864 research outputs found
Photometry of SN 2002ic and Implications for the Progenitor Mass-Loss History
We present new pre-maximum and late-time optical photometry of the Type
Ia/IIn supernova 2002ic. These observations are combined with the published
V-band magnitudes of Hamuy et al. (2003) and the VLT spectrophotometry of Wang
et al. (2004) to construct the most extensive light curve to date of this
unusual supernova. The observed flux at late time is significantly higher
relative to the flux at maximum than that of any other observed Type Ia
supernova and continues to fade very slowly a year after explosion. Our
analysis of the light curve suggests that a non-Type Ia supernova component
becomes prominent days after explosion. Modeling of the non-Type Ia
supernova component as heating from the shock interaction of the supernova
ejecta with pre-existing circumstellar material suggests the presence of a
cm gap or trough between the progenitor system and the
surrounding circumstellar material. This gap could be due to significantly
lower mass-loss years prior to explosion or
evacuation of the circumstellar material by a low-density fast wind. The latter
is consistent with observed properties of proto-planetary nebulae and with
models of white-dwarf + asymptotic giant branch star progenitor systems with
the asymptotic giant branch star in the proto-planetary nebula phase.Comment: accepted for publication in Ap
Offspring Production among the Extended Relatives of Samoan Men and Fa'afafine
Androphilia refers to sexual attraction to adult males, whereas gynephilia refers to sexual attraction to adult females. Male androphilia is an evolutionary paradox. Its development is at least partially influenced by genetic factors, yet male androphiles exhibit lower reproductive output, thus raising the question of how genetic factors underlying its development persist. The sexual antagonism hypothesis posits that the fitness costs associated with genetic factors underlying male androphilia are offset because these same factors lead to elevated reproduction on the part of the female relatives of androphilic males. Western samples drawn from low fertility populations have yielded inconsistent results when testing this hypothesis. Some studies documented elevated reproduction among the matrilineal female kin of androphilic males, whereas others found such effects in the paternal line. Samoa is a high-fertility population in which individuals reproduce closer to their maximum capacities. This study compared the reproductive output of the paternal and maternal line grandmothers, aunts, and uncles of 86 Samoan androphilic males, known locally as fa'afafine, and 86 Samoan gynephilic males. Reproductive output was elevated in the paternal and maternal line grandmothers, but not aunts or uncles, of fa'afafine. These findings are consistent with the sexual antagonism hypothesis and suggest that male androphilia is associated with elevated reproduction among extended relatives in both the maternal and paternal line. Discussion focuses on how this study, in conjunction with the broader literature, informs various models for the evolution of male androphilia via elevated reproduction on the part of female kin
Need for Alloparental Care and Attitudes Toward Homosexuals in 58 Countries: Implications for the Kin Selection Hypothesis
Homosexuality is an evolutionary puzzle. Many theories attempt to explain how a trait undermining individual reproduction can be maintained, but experimental testing of their predictions remains scarce. The kin selection hypothesis (KSH) is an important theoretical framework to account for the evolution of human homosexuality, postulating that its direct cost to reproduction can be offset by inclusive fitness gains through alloparental assistance to kin. Consistent evidence in support of the KSH has only been garnered from research on Samoan fa’afafine (i.e. feminine, same-sex attracted males), whereas research in numerous industrialized societies has repeatedly failed to secure empirical support for the theory. Here, we propose an alternative test of the KSH by investigating how need for alloparental care influences women’s attitudes toward homosexuality (AtH). AtH would influence the likelihood of women receiving alloparental care from homosexual kin. We applied logistic regression analysis to a large dataset (17,295 women in 58 countries) derived from the World Values Survey. As predicted by the KSH, women who are potentially most in need of alloparental support exhibit significantly more positive attitudes toward homosexuals. For single mothers who expressed parental care concerns, each additional child mothered was associated with an increase of 1.24 in their odds of exhibiting positive attitudes toward homosexuals. Our study is the first to provide circumstantial evidence in support of the KSH on a global scale
