119160740
GAMMA-RAY OBSERVATIONS OF THE Be/PULSAR BINARY 1A 0535+262 DURING A GIANT X-RAY OUTBURST
Giant X-ray outbursts, with luminosities of about 10(37) erg s(-1), are observed roughly every five years from the nearby Be/pulsar binary 1A 0535+262. In this article, we present observations of the source with VERITAS at very high energies (VHEs; E > 100 GeV) triggered by the X-ray outburst in 2009 December. The observations started shortly after the onset of the outburst and provided comprehensive coverage of the episode, as well as the 111 day binary orbit. No VHE emission is evident at any time. We also examined data from the contemporaneous observations of 1A 0535+262 with the Fermi/Large Area Telescope at high-energy photons (E > 0.1 GeV) and failed to detect the source at GeV energies. The X-ray continua measured with the Swift/X-Ray Telescope and the RXTE/PCA can be well described by the combination of blackbody and Comptonized emission from thermal electrons. Therefore, the gamma-ray and X-ray observations suggest the absence of a significant population of non-thermal particles in the system. This distinguishes 1A 0535+262 from those Be X-ray binaries (such as PSR B1259-63 and LS I +61 degrees 303) that have been detected at GeV-TeV energies. We discuss the implications of the results on theoretical models.
125665211
Branching fractions in $B \to \phi$ h and search for direct CP violation in $B^\pm \to \phi K^\pm$
29318124
Discovery of Variability in the Very High Energy γ-Ray Emission of 1ES 1218+304 with VERITAS
We present results from an intensive VERITAS monitoring campaign of the high-frequency peaked BL Lac object 1ES 1218+304 in 2008/2009. Although 1ES 1218+304 was detected previously by MAGIC and VERITAS at a persistent level of ~6% of the Crab Nebula flux, the new VERITAS data reveal a prominent flare reaching ~20% of the Crab. While very high energy (VHE) flares are quite common in many nearby blazars, the case of 1ES 1218+304 (redshift z = 0.182) is particularly interesting since it belongs to a group of blazars that exhibit unusually hard VHE spectra considering their redshifts. When correcting the measured spectra for absorption by the extragalactic background light, 1ES 1218+304 and a number of other blazars are found to have differential photon indices Γ≤ 1.5. The difficulty in modeling these hard spectral energy distributions in blazar jets has led to a range of theoretical γ-ray emission scenarios, one of which is strongly constrained by these new VERITAS observations. We consider the implications of the observed light curve of 1ES 1218+304, which shows day scale flux variations, for shock acceleration scenarios in relativistic jets, and in particular for the viability of kiloparsec-scale jet emission scenarios.
17001801
Observation of Extended VHE Emission from the Supernova Remnant IC 443 with VERITAS
We present evidence that the very-high-energy (VHE, E > 100 GeV) gamma-ray emission coincident with the supernova remnant IC 443 is extended. IC 443 contains one of the best-studied sites of supernova remnant/molecular cloud interaction and the pulsar wind nebula CXOU J061705.3+222127, both of which are important targets for VHE observations. VERITAS observed IC 443 for 37.9 hours during 2007 and detected emission above 300 GeV with an excess of 247 events, resulting in a significance of 8.3 standard deviations (sigma) before trials and 7.5 sigma after trials in a point-source search. The emission is centered at 06 16 51 +22 30 11 (J2000) +- 0.03_stat +- 0.08_sys degrees, with an intrinsic extension of 0.16 +- 0.03_stat +- 0.04_sys degrees. The VHE spectrum is well fit by a power law (dN/dE = N_0 * (E/TeV)^-Gamma) with a photon index of 2.99 +- 0.38_stat +- 0.3_sys and an integral flux above 300 GeV of (4.63 +- 0.90_stat +- 0.93_sys) * 10^-12 cm^-2 s^-1. These results are discussed in the context of existing models for gamma-ray production in IC 443.
18988438
VERITAS Discovery of >200 GeV Gamma-Ray Emission from the Intermediate-Frequency-Peaked BL Lacertae Object W Comae
We report the detection of very high-energy -ray emission from the intermediate-frequencypeaked BLLacertae object WComae (z = 0.102) by VERITAS, an array of four imaging atmospheric-Cherenkov telescopes. The source was observed between January and April 2008. A strong outburst of -ray emission was measured in the middle of March, lasting for only four days. The energy spectrum measured during the two highest flare nights is fit by a power-law and is found to be very steep, with a differential photon spectral index of = 3 .81±0.35stat±0.34syst. The integral photon flux above 200GeV during those two nights corresponds to roughly 9% of the flux from the Crab Nebula. Quasi-simultaneous Swift observations at X-ray energies were triggered by the VERITAS observations. The spectral energy distribution of the flare data can be described by synchrotron-self-Compton (SSC) or external-Compton (EC) leptonic jet models, with the latter offering a more natural set of parameters to fit the data.
