10 research outputs found
SN 2004aw: Confirming Diversity of Type Ic Supernovae
Optical and near-infrared observations of the Type Ic supernova (SN) 2004aw
are presented, obtained from day -3 to day +413 with respect to the B-band
maximum. The photometric evolution is characterised by a comparatively slow
post-maximum decline of the light curves. The peaks in redder bands are
significantly delayed relative to the bluer bands, the I-band maximum occurring
8.4 days later than that in B. With an absolute peak magnitude of -18.02 in the
V band the SN can be considered fairly bright, but not exceptional. This also
holds for the U through I bolometric light curve, where SN 2004aw has a
position intermediate between SNe 2002ap and 1998bw. Spectroscopically SN
2004aw provides a link between a normal Type Ic supernova like SN 1994I and the
group of broad-lined SNe Ic. The spectral evolution is rather slow, with a
spectrum at day +64 being still predominantly photospheric. The shape of the
nebular [O I] 6300,6364 line indicates a highly aspherical explosion. Helium
cannot be unambiguously identified in the spectra, even in the near-infrared.
Using an analytical description of the light curve peak we find that the total
mass of the ejecta in SN 2004aw is 3.5-8.0 M_Sun, significantly larger than in
SN 1994I, although not as large as in SN 1998bw. The same model suggests that
about 0.3 M_Sun of {56}Ni has been synthesised in the explosion. No connection
to a GRB can be firmly established.Comment: 22 pages, 15 figures, 6tables, LaTeX, MNRAS online-early, references
and affiliations updated, style correction
SN 2005cs in M51 II. Complete Evolution in the Optical and the Near-Infrared
We present the results of the one year long observational campaign of the
type II-plateau SN 2005cs, which exploded in the nearby spiral galaxy M51 (the
Whirlpool Galaxy). This extensive dataset makes SN 2005cs the best observed
low-luminosity, 56Ni-poor type II-plateau event so far and one of the best
core-collapse supernovae ever. The optical and near-infrared spectra show
narrow P-Cygni lines characteristic of this SN family, which are indicative of
a very low expansion velocity (about 1000 km/s) of the ejected material. The
optical light curves cover both the plateau phase and the late-time radioactive
tail, until about 380 days after core-collapse. Numerous unfiltered
observations obtained by amateur astronomers give us the rare opportunity to
monitor the fast rise to maximum light, lasting about 2 days. In addition to
optical observations, we also present near-infrared light curves that (together
with already published UV observations) allow us to construct for the first
time a reliable bolometric light curve for an object of this class. Finally,
comparing the observed data with those derived from a semi-analytic model, we
infer for SN 2005cs a 56Ni mass of about 0.003 solar masses, a total ejected
mass of 8-13 solar masses and an explosion energy of about 3 x 10^50 erg.Comment: 18 pages, 18 figures, accepted for publication in MNRA
The underluminous Type Ia Supernova 2005bl and the class of objects similar to SN 1991bg
Optical observations of the Type Ia supernova (SN Ia) 2005bl in NGC 4070,
obtained from -6 to +66 d with respect to the B-band maximum, are presented.
The photometric evolution is characterised by rapidly-declining light curves
and red colours at peak and soon thereafter. With M_B,max = -17.24 the SN is an
underluminous SN Ia, similar to the peculiar SNe 1991bg and 1999by. This
similarity also holds for the spectroscopic appearance, the only remarkable
difference being the likely presence of carbon in pre-maximum spectra of SN
2005bl. A comparison study among underluminous SNe Ia is performed, based on a
number of spectrophotometric parameters. Previously reported correlations of
the light-curve decline rate with peak luminosity and R(Si) are confirmed, and
a large range of post-maximum Si II lambda6355 velocity gradients is
encountered. 1D synthetic spectra for SN 2005bl are presented, which confirm
the presence of carbon and suggest an overall low burning efficiency with a
significant amount of leftover unburned material. Also, the Fe content in
pre-maximum spectra is very low, which may point to a low metallicity of the
precursor. Implications for possible progenitor scenarios of underluminous SNe
Ia are briefly discussed.Comment: 24 pages, 24 figures, accepted for publication in MNRA
WeCAPP -Wendelstein Calar Alto pixellensing project I
We present WeCAPP, a long term monitoring project searching for microlensing events towards M 3
The temporal spectrum of the sdB pulsating star HS 2201+2610 at 2 ms resolution
In this article we present the results of more than 180 hours of time-series
photometry on the low gravity (, 300 K,
by number) sdB pulsating star HS 2201+2610, obtained between
September 2000 and August 2001.
The temporal spectrum is resolved and shows 5 close frequencies:
three main signals at 2860.94, 2824.10 and 2880.69 μHz, with amplitudes
of about 1%, 0.5% and 0.1% respectively, are detected from
single run observations; two further peaks with very low amplitude
(<0.07%) at 2738.01 and 2921.82 μHz are confirmed by phase analysis
on several independent runs.
Due to the small number of detected frequencies, it is not possible to obtain
a univocal identification of the excited modes and perform a detailed
seismological analysis of the star.
No clear signatures of rotational splitting are seen.
Nevertheless, the observed period spectrum is well inside the excited
period window obtained from pulsation calculations with nonadiabatic models
having effective temperature and surface gravity close to the spectroscopic
estimates.
Due to its relatively simple temporal spectrum, HS 2201+2610 is a very good
candidate for trying to measure the secular variation of the pulsation periods
in time.
With this purpose a long-term monitoring of the star was started.
The results of the first 11 months show amplitude variations up to ~20%
on time-scales of months, which are probably real, and allow us to measure the
pulsation frequencies with an unprecedented 0.02 μHz resolution
The temporal spectrum of the sdB pulsating star HS 2201+2610 at 2 ms resolution
In this article we present the results of more than 180 hours of time-series
photometry on the low gravity (, 300 K,
by number) sdB pulsating star HS 2201+2610, obtained between
September 2000 and August 2001.
The temporal spectrum is resolved and shows 5 close frequencies:
three main signals at 2860.94, 2824.10 and 2880.69 μHz, with amplitudes
of about 1%, 0.5% and 0.1% respectively, are detected from
single run observations; two further peaks with very low amplitude
(<0.07%) at 2738.01 and 2921.82 μHz are confirmed by phase analysis
on several independent runs.
Due to the small number of detected frequencies, it is not possible to obtain
a univocal identification of the excited modes and perform a detailed
seismological analysis of the star.
No clear signatures of rotational splitting are seen.
Nevertheless, the observed period spectrum is well inside the excited
period window obtained from pulsation calculations with nonadiabatic models
having effective temperature and surface gravity close to the spectroscopic
estimates.
Due to its relatively simple temporal spectrum, HS 2201+2610 is a very good
candidate for trying to measure the secular variation of the pulsation periods
in time.
With this purpose a long-term monitoring of the star was started.
The results of the first 11 months show amplitude variations up to ~20%
on time-scales of months, which are probably real, and allow us to measure the
pulsation frequencies with an unprecedented 0.02 μHz resolution