Precision measurements of large scale structure with future type Ia supernova surveys
Type Ia supernovae are currently the best known standard candles at
cosmological distances. In addition to providing a powerful probe of dark
energy they are an ideal source of information about the peculiar velocity
field of the local universe. Even with the very small number of supernovae
presently available it has been possible to measure the dipole and quadrupole
of the local velocity field out to z~0.025. With future continuous all-sky
surveys like the LSST project the luminosity distances of tens of thousands of
nearby supernovae will be measured accurately. This will allow for a
determination of the local velocity structure of the universe as a function of
redshift with unprecedented accuracy, provided the redshifts of the host
galaxies are known. Using catalogues of mock surveys we estimate that future
low redshift supernova surveys will be able to probe sigma-8 to a precision of
roughly 5% at 95% C.L. This is comparable to the precision in future galaxy and
weak lensing surveys and with a relatively modest observational effort it will
provide a crucial cross-check on future measurements of the matter power
spectrum.Comment: 18 pages, 9 figures, submitted to JCA
A dose-finding study of carboplatin–epirubicin–docetaxel in advanced epithelial ovarian cancer
The docetaxel–carboplatin combination is active and well tolerated in patients with epithelial ovarian cancer. We added epirubicin to this combination to investigate additional benefits of anthracyclines in epithelial ovarian cancer. Twenty-one patients, FIGO Ic-IV, performance status 0–1, were treated in four dose cohorts. Docetaxel was fixed at 75 mg m−2, carboplatin doses were AUC 4–5 and epirubicin doses were 50–60 mg m−2. Drugs were given on day 1, every 3 weeks, except in cohort 3, where epirubicin was given on day 8. Dexamethasone was given prophylactically. One dose-limiting toxicity occurred in cohorts 1, 2 and 4, two occurred in cohort 3. Complicated neutropenia occurred in two patients in cohorts 1 and 2 and one patient in cohorts 3 and 4. Two patients experienced grade III diarrhoea or stomatitis in cohort 1 and two in cohort 3. There were no treatment-related deaths. Grade II sensory neuropathy occurred in one patient. No cardiac toxicity or significant oedema was observed. The overall response rate was 36%, and 62% were CA125 responders. The predefined maximum tolerated dose was exceeded in cohort 3. The cohort 4 dose level (epirubicin 50 mg m−2, carboplatin AUC 4, docetaxel 75 mg m−2), warrants further study
Chandra Observations of Type Ia Supernovae: Upper Limits to the X-ray Flux of SN 2002bo, SN 2002ic, SN 2005gj, and SN 2005ke
We set sensitive upper limits to the X-ray emission of four Type Ia
supernovae (SNe Ia) using the Chandra X-ray Observatory. SN 2002bo, a normal,
although reddened, nearby SN Ia, was observed 9.3 days after explosion. For an
absorbed, high temperature bremsstrahlung model the flux limits are 3.2E-16
ergs/cm^2/s (0.5-2 keV band) and 4.1E-15 ergs/cm^2/s (2-10 keV band). Using
conservative model assumptions and a 10 km/s wind speed, we derive a mass loss
rate of \dot{M} ~ 2E-5 M_\odot/yr, which is comparable to limits set by the
non-detection of Halpha lines from other SNe Ia. Two other objects, SN 2002ic
and SN 2005gj, observed 260 and 80 days after explosion, respectively, are the
only SNe Ia showing evidence for circumstellar interaction. The SN 2002ic X-ray
flux upper limits are ~4 times below predictions of the interaction model
currently favored to explain the bright optical emission. To resolve this
discrepancy we invoke the mixing of cool dense ejecta fragments into the
forward shock region, which produces increased X-ray absorption. A modest
amount of mixing allows us to accommodate the Chandra upper limit. SN 2005gj is
less well studied at this time. Assuming the same circumstellar environment as
for SN 2002i, the X-ray flux upper limits for SN 2005gj are ~4 times below the
predictions, suggesting that mixing of cool ejecta into the forward shock has
also occurred here. Our reanalysis of Swift and Chandra data on SN 2005ke does
