a linear diameter of 2.5±0.4 pc at a distance of 725±70 kpc, implying an average expansion velocity of 11,000±2000 km s-1 over 110 yr. Low-dispersion Faint Object Spectrograph spectra over 3200-4800 Ă
reveal that the absorption arises principally from Ca II H and K (equivalent width 215 Ă
), with weaker absorption features of Ca I 4227 Ă
and Fe I 3720 Ă
. The flux at Ca II line center indicates a foreground starlight fraction of 0.21, which places SNR 1885 some 64 pc to the near side of the midpoint of the M31 bulge, comparable to its projected 55 pc distance from the nucleus. The absorption line profiles suggest an approximately spherically symmetric, bell-shaped density distribution of supernova ejecta freely expanding at up to 13,100±1500 km s-1. We estimate Ca I, Ca II, and Fe I masses of 2.9Ă10â4 Mâ, 0.005 Mâ, and 0.013 Mâ, respectively. If the ionization state of iron is similar to the observed ionization state of calcium, MCa II/MCa I=16, then the mass of Fe II is 0.21 Mâ, consistent with that expected for either normal or subluminous SN Ia
Carbon Monoxide in the Type Ic SN 2000ew
We present K-band (1.9 -- 2.5 micron) spectra of the Type Ic SN 2000ew
observed with IRCS on the Subaru Telescope. These data show the first detection
of carbon monoxide (CO) emission in a Type Ic supernova. The detection of CO in
SN 2000ew provides further evidence that molecule formation may be a common
occurrence in core-collapse supernova ejecta. The spectrum also contains narrow
emission lines of [Fe II] and He I probably from dense clumps of hydrogen-poor
circumstellar gas surrounding SN 2000ew. Our spectrum of SN 2000ew shows no
trace of an unidentified feature seen near 2.26 micron, just blueward of the CO
emission, in the spectrum of SN 1987A and we discuss proposed detections of
this feature in other Type II supernovae.Comment: 7 Pages, 3 Figures Submitted to PASJ for Subaru Special Issu
Low Carbon Abundance in Type Ia Supernovae
We investigate the quantity and composition of unburned material in the outer
layers of three normal Type Ia supernovae (SNe Ia): 2000dn, 2002cr and 20 04bw.
Pristine matter from a white dwarf progenitor is expected to be a mixture of
oxygen and carbon in approximately equal abundance. Using near-infrared (NIR,
0.7-2.5 microns) spectra, we find that oxygen is abundant while carbon is
severely depleted with low upper limits in the outer third of the ejected mass.
Strong features from the OI line at rest wavelength = 0.7773 microns are
observed through a wide range of expansion velocities approx. 9,000 - 18,000
km/s. This large velocity domain corresponds to a physical region of the
supernova with a large radial depth. We show that the ionization of C and O
will be substantially the same in this region. CI lines in the NIR are expected
to be 7-50 times stronger than those from OI but there is only marginal
evidence of CI in the spectra and none of CII. We deduce that for these three
normal SNe Ia, oxygen is more abundant than carbon by factors of 100 - 1,000.
MgII is also detected in a velocity range similar to that of OI. The presence
of O and Mg combined with the absence of C indicates that for these SNe Ia,
nuclear burning has reached all but the extreme outer layers; any unburned
material must have expansion velocities greater than 18,000 km/s. This result
favors deflagration to detonation transition (DD) models over pure deflagration
models for SNe Ia.Comment: accepted for publication in Ap
Spitzer measurements of atomic and molecular abundances in the Type IIP SN 2005af
We present results based on Spitzer Space Telescope mid-infrared (3.6-30
micron) observations of the nearby IIP supernova 2005af. We report the first
ever detection of the SiO molecule in a Type IIP supernova. Together with the
detection of the CO fundamental, this is an exciting finding as it may signal
the onset of dust condensation in the ejecta. From a wealth of fine-structure
lines we provide abundance estimates for stable Ni, Ar, and Ne which, via
spectral synthesis, may be used to constrain nucleosynthesis models.Comment: ApJ Letters (accepted
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