174 research outputs found
On the Merging Cluster Abell 578 and Its Central Radio Galaxy 4C +67.13
Here we analyze radio, optical, and X-ray data for a peculiar cluster Abell
578. This cluster is not fully relaxed and consists of two merging sub-systems.
The brightest cluster galaxy, CGPG 0719.8+6704, is a pair of interacting
ellipticals with projected separation 10 kpc, the brighter of which hosts
the radio source 4C +67.13. The Fanaroff-Riley type-II radio morphology of 4C
+67.13 is unusual for central radio galaxies in local Abell clusters. Our new
optical spectroscopy revealed that both nuclei of the CGPG 0719.8+6704 pair are
active, albeit at low accretion rates corresponding to the Eddington ratio
(for the estimated black hole masses of and ). The gathered X-ray ({\it Chandra})
data allowed us to confirm and to quantify robustly the previously noted
elongation of the gaseous atmosphere in the dominant sub-cluster, as well as a
large spatial offset (\,kpc projected) between the position of the
brightest cluster galaxy and the cluster center inferred from the modeling of
the X-ray surface brightness distribution. Detailed analysis of the brightness
profiles and temperature revealed also that the cluster gas in the vicinity of
4C\,+67.13 is compressed (by a factor of about ) and heated (from
\,keV up to 2.7\,keV), consistent with the presence of a weak shock
(Mach number ) driven by the expanding jet cocoon. This would then
require the jet kinetic power of the order of \,erg\,s,
implying either a very high efficiency of the jet production for the current
accretion rate, or a highly modulated jet/accretion activity in the system.Comment: 12 pages, 11 figures, accepted for publication in Ap
The Hardness-Intensity Diagram of Cygnus X-3: Revisiting the Radio/X-Ray States
Cygnus X-3 is one of the brightest X-ray and radio sources in the Galaxy, and
is well known for its erratic behaviour in X-rays as well as in the radio,
occasionally producing major radio flares associated with relativistic
ejections. However, even after many years of observations in various wavelength
bands Cyg X-3 still eludes clear physical understanding. Studying different
emission bands simultaneously in microquasars has proved to be a fruitful
approach towards understanding these systems, especially by shedding light on
the accretion disc/jet connection. We continue this legacy by constructing a
hardness-intensity diagram (HID) from archival Rossi X-ray Timing Explorer data
and linking simultaneous radio observations to it. We find that surprisingly
Cyg X-3 sketches a similar shape in the HID to that seen in other transient
black hole X-ray binaries during outburst but with distinct differences.
Together with the results of this analysis and previous studies of Cyg X-3 we
conclude that the X-ray states can be assigned to six distinct states. This
categorization relies heavily on the simultaneous radio observations and we
identify one new X-ray state, the hypersoft state, similar to the ultrasoft
state, which is associated to the quenched radio state during which there is no
or very faint radio emission. Recent observations of GeV flux observed from Cyg
X-3 (Tavani et al. 2009; Fermi LAT Collaboration et al. 2009) during a soft
X-ray and/or radio quenched state at the onset of a major radio flare hint that
a very energetic process is at work during this time, which is also when the
hypersoft X-ray state is observed. In addition, Cyg X-3 shows flaring with a
wide range of hardness.Comment: 17 pages, 9 figures, accepted for publication in MNRA
On the Interaction of the PKS B1358-113 Radio Galaxy with the Abell 1836 Cluster
[abridged] Here we present the analysis of multifrequency data gathered for
the FRII radio galaxy PKS B1358-113, hosted in the brightest cluster galaxy of
Abell 1836. The galaxy harbors one of the most massive black holes known to
date and our analysis of the optical data reveals that this black hole is only
weakly active. Based on new Chandra and XMM-Newton X-ray observations and
archival radio data we derive the preferred range for the jet kinetic
luminosity erg s. This is above the values
implied by various scaling relations proposed for radio sources in galaxy
clusters, being instead very close to the maximum jet power allowed for the
given accretion rate. We constrain the radio source lifetime as
Myrs, and the total amount of deposited jet energy \,ergs. The detailed analysis of the X-ray data provides indication for
the presence of a bow-shock driven by the expanding radio lobes into the Abell
1836 cluster environment, with the corresponding Mach number . This,
together with the recently growing evidence that powerful FRII radio galaxies
may not be uncommon in the centers of clusters at higher redshifts, supports
the idea that jet-induced shock heating may indeed play an important role in
shaping the properties of clusters, galaxy groups, and galaxies in formation.
