9 research outputs found
Nucleosynthesis in ONeMg Novae: Models versus Observations to Constrain the Masses of ONeMg White Dwarfs and Their Envelopes
Nucleosynthesis in ONeMg novae has been investigated with the wide ranges of
three parameters, i.e., the white dwarf mass, the envelope mass at ignition,
and the initial composition. A quasi-analytic one-zone approach is used with an
up-to-date nuclear reaction network. The nucleosynthesis results show
correlation with the peak temperatures or the cooling timescales during
outbursts. Among the combinations of white dwarf and envelope masses which give
the same peak temperature, the explosion is more violent for a lower white
dwarf mass owing to its smaller gravitational potential. Comparison of the
nucleosynthesis results with observations implies that at least two-third of
the white dwarf masses for the observed ONeMg novae are ,
which are significantly lower than estimated by previous hydrodynamic studies
but consistent with the observations of V1974 Cyg. Moreover, the envelope
masses derived from the comparison are , which are in
good agreement with the ejecta masses estimated from observations but
significantly higher than in previous hydrodynamic studies. With such a low
mass white dwarf and a high mass envelope, the nova can produce interesting
amounts of -ray emitters Be, Na, and Al. We suggest
that V1974 Cyg has produced Na as high as the upper limit derived from
the COMPTEL survey. In addition, a non-negligible part of the Galactic
Al may originate from ONeMg novae, if not the major contributors. Both
the future INTEGRAL survey for these -ray emitters and abundance
estimates derived from ultraviolet, optical, and near infrared spectroscopies
will impose a severe constraint on the current nova models.Comment: 21 pages, 23 figures, to appear in the Astrophysical Journal, Vol.
523, No.1, September 20, 1999; preprint with embedded images can be obtained
from http://th.nao.ac.jp/~wanajo/journal/onenova.p
Discovery of the optical counterpart and early optical observations of GRB990712
We present the discovery observations of the optical counterpart of the
gamma-ray burster GRB990712 taken 4.16 hours after the outburst and discuss its
light curve observed in the V, R and I bands during the first ~35 days after
the outburst. The observed light curves were fitted with a power-law decay for
the optical transient (OT), plus an additional component which was treated in
two different ways. First, the additional component was assumed to be an
underlying galaxy of constant brightness. The resulting slope of the decay is
0.97+/-0.05 and the magnitudes of the underlying galaxy are: V = 22.3 +/- 0.05,
R = 21.75 +/- 0.05 and I = 21.35 +/- 0.05. Second, the additional component was
assumed to be a galaxy plus an underlying supernova with a time-variable
brightness identical to that of GRB980425, appropriately scaled to the redshift
of GRB990712. The resulting slope of the decay is similar, but the
goodness-of-fit is worse which would imply that either this GRB is not
associated with an underlying supernova or the underlying supernova is much
fainter than the supernova associated with GRB980425. The galaxy in this case
is fainter: V = 22.7 +/- 0.05, R = 22.25 +/- 0.05 and I = 22.15 +/- 0.05; and
the OT plus the underlying supernova at a given time is brighter. Measurements
of the brightnesses of the OT and the galaxy by late-time HST observation and
ground-based observations can thus assess the presence of an underlying
supernova.Comment: To appear in Ap
International incidence of childhood cancer, 2001-10: a population-based registry study
Background Cancer is a major cause of death in children worldwide, and the recorded incidence tends to increase with time. Internationally comparable data on childhood cancer incidence in the past two decades are scarce. This study aimed to provide internationally comparable local data on the incidence of childhood cancer to promote research of causes and implementation of childhood cancer control. Methods This population-based registry study, devised by the International Agency for Research on Cancer in collaboration with the International Association of Cancer Registries, collected data on all malignancies and non-malignant neoplasms of the CNS diagnosed before age 20 years in populations covered by high-quality cancer registries with complete data for 2001-10. Incidence rates per million person-years for the 0-14 years and 0-19 years age groups were age-adjusted using the world standard population to provide age-standardised incidence rates (WSRs), using the age-specific incidence rates (ASR) for individual age groups (0-14 years, 5-9 years, 10-14 years, and 15-19 years). All rates were reported for 19 geographical areas or ethnicities by sex, age group, and cancer type. The regional WSRs for children aged 0-14 years were compared with comparable data obtained in the 1980s. Findings Of 532 invited cancer registries, 153 registries from 62 countries, departments, and territories met quality standards, and contributed data for the entire decade of 2001-10. 385 509 incident cases in children aged 0-19 years occurring in 2-6 billion person-years were included. The overall WSR was 140.6 per million person-years in children aged 0-14 years (based on 284 649 cases), and the most common cancers were leukaemia (WSR 46.4), followed by CNS tumours (WSR 28.2), and lymphomas (WSR 15.2). In children aged 15-19 years (based on 100 860 cases), the ASR was 185.3 per million person-years, the most common being lymphomas (ASR 41.8) and the group of epithelial tumours and melanoma (ASR 39.5). Incidence varied considerably between and within the described regions, and by cancer type, sex, age, and racial and ethnic group. Since the 1980s, the global WSR of registered cancers in children aged 0-14 years has increased from 124.0 (95% CI 123.3-124.7) to 140.6 (140.1-141.1) per million person-years. Interpretation This unique global source of childhood cancer incidence will be used for aetiological research and to inform public health policy, potentially contributing towards attaining several targets of the Sustainable Development Goals. The observed geographical, racial and ethnic, age, sex, and temporal variations require constant monitoring and research. Funding International Agency for Research on Cancer and the Union for International Cancer Control