532 research outputs found
On The Progenitor of the Type II-Plateau Supernova 2003gd in Messier 74
HST WFPC2 archival F606W and F300W images obtained within one year prior to
the explosion of the nearby Type II supernova (SN) 2003gd in Messier 74 (NGC
628) have been analyzed to isolate the progenitor star. The SN site was located
using precise astrometry applied to the HST images. Two plausible candidates
are identified within 0.6" of the SN position in the F606W image. Neither
candidate was detected in the F300W image. SN 2003gd appears to be of Type
II-plateau (II-P), with age ~87 d on June 17 UT and with low reddening [E(B-V)
= 0.13 mag]. The most likely of the two progenitor candidates has M_V_0 ~ -3.5
mag (for an extinction-corrected distance modulus of 29.3 mag) and, based on
additional color information derived from a high-quality, archival ground-based
I-band image, we estimate that this star was a red supergiant with initial mass
M_ZAMS ~ 8 -- 9 Msun. This mass estimate is somewhat lower than, but relatively
consistent with, recent limits placed on the progenitor masses of other SNe
II-P, using HST data. Future HST imaging with the Advanced Camera for Surveys,
when the SN has faded considerably, will be extremely useful in pinpointing the
exact SN location and securing identification of the progenitor. If our
proposed candidate is confirmed, it will be only the sixth SN progenitor ever
directly identified.Comment: 10 pages, 6 figures, to appear now in PASP, 2003 Nov. This update
includes more detailed light and color curves for the S
A Preliminary Indication of Evolution of Type Ia Supernovae from their Risetimes
We have compared the risetime for samples of nearby and high-redshift type Ia
supernovae (SNe Ia).
The fiducial risetime of the nearby SNe Ia is 2.5+/-0.4 days longer than the
proemial risetime determined by Goldhaber (1998a,b) for high-redshift SNe
Ia from the Supernova Cosmology Project.
The statistical likelihood that the two samples have different fiducial
risetimes is high (5.8 sigma) and indicates possible evolution between the
samples of SNe Ia. We consider the likely effects of several sources of
systematic error, but none of these resolves the difference in the risetimes.
Currently, we cannot directly determine the impact of the apparent evolution
on previous determinations of cosmological parameters.Comment: Accepted by the Astronomical Journal, 11 pages, 5 figure
Possible Recovery of SN 1961V In Hubble Space Telescope Archival Images
SN 1961V in NGC 1058 was originally classified by Fritz Zwicky as a ``Type
V'' supernova. However, it has been argued that SN 1961V was not a genuine
supernova, but instead the superoutburst of an eta Carinae-like luminous blue
variable star. In particular, Filippenko et al. (1995, AJ, 110, 2261) used
pre-refurbishment HST WFPC images and the known radio position of SN 1961V to
conclude that the star survived the eruption and is likely coincident with a V
\~ 25.6 mag, V-I ~ 1.9 mag object. Recently, Stockdale et al. (2001, AJ, 122,
283) recovered the fading SN 1961V at radio wavelengths and argue that its
behavior is similar that of some Type II supernovae. We have analyzed
post-refurbishment archival HST WFPC2 data and find that the new radio position
is still consistent with the Filippenko et al. object, which has not changed in
brightness or color, but is also consistent with an adjacent, fainter (I ~ 24.3
mag) and very red (V-I > 1.0 mag) object. We suggest that this fainter object
could be the survivor of SN 1961V. Forthcoming HST observations may settle this
issue.Comment: 8 pages, 6 figures, to appear in the PASP (2002 July issue
Reading the Spectra of the Most Peculiar Type Ia Supernova 2002cx
In spite of the apparent lack of Si II and S II features in its spectra, SN
2002cx was classified as a peculiar Type Ia supernova (SN Ia) on the basis of
its overall photometric and spectroscopic behavior. Spectra obtained near
maximum light contained Fe III features, as in SN 1991T-like events, but the
blueshifts of the Fe III absorptions were exceptionally low. The luminosity
also was low. We use the supernova synthetic--spectrum code SYNOW to study line
identifications in SN 2002cx. We find that the maximum-light spectra appear to
contain weak features of Si II, S II, Si III, and Ca II, which strengthens the
connection with SN 1991T-like events. We show that later spectra, obtained 12,
25, and 56 days after maximum, consist of P-Cygni resonance-scattering features
due to permitted Fe II and Co II lines. SN 2002cx had been thought to have made
the transition from a permitted-line to a forbidden-line spectrum between 25
and 56 days. Owing to the low expansion velocities the postmaximum spectral
features are narrower and easier to identify than they are in other SNe Ia. SN
2002cx will lead to improved line identifications in other SNe Ia and clarify
when the transition from a permitted-line to a forbidden-line spectrum occurs.
