2572254
Characterization of the Crab Pulsar's Timing Noise
We present a power spectral analysis of the Crab pulsar’s timing noise, mainly using radio measurements from Jodrell Bank taken over the period 1982-1989, an interval bounded by sparse data sampling and a large glitch. The power spectral analysis is complicated by nonuniform data sampling and the presence of a steep red power spectrum that can distort power spectra measurement by causing severe power “leakage”. We develop a simple windowing method for computing red noise power spectra of uniformly sampled data sets and test it on Monte Carlo generated sample realizations of red power-law noise. We generalize time-domain methods of generating power-law red noise with even integer spectral indices to the case of noninteger spectral indices. The Jodrell Bank pulse phase residuals are dense and smooth enough that an interpolation onto a uniform time series is possible. A windowed power spectrum is computed revealing a periodic or nearly periodic component with a period of 568± 10 days and a 1/f 3 power-law noise component in pulse phase with a noise strength Sφ = (1.24±0.067)×10−16 cycles/sec over the analysis frequency range f = 0.003 − 0.1 cycles/day. This result deviates from past analyses which characterized the pulse phase timing residuals as either 1/f 4 power-law noise or a quasiperiodic process. The analysis was checked using the Deeter polynomial method of power spectrum estimation that was developed for the case of nonuniform sampling, but has lower spectral resolution. The timing noise is consistent with a torque noise spectrum rising with analysis frequency as f implying blue torque noise, a result not predicted by current models of pulsar timing noise. If the periodic or nearly periodic component is due to a binary companion, we find a mass function f(M) = (6.8 ± 2.4) × 10−16 M⊙ and a companion mass, Mc ≥ 3.2M⊕ assuming a Crab pulsar mass of 1.4M⊙.
647674
A Decade in the Life of EXO 2030+375: A Multiwavelength Study of an Accreting X-Ray Pulsar
Using BATSE and RXTE observations from 1991 April to 2001 August, we have detected 71 outbursts from 82 periastron passages of EXO 2030+375, a 42 s transient X-ray pulsar with a Be star companion, including several outbursts from 1993 August to 1996 April, when the source was previously believed to be quiescent. Combining BATSE, RXTE, and EXOSAT data, we have derived an improved orbital solution. Applying this solution results in a smooth profile for the spin-up rate during the giant outburst and results in evidence for a correlation between the spin-up rate and observed flux in the brighter BATSE outbursts. Infrared and H? measurements show a decline in the density of the circumstellar disk around the Be star. This decline is followed by a sudden drop in the X-ray flux and a turnover from a spin-up trend to spin-down in the frequency history. This is the first Be/X-ray binary that shows an extended interval, about 2.5 yr, in which the global trend is spin-down, but the outbursts continue. In 1995 the orbital phase of EXO 2030+375's outbursts shifted from peaking about 6 days after periastron to peaking before periastron. The outburst phase slowly recovered to peaking at about 2.5 days after periastron. We interpret this shift in orbital phase followed by a slow recovery as evidence of a global one-armed oscillation propagating in the Be disk. This is further supported by changes in the shape of the H? profile, which are commonly believed to be produced by a reconfiguration of the Be disk. The truncated viscous decretion disk model provides an explanation for the long series of normal outbursts and the evidence of an accretion disk in the brighter normal outbursts. Long-term multiwavelength observations such as these clearly add considerably to our knowledge of Be/X-ray binaries and the relationship among optical, infrared, and X-ray observations.
