3,700 research outputs found
Photometric study of southern SU UMa-type dwarf novae and candidates -- III: NSV 10934, MM Sco, AB Nor, CAL 86
We photometrically observed four southern dwarf novae in outburst (NSV 10934,
MM Sco, AB Nor and CAL 86). NSV 10934 was confirmed to be an SU UMa-type dwarf
nova with a mean superhump period of 0.07478(1) d. This star also showed
transient appearance of quasi-periodic oscillations (QPOs) during the final
growing stage of the superhumps. Combined with the recent theoretical
interpretation and with the rather unusual rapid terminal fading of normal
outbursts, NSV 10934 may be a candidate intermediate polar showing SU UMa-type
properties. The mean superhump periods of MM Sco and AB Nor were determined to
be 0.06136(4) d and 0.08438(2) d, respectively. We suggest that AB Nor belongs
to a rather rare class of long-period SU UMa-type dwarf novae with low
mass-transfer rates. We also observed an outburst of the suspected SU UMa-type
dwarf nova CAL 86. We identified this outburst as a normal outburst and
determined the mean decline rate of 1.1 mag/d.Comment: 13 pages, 23 figures, to appear in MNRAS. For more information, see
http://www.kusastro.kyoto-u.ac.jp/vsnet
Earliest detection of the optical afterglow of GRB 030329 and its variability
We report the earliest detection of an extremely bright optical afterglow of
the gamma-ray burst (GRB) 030329 using a 30cm-telescope at Tokyo Institute of
Technology (Tokyo, JAPAN). Our observation started 67 minutes after the burst,
and continued for succeeding two nights until the afterglow faded below the
sensitivity limit of the telescope (approximately 18 mag). Combining our data
with those reported in GCN Circulars, we find that the early afterglow light
curve of the first half day is described by a broken power-law (t^{- alpha})
function with indices alpha_{1} = 0.88 +/- 0.01 (0.047 < t < t_{b1} days),
alpha_{2} = 1.18 +/- 0.01 (t_{b1} < t < t_{b2} days), and alpha_{3} = 1.81 +/-
0.04 (t_{b2} < t < 1.2 days), where t_{b1} ~ 0.26 days and t_{b2} ~ 0.54 days,
respectively. The change of the power-law index at the first break at t ~ 0.26
days is consistent with that expected from a ``cooling-break'' when the cooling
frequency crossed the optical band. If the interpretation is correct, the decay
index before the cooling-break implies a uniform ISM environment.Comment: 13 pages, 1 table and 2 figures. Accepted to the Astrophysical
Journal Letter
Studies of the Relativistic Binary Pulsar PSR B1534+12. II. Origin and Evolution
We have recently measured the angle between the spin and orbital angular
momenta of PSR B1534+12 to be either 25+/-4 deg or 155+/-4 deg. This
misalignment was almost certainly caused by an asymmetry in the supernova
explosion that formed its companion neutron star. Here we combine the
misalignment measurement with measurements of the pulsar and companion masses,
the orbital elements, proper motion, and interstellar scintillation. We show
that the orbit of the binary in the Galaxy is inconsistent with a velocity kick
large enough to produce a nearly antialigned spin axis, so the true
misalignment must be ~25 deg. Similar arguments lead to bounds on the mass of
the companion star immediately before its supernova: 3+/-1 Msun. The result is
a coherent scenario for the formation of the observed binary. After the first
supernova explosion, the neutron star that would eventually become the observed
pulsar was in a Be/X-ray type binary system with a companion of at least 10--12
Msun. During hydrogen (or possibly helium) shell burning, mass transfer
occurred in a common envelope phase, leaving the neutron star in a roughly
half-day orbit with a helium star with mass above ~3.3 Msun. A second phase of
mass transfer was then initiated by Roche lobe overflow during shell helium
burning, further reducing both the helium star mass and orbital period before
the second supernova. Scenarios that avoid Roche lobe overflow by the helium
star require larger helium star masses and predict space velocities
inconsistent with our measurements. The companion neutron star experienced a
velocity kick of 230+/-60 km/s at birth, leading to a systemic kick to the
binary of 180+/-60 km/s.Comment: 9 pages, submitted to ApJ. Abstract shortened. Version with
high-resolution figures available at
http://www.astro.ubc.ca/people/stairs/papers/tds04_orig.ps.g
A discussion of a luxury apparel brand strategy in an emerging market: Conceptual model with network perspectives
This study explores the Burberry apparel brand’s position and its strategic behaviour seeking new customers in the new market. This exploratory research pays particular attention to business potential and opportunities in an emerging market, Vietnam. To evaluate Burberry’s strategies and the potential, the collaborative network relationships are discussed in details, that is followed by the discussion of the key themes for Burberry to consider in the Vietnamese market, where Burberry has recently begun expanding its businesses. The outcome of the study suggests that the Western luxury brand apparel needs to understand the targeted markets’ systems and consumer behaviour, from there it is inevitable to design strategic plan how to engage the stakeholders in the ubiquitous supply chain relationships. In the end, a conceptual model with network perspectives is proposed: The model will be an analytical framework with key agenda items for the luxury brand which aims to enter the new market, and also the research limitations and further research opportunities are discussed
ASCA Observations of the Jet Source XTE J1748-288
XTE J1748-288 is a new X-ray transient with a one-sided radio jet. It was
observed with ASCA on 1998/09/06 and 1998/09/26, 100 days after the onset of
the radio-X-ray outburst. The spectra were fitted with an attenuated power-law
model, and the 2-6-keV flux was 4.6 * 10^{-11} erg s^{-1} cm^{-2} and 2.2 *
10^{-12} on 09/06 and 09/26, respectively. The light curve showed that the
steady exponential decay with an e-folding time of 14 days lasted over 100 days
