101 research outputs found
Optical variabilities in Be/X-ray binary system:GRO J2058+42
We present an analysis of long-term optical monitoring observations and
optical spectroscopic observations of the counterpart to CXOU J205847.5+414637
(high mass X-ray binary system). We search for a variability in the light curve
of Be star. We used differential magnitudes in the time series analysis. The
variability search in the optical light curve was made by using different
algorithms. The reduction and analysis of spectra were done by using MIDAS and
its suitable packages. We have performed a frequency search which gave us the
value 2.404 1/day. This value is attributed to the non-radial pulsation of Be
star. H alpha emission line profiles always show double-peaked emissions with a
mean equivalent width of 2.31 \pm 0.19 \AA ~and a peak separation of 516 \pm 45
km/s. This suggests that Be star disk is still present. CXOU J205847.5+414637
is in X-ray quiescent state.Comment: 8 pages, 9 figures. To appear at Astronomy and Astrophysic
Distorted cyclotron line profile in Cep X-4 as observed by NuSTAR
We present spectral analysis of NuSTAR and Swift observations of Cep X-4
during its outburst in 2014. We observed the source once during the peak of the
outburst and once during the decay, finding good agreement in the spectral
shape between the observations. We describe the continuum using a powerlaw with
a Fermi-Dirac cutoff at high energies. Cep X-4 has a very strong cyclotron
resonant scattering feature (CRSF) around 30 keV. A simple absorption-like line
with a Gaussian optical depth or a pseudo-Lorentzian profile both fail to
describe the shape of the CRSF accurately, leaving significant deviations at
the red side of the line. We characterize this asymmetry with a second
absorption feature around 19 keV. The line energy of the CRSF, which is not
influenced by the addition of this feature, shows a small but significant
positive luminosity dependence. With luminosities between (1-6)e36 erg/s, Cep
X-4 is below the theoretical limit where such a correlation is expected. This
behavior is similar to Vela X-1 and we discuss parallels between the two
systems.Comment: 6 pages, 4 figure, accepted for publication in ApJ letter
Soft X-ray emission lines in the X-ray binary Swift J1858.6–0814 observed with XMM–Newton Reflection Grating Spectrometer:disc atmosphere or wind?
Neuronal XBP-1 Activates Intestinal Lysosomes to Improve Proteostasis in C. elegans
The unfolded protein response of the endoplasmic reticulum (UPRER) is a crucial mediator of secretory pathway homeostasis. Expression of the spliced and active form of the UPRER transcription factor XBP-1, XBP-1s, in the nervous system triggers activation of the UPRER in the intestine of Caenorhabditis elegans (C. elegans) through release of a secreted signal, leading to increased longevity. We find that expression of XBP-1s in the neurons or intestine of the worm strikingly improves proteostasis in multiple tissues, through increased clearance of toxic proteins. To identify the mechanisms behind this enhanced proteostasis, we conducted intestine-specific RNA-seq analysis to identify genes upregulated in the intestine when XBP-1s is expressed in neurons. This revealed that neuronal XBP-1s increases the expression of genes involved in lysosome function. Lysosomes in the intestine of animals expressing neuronal XBP-1s are more acidic, and lysosomal protease activity is higher. Moreover, intestinal lysosome function is necessary for enhanced lifespan and proteostasis. These findings suggest that activation of the UPRER in the intestine through neuronal signaling can increase the activity of lysosomes, leading to extended longevity and improved proteostasis across tissues
Soft X-ray emission lines in the X-ray binary Swift J1858.6-0814 observed with XMM-Newton-RGS: disc atmosphere or wind?
We find soft X-ray emission lines from the X-ray binary Swift J1858.6-0814 in
data from XMM-Newton-RGS: N VII, O VII and O VIII, as well as notable residuals
short of a detection at Ne IX and other higher ionisation transitions. These
could be associated with the disc atmosphere, as in accretion disc corona
sources, or with a wind, as has been detected in Swift J1858.6-0814 in emission
lines at optical wavelengths. Indeed, the N VII line is redshifted, consistent
with being the emitting component of a P-Cygni profile. We find that the
emitting plasma has an ionisation parameter and a
density cm. From this, we infer that the emitting
plasma must be within cm of the ionising source,
for a neutron star, and from the
line width that it is at least away
( cm). We compare this with known classes of
emission line regions in other X-ray binaries and active galactic nuclei.Comment: 10 pages, 7 figures, MNRAS accepte
Recent RXTE/ASM and ROTSEIIId Observations of EXO 2030+375
Using the archival RXTE/ASM and SWIFT/BAT observations, the new orbital
phases of Type I outbursts of EXO 2030+375 are estimated. A possible
correlation between the Type II outburst and optical brightness variations is
investigated. In order to estimate the phases of Type I outbursts, we fitted
Gaussian profiles to the RXTE/ASM and SWIFT/BAT light curves. The time
corresponding to the maximum value of the profiles is treated as the arrival
time of Type I outburst. We used differential magnitudes in the time-series
analysis of the optical light curve. MIDAS and its suitable packages were used
to reduce and analyze the spectra. Prior to the Type II outburst, orbital
phases of Type I outbursts were delayed for 6 days after the periastron
passage, which is consistent with findings of Wilson et al., (2002, 2005).
After the giant Type II outburst, the phase of Type I outbursts underwent a
sudden shift of 13 days after the periastron passage. The amplitudes of Type I
outbursts were increased between MJD 52500 and 53500. These amplitudes then
decreased for 10 orbital cycles until the Type II outburst was triggered. If
the change of outburst amplitudes correlated with the mass accretion, then
during the decrease of these amplitudes mass should be deposited in a disk
around neutron star temporarily. The release of this stored mass may ignite the
Type II outburst. We report that the optical light curve became fainter by 0.4
mag during the decrease of amplitude of the Type I outbursts. The observed
H profiles and their equivalent widths during the decay and after the
giant outburst are consistent with previous observations of the system.Comment: to appear at Astronomy and Astrophysic
Tyramine acts downstream of neuronal XBP-1s to coordinate inter-tissue UPRER activation and behavior in C. elegans
In C. elegans, expression of the UPRER transcription factor xbp-1s in neurons cell non-autonomously activates the UPRER in the intestine, leading to enhanced proteostasis and lifespan. To better understand this signaling pathway, we isolated neurons from animals expressing neuronal xbp-1s for transcriptomic analysis, revealing a striking remodeling of transcripts involved in neuronal signaling. We then identified signaling molecules required for cell non-autonomous intestinal UPRER activation, including the biogenic amine tyramine. Expression of xbp-1s in just two pairs of neurons that synthesize tyramine, the RIM and RIC interneurons, induced intestinal UPRER activation and extended longevity, and exposure to stress led to splicing and activation of xbp-1 in these neurons. In addition, we found that neuronal xbp-1s modulates feeding behavior and reproduction, dependent upon tyramine synthesis. XBP-1s therefore remodels neuronal signaling to coordinately modulate intestinal physiology and stress-responsive behavior, functioning as a global regulator of organismal responses to stress
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