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Posts: 131433
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RE: SNR CTA 1
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Title: Discovery of TeV Gamma-ray Emission from CTA 1 by VERITAS
Authors: E. Aliu, S. Archambault, T. Arlen, T. Aune, M. Beilicke, W. Benbow, A. Bouvier, J. H. Buckley, V. Bugaev, A. Cesarini, L. Ciupik, E. Collins-Hughes, M. P. Connolly, W. Cui, R. Dickherber, C. Duke, J. Dumm, V. V. Dwarkadas, M. Errando, A. Falcone, S. Federici, Q. Feng, J. P. Finley, G. Finnegan, L. Fortson, A. Furniss, N. Galante, D. Gall, G. H. Gillanders, S. Godambe, E. V. Gotthelf, S. Griffin, J. Grube, G. Gyuk, D. Hanna, J. Holder, G. Hughes, T. B. Humensky, P. Kaaret, O. Kargaltsev, N. Karlsson, Y. Khassen, D. Kieda, H. Krawczynski, F. Krennrich, M. J. Lang, K. Lee, A. S Madhavan, G. Maier, P. Majumdar, S. McArthur, A. McCann, P. Moriarty, R. Mukherjee, T. Nelson, A. O'Faolain de Bhroithe, R. A. Ong, M. Orr, A. N. Otte, N. Park, J. S. Perkins, M. Pohl, H. Prokoph, J. Quinn, K. Ragan, et al. (26 additional authors not shown)

We report the discovery of TeV gamma-ray emission coincident with the shell-type radio supernova remnant (SNR) CTA 1 using the VERITAS gamma-ray observatory. The source, VER J0006+729, was detected as a 6.5 standard deviation excess over background and shows an extended morphology, approximated by a two-dimensional Gaussian of semi-major (semi-minor) axis 0.30 degree (0.24 degree) and a centroid 5' from the Fermi gamma-ray pulsar PSR J0007+7303 and its X-ray pulsar wind nebula (PWN). The photon spectrum is well described by a power-law dN/dE = N_0 (E/3 TeV)^(-\Gamma), with a differential spectral index of \Gamma = 2.2 0.2_stat 0.3_sys, and normalisation N_0 = (9.1 1.3_stat 1.7_sys) x 10^(-14) cm^(-2) s^(-1) TeV^(-1). The integral flux, F_\gamma = 4.0 x 10^(-12) erg cm^(-2) s^(-1) above 1 TeV, corresponds to 0.2% of the pulsar spin-down power at 1.4 kpc. The energetics, co-location with the SNR, and the relatively small extent of the TeV emission strongly argue for the PWN origin of the TeV photons. We consider the origin of the TeV emission in CTA 1.

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Posts: 131433
Date:
CTA 1
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Title: VERITAS Observation of CTA1
Authors: Nahee Park, for the VERITAS Collaboration

CTA 1 (G119.5+10.2) is a composite supernova remnant (SNR) with a shell-type structure, visible in the radio band, surrounding a smaller pulsar wind nebula. Fermi detected a radio-quiet pulsar PSR J0007+7303 within the radio shell. 26.5 hours of VERITAS observation revealed extended TeV emission from CTA 1. The centroid of the TeV emission is located near the Fermi pulsar. The integral flux of the emission was ~4% of the Crab Nebula flux (>1TeV). We present an update on the source analysis with additional exposure and possible interpretations.

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Posts: 131433
Date:
G119.5+10.2
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Title: Investigation of CTA 1 with Suzaku Observation
Authors: Lupin C. C. Lin, Jumpei Takata, Albert K. H. Kong, C. Y. Hui, Teruaki Enoto, H. K. Chang, Regina H. H. Huang, J. S. Liang, Shinpei Shibata, C. Y. Hwang

We report on an 105 ks Suzaku observation of the supernova remnant CTA 1 (G119.5+10.2). The Suzaku soft X-ray observation was carried out with both timing mode and imaging mode. A ~ 10' extended feature, which is interpreted as a bow-shock component of the pulsar wind nebula (PWN), is revealed in this deep observation for the first time. The nebular spectrum can be modelled by a power-law with a photon index of ~ 1.8 which suggests a slow synchrotron cooling scenario. The photon index is approximately constant across this extended feature. We compare and discuss our observations of this complex nebula with previous X-ray investigations. We do not obtain any significant pulsation from the central pulsar in the soft (0.2-12 keV) and hard (10-60 keV) X-ray data. The non-detection is mainly due to the loss of the precise imaging ability to accurately determine the source contribution. The spectra of XIS and HXD can be directly connected without a significant spectral break according to our analysis. Future observations of NuSTAR and Astro-H would be able to resolve the contamination and provide an accurate hard X-ray measurement of CTA 1.