We speculate on a possible bias against detecting jet-driven shocks in poorer
environments, resulting from an inefficient electron heating at the shock
front, combined with a relatively long electron-ion equilibration timescale.Comment: Version accepted to Ap
The effects of prostaglandin E-2 treatment on the secretory function of mare corpus luteum depends on the site of application : an in vivo study
Research Areas: Veterinary SciencesWe examined the effect of prostaglandin (PG) E2 on the secretory function of equine corpus luteum (CL), according to the application site: intra-CL injection vs. an intrauterine (intra-U) administration. Moreover, the effect of intra-CL injection vs. intra-U administration of both luteotropic factors: PGE2 and human chorionic gonadotropin (hCG) as a positive control, on CL function was additionally compared. Mares were assigned to the groups (n = 6 per group): (1) an intra-CL saline injection (control); (2) an intra-CL injection of PGE2 (5 mg/ml); (3) an intra-CL injection of hCG (1,500 IU/ml); (4) an intra-U saline administration (control); (5) an intra-U administration of PGE2 (5 mg/5 ml); (6) an intra-U administration of hCG (1,500 IU/5 ml). Progesterone (P4) and PGE2 concentrations were measured in blood plasma samples collected at −2, −1, and 0 (pre-treatment), and at 1, 2, 3, 4, 6, 8, 10, 12, and 24 h after treatments. Moreover, effects of different doses of PGE2 application on the concentration of total PGF2α (PGF2α and its main metabolite 13,14-dihydro-15-keto-prostaglandin F2α– PGFM) was determined. The time point of PGE2, hCG, or saline administration was defined as hour “0” of the experiment. An intra-CL injection of PGE2 increased P4 and PGE2 concentrations between 3 and 4 h or at 3 and 12 h, respectively (p < 0.05). While intra-U administration of PGE2 elevated P4 concentrations between 8 and 24 h, PGE2 was upregulated at 1 h and between 3 and 4 h (p < 0.05). An intra-CL injection of hCG increased P4 concentrations at 1, 6, and 12 h (p < 0.05), while its intra-U administration enhanced P4 and PGE2 concentrations between 1 and 12 h or at 3 h and between 6 and 10 h, respectively (p < 0.05). An application of PGE2, dependently on the dose, supports equine CL function, regardless of the application site, consequently leading to differences in both P4 and PGE2 concentrations in blood plasmainfo:eu-repo/semantics/publishedVersio
Effects of the stellar wind on X-ray spectra of Cygnus X-3
We study X-ray spectra of Cyg X-3 from BeppoSAX, taking into account
absorption and emission in the strong stellar wind of its companion. We find
the intrinsic X-ray spectra are well modelled by disc blackbody emission, its
upscattering by hot electrons with a hybrid distribution, and by Compton
reflection. These spectra are strongly modified by absorption and reprocessing
in the stellar wind, which we model using the photoionization code cloudy. The
form of the observed spectra implies the wind is composed of two phases. A hot
tenuous plasma containing most of the wind mass is required to account for the
observed features of very strongly ionized Fe. Small dense cool clumps filling
<0.01 of the volume are required to absorb the soft X-ray excess, which is
emitted by the hot phase but not present in the data. The total mass-loss rate
is found to be (0.6--1.6) x 10^-5 solar masses per year. We also discuss the
feasibility of the continuum model dominated by Compton reflection, which we
find to best describe our data. The intrinsic luminosities of our models
suggest that the compact object is a black hole.Comment: MNRAS, in pres
Long-term results after percutaneous transluminal angioplasty of the subclavian artery
Wstęp. Zespół podkradania tętnicy podobojczykowej jest istotnym problemem
klinicznym, w którym przewlekłe niedokrwienie kończyny górnej może powodować
zaburzenia ukrwienia mózgu. Obecnie postępowaniem z wyboru w przypadku całkowitej
niedrożności tętnicy podobojczykowej jest leczenie chirurgiczne, natomiast w
przypadkach zwężeń stosuje się techniki śródnaczyniowe.
Materiał i metody. W klinice, w której pracują autorzy, w latach 1989–1998
u 74 chorych (44 kobiet i 30 mężczyzn w wieku 20–71 lat; średnio 49 lat) wykonano
przezskórną dylatację (PTA, percutaneous transluminal angioplasty) z powodu
zwężenia tętnicy podobojczykowej. Dobre wyniki angioplastyki uzyskano u 69 chorych
(93,2%). Zgody na ponowne wykonanie zabiegów nie wyraziło 5 pacjentów (8,1%),
u których doszło do szybkiego nawrotu zwężenia. Celem pracy była analiza odległych
wyników PTA u 52 chorych w okresie 16–128 miesięcy (średnio 51 miesięcy) od
wykonanego zabiegu.