119206977
Magnetar Twists: Fermi/Gamma ray Burst Monitor (GBM) detection of SGR J1550-5418
SGRJ1550–5418 (previously known as AXP1E1547.0–5408 or PSRJ1550–5418) went into three active bursting episodes in 2008 October and in 2009 January and March, emitting hundreds of typical Soft Gamma Repeater (SGR) bursts in soft gamma-rays. The second episode was especially intense, and our untriggered burst search on Fermi/GBM data (8−1000 keV) revealed ∼450 bursts emitted over 24 hours during the peak of this activity. Using the GBM data, we identified a ∼150-s-long enhanced persistent emission during 2009 January 22 that exhibited intriguing timing and spectral properties: (i) clear pulsations up to ∼110 keV at the spin period of the neutron star (P ∼ 2.07 s, the fastest of all magnetars), (ii) an additional (to a powerlaw) blackbody component required for the enhanced emission spectra with Sabancı University, Orhanlı-Tuzla, İstanbul 34956, Turkey Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812, USA Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA Astronomical Institute Anton Pannekoek, University of Amsterdam, PO Box 94249, 1090 GE Amsterdam, The Netherlands Universities Space Research Associations, NSSTC, Huntsville, AL 35805, USA NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD, 21218, USA Max-Planck Institut für extraterrestrische Physik, 85748 Garching, Germany Spitzer Science Center/California Institute of Technology, Pasadena, CA 91125, USA Dynetics, Inc., 1000 Explorer Boulevard, Huntsville, AL 35806, USA
14656206
Long-Term Spectral and Timing Behavior of the Black Hole Candidate XTE J1908+094
We present the long-term X-ray light curves and detailed spectral and timing analyses of XTE J1908+094 using the Rossi X-Ray Timing Explorer Proportional Counter Array observations covering two outbursts in 2002 and early 2003. At the onset of the first outburst, the source was found in a spectrally low/hard state lasting for ~40 days, followed by a 3 day long transition to the high/soft state. The source flux (in 2-10 keV) reached ~100 mcrab on 2002 April 6, then decayed rapidly. In power spectra, we detect strong band-limited noise and varying low-frequency quasi-periodic oscillations that evolved from ~0.5 to ~5 Hz during the initial low/hard state of the source. We find that the second outburst closely resembled the spectral evolution of the first. The X-ray transient's overall outburst characteristics led us to classify XTE J1908+094 as a black hole candidate. Here we also derive precise X-ray position of the source using Chandra observations that were performed during the decay phase of the first outburst and following the second outburst.
6352171
Large Torque Variations in Two Soft Gamma Repeaters
We have monitored the pulse frequencies of the two soft gamma repeaters SGR 1806-20 and SGR 1900+14 through the beginning of year 2001 using primarily Rossi X-Ray Timing Explorer Proportional Counter Array observations. In both sources, we observe large changes in the spin-down torque up to a factor of ~4, which persist for several months. Using long-baseline phase-connected timing solutions as well as the overall frequency histories, we construct torque noise power spectra for each SGR. The power spectrum of each source is very red (power-law slope ~-3.5). The torque noise power levels are consistent with some accreting systems on timescales of ~1 yr, yet the full power spectrum is much steeper in frequency than any known accreting source. To the best of our knowledge, torque noise power spectra with a comparably steep frequency dependence have been seen only in young, glitching radio pulsars (e.g., Vela). The observed changes in spin-down rate do not correlate with burst activity; therefore, the physical mechanisms behind each phenomenon are also likely unrelated. Within the context of the magnetar model, seismic activity cannot account for both the bursts and the long-term torque changes unless the seismically active regions are decoupled from one another.
113172
On the Dramatic Spin-up/Spin-down Torque Reversals in Accreting Pulsars
Dramatic torque reversals between spin-up and spin-down have been observed in half of the persistent X-ray 
pulsars monitored by the BATSE all-sky monitor on the Compton Gamma Ray Observatory. Theoretical models 
developed to explain early pulsar timing data can explain spin-down torques via a disk-magnetosphere interaction 
if the star nearly corotates with the inner accretion disk. To produce the observed BATSE torque reversals, however, these equilibrium models require the disk to alternate between two mass accretion rates, with ˙M5 producing accretion torques of similar magnitude but always of opposite sign. Moreover, in at least one pulsar (GX 114) undergoing secular spin-down, the neutron star spins down faster during brief (~20 day) hard X-ray flares—this is opposite the correlation expected from standard theory, assuming that BATSE pulsed flux increases with mass accretion rate. The 10 day to 10 yr intervals between torque reversals in these systems are much longer than any characteristic magnetic or viscous timescale near the inner disk boundary and are more suggestive of a global disk phenomenon. 
 
We discuss possible explanations of the observed torque behavior. Despite the preferred sense of rotation defined by the binary orbit, the BATSE observations are urprisingly consistent with an earlier suggestion for GX 1+4: the disks in these systems somehow alternate between episodes of prograde and retrograde rotation. We are unaware of any mechanism that could produce a stable retrograde disk in a binary undergoing Roche lobe overflow, but such flip-flop behavior does occur in numerical simulations of wind-fed systems. One possibility is that the disks in some of these binaries are fed by an X-ray–excited wind.
