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Observation Date (UT) Observation Lat

Canonical Name:Crab
TeVCat Name:TeV J0534+220
Other Names:G184.6−5.8, 3C144, SN1054
2HWC J0534+220
eHWC J0534+220
LHAASO J0534+2202
Source Type:PWN
R.A.:05 34 30.9 (hh mm ss)
Dec.:+22 00 44.5 (dd mm ss)
Gal Long: 184.56 (deg)
Gal Lat: -5.79 (deg)
Distance: 2 kpc
Flux:1 (Crab Units)
Energy Threshold:700 GeV
Spectral Index:2.5
Extended:Yes
Size (X):0.01 (deg)
Size (Y):0.01 (deg)
Discovery Date:1989-07
Discovered By: Whipple
Green's Catalog:Link
TeVCat SubCat:Default Catalog

Source Notes:

Source position and its uncertainty:

From H.E.S.S. Collaboration (2019):
This is the position reported in TeVCat. - R.A. (J2000): 05h 34m 30.9s +/- 0.1s (stat) +/- 1.3s (sys)
- Dec. (J2000): +22d 00' 44.5'' +/- 1.1'' (stat) +/- 20'' (sys)
- "... which is within uncertainties compatible with the Crab pulsar location"

From Holler et al. for the H.E.S.S. Collaboration (2017):
- R.A. (J2000): 05h 34m 30.9s +/- 1.2s (stat) +/- 20s (sys)
- Dec. (J2000): +22d 00' 44.5'' +/- 1.1'' (stat) +/- 20'' (sys)
- "at a distance of 16.8'' from, and within uncertainties compatible
with, the Crab pulsar location."

From Aharonian et al. (2004):
- R.A. (J2000): 05h 34m 31.1s +/- 0.2s(stat) +/- 1.8s(sys)
- Dec. (J2000): +22d 00' 52" +/- 3"(stat) +/- 25" (syst)
- This position is shifted by 12.4" +/- 3.1"(stat) +/- 25"(syst) to the west of the
nominal position of the pulsar (RA: 05h 34m 31.97s, Dec. 22d 00' 52.1"; J2000)

Emission components:

In addition to this steady gamma-ray emission from the nebula,
a pulsed component at lower energies has also been
detected Aliu et al. (2008), Otte et al. (2011), Saito (2011)

The Crab was included in the list of sources from wich ultra-high energy photons were detected
by LHAASO:
From Cao et al. (2021):
- "At 100 TeV, the angular and energy resolutions are about 15–20 arcmin
and better than 20%, respectively, allowing adequate spectroscopic and
morphological studies."
- "The statistical significance of the detection above 100 TeV is calculated
using a 0.3deg extension template"
- "Crab Units (CU), flux of the Crab Nebula at 100 TeV; 1 CU = 6.1 x 10-17 photons TeV-1 cm-2 s-1)"
- Significance above 100 TeV: 17.8 sigma
- E_max (PeV): 0.88 +/- 0.11
- On-source events/Off-source events: 67/5.5
- Exposure (hr): 2236.4

- "An energy spectrum approaching 1 PeV provides the first
model-independent evidence that the Crab Nebula operates as an
electron PeVatron. In KM2A, Crab is detected as a point-like source."

Source Extent:

From H.E.S.S. Collaboration (2019):
Details of the extended nature of the Crab Nebula emission at TeV
energies are presented:
- "Here we report that the Crab nebula has an angular extension at
gamma-ray energies of 52 arcseconds (assuming a Gaussian source
width), significantly larger than at X-ray energies."
- "The comparison of data to simulations reveals that the nebula is
extended. We can reproduce the data only by simulating an extended
source. We do this by convolving the angular resolution function with
a two-dimensional Gaussian with a best-fit value of:
52.2'' +/- 2.9''(stat) +/- 6.6''(sys)
The systematic uncertainty is related to the calibration and analysis
method, to the spectral shape used to simulate the angular resolution,
and to the fit method."
- "We therefore conclude that we measure the Crab nebula as a
substantially extended gamma-ray source at photon energies above
700 GeV."
- "By splitting our data into two parts, below and above 5 TeV, we
have also searched for energy dependent changes of the TeV gamma-ray
extension. Such changes are ultimately also expected to show up in TeV
gamma-ray data. While the Crab PWN is significantly extended in both
energy bins, our data are currently not precise enough to establish
this energy dependence of the PWN extension."

