44 research outputs found
An X-ray Outburst from the Rapidly Accreting Young Star That Illuminates McNeil's Nebula
Young, low-mass stars are luminous X-ray sources whose powerful X-ray flares
may exert a profound influence over the process of planet formation. The origin
of such emission is uncertain. Although many or perhaps most recently formed,
low-mass stars emit X-rays as a consequence of solar-like coronal activity, it
has also been suggested that X-ray emission may be a direct result of mass
accretion onto the forming star. Here we report X-ray imaging spectroscopy
observations which reveal a factor ~50 increase in the X-ray flux from a young
star that is presently undergoing a spectacular optical/IR outburst. The
outburst is thought to be due to the sudden onset of a phase of rapid
accretion. The coincidence of a surge in X-ray brightness with the optical/IR
eruption demonstrates that strongly enhanced high-energy emission from young
stars can occur as a consequence of high accretion rates. We suggest that such
accretion- enhanced X-ray emission from erupting young stars may be
short-lived, because intense star-disk magnetospheric interactions are quenched
rapidly by the subsequent accretion flood.Comment: 15 pages, 3 figures; published in Natur
Stage and treatment variation with age in postmenopausal women with breast cancer: compliance with guidelines
Breast cancer-specific mortality is static in older women despite having fallen in younger age groups, possibly due to lack of screening
and differences in treatment. This study compared stage and treatment between two cohorts of postmenopausal women (55â69 vs
470 years) in a single cancer network over 6 months. A total of 378 patients were studied (470: N ÂŒ 167, 55â69 years: N ÂŒ 210).
Older women presented with more advanced disease (470: metastatic/locally advanced 12%, 55â69 years: 3%, Po0.01). Those
with operable cancer had a worse prognosis (Nottingham Prognostic Index (NPI) 470: median NPI 4.4, 55â69 years: 4.25, Po0.03).
These stage differences were partially explained by higher screening rates in the younger cohort. Primary endocrine therapy was used
in 42% of older patients compared with 3% in the younger group (Po0.001). Older women with cancers suitable for breast
conservation were more likely to choose mastectomy (470: 57.5% mastectomy rate vs 55â69 years: 20.6%, Po0.01). Nodal
surgery was less frequent in older patients (470: 6.7% no nodal surgery, 55â69 years: 0.5%, Po0.01) and was more likely to be
inadequate (470: 10.7% o4 nodes excised, 55â69 years: 3.4%, Po0.02). In summary, older women presented with more advanced
breast cancer, than younger postmenopausal women and were treated less comprehensively
The First Decade of Science with Chandra and XMM-Newton
NASA's Chandra X-ray Observatory and ESA's XMM-Newton made their first
observations one decade ago. The unprecedented and complementary capabilities
of these observatories to detect, image, and measure the energy of cosmic
X-rays, achieved less than 50 years after the first detection of an extra-solar
X-ray source, represent an increase in sensitivity comparable in going from
naked-eye observations to the most powerful optical telescopes over the past
400 years! In this review, we highlight some of the many discoveries made by
Chandra and XMM-Newton that have transformed 21st century astronomy and briefly
discuss prospects for future research.Comment: 8 pages, 10 figures, published in Natur
Past, Present, and Future X-Ray and Gamma-Ray Missions
X- and -ray astronomy began in the early sixties of the last century with balloons flights, sounding rocket experiment and satellites. Long before space satellite detected X- and -rays emitted by cosmic sources, scientists had known that the Universe should be producing these photons. In this chapter we provided an overview of past and present missions that has made the X- and -ray astronomy an integral part of astronomical research, and prospects of future developments