28803633
Measurement of the Cross Section for High-$p_T$ Hadron Production in Scattering of 160 GeV/c Muons off Nucleons
The cross section for production of charged hadrons with high transversemomenta in scattering of 160 GeV/c muons off nucleons at low photonvirtualities has been measured at the COMPASS experiment at CERN. The results,which cover transverse momenta from 1.1 to 3.6 GeV/c, are compared to anext-to-leading order perturbative Quantum Chromodynamics (NLO pQCD)calculation in order to evaluate the applicability of pQCD to this process inthe kinematic domain of the experiment. The shape of the calculateddifferential cross section as a function of transverse momentum is found to bein good agreement with the experimental data, but the normalization isunderestimated by NLO pQCD. This discrepancy may point towards the relevance ofterms beyond NLO in the pQCD framework. The dependence of the cross section onthe pseudo-rapidity and on the charge of the hadrons is also discussed.
19221010
Search for signatures of extra dimensions in the diphoton mass spectrum at the large hadron collider.
A search for signatures of extra spatial dimensions in the diphoton invariant-mass spectrum has been performed with the CMS detector at the LHC. No excess of events above the standard model expectation is observed using a data sample collected in proton-proton collisions at √s=7 TeV corresponding to an integrated luminosity of 2.2 fb(-1). In the context of the large-extra-dimensions model, lower limits are set on the effective Planck scale in the range of 2.3-3.8 TeV at the 95% confidence level. These limits are the most restrictive bounds on virtual-graviton exchange to date. The most restrictive lower limits to date are also set on the mass of the first graviton excitation in the Randall-Sundrum model in the range of 0.86-1.84 TeV, for values of the associated coupling parameter between 0.01 and 0.10.
118837794
Observation of Z decays to four leptons with the CMS detector at the LHC
A bstractThe first observation of the Z boson decaying to four leptons in proton-proton collisions is presented. The analyzed data set corresponds to an integrated luminosity of 5.02 fb−1 at $ \sqrt{s}=7 $ TeV collected by the CMS detector at the Large Hadron Collider. A pronounced resonance peak, with a statistical significance of 9.7 σ, is observed in the distribution of the invariant mass of four leptons (electrons and/or muons) with mass and width consistent with expectations for Z boson decays. The branching fraction and cross section reported here are defined by phase space restrictions on the leptons, namely, 80 < m4ℓ < 100 GeV, where m4ℓ is the invariant mass of the four leptons, and mℓℓ > 4 GeV for all pairs of leptons, where mℓℓ is the two-lepton invariant mass. The measured branching fraction is $ \mathcal{B}\left( {Z\to 4\ell } \right)=\left( {4.2_{-0.8}^{+0.9}\left( {\mathrm{stat}.} \right)\pm 0.2\left( {\mathrm{syst}.} \right)} \right)\times {10^{-6 }} $ and agrees with the standard model prediction of 4.45 × 10−6. The measured cross section times branching fraction is $ \sigma \left( {\mathrm{pp}\to \mathrm{Z}} \right)\mathcal{B}\left( {\mathrm{Z}\to 4\ell } \right)=112_{-20}^{+23}\left( {\mathrm{stat}.} \right)_{-5}^{+7}\left( {\mathrm{syst}.} \right)_{-2}^{+3}\left( {\mathrm{lumi}.} \right) $ fb, also consistent with the standard model prediction of 120 fb. The four-lepton mass peak arising from Z → 4ℓ decays provides a calibration channel for the Higgs boson search in the H → ZZ → 4ℓ decay mode.
119116907
Studies of jet mass in dijet and W/Z + jet events
A bstract
 Invariant mass spectra for jets reconstructed using the anti-kT and CambridgeAachen algorithms are studied for different jet “grooming” techniques in data corresponding to an integrated luminosity of 5 fb−1, recorded with the CMS detector in proton-proton collisions at the LHC at a center-of-mass energy of 7 TeV. Leading-order QCD predictions for inclusive dijet and W/Z+jet production combined with parton-shower Monte Carlo models are found to agree overall with the data, and the agreement improves with the implementation of jet grooming methods used to distinguish merged jets of large transverse momentum from softer QCD gluon radiation.
122803232
Search for Microscopic Black Hole Signatures at the Large Hadron Collider
A search for microscopic black hole production and decay in pp collisions at a center-of-mass energy of 7 TeV has been conducted by the CMS Collaboration at the LHC, using a data sample corresponding to an integrated luminosity of 35 inverse picobarns. Events with large total transverse energy are analyzed for the presence of multiple high-energy jets, leptons, and photons, typical of a signal expected from a microscopic black hole. Good agreement with the expected standard model backgrounds, dominated by QCD multijet production, is observed for various final-state multiplicities. Limits on the minimum black hole mass are set, in the range 3.5 -- 4.5 TeV, for a variety of parameters in a model with large extra dimensions, along with model-independent limits on new physics in these final states. These are the first direct limits on black hole production at a particle accelerator.