From Yeung & Horns (2019):
- "Analyzing the LAT data accumulated over approx. 9.1 years with a
properly refined model for the Crab pulsar’s spectrum, we determined
the 68% containment radius (R68) of the Crab Nebula to be:
... 0.0330 deg +/- 0.0025deg (stat) +0.0012 deg (sys) -0.0075deg (sys)
1.980' +/- 0.150' (stat) +0.070' (sys) -0.450' (sys) in the 5–500 GeV band."
- "The estimated systematic uncertainty is based on two factors:
(1) different analysis methods, morphological models and event types, and
(2) the point-spread-function evaluated with observations of Mkn 421."
- "When comparing the Fermi LAT and H.E.S.S. results on the spatial
extension, we find evidence for an energy-dependent shrinking of the
Crab Nebula’s gamma-ray extension", R68 that can be formulated as:
... R68 = F (E/E0) ^-A deg
with the following parameters:
- F: 0.0357 +/- 0.0021
- E0: 44 GeV
- A: 0.155 +- 0.035

From The Fermi LAT Collaboration & Biteau (2018):
- Evidence for extension from the inverse Compton (IC) emission
component of the Crab Nebula was found.
- "Our analysis detects an extension of:
0.030 deg +/- 0.003 deg (stat) +/- 0.007 deg (sys)
in FHES J0534.5+2201 which is associated with the IC component of the
Crab Nebula (3FGL J0534.5+2201i)."
- this quantity refers to the 68% confidence radius

From Holler et al. for the H.E.S.S. Collaboration (2017):
- By developing time-dependant simulations of the variation of the
instrument PSF with observation and instrument conditions, the PSF of
H.E.S.S. was characterised in detail:
- "Employing such simulations, we substantially improve our
understanding of the H.E.S.S. PSF and are now able to probe source
extensions well below one arcminute scale. We present the results of
this new approach applied to known VHE gamma-ray sources and show how
this enables us to reveal for the first time the extension of the Crab
nebula at TeV gamma-ray energies, with a width of 52 arcsec assuming a
Gaussian source shape."
- "We find the best-fit extension to be 52.2'' +/- 2.9'' (stat) +/- 7.8'' (sys),
with a preference of an extension of the Crab nebula over a point-source
assumption of TS approx. 83 (TS is the likelikhood ratio test statistic
and sqrt(TS) can be interpreted as statistical significance)."
- the extension is quoted in terms of the width of a 2D Gaussian and
is equivalent to 0.0145 deg

Flux:

From Abeysekara et al. (2017):
- 2HWC J0534+220, associated with the Crab (separated from it by
0.01deg), is the third brightest source in the sky at 7 TeV
- "We note here that, when taking into account the full extent of each
source, the Crab Nebula is only the third brightest source in the sky
at 7 TeV in the 2HWC catalog. The brightest sources are 2HWC J1837-065
(possibly associated with HESS J1837-069 and/or HESS J1841-055) and
2HWC J1825-134 (possibly associated with HESS J1825-137 and/or
HESS J1826-130 - it is located at about 0.4deg from each of them)."

Spectral Information:

From HAWC Collaboration (2019):
- The authors find that the energy spectrum of the Crab Nebula is well
fit by a log parabola shape with emission up to at least 100 TeV:
- dN/dE = F0 (E/E0) ^(-A x -B x ln(E/E0))
- E0: 7 TeV
- F0: 2.35 +/- 0.04(stat) +0.20(syst) -0.21(sys) x10e-13 TeV-1 cm-2 s-1
- A: 2.79 +/- 0.02(stat) +0.01(syst) -0.03(syst)
- B: 0.10 +/- 0.01(stat) +/- 0.02(syst)

From Nigro et al. (2019):
- "By combining data from Fermi-LAT, and from four of the currently
operating imaging atmospheric Cherenkov telescopes, we produced a
joint maximum likelihood fit of the Crab nebula spectrum."
- A spectral model of log-parabolic form was used such that:
dF/dE = F0 (E/E0) ^(-A x -B x log10(E/E0))
- E0 was fixed to 1 TeV for each data set
- F0, A and B are listed for each of the data sets:
- F0 is given in 10e-11 TeV-1 cm-2 s-1
... Fermi-LAT: F0 = 4.04 ± 1.01; A = 2.37 ± 0.24; B = 0.14 ± 0.13
... MAGIC: F0 = 4.15 ± 0.30; A = 2.60 ± 0.10; B = 0.44 ± 0.11
... VERITAS: F0 = 3.76 ± 0.36; A = 2.44 ± 0.09; B = 0.26 ± 0.17
... FACT: F0 = 3.49 ± 0.30; A = 2.54 ± 0.22; B = 0.42 ± 0.31
... H.E.S.S.: F0 = 4.47 ± 0.29; A = 2.39 ± 0.18; B = 0.37 ± 0.22
... Joint fit: F0 = 3.85 ± 0.11; A = 2.51 ± 0.03; B = 0.24 ± 0.02