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Posts: 131433
Date:
MGRO J2019+37 and MGRO J2031+41
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Title: Spectrum and Morphology of the Two Brightest Milagro Sources in the Cygnus Region: MGRO J2019+37 and MGRO J2031+41
Authors: A. A. Abdo, B. T. Allen, T. Aune, D. Berley, E. Bonamente, G. E. Christopher, T. DeYoung, B. L. Dingus, R. W. Ellsworth, J. G. Galbraith-Frew, M. M. Gonzalez, J. A. Goodman, C. M. Hoffman, P. H. Huentemeyer, B. E. Kolterman, J. T. Linnemann, J. E. McEnery, A. I. Mincer, T. Morgan, P. Nemethy, J. Pretz, J. M. Ryan, P. M. Saz Parkinson, G. Sinnis, A. J. Smith, V. Vasileiou, G. P. Walker, D. A. Williams, G. B. Yodh

The Cygnus region is a very bright and complex portion of the TeV sky, host to unidentified sources and a diffuse excess with respect to conventional cosmic-ray propagation models. Two of the brightest TeV sources, MGRO J2019+37 and MGRO J2031+41, are analysed using Milagro data with a new technique, and their emission is tested under two different spectral assumptions: a power law and a power law with an exponential cutoff. The new analysis technique is based on an energy estimator that uses the fraction of photomultiplier tubes in the observatory that detect the extensive air shower. The photon spectrum is measured in the range 1 to 200 TeV using the last 3 years of Milagro data (2005-2008), with the detector in its final configuration. MGRO J2019+37 is detected with a significance of 12.3 standard deviations (\sigma), and is better fit by a power law with an exponential cutoff than by a simple power law, with a probability >98% (F-test). The best-fitting parameters for the power law with exponential cutoff model are a normalisation at 10 TeV of 7^{+5}_{-2} x 10^{-10} \mathrm{s^{-1}\: m^{-2}\: TeV^{-1}}, a spectral index of 2.0^{+0.5}_{-1.0} and a cutoff energy of 29^{+50}_{-16} TeV. MGRO J2031+41 is detected with a significance of 7.3\sigma, with no evidence of a cutoff. The best-fitting parameters for a power law are a normalisation of 2.4^{+0.6}_{-0.5} x 10^{-10} \mathrm{s^{-1}\: m^{-2}\: TeV^{-1}} and a spectral index of 3.08^{+0.19}_{-0.17}. The overall flux is subject to an ~30% systematic uncertainty. The systematic uncertainty on the power law indices is ~0.1. A comparison with previous results from TeV J2032+4130, MGRO J2031+41 and MGRO J2019+37 is also presented.

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Posts: 131433
Date:
SNR CTB 37
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Title: Distances of the TeV SNR complex CTB 37 towards the Galactic Bar
Authors: Wenwu Tian, Denis Leahy

Three supernova remnants form the CTB 37 complex: CTB 37A (G348.5+0.1, associated with the TeV gamma-ray source HESS J1714-385), CTB 37B (G348.7+0.3, associated with HESS J1713-381 and the magnetar CXOU J171405.7.381031), and G348.5-0.0. We use 21 cm HI absorption measurements to constrain the kinematic distances to these SNRs, which have not previously been determined well. We revise the kinematic distance for CTB 37A to be in the range 6.3 to 9.5 kpc (previously ~11.3 kpc) because it is beyond the near 3-kpc arm and in front of the far side of the CO cloud at -145 km s^{-1} towards l=348.5. G348.5-0.0 has a HI column density (N_{HI} ~6.1 x 10^{21} cm^{-2}) lower than CTB 37A (~7.1 x 10^{21} cm^{-2}). Also, G348.5-0.0 does not have the major absorption feature at -107 km s^{-1} that CTB 37A shows. This is caused by the near 3-kpc arm, so G348.5-0.0 is at a distance of \le 6.3 kpc. CTB 37B is at a distance of ~13.2 kpc (previously 5 to 9 kpc) based on: 1) it has an absorption feature at -105 km s^{-1} from the far 3-kpc arm, so CTB 37B is behind it; 2) there is absorption at -30 km s^{-1} but not at -26 km s^{-1}, which yields the distance value; 3) the HI column density towards CTB 37B (~8.3 x 10^{21} cm^{-2}) is larger than CTB 37A. In summary, CTB 37A, CTB 37B and G348.5+0.0 are all at different distances and are only by chance nearby each other on the sky. In addition, we conclude that CTB 37 A and B are not associated with the historical Supernova AD 393.

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Posts: 131433
Date:
Cygnus OB1 region
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Title: Observations of SNR CTA 1 and the Cyg OB1 region with VERITAS
Authors: Ester Aliu

The Cygnus region is a nearby very active star forming region, containing several OB associations, considered as tracers of young pulsars. Above 12 TeV, the Milagro Collaboration has reported the discovery of a very large source, MGRO J2019+37, lying towards the Cyg OB1 association, at the edge of the Cygnus region. The young and energetic pulsar PSR J2021+3651 has been proposed to power this emission. We present here the result of deep VERITAS observations of this region at energies above 650 GeV. These observations unveil extended and complex TeV emission compatible with MGRO J2019+37, likely made of multiple sources, and a clearly separated point source emission from the direction of CTB 87, a pulsar wind nebula candidate. We will also report on the detection of TeV emission from the young Galactic SNR CTA 1, likely powered by the first pulsar discovered through its gamma-ray radiation.

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Posts: 131433
Date:
SNR CTA 1
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Scientists were putting a new space telescope through its paces when they found something odd -- a pulsating star, or pulsar, beaming only in gamma rays.
The discovery, published in this week's issue of Science, is the first finding from NASA's Fermi Gamma Ray Space Telescope, which was launched in June. It solves a mystery uncovered by a predecessor telescope and offers an explanation to a host of similar unexplained phenomena.
The pulsar detected by Fermi is associated with a supernova remnant known as CTA 1, the remains of a massive star in the Milky Way galaxy that exploded about 10,000 years ago. It is located about 4,600 light-years away in the constellation Cepheus.
Typically, supernova remains include the dead star's collapsed core -- known as a neutron star because its protons and electrons have combined to form neutrons.

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