1,730 research outputs found
Disc-loss episode in the Be shell optical counterpart to the high-mass X-ray binary IGR J21343+4738
The main goal of this work is to determine the properties of the optical
counterpart to the INTEGRAL source IGR J21343+4738, and study its long-term
optical variability. We present optical photometric BVRI and spectroscopic
observations covering the wavelength band 4000-7500 A. We find that the optical
counterpart to IGR J21343+4738 is a V=14.1 B1IVe shell star located at a
distance of ~8.5 kpc. The Halpha line changed from an absorption dominated
profile to an emission dominated profile, and then back again into absorption.
In addition, fast V/R asymmetries were observed once the disc developed.
Although the Balmer lines are the most strongly affected by shell absorption,
we find that shell characteristics are also observed in He I lines. The optical
spectral variability of IGR J21343+4738 is attributed to the formation of an
equatorial disc around the Be star and the development of an enhanced density
perturbation that revolves inside the disc. We have witnessed the formation and
dissipation of the circumstellar disc. The strong shell profile of the Halpha
and He I lines and the fact that no transition from shell phase to a pure
emission phase is seen imply that we are seeing the system near edge-on.Comment: accepted for publication in A&
Three-family left-right symmetry with low-scale seesaw mechanism
We suggest a new left-right symmetric model implementing a low-scale seesaw
mechanism in which quantum consistency requires three families of fermions. The
symmetry breaking route to the Standard Model determines the profile of the
"next" expected new physics, characterized either by the simplest left-right
gauge symmetry or by the 3-3-1 scenario. The resulting gauge bosons
can be probed at the LHC and provide a production portal for the right-handed
neutrinos. On the other hand, its flavor changing interactions would affect the
K, D and B neutral meson systems.Comment: 10 pages, 2 figures. Revised version as accepted by JHE
A Model of Comprehensive Unification
Comprehensive - that is, gauge and family - unification using spinors has
many attractive features, but it has been challenged to explain chirality.
Here, by combining an orbifold construction with more traditional ideas, we
address that difficulty. Our candidate model features three chiral families and
leads to an acceptable result for quantitative unification of couplings. A
potential target for accelerator and astronomical searches emerges.Comment: 5 pages, 2 figures. Published versio
Discovery of X-ray pulsations in the Be/X-ray binary IGR J06074+2205
IGR J06074+2205 is a poorly studied X-ray source with a Be star companion. It
has been proposed to belong to the group of Be/X-ray binaries. In Be/X-ray
binaries, accretion onto the neutron star occurs via the transfer of material
from the Be star's circumstellar disk. Thus, in the absence of the disk, no
X-ray should be detected. The main goal of this work is to study the quiescent
X-ray emission of IGR J06074+2205 during a disk-loss episode. We show that at
the time of the XMM-Newton observation the decretion disk around the Be star
had vanished. Still, accretion appears as the source of energy that powers the
high-energy radiation in IGR J06074+2205. We report the discovery of X-ray
pulsations with a pulse period of 373.2 s and a pulse fraction of ~50%. The
keV spectrum is well described by an absorbed power law and blackbody
components with the best fitting parameters: cm, keV, and The
absorbed X-ray luminosity is erg s
assuming a distance of 4.5 kpc. The detection of X-ray pulsations confirms the
nature of IGR J06074+2205 as a Be/X-ray binary. We discuss various scenarios to
explain the quiescent X-ray emission of this pulsar. We rule out cooling of the
neutron star surface and magnetospheric emission and conclude that accretion is
the most likely scenario. The origin of the accreted material remains an open
question.Comment: accepted for publication in A&
A 0535+26: Back in business
In May/June 2005, after 10 years of inactivity, the Be/X-ray binary system A
0535+26 underwent a major X-ray outburst. In this paper data are presented from
10 years of optical, IR and X-ray monitoring showing the behaviour of the
system during the quiescent epoch and the lead up to the new outburst. The
results show the system going through a period when the Be star in the system
had a minimal circumstellar disk and then a dramatic disk recovery leading,
presumably, to the latest flare up of X-ray emission. The data are interpreted
in terms of the state of the disk and its interaction with the neutron star
companion.Comment: Accepted for publication in MNRA
Multiwavelength observations of the Be/X-ray binary 4U1145-619
We report optical and infrared observations of the massive X-ray binary
system 4U1145-619 (V801 Cen) which show that the circumstellar disc of the Be
star component is in decline. Infrared J,H,K,L magnitudes of V801Cen have been
monitored from 1993 March to 1996 April. H alpha spectra have been obtained
throughout the same period. We find that both the infrared excess and the
Balmer emission have been in decline throughout the period of observations. A
13 year optical and X-ray history of the source has been collated, revealing a
possible correlation between the optical and X-ray activity. In addition, we
have used u,v,b,y,beta indices, corrected for both circumstellar and
interstellar effects, to calculate the physical parameters of the underlying B
star.Comment: 8 pages postscript. Accepted by MNRA
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