120882870
Veritas: Status summary 2009
VERITAS is a ground-based gamma-ray observatory that uses the imaging atmospheric Cherenkov technique and operates in the very-high energy (VHE) region of the gamma-ray spectrum from 100 GeV to 50 TeV. The observatory consists of an array of four 12 m-diameter imaging atmospheric Cherenkov telescopes located in southern Arizona, USA. The four-telescope array has been fully operational since September 2007, and over the last two years, VERITAS has been operating with high reliability and sensitivity. It is currently one of the most sensitive VHE observatories. This paper summarizes the status of VERITAS as of October 2009, and describes the detection of several new VHE gamma-ray sources.
12344241
A quantum-enhanced prototype gravitational-wave detector
The quantum nature of the electromagnetic field imposes a fundamental limit on the sensitivity of optical precision measurements such as spectroscopy, microscopy and interferometry. The so-called quantum limit is set by the zero-point fluctuations of the electromagnetic field, which constrain the precision with which optical signals can be measured. In the world of precision measurement, laser-interferometric gravitational-wave detectors, are the most sensitive position meters ever operated, capable of measuring distance changes of the order of 10- 18 m r.m.s. over kilometre separations caused by gravitational waves from astronomical sources. The sensitivity of currently operational and future gravitational-wave detectors is limited by quantum optical noise. Here, we demonstrate a 44% improvement in displacement sensitivity of a prototype gravitational-wave detector with suspended quasi-free mirrors at frequencies where the sensitivity is shot-noise-limited, by injecting a squeezed state of light. This demonstration is a critical step towards implementation of squeezing-enhancement in large-scale gravitational-wave detectors.
123430113
Study of flavor-tagged baryon production in B decay
R. Ammar, 1 P. Baringer, 1 A. Bean, 1 D. Besson, 1 D. Coppage, 1 N. Copty, 1 R. Davis, 1 N. Hancock, 1 S. Kotov, 1 I. Kravchenko, 1 N. Kwak, 1 Y. Kubota, 2 M. Lattery, 2 J. K. Nelson, 2 S. Patton, 2 R. Poling, 2 T. Riehle, 2 V. Savinov, 2 R. Wang, 2 M. S. Alam, 3 I. J. Kim, 3 Z. Ling, 3 A. H. Mahmood, 3 J. J. O’Neill, 3 H. Severini, 3 C. R. Sun, 3 S. Timm, 3 F. Wappler, 3 G. Crawford, 4 J. E. Duboscq, 4 R. Fulton, 4 D. Fujino, 4 K. K. Gan, 4 K. Honscheid, 4 H. Kagan, 4 R. Kass, 4 J. Lee, 4 M. Sung, 4 C. White, 4 R. Wanke, 4 A. Wolf, 4 M. M. Zoeller, 4 X. Fu, 5 B. Nemati, 5 W. R. Ross, 5 P. Skubic, 5 M. Wood, 5 M. Bishai, 6 J. Fast, 6 E. Gerndt, 6 J. W. Hinson, 6 T. Miao, 6 D. H. Miller, 6 M. Modesitt, 6 E. I. Shibata, 6 I. P. J. Shipsey, 6 P. N. Wang, 6 L. Gibbons, 7 S. D. Johnson, 7 Y. Kwon, 7 S. Roberts, 7 E. H. Thorndike, 7 T. E. Coan, 8 J. Dominick, 8 V. Fadeyev, 8 I. Korolkov, 8 M. Lambrecht, 8 S. Sanghera, 8 V. Shelkov, 8 R. Stroynowski, 8 I. Volobouev, 8 G. Wei, 8 M. Artuso, 9 M. Gao, 9 M. Goldberg, 9 D. He, 9 N. Horwitz, 9 S. Kopp, 9 G. C. Moneti, 9 R. Mountain, 9 F. Muheim, 9 Y. Mukhin, 9 S. Playfer, 9 T. Skwarnicki, 9 S. Stone, 9 X. Xing, 9 J. Bartelt, 10 S. E. Csorna, 10 V. Jain, 10 S. Marka, 10 D. Gibaut, 11 K. Kinoshita, 11 P. Pomianowski, 11 S. Schrenk, 11 B. Barish, 12 M. Chadha, 12 S. Chan, 12 D. F. Cowen, 12 G. Eigen, 12 J. S. Miller, 12 C. O’Grady, 12 J. Urheim, 12 A. J. Weinstein, 12 F. Wurthwein, 12 D. M. Asner, 13 M. Athanas, 13 D. W. Bliss, 13 W. S. Brower, 13 G. Masek, 13 H. P. Paar, 13 J. Gronberg, 14 C. M. Korte, 14 R. Kutschke, 14 S. Menary, 14 R. J. Morrison, 14 S. Nakanishi, 14 H. N. Nelson, 14 T. K. Nelson, 14 C. Qiao, 14 J. D. Richman, 14 D. Roberts, 14 A. Ryd, 14 H. Tajima, 14 M. S. Witherell, 14 R. Balest, 15 K. Cho, 15 W. T. Ford, 15 M. Lohner, 15 H. Park, 15 P. Rankin, 15 J. Roy, 15 J. G. Smith, 15 J. P. Alexander, 16 C. Bebek, 16 B. E. Berger, 16 K. Berkelman, 16 K. Bloom, 16 T. E. Browder, 16,* D. G. Cassel, 16 H. A. Cho, 16 D. M. Coffman, 16 D. S. Crowcroft, 16 M. Dickson, 16 P. S. Drell, 16 D. J. Dumas, 16 R. Ehrlich, 16 R. Elia, 16 P. Gaidarev, 16 B. Gittelman, 16 S. W. Gray, 16 D. L. Hartill, 16 B. K. Heltsley, 