Wyniki. U 39 (75%) chorych odnotowano poprawę stanu klinicznego potwierdzoną
badaniem duplex-doppler,a także zrównanie wartości ciśnienia tętniczego na tętnicach
ramiennych. U żadnego z pacjentów nie stwierdzono objawów przewlekłego niedokrwienia
mózgu lub kończyny górnej. W tym okresie u 8 chorych obserwowano nawrót zwężenia
tętnicy podobojczykowej. Ocena morfologiczna wykazała poniżej 50-procentowe
zwężenia światła naczynia, powodujące różnice ciśnienia krwi na tętnicy ramiennej
poniżej 20 mm Hg.Introduction. Subclavian steal syndrome is a clinical problem of great
importance, in which chronic upper limb ischaemia can cause a deficit of blood
supply to the brain. Nowadays surgery is the routine approach to the management
of complete subclavian artery (SA) occlusion; in the case of stenosis endovascular
procedure is preferable.
Material and methods. We treated 74 patients with percutaneous transluminal
angioplasty (PTA) for SA stenosis in our Department in the years 1989–1998 (44
females, 30 male; age 20–71 years, mean 49 years). Good results after angioplasty
were obtained in 69 patients (93.2%). Five patients (8.1%) had only a temporary
improvement but they refused further procedures. Analysis of the long-term results
after SA PTA was the aim of the study. Fifty-two patients were followed-up for
16 to 128 months (mean 51 months).
Results. Thirty-nine patients (75%) had clinical improvement and normal
vertebral artery blood flow direction confirmed by duplex-doppler, as well as
equal brachial pressures. None of the patients complained of any signs of chronic
brain or hand ischaemia. During follow-up 8 patients (15.4%) were diagnosed with
subclavian artery stenosis, however lesser than 50%, causing a difference of brachial
pressure up to 20 mm Hg
A giant radio flare from Cygnus X-3 with associated Gamma-ray emission
With frequent flaring activity of its relativistic jets, Cygnus X-3 is one of
the most active microquasars and is the only Galactic black hole candidate with
confirmed high energy Gamma-ray emission, thanks to detections by Fermi/LAT and
AGILE. In 2011, Cygnus X-3 was observed to transit to a soft X-ray state, which
is known to be associated with high-energy Gamma-ray emission. We present the
results of a multi-wavelength campaign covering a quenched state, when radio
emission from Cygnus X-3 is at its weakest and the X-ray spectrum is very soft.
A giant (~ 20 Jy) optically thin radio flare marks the end of the quenched
state, accompanied by rising non-thermal hard X-rays. Fermi/LAT observations (E
>100 MeV) reveal renewed Gamma-ray activity associated with this giant radio
flare, suggesting a common origin for all non-thermal components. In addition,
current observations unambiguously show that the Gamma-ray emission is not
exclusively related to the rare giant radio flares. A 3-week period of
Gamma-ray emission is also detected when Cygnus X-3 was weakly flaring in
radio, right before transition to the radio quenched state. No Gamma rays are
observed during the ~ one-month long quenched state, when the radio flux is
weakest. Our results suggest transitions into and out of the ultrasoft X-ray
(radio quenched) state trigger Gamma-ray emission, implying a connection to the
accretion process, and also that the Gamma-ray activity is related to the level
of radio flux (and possibly shock formation), strengthening the connection to
the relativistic jets.Comment: Accepted for publication in MNRAS. 10 pages 5 figures, 1 tabl
Discovery of extreme particle acceleration in the microquasar Cygnus X-3
The study of relativistic particle acceleration is a major topic of
high-energy astrophysics. It is well known that massive black holes in active
galaxies can release a substantial fraction of their accretion power into
energetic particles, producing gamma-rays and relativistic jets. Galactic
microquasars (hosting a compact star of 1-10 solar masses which accretes matter
from a binary companion) also produce relativistic jets. However, no direct
evidence of particle acceleration above GeV energies has ever been obtained in
microquasar ejections, leaving open the issue of the occurrence and timing of
extreme matter energization during jet formation. Here we report the detection
of transient gamma-ray emission above 100 MeV from the microquasar Cygnus X-3,
an exceptional X-ray binary which sporadically produces powerful radio jets.
Four gamma-ray flares (each lasting 1-2 days) were detected by the AGILE
satellite simultaneously with special spectral states of Cygnus X-3 during the
period mid-2007/mid-2009. Our observations show that very efficient particle
acceleration and gamma-ray propagation out of the inner disk of a microquasar
usually occur a few days before major relativistic jet ejections. Flaring
particle energies can be thousands of times larger than previously detected
maximum values (with Lorentz factors of 105 and 102 for electrons and protons,
respectively). We show that the transitional nature of gamma-ray flares and
particle acceleration above GeV energies in Cygnus X-3 is clearly linked to
special radio/X-ray states preceding strong radio flares. Thus gamma-rays
provide unique insight into the nature of physical processes in microquasars.Comment: 29 pages (including Supplementary Information), 8 figures, 2 tables
version submitted to Nature on August 7, 2009 (accepted version available at
http://www.nature.com/nature/journal/vaop/ncurrent/pdf/nature08578.pdf
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