1,365,969 research outputs found
Soft gamma repeaters outside the Local group
We propose that the best sites to search for SGRs outside the Local group are
galaxies with active massive star formation. Different possibilities to observe
SGR activity from these sites are discussed. In particular we searched for
giant flares from nearby galaxies ( -- 4 Mpc) M82,
M83, NGC 253, and NGC 4945 in the BATSE data. No candidates alike giant SGR
flares were found. The absence of such detections implies that the rate of
giant flares with energy release in the initial spike above
erg is less then 1/25 yr in our Galaxy. However, hyperflares similar to
the one of 27 December 2004 can be observed from larger distances.
Nevertheless, we do not see any significant excess of short GRBs from the Virgo
galaxy cluster and from galaxies Arp 299 and NGC 3256 with extremely high star
formation rate. This implies that the galactic rate of hyperflares with energy
release erg is less than yr. With this
constraint the fraction of possible extragalactic SGR hyperflares among BATSE
short GRBs should not exceed few percents. We present a list of short GRBs
coincident with galaxies mentioned above, and discuss the possibility that some
of them are SGR giant flares. We propose that the best target for observations
of extragalactic SGR flares by {\it Swift} is the Virgo cluster.Comment: 14 pages with 3 figures; accepted to MNRAS (final version
Reputational Risk and Impact Assessment of Corporate Social Responsibility on Profitability and Growth of Manufacturing Companies in Nigeria
This paper examines factors affecting corporate concerns about reputation and its impact on profitability and growth of the companies
Selection Wages and Discrimination
Applicants for any given job are more or less suited to fill it, and the firm will select the best among them. Increasing the wage offer attracts more applicants and makes it possible to raise the hiring standard and improve the productivity of the staff. Wages that optimize on the trade-off between the wage level and the productivity of the workforce are known as selection wages. As men react more strongly to wage differentials than females, the trade-off is more pronounced for men and a profit-maximizing firm will offer a higher wage for men than for women in equilibrium
Projection of relativistically moving objects on a two-dimensional plane, the `train' paradox and the visibility of the Lorentz contraction
Although many papers have appeared on the theory of photographing
relativistically moving objects, pioneered by the classic work of Penrose and
Terrell, three problems remain outstanding. (1) There does not seem to exist a
general formula which gives the projection of a relativistically moving object,
applicable to any object no matter how complicated, on a two-dimensional plane
in conformity with Terrell's observation. (2) No resolution seems to have been
provided for the associated so-called `train' paradox. (3) No analytical
demonstration seems to have been offered on how the Lorentz contraction may be
actually detected on a photograph. This paper addresses all of these three
problems. The analysis does not require any more than trigonometry and
elementary differentiation.Comment: LaTeX, 14 pages, 6 figures, misprint correcte
The Densities of Planets in Multiple Stellar Systems
We analyze the effect of companion stars on the bulk density of 29 planets
orbiting 15 stars in the Kepler field. These stars have at least one stellar
companion within 2", and the planets have measured masses and radii, allowing
an estimate of their bulk density. The transit dilution by the companion star
requires the planet radii to be revised upward, even if the planet orbits the
primary star; as a consequence, the planetary bulk density decreases. We find
that, if planets orbited a faint companion star, they would be more
volatile-rich, and in several cases their densities would become
unrealistically low, requiring large, inflated atmospheres or unusually large
mass fractions in a H/He envelope. In addition, for planets detected in radial
velocity data, the primary star has to be the host. We can exclude 14 planets
from orbiting the companion star; the remaining 15 planets in seven planetary
systems could orbit either the primary or the secondary star, and for five of
these planets the decrease in density would be substantial even if they orbited
the primary, since the companion is of almost equal brightness as the primary.
Substantial follow-up work is required in order to accurately determine the
radii of transiting planets. Of particular interest are small, rocky planets
that may be habitable; a lower mean density might imply a more volatile-rich
composition. Reliable radii, masses, and thus bulk densities will allow us to
identify which small planets are truly Earth-like.Comment: Accepted by AJ; 22 page
AL 3 (BH 261): a new globular cluster in the Galaxy
AL~3 (BH 261), previously classified as a faint open cluster candidate, is
shown to be a new globular cluster in the Milky Way, by means of B, V and I
Color-Magnitude Diagrams. The main feature of AL~3 is a prominent blue extended
Horizontal Branch. Its Color-Magnitude Diagrams match those of the intermediate
metallicity cluster M~5. The cluster is projected in a rich bulge field, also
contaminated by the disk main sequence. The globular cluster is located in the
Galactic bulge at a distance from the Sun d = 6.00.5 kpc. The
reddening is E(B-V)=0.360.03 and the metallicity is estimated to be [Fe/H]
-1.30.25. AL~3 is probably one of the least massive globular
clusters of the Galaxy.Comment: 6 figures. Astrophysical Journal Letters, in pres
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