16 S. Henderson, 16 C. D. Jones, 16 S. L. Jones, 16 J. Kandaswamy, 16 N. Katayama, 16 P. C. Kim, 16 D. L. Kreinick, 16 T. Lee, 16 Y. Liu, 16 G. S. Ludwig, 16 J. Masui, 16 J. Mevissen, 16 N. B. Mistry, 16 C. R. Ng, 16 E. Nordberg, 16 J. R. Patterson, 16 D. Peterson, 16 D. Riley, 16 A. Soffer, 16 C. Ward, 16 P. Avery, 17 A. Freyberger, 17 K. Lingel, 17 C. Prescott, 17 J. Rodriguez, 17 S. Yang, 17 J. Yelton, 17 G. Brandenburg, 18 D. Cinabro, 18 T. Liu, 18 M. Saulnier, 18 R. Wilson, 18 H. Yamamoto, 18 T. Bergfeld, 19 B. I. Eisenstein, 19 J. Ernst, 19 G. E. Gladding, 19 G. D. Gollin, 19 M. Palmer, 19 M. Selen, 19 J. J. Thaler, 19 K. W. Edwards, 20 K. W. McLean, 20 M. Ogg, 20 A. Bellerive, 21 D. I. Britton, 21 E. R. F. Hyatt, 21 R. Janicek, 21 D. B. MacFarlane, 21 P. M. Patel, 21 B. Spaan, 21 and A. J. Sadoff 22 ~CLEO Collaboration!
15494223
Implications For The Origin Of GRB 051103 From LIGO Observations
We present the results of a LIGO search for gravitational waves (GWs) associated with GRB 051103, a short-duration hard-spectrum gamma-ray burst (GRB) whose electromagnetically determined sky position is coincident with the spiral galaxy M81, which is 3.6 Mpc from Earth. Possible progenitors for short-hard GRBs include compact object mergers and soft gamma repeater (SGR) giant flares. A merger progenitor would produce a characteristic GW signal that should be detectable at a distance of M81, while GW emission from an SGR is not expected to be detectable at that distance. We found no evidence of a GW signal associated with GRB 051103. Assuming weakly beamed γ-ray emission with a jet semi-angle of 30°, we exclude a binary neutron star merger in M81 as the progenitor with a confidence of 98%. Neutron star-black hole mergers are excluded with >99% confidence. If the event occurred in M81, then our findings support the hypothesis that GRB 051103 was due to an SGR giant flare, making it one of the most distant extragalactic magnetars observed to date.
11210560
Search for gravitational waves associated with 39 gamma-ray bursts using data from the second, third, and fourth LIGO runs
We present the results of a search for short-duration gravitational-wave bursts associated with 39 gamma-ray bursts (GRBs) detected by gamma-ray satellite experiments during LIGO’s S2, S3, and S4 science runs. The search involves calculating the crosscorrelation between two interferometer data streams surrounding the GRB trigger time. We search for associated gravitational radiation from single GRBs, and also apply statistical tests to search for a gravitational-wave signature associated with the whole sample. For the sample examined, we find no evidence for the association of gravitational radiation with GRBs, either on a single-GRB basis or on a statistical basis. Simulating gravitational-wave bursts with sine-Gaussian waveforms, we set upper limits on the root-sum-square of the gravitational-wave strain amplitude of such waveforms at the times of the GRB triggers. We also demonstrate how a sample of several GRBs can be used collectively to set constraints on population models. The small number of GRBs and the significant change in sensitivity of the detectors over the three runs, however, limits the usefulness of a population study for the S2, S3, and S4 runs. Finally, we discuss prospects for the search sensitivity for the ongoing S5 run, and beyond for the next generation of detectors.
27328226
Lock Acquisition Scheme For The Advanced LIGO Optical configuration
The lock acquisition scheme for the Advanced LIGO optical configuration, which makes use of "resonant sideband extraction", is under investigation in the 40 meter prototype interferometer at Caltech. The 40m has a similar optical configuration to the one planned for Advanced LIGO which has 5 degrees of freedom for length control. So far we have succeeded in locking the 5 degrees of freedom routinely. The differential mode of arm cavities was locked in the same state as the final setup, and the peak of optical resonance was verified to be around 4 kHz. Currently, since an offset remains in the common mode of the arm cavities, another optical resonance can be seen in common mode optical gain.