438 research outputs found
Growth of Intermediate-Mass Black Holes in Globular Clusters
We present results of numerical simulations of sequences of binary-single
scattering events of black holes in dense stellar environments. The simulations
cover a wide range of mass ratios from equal mass objects to 1000:10:10 solar
masses and compare purely Newtonian simulations to simulations in which
Newtonian encounters are interspersed with gravitational wave emission from the
binary. In both cases, the sequence is terminated when the binary's merger time
due to gravitational radiation is less than the arrival time of the next
interloper. We find that black hole binaries typically merge with a very high
eccentricity (0.93 < e < 0.95 pure Newtonian; 0.85 < e < 0.90 with
gravitational wave emission) and that adding gravitational wave emission
decreases the time to harden a binary until merger by ~ 30% to 40%. We discuss
the implications of this work for the formation of intermediate-mass black
holes and gravitational wave detection.Comment: 28 pages including 9 figures, submitted to Ap
A Single Circumbinary Disk in the HD 98800 Quadruple System
We present sub-arcsecond thermal infrared imaging of HD 98800, a young
quadruple system composed of a pair of low-mass spectroscopic binaries
separated by 0.8'' (38 AU), each with a K-dwarf primary. Images at wavelengths
ranging from 5 to 24.5 microns show unequivocally that the optically fainter
binary, HD 98800B, is the sole source of a comparatively large infrared excess
upon which a silicate emission feature is superposed. The excess is detected
only at wavelengths of 7.9 microns and longer, peaks at 25 microns, and has a
best-fit black-body temperature of 150 K, indicating that most of the dust lies
at distances greater than the orbital separation of the spectroscopic binary.
We estimate the radial extent of the dust with a disk model that approximates
radiation from the spectroscopic binary as a single source of equivalent
luminosity. Given the data, the most-likely values of disk properties in the
ranges considered are R_in = 5.0 +/- 2.5 AU, DeltaR = 13+/-8 AU, lambda_0 =
2(+4/-1.5) microns, gamma = 0+/-2.5, and sigma_total = 16+/-3 AU^2, where R_in
is the inner radius, DeltaR is the radial extent of the disk, lambda_0 is the
effective grain size, gamma is the radial power-law exponent of the optical
depth, tau, and sigma_total is the total cross-section of the grains. The range
of implied disk masses is 0.001--0.1 times that of the moon. These results show
that, for a wide range of possible disk properties, a circumbinary disk is far
more likely than a narrow ring.Comment: 11 page Latex manuscript with 3 postscript figures. Accepted for
publication in Astrophysical Journal Letters. Postscript version of complete
paper also available at
http://www.hep.upenn.edu/PORG/web/papers/koerner00a.p
Multi-Wavelength Coverage of State Transitions in the New Black Hole X-Ray Binary Swift J1910.2-0546
Understanding how black holes accrete and supply feedback to their
environment is one of the outstanding challenges of modern astrophysics. Swift
J1910.2-0546 is a candidate black hole low-mass X-ray binary that was
discovered in 2012 when it entered an accretion outburst. To investigate the
binary configuration and the accretion morphology we monitored the evolution of
the outburst for ~3 months at X-ray, UV, optical (B,V,R,I), and near-infrared
(J,H,K) wavelengths using Swift and SMARTS. The source evolved from a hard to a
soft X-ray spectral state with a relatively cold accretion disk that peaked at
~0.5 keV. A Chandra/HETG spectrum obtained during this soft state did not
reveal signatures of an ionized disk wind. Both the low disk temperature and
the absence of a detectable wind could indicate that the system is viewed at
relatively low inclination. The multi-wavelength light curves revealed two
notable features that appear to be related to X-ray state changes. Firstly, a
prominent flux decrease was observed in all wavebands ~1-2 weeks before the
source entered the soft state. This dip occurred in (0.6-10 keV) X-rays ~6 days
later than at longer wavelengths, which could possibly reflect the viscous time
scale of the disk. Secondly, about two weeks after the source transitioned back
into the hard state, the UV emission significantly increased while the X-rays
steadily decayed. We discuss how these observations may reflect changes in the
accretion flow morphology, perhaps related to the quenching/launch of a jet or
the collapse/recovery of a hot flow.Comment: 8 pages, 5 figures, 1 table. To be published in Ap
A case of recurrent epilepsy-associated rosette-forming glioneuronal tumor with anaplastic transformation in the absence of therapy.