not confirm a previously reported X-ray detection. The host galaxies NGC 3190
(SN 2002bo) and NGC 1371 (SN 2005ke) each harbor a low luminosity (L_X ~ 3-4E40
ergs/s) active nucleus in addition to wide-spread diffuse soft X-ray emission.Comment: 16 pages, to appear in ApJ (20 Nov 2007
Circumstellar interaction of the type Ia supernova 2002ic
We propose a model to account for the bolometric light curve, quasi-continuum
and the Ca II emission features of the peculiar type Ia supernova (SN) 2002ic,
which exploded in a dense circumstellar envelope. The model suggests that the
SN Ia had the maximum possible kinetic energy and that the ejecta expand in an
approximately spherically symmetric (possibly clumpy) circumstellar
environment. The Ca II and quasi-continuum are emitted by shocked SN ejecta
that underwent deformation and fragmentation in the intershock layer. Modeling
of the Ca II triplet implies that the contribution of the O I 8446 A line is
about 25% of the 8500 A feature on day 234, which permits us to recover the
flux in the Ca II 8579 A triplet from the flux of 8500 A blend reported by Deng
et al. (2004). We use the Ca II doublet and triplet fluxes on day 234 to derive
the electron temperature (~4400 K) in the Ca II line-emitting zone and the
ratio of the total area of dense fragments to the area of the shell, S/S_0 ~
100. We argue that Ca II bands and quasi-continuum originate from different
zones of the shocked ejecta that reflect the abundance stratification of the
supernova.Comment: 12 pages, MNRAS, in pres
Yang-Mills condensate dark energy coupled with matter and radiation
The coincidence problem is studied for the dark energy model of effective
Yang-Mills condensate in a flat expanding universe during the matter-dominated
stage. The YMC energy is taken to represent the dark energy, which
is coupled either with the matter, or with both the matter and the radiation
components. The effective YM Lagrangian is completely determined by quantum
field theory up to 1-loop order. It is found that under very generic initial
conditions and for a variety of forms of coupling, the existence of the scaling
solution during the early stages and the subsequent exit from the scaling
regime are inevitable. The transition to the accelerating stage always occurs
around a redshift . Moreover, when the Yang-Mills
condensate transfers energy into matter or into both matter and radiation, the
equation of state of the Yang-Mills condensate can cross over -1 around
, and takes on a current value . This is consistent with
the recent preliminary observations on supernovae Ia. Therefore, the
coincidence problem can be naturally solved in the effective YMC dark energy
models.Comment: 24 pages, 18 figure
The Unique Type Ib Supernova 2005bf: A WN Star Explosion Model for Peculiar Light Curves and Spectra
Observations and modeling for the light curve (LC) and spectra of supernova
(SN) 2005bf are reported. This SN showed unique features: the LC had two
maxima, and declined rapidly after the second maximum, while the spectra showed
strengthening He lines whose velocity increased with time. The double-peaked LC
can be reproduced by a double-peaked Ni distribution, with most
Ni at low velocity and a small amount at high velocity. The rapid
post-maximum decline requires a large fraction of the -rays to escape
from the Ni-dominated region, possibly because of low-density ``holes''.
The presence of Balmer lines in the spectrum suggests that the He layer of the
progenitor was substantially intact. Increasing -ray deposition in the
He layer due to enhanced -ray escape from the Ni-dominated
region may explain both the delayed strengthening and the increasing velocity
of the He lines. The SN has massive ejecta (\sim6-7\Msun), normal kinetic
energy ( ergs), high peak bolometric luminosity
( erg s) for an epoch as late as 40 days,
and a large Ni mass (\sim0.32\Msun). These properties, and the
presence of a small amount of H suggest that the progenitor was initially
massive (M\sim 25-30 \Msun) and had lost most of its H envelope, and was
possibly a WN star. The double-peaked Ni distribution suggests that the
explosion may have formed jets that did not reach the He layer. The properties
of SN 2005bf resemble those of the explosion of Cassiopeia A.Comment: 10 pages, 4 figures. Figure of UBVr'i'JHKs light curves is revised.
Accepted for publication in the Astrophysical Journal (Letters) on 5 October
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