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Register a new userPhase-resolved energy spectra of the Crab Pulsar in the range of 50-400 GeV measured with the MAGIC Telescopes
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MAGIC Collaboration: J. Aleksic
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We use 73 h of stereoscopic data taken with the MAGIC telescopes to investigate the very high-energy (VHE) gamma-ray emission of the Crab pulsar. Our data show a highly significant pulsed signal in the energy range from 50 to 400 GeV in both the main pulse (P1) and the interpulse (P2) phase regions. We provide the widest spectra to date of the VHE components of both peaks, and these spectra extend to the energy range of satellite-borne observatories. The good resolution and background rejection of the stereoscopic MAGIC system allows us to cross-check the correctness of each spectral point of the pulsar by comparison with the corresponding (strong and well-known) Crab nebula flux. The spectra of both P1 and P2 are compatible with power laws with photon indices of 4.0 pm 0.8 (P1) and 3.42 pm 0.26 (P2), respectively, and the ratio P1/P2 between the photon counts of the two pulses is 0.54 pm 0.12. The VHE emission can be understood as an additional component produced by the inverse Compton scattering of secondary and tertiary epm pairs on IR-UV photons.
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The Crab pulsar is the only astronomical pulsed source detected at very high energy (VHE, E>100GeV) gamma-rays. The emission mechanism of VHE pulsation is not yet fully understood, although several theoretical models have been proposed. In order to test the new models, we measured the light curve and the spectra of the Crab pulsar with high precision by means of deep observations. We analyzed 135 hours of selected MAGIC data taken between 2009 and 2013 in stereoscopic mode. In order to discuss the spectral shape in connection with lower energies, 4.6 years of {it Fermi}-LAT data were also analyzed. The known two pulses per period were detected with a significance of $8.0 sigma$ and $12.6 sigma$. In addition, significant emission was found between the two pulses with $6.2 sigma$. We discovered the bridge emission above 50 GeV between the two main pulses. This emission can not be explained with the existing theories. These data can be used for testing new theoretical models.
We report on the observations of the Crab pulsar with the MAGIC telesopes. Data were taken both in the mono-mode ($>25$ GeV) and in the stereo-mode ($>50$ GeV). Clear signals from the two peaks were detected with both modes and the phase resolved energy spectra were calculated. By comparing with the measurements done by Fermi-LAT, we found that the energy spectra of the Crab pulsar does not follow a power law with an exponential cutoff, but that it extends as a power law after the break at around 5 GeV. This suggests that the emission above 25 GeV is not dominated by the curvatura radiation, which is inconsistent with the standard prediction of the OG and SG models.
The Crab pulsar is the only astronomical pulsed source detected above 100 GeV. The emission mechanism of very high energy gamma-ray pulsation is not yet fully understood, although several theoretical models have been proposed. In order to test the new models, we measured the light curve and the spectra of the Crab pulsar with high precision by means of deep observations. We analyzed 135 hours of selected MAGIC data taken between 2009 and 2013 in stereoscopic mode. In order to discuss the spectral shape in connection with lower energies, 4.6 years of Fermi-LAT data were also analyzed. The known two pulses per period were detected with a significance of 8.0 sigma and 12.6 sigma. In addition, significant bridge emission was found between the two pulses with 6.2 sigma. This emission can not be explained with the existing theories. These data can be used for testing new theoretical models.
The MAGIC stereoscopic system collected 69 hours of Crab Nebula data between October 2009 and April 2011. Analysis of this data sample using the latest improvements in the MAGIC stereoscopic software provided an unprecedented precision of spectral and night-by-night light curve determination at gamma rays. We derived a differential spectrum with a single instrument from 50 GeV up to almost 30 TeV with 5 bins per energy decade. At low energies, MAGIC results, combined with Fermi-LAT data, show a flat and broad Inverse Compton peak. The overall fit to the data between 1 GeV and 30 TeV is not well described by a log-parabola function. We find that a modified log-parabola function with an exponent of 2.5 instead of 2 provides a good description of the data ($chi^2=35/26$). Using systematic uncertainties of red the MAGIC and Fermi-LAT measurements we determine the position of the Inverse Compton peak to be at (53 $pm$ 3stat + 31syst -13syst) GeV, which is the most precise estimation up to date and is dominated by the systematic effects. There is no hint of the integral flux variability on daily scales at energies above 300 GeV when systematic uncertainties are included in the flux measurement. We consider three state- of-the-art theoretical models to describe the overall spectral energy distribution of the Crab Nebula. The constant B-field model cannot satisfactorily reproduce the VHE spectral measurements presented in this work, having particular difficulty reproducing the broadness of the observed IC peak. Most probably this implies that the assumption of the homogeneity of the magnetic field inside the nebula is incorrect. On the other hand, the time-dependent 1D spectral model provides a good fit of the new VHE results when considering a 80 {mu}G magnetic field. However, it fails to match the data when including the morphology of the nebula at lower wavelengths.
Context{The high energy emission regions of rotation powered pulsars are studied using folded light curve (FLCs) and phase resolved spectra (PRS).} aims{This work uses the NICER observatory to obtain the highest resolution FLC and PRS of the Crab pulsar at soft X-ray energies.} methods{NICER has accumulated about 347 ksec of data on the Crab pulsar. The data are processed using the standard analysis pipeline. Stringent filtering is done for spectral analysis. The individual detectors are calibrated in terms of long time light curve (LTLC), raw spectrum and deadtime. The arrival times of the photons are referred to the solar systems barycenter and the rotation frequency $ u$ and its time derivative $dot u$ are used to derive the rotation phase of each photon.} results{The LTLCs, raw spectra and deadtimes of the individual detectors are statistically similar; the latter two show no evolution with epoch; detector deadtime is independent of photon energy. The deadtime for the Crab pulsar, taking into account the two types of deadtime, is only approx 7% to 8% larger than that obtained using the cleaned events. Detector 00 behaves slightly differently from the rest, but can be used for spectral work. The PRS of the two peaks of the Crab pulsar are obtained at a resolution of better than 1/512 in rotation phase. The FLC very close to the first peak rises slowly and falls faster. The spectral index of the PRS is almost constant very close to the first peak.} conclusions{The high resolution FLC and PRS of the {{peaks}} of the Crab pulsar provide important constraints for the formation of caustics in the emission zone.}
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