109 research outputs found
GX 339-4: back to life
We report preliminary results of a RossiXTE campaign on the 2002 outburst of
the black-hole candidate GX 339-4. We show power density spectra of five
observations during the early phase of the outburst. The first four power
spectra show a smooth transition between a Low State and a Very High State. The
fifth power spectrum resembles a High State, but a strong 6 Hz QPO appears
suddenly within 16 seconds.Comment: 3 pages, 3 figures; to appear in Proceedings of the 4th Microquasar
Workshop, eds. Ph Durouchoux, Y. Fuchs and J. Rodriguez, published by the
Center for Space Physics: Kolkat
The MURALES survey. I. A dual AGN in the radio galaxy 3C459?
We observed the FRII radio galaxy 3C459 (z=0.22) with the MUSE spectrograph
at the Very Large Telescope (VLT) as part of the MURALES project (a MUse RAdio
Loud Emission line Snapshot survey). We detected diffuse nuclear emission and a
filamentary ionized gas structure forming a one-sided, triangular-shaped region
extending out to 80 kpc. The central emission line region is dominated by
two compact knots of similar flux: the first (N1) cospatial with the radio core
and the (N2) second located 1.2" (5.3 kpc) to the SE. The two regions differ
dramatically from the point of view of velocity (with an offset of ~400 km/s),
line widths, and line ratios. This suggests that we are observing a dual AGN
system formed by a radio loud AGN and type 2 QSO companion, which is the result
of the recent merger that also produced its disturbed host morphology. The
alternative possibility that N2 is just a bright emission line knot resulting
from, for example, a jet-cloud interaction, is disfavored because of 1) the
presence of a high ionization bicone whose apex is located at N2; 2) the
observed narrow line widths; 3) its line luminosity (~10^42 erg s-1) typical of
luminous QSOs; and 4) its location, which is offset from the jet path. The
putative secondary AGN must be highly obscured, since we do not detect any
emission in the Chandra and infrared Hubble Space Telescope images.Comment: 6 pages, 6 figures, A&A in pres
Prolonged oral cannabinoid administration prevents neuroinflammation, lowers β-amyloid levels and improves cognitive performance in Tg APP 2576 mice
Background: Alzheimer’s disease (AD) brain shows an ongoing inflammatory condition and non-steroidal antiinflammatories
diminish the risk of suffering the neurologic disease. Cannabinoids are neuroprotective and antiinflammatory
agents with therapeutic potential.
Methods: We have studied the effects of prolonged oral administration of transgenic amyloid precursor protein
(APP) mice with two pharmacologically different cannabinoids (WIN 55,212-2 and JWH-133, 0.2 mg/kg/day in the
drinking water during 4 months) on inflammatory and cognitive parameters, and on 18F-fluoro-deoxyglucose
(18FDG) uptake by positron emission tomography (PET).
Results: Novel object recognition was significantly reduced in 11 month old Tg APP mice and 4 month
administration of JWH was able to normalize this cognitive deficit, although WIN was ineffective. Wild type mice
cognitive performance was unaltered by cannabinoid administration. Tg APP mice showed decreased 18FDG
uptake in hippocampus and cortical regions, which was counteracted by oral JWH treatment. Hippocampal GFAP
immunoreactivity and cortical protein expression was unaffected by genotype or treatment. In contrast, the density
of Iba1 positive microglia was increased in Tg APP mice, and normalized following JWH chronic treatment. Both
cannabinoids were effective at reducing the enhancement of COX-2 protein levels and TNF-a mRNA expression
found in the AD model. Increased cortical b-amyloid (Ab) levels were significantly reduced in the mouse model by
both cannabinoids. Noteworthy both cannabinoids enhanced Ab transport across choroid plexus cells in vitro.
Conclusions: In summary we have shown that chronically administered cannabinoid showed marked beneficial
effects concomitant with inflammation reduction and increased Ab clearanceThis work was supported by the Spanish Ministry of Science and
Technology (SAF 2005-02845 to M.L.C). A.M.M-M. was recipient a fellowship
from the Ministry of Education and Scienc
NuSTAR Detection of the Blazar B2 1023+25 at Redshift 5.3
B2 1023+25 is an extremely radio-loud quasar at z = 5.3 that was first identified as a likely high-redshift blazar candidate in the SDSS+FIRST quasar catalog. Here, we use the Nuclear Spectroscopic Telescope Array (NuSTAR) to investigate its non-thermal jet emission, whose high-energy component we detected in the hard X-ray energy band. The X-ray flux is ~ 5.5 x 10^(-14)erg cm^(-2) s^(-1) (5-10 keV) and the photon spectral index is Γ_X ≃ 1.3-1.6. Modeling the full spectral energy distribution, we find that the jet is oriented close to the line of sight, with a viewing angle of ~3°, and has significant Doppler boosting, with a large bulk Lorentz factor ~13, which confirms the identification of B2 1023+25 as a blazar. B2 1023+25 is the first object at redshift larger than 5 detected by NuSTAR, demonstrating the ability of NuSTAR to investigate the early X-ray universe and to study extremely active supermassive black holes located at very high redshift
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Swift Detects a Remarkable Gamma-Ray Burst, GRB 060614, That Introduces a New Classification Scheme
Gamma ray bursts (GRBs) are known to come in two duration classes, separated at {approx}2 s. Long bursts originate from star forming regions in galaxies, have accompanying supernovae (SNe) when near enough to observe and are likely caused by massive-star collapsars. Recent observations show that short bursts originate in regions within their host galaxies with lower star formation rates, consistent with binary neutron star (NS) or NS - black hole (BH) mergers. Moreover, although their hosts are predominantly nearby galaxies, no SNe have been so far associated with short GRBs. We report here on the bright, nearby GRB 060614 that does not fit in either class. Its {approx}102 s duration groups it with long GRBs, while its temporal lag and peak luminosity fall entirely within the short GRB subclass. Moreover, very deep optical observations exclude an accompanying supernova, similar to short GRBs. This combination of a long duration event without accompanying SN poses a challenge to both a collapsar and merging NS interpretation and opens the door on a new GRB classification scheme that straddles both long and short bursts
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