3,458 research outputs found
Discovery, photometry, and astrometry of 49 classical nova candidates in M81 galaxy
This paper reports on a search for new classical nova candidates in the M81
galaxy based on archival, as well as recent, new images. We used images from
1999-2007 to search for optical transients in M81. The positions of the
identified classical nova candidates were used to study their spatial
distribution. Kolmogorov - Smirnov test (KS) and bottom-to-top (BTR) ratio
diagnostic were used to analyze the nova candidate distribution and
differentiate between the disk and the bulge populations. In total, 49
classical nova candidates were discovered. In this study, we present the
precise positions and photometry of these objects, plus the photometry of an
additional 9 classical nova candidates found by Neill and Shara (2004). With
our large sample, we find a different spatial distribution of classical nova
candidates when compared to the results of earlier studies. Also, an
extraordinarily bright nova was found and studied in detail.Comment: Accepted for publication in Astronomy & Astrophysics, 23 pages, 8
figure
Constraints on the Progenitor System of the Type Ia Supernova SN 2011fe/PTF11kly
Type Ia supernovae (SNe) serve as a fundamental pillar of modern cosmology,
owing to their large luminosity and a well-defined relationship between
light-curve shape and peak brightness. The precision distance measurements
enabled by SNe Ia first revealed the accelerating expansion of the universe,
now widely believed (though hardly understood) to require the presence of a
mysterious "dark" energy. General consensus holds that Type Ia SNe result from
thermonuclear explosions of a white dwarf (WD) in a binary system; however,
little is known of the precise nature of the companion star and the physical
properties of the progenitor system. Here we make use of extensive historical
imaging obtained at the location of SN 2011fe/PTF11kly, the closest SN Ia
discovered in the digital imaging era, to constrain the visible-light
luminosity of the progenitor to be 10-100 times fainter than previous limits on
other SN Ia progenitors. This directly rules out luminous red giants and the
vast majority of helium stars as the mass-donating companion to the exploding
white dwarf. Any evolved red companion must have been born with mass less than
3.5 times the mass of the Sun. These observations favour a scenario where the
exploding WD of SN 2011fe/PTF11kly, accreted matter either from another WD, or
by Roche-lobe overflow from a subgiant or main-sequence companion star.Comment: 22 pages, 6 figures, submitte
The King’s New Clothes in the Eyes of the Beholder: Developing a Measurement Scale for Attitude Towards Corruption.
This study investigates the validity and reliability of a developing scale on attitude towards corruption. It correlates this scale with existing and related behavioural measures, both ethical (money ethic, work ethic and corruption perception) and non-ethical (organisational commitment and job satisfaction). Survey data was obtained from 1833 respondents in Nigeria. Findings confirm the 20-item measure as a multidimensional construct loading on 4 factors with a reliability coefficient (0.62) and with evidence of construct validity. Significant relationships were also found between attitude towards corruption and both the ethical and non-ethical behavioural measures investigated. Some further research directions were suggested
X-ray observations of the Large Magellanic Cloud pulsar PSR B0540-69 and its PWN
PSR B0540-69 is a young pulsar in the Large Magellanic Cloud that has similar
properties with respect to the Crab Pulsar, and is embedded in a Pulsar Wind
Nebula. We have analyzed the complete archival RXTE dataset of observations of
this source, together with new Swift-XRT and INTEGRAL-IBIS data. Accurate
lightcurves are produced in various energy bands between 2 and 60 keV, showing
no significant energy variations of the pulse shape. The spectral analysis
shows that the pulsed spectrum is curved, and is best fitted up to 100 keV by a
log-parabolic model: this strengthens the similarities with the Crab pulsar,
and is discussed in the light of a phenomenologic multicomponent model. The
total emission from this source is studied, the relative contributions of the
pulsar and the PWN emission are derived, and discussed in the context of other
INTEGRAL detected pulsar/PWN systems.Comment: 11 pages, 11 figures. Accepted for publication in MNRA
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