Rosette-forming glioneuronal tumor (RGNT) most commonly occurs adjacent to the fourth ventricle and therefore rarely presents with epilepsy. Recent reports describe RGNT occurrence in other anatomical locations with considerable morphologic and genetic overlap with the epilepsy-associated dysembryoplastic neuroepithelial tumor (DNET). Examples of RGNT or DNET with anaplastic change are rare, and typically occur in the setting of radiation treatment. We present the case of a 5-year-old girl with seizures, who underwent near total resection of a cystic temporal lobe lesion. Pathology showed morphologic and immunohistochemical features of RGNT, albeit with focally overlapping DNET-like patterns. Resections of residual or recurrent tumor were performed 1 year and 5 years after the initial resection, but no adjuvant radiation or chemotherapy was given. Ten years after the initial resection, surveillance imaging identified new and enhancing nodules, leading to another gross total resection. This specimen showed areas similar to the original tumor, but also high-grade foci with oligodendroglial morphology, increased cellularity, palisading necrosis, microvascular proliferation, and up to 13 mitotic figures per 10 high power fields. Ancillary studies the status by sequencing showed wild-type of the isocitrate dehydrogenase 1 (IDH1), IDH2, and human histone 3.3 (H3F3A) genes, and BRAF studies were negative for mutation or rearrangement. Fluorescence in situ hybridization (FISH) showed codeletion of 1p and 19q limited to the high-grade regions. By immunohistochemistry there was loss of nuclear alpha-thalassemia mental retardation syndrome, X-linked (ATRX) expression only in the high-grade region. Next-generation sequencing showed an fibroblast growth factor receptor receptor 1 (FGFR1) kinase domain internal tandem duplication in three resection specimens. ATRX mutation in the high-grade tumor was confirmed by sequencing which showed a frameshift mutation (p.R1427fs), while the apparent 1p/19q-codeletion by FISH was due to loss of chromosome arm 1p and only partial loss of 19q. Exceptional features of this case include the temporal lobe location, 1p/19q loss by FISH without true whole-arm codeletion, and anaplastic transformation associated with ATRX mutation without radiation or chemotherapy
Exploring Accretion and Disk-Jet Connections in the LLAGN M81*
We report on a year-long effort to monitor the central supermassive black
hole in M81 in the X-ray and radio bands. Using Chandra and the VLA, we
obtained quasi-simultaneous observations of M81* on seven occasions during
2006. The X-ray and radio luminosity of M81* are not strongly correlated on the
approximately 20-day sampling timescale of our observations, which is
commensurate with viscous timescales in the inner flow and orbital timecales in
a radially-truncated disk. This suggests that short-term variations in black
hole activity may not be rigidly governed by the "fundamental plane", but
rather adhere to the plane in a time-averaged sense. Fits to the X-ray spectra
of M81* with bremsstrahlung models give temperatures that are inconsistent with
the outer regions of very simple advection-dominated inflows. However, our
results are consistent with the X-ray emission originating in a transition
region where a truncated disk and advective flow may overlap. We discuss our
results in the context of models for black holes accreting at small fractions
of their Eddington limit, and the fundamental plane of black hole accretion.Comment: Accepted for publication in Ap
FOXP3+ T cells in uterine sarcomas are associated with favorable prognosis, low extracellular matrix expression and reduced YAP activation.
Uterine sarcomas are rare but deadly malignancies without effective treatment. Immunotherapy is a promising new approach to treat these tumors but has shown heterogeneous effects in sarcoma patients. With the goal of identifying key factors for improved patient treatment, we characterized the tumor immune landscape in 58 uterine sarcoma cases with full clinicopathological annotation. Immune cell characterization revealed the overall prevalence of FOXP3+ cells and pro-tumor M2-like macrophages. Hierarchical clustering of patients showed four tumor type-independent immune signatures, where infiltration of FOXP3+ cells and M1-like macrophages associated with favorable prognosis. High CD8+/FOXP3+ ratio in UUS and ESS correlated with poor survival, upregulation of immunosuppressive markers, extracellular matrix (ECM)-related genes and proteins, and YAP activation. This study shows that uterine sarcomas present distinct immune signatures with prognostic value, independent of tumor type, and suggests that targeting the ECM could be beneficial for future treatments
On the complementarity of pulsar timing and space laser interferometry for the individual detection of supermassive black hole binaries
Gravitational waves coming from Super Massive Black Hole Binaries (SMBHBs)
are targeted by both Pulsar Timing Array (PTA) and Space Laser Interferometry
(SLI). The possibility of a single SMBHB being tracked first by PTA, through
inspiral, and later by SLI, up to merger and ring down, has been previously
suggested. Although the bounding parameters are drawn by the current PTA or the
upcoming Square Kilometer Array (SKA), and by the New Gravitational Observatory
(NGO), derived from the Laser Interferometer Space Antenna (LISA), this paper
also addresses sequential detection beyond specific project constraints. We
consider PTA-SKA, which is sensitive from 10^(-9) to p x 10^(-7) Hz (p=4, 8),
and SLI, which operates from s x 10^(-5) up to 1 Hz (s = 1, 3). A SMBHB in the
range 2x 10^(8) - 2 x 10^(9) solar masses (the masses are normalised to a (1+z)
factor, the red shift lying between z = 0.2 and z=1.5) moves from the PTA-SKA
to the SLI band over a period ranging from two months to fifty years. By
combining three Super Massive Black Hole (SMBH)-host relations with three
accretion prescriptions, nine astrophysical scenarios are formed. They are then
related to three levels of pulsar timing residuals (50, 5, 1 ns), generating
twenty-seven cases. For residuals of 1 ns, sequential detection probability
will never be better than 4.7 x 10^(-4) y^(-2) or 3.3 x 10^(-6) y^(-2) (per
year to merger and per year of survey), according to the best and worst
astrophysical scenarios, respectively; put differently this means one
sequential detection every 46 or 550 years for an equivalent maximum time to
merger and duration of the survey. The chances of sequential detection are
further reduced by increasing values of the s parameter (they vanish for s =
10) and of the SLI noise, and by decreasing values of the remnant spin. REST OF
THE ABSTRACT IN THE PDF FILE.Comment: To appear in the Astrophysical Journa
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