From Abeysekara et al. for the HAWC Collaboration (2017):
- the spectrum is described by a log-parabola function such that:
F(E) = F0 (E/E0) ^(-A - B x ln(E/E0))
- the parameters found are the following:
- log10(F0): -12.6 +/- 0.02
- A: 2.63 +/- 0..03
- B: 0.15 +/- 0.03

From Holler et al. for the H.E.S.S. Collaboration (2015):
- the spectrum is described by a power law with an exponential cutoff
such that: dN/dE = F0 (E/E0) ^(-A)(-B)(-ln(E/E0) TeV-1 cm-2 s-1
- the parameters found are the following:
- F0: 1.79 +/- 0.03 x10e-10
- E0: 0.521 TeV
- A: 2.10 +/- 0.04
- B: 0.24 +/- 0.01

From Meagher et al. for the VERITAS Collaboration (2015):
- the spectrum is described by a log-parabola function such that:
dN/dE = F0 (E/E0) ^(-A + B x log(E/E0))
- the parameters found are the following:
- F0: 3.75 +/- 0.03 x10e-11 TeV-1 cm-2 s-1
- A: 2.467 +/- 0.006
- B: -0.16 +/- 0.01
- the fit is performed between 115 GeV and 42 TeV

From Aleksic et al. for the MAGIC Collaboration (2015):
- the spectrum is described by a log-parabola function such that:
dN/dE = F0 (E/E0)^(-A + B x log(E/E0))
- the parameters found are the following:
- F0: 3.23 +/- 0.03 x10e-11 TeV-1 cm-2 s-1
- A: 2.47 +/- 0.01
- B: -0.24 +/- 0.01
- the fit is performed from 50 GeV up to 30 TeV

From Aharonian et al. for the H.E.S.S. Collaboration (2006):
- the spectrum is described by a power-law function with an
exponential cutoff such that dN/dE = F0 (E/E0) ^-A exp (-E/Ec)
- the parameters found are the following:
- F0: 3.76 +/- 0.07 x10e-11 cm-2 s-1 TeV-1
- E0: 1 TeV
- A: 2.39 +/- 0.03
- Ec: 14.3 +/- 2.1 TeV
- the fit was performed from 440 GeV to 40 TeV

From Tickoo et al. for the TACTIC Collaboration (2005):
- the spectrum is described by a power-law function such that:
dN/dE = F0 (E/E0) ^-A cm-2 s-1 TeV-1
- the parameters found are the following:
- F0: 3.18 +/- 0.41 x10e-11
- E0: 1 TeV
- A: 2.65 +/- 0.11

From Aharonian et al. for the HEGRA Collaboration (2004):
- the spectrum is described by a power-law function such that:
dN/dE = F0 (E/E0) ^-A
- the parameters found are the following:
- F0: 2.83 +/- 0.04 x10e-11 TeV-1 cm-2 s-1
- E0: 1 TeV
- A: 2.62 +/- 0.02
- the fit was performed from 500 GeV to 80 TeV

From Hillas et al. for the Whipple Collaboration (1998):
- the spectrum is described by a power-law function such that:
dN/dE = F0 (E/E0) ^-A
- the parameters found are the following:
- F0: 3.20 +/- 0.17 x10e-7 TeV-1 m-2 s-1
- E0: 1 TeV
- A: 2.49 +/- 0.06
- the fit was performed from 500 GeV to 8 TeV

Emission above 56 GeV:

From HAWC Collaboration (2019):
- This source overlaps with eHWC J0534+220 one of nine sources in the
first catalog of gamma-ray sources emitting above 56 TeV presented by
the HAWC Collaboration
- The properties given in the eHWC catalog are the following:
... Source name: eHWC J0534+220
... R.A. (deg): 83.61 +/- 0.02
... Dec. (deg): 22.00 +/- 0.03
... Extension > 56 TeV (deg): point source
... F (10e-14 ph cm-2 s-1): 1.2 +/- 0.2
... sqrt(TS) > 56 TeV: 12.0
... Nearest 2HWC source: J0534+220
... Distance to 2HWC source (deg): 0.02
... sqrt(TS) > 100 TeV: 4.44

Pevatron:

From Mitchell (2021):
- this source is included in a list of Galactic sources currently known
to produce gamma-ray emission above 100 TeV.



Seen by: Whipple, HEGRA, CAT, H.E.S.S., MAGIC, Milagro, Telescope Array, CANGAROO, TACTIC, VERITAS, ARGO-YBJ, FACT, HAWC, LHAASO, CTA pSCT
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