and 4 orders of magnitude from the peak of the outburst. The celestial region
including the source had been observed with ASCA on 1993/10/01 and 1994/09/22,
years before the discovery. In those period, the flux was < 10^{-13} erg s^{-1}
cm^{-2}, below ASCA's detection limit. The jet blob colliding to the
environmental matter was supposedly not the X-ray source, although the emission
mechanism has not been determined. A possible detection of a K line from highly
ionized iron is discussed.Comment: 11 pages, 4 figures, submitted to ApJL. Fig2 is replaced with correct
on
An X-ray and Optical Investigation of the Starburst-driven Superwind in the Galaxy Merger Arp 299
We present a detailed investigation of the X-ray and optical properties of
the starburst-merger system Arp299 (NGC 3690, Mrk 171), with an emphasis on its
spectacular gaseous nebula. We analyse \rosat and \asca X-ray data and optical
spectra and narrow-band images. We suggest that the on-going galaxy collision
has tidally-redistributed the ISM of the merging galaxies. The optical
emission-line nebula results as this gas is photoionized by radiation that
escapes from the starburst, and is shock-heated, accelerated, and pressurized
by a `superwind' driven by the collective effect of the starburst supernovae
and stellar winds. The X-ray nebula in Arp 299 is is plausibly a mass-loaded
flow of adiabatically-cooling gas that carries out a substantial fraction of
the energy and metals injected by the starburst at close to the escape velocity
from Arp 299. The mass outflow rate likely exceeds the star-formation rate in
this system. We conclude that powerful starbursts are able to heat (and
possibly eject) a significant fraction of the ISM in merging galaxies.Comment: 54 pages, 17 postscript figures, AAS late
The Evolution of X-ray Bursts in the "Bursting Pulsar" GRO J1744-28
GRO J1744-28, commonly known as the `Bursting Pulsar', is a low mass X-ray
binary containing a neutron star and an evolved giant star. This system,
together with the Rapid Burster (MXB 1730-33), are the only two systems that
display the so-called Type II X-ray bursts. These type of bursts, which last
for 10s of seconds, are thought to be caused by viscous instabilities in the
disk; however the Type II bursts seen in GRO J1744-28 are qualitatively very
different from those seen in the archetypal Type II bursting source the Rapid
Burster. To understand these differences and to create a framework for future
study, we perform a study of all X-ray observations of all 3 known outbursts of
the Bursting Pulsar which contained Type II bursts, including a population
study of all Type II X-ray bursts seen by RXTE. We find that the bursts from
this source are best described in four distinct phenomena or `classes' and that
the characteristics of the bursts evolve in a predictable way. We compare our
results with what is known for the Rapid Burster and put out results in the
context of models that try to explain this phenomena.Comment: Accepted to MNRAS Aug 17 201
Pathogenic variation of Phakopsora pachyrhizi populations in Brazil.
The obligate basidiomycete Phakopsora pachyrhizi is the causal agent of soybean rust that has potential to reduce the yield of soybean drastically. Soybean production in Brazil has been threatened by the rust since the pathogen was first discovered in 2001. To understand pathogenic variation of the rust populations in South America, an evaluation system for soybean rust resistance has been constructed using a set of 16 differential varieties. In this study, the evaluation system was used to investigate pathogenic variation among the P. pachyrhizi populations in Brazil. Samples of P. pachyrhizi were collected from the diseased soybeans in Brazil in the 2007-2008 and 2008-2009 soybean cultivation seasons. In the first season, two rust samples showed similar pattern of the infection types on the differential set, suggesting that the same or similar pathogen population was present in the two locations. The other samples were likely different pathogenic populations. In the second season, different patterns of the infection types were found among the samples. Comparison of the evaluation data from the two seasons demonstrated that pathogenic variation between the seasons was detected in the populations from Rio Grande do Sul and Paraná but was not remarkable in those from Rondônia. This study provides useful knowledge about P. pachyrhizi populations in Brazil to identify the resistant soybean genotypes and target effective cultivars against certain pathogen populations.Edição do Proceedings of the National Soybean Rust Symposium, New Orleans, 2009
Variability of the X-ray P Cygni Line Profiles from Circinus X-1 Near Zero Phase
The luminous X-ray binary Circinus X-1 has been observed twice near zero
orbital phase using the High-Energy Transmission Grating Spectrometer (HETGS)
onboard Chandra. The source was in a high-flux state during a flare for the
first observation, and it was in a low-flux state during a dip for the second.
Spectra from both flux states show clear P Cygni lines, predominantly from
H-like and He-like ion species. These indicate the presence of a high-velocity
outflow from the Cir X-1 system which we interpret as an equatorial
accretion-disk wind, and from the blueshifted resonance absorption lines we
determine outflow velocities of 200 - 1900 km/s with no clear velocity
differences between the two flux states. The line strengths and profiles,
however, are strongly variable both between the two observations as well as
within the individual observations. We characterize this variability and
suggest that it is due to both changes in the amount of absorbing material
along the line of sight as well as changes in the ionization level of the wind.
We also refine constraints on the accretion-disk wind model using improved
plasma diagnostics such as the He-like Mg XI triplet, and we consider the
possibility that the X-ray absorption features seen from superluminal jet
sources can generally be explained via high-velocity outflows.Comment: 12 pages, 8 figures, accepted by ApJ (Main
- …