In the context of current SN Ia explosion models, we suggest that the
properties of SN 2002cx may be consistent with 3D deflagration models, which
are not favored for normal SNe Ia.Comment: 21 pages including 7 figures and 4 tables; accepted by PAS
The current status of process planning for multi-material rapid prototyping fabrication
doi:10.4028/www.scientific.net/AMR.118-120.625 The current status of process planning for multi-material rapid prototyping fabricatio
The Light Echo Around Supernova 2003gd in Messier 74
We confirm the discovery of a light echo around the Type II-plateau Supernova
2003gd in Messier 74 (NGC 628), seen in images obtained with the High
Resolution Channel of the Advanced Camera for Surveys on-board the Hubble Space
Telescope (HST), as part of a larger Snapshot program on the late-time emission
from supernovae. The analysis of the echo we present suggests that it is due to
the SN light pulse scattered by a sheet of dust grains located about 113 pc in
front of the SN, and that these grains are not unlike those assumed to be in
the diffuse Galactic interstellar medium, both in composition and in size
distribution. The echo is less consistent with scattering off carbon-rich
grains, and, if anything, the grains may be somewhat more silicate-rich than
the Galactic dust composition. The echo also appears to be more consistent with
a SN distance closer to 7 Mpc than 9 Mpc. This further supports the conclusion
we reached elsewhere that the initial mass for the SN progenitor was relatively
low (about 8--9 M_suns). HST should be used to continue to monitor the echo in
several bands, particularly in the blue, to better constrain its origin.Comment: 8 pages, 4 figures, To appear in PASP (2006 March); disregard
previous versio
Evidence for Extremely High Dust Polarization Efficiency in NGC 3184
Recent studies have found the Type II-plateau supernova (SN) 1999gi to be
highly polarized (p_max = 5.8%, where p_max is the highest degree of
polarization measured in the optical bandpass; Leonard & Filippenko 2001) and
minimally reddened (E[B-V] = 0.21 +/- 0.09 mag; Leonard et al. 2002). From
multiple lines of evidence, including the convincing fit of a ``Serkowski''
interstellar polarization (ISP) curve to the continuum polarization shape, we
conclude that the bulk of the observed polarization is likely due to dust along
the line of sight (l-o-s), and is not intrinsic to SN 1999gi. We present new
spectropolarimetric observations of four distant Galactic stars close to the
l-o-s to SN 1999gi (two are within 0.02 degrees), and find that all are null to
within 0.2%, effectively eliminating Galactic dust as the cause of the high
polarization. The high ISP coupled with the low reddening implies an
extraordinarily high polarization efficiency for the dust along this l-o-s in
NGC 3184: ISP / E(B-V) = 31^{+22}_{-9} % mag^{-1}. This is inconsistent with
the empirical Galactic limit (ISP / E[B-V] < 9% mag^{-1}), and represents the
highest polarization efficiency yet confirmed for a single sight line in either
the Milky Way or an external galaxy.Comment: 27 pages, accepted for publication by the Astronomical Journa
- …