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Observation Date (UT) Observation Lat

Canonical Name:LHAASO J2226+6057
TeVCat Name:TeV J2227+609
Other Names:VER J2227+608
Boomerang Nebula
SNR G106.3+2.7
PSR J2229+6114
Source Type:UNID
R.A.:22 27 00 (hh mm ss)
Dec.:+60 57 00 (dd mm ss)
Gal Long: 106.28 (deg)
Gal Lat: 2.84 (deg)
Flux:1.05 (Crab Units)
Energy Threshold:100000 GeV
Spectral Index:3.01
Size (X):0.00 (deg)
Size (Y):0.00 (deg)
Discovery Date:2021-05
Discovered By: LHAASO
TeVCat SubCat:Default Catalog

Source Notes:

Details of the source detection:

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: 13.6 sigma
- E_max (PeV): 0.57 +/- 0.19
- Differential photon flux at 100 TeV (CU): 1.05 +/- 0.16
- On-source events/Off-source events: 60/6.2
- Exposure (hr): 2401.3

Source Position:

From Cao et al. (2021):
- R.A. (J2000): 336.75 = 22h 27m 00s
- Dec. (J2000): +60.95 = +60d 57m

Spectral Properties:

From Cao et al. (2021):
- "For the three most significantly detected sources, LHAASO J1825-1326,
LHAASO J1908+0621 and LHAASO J2226+6057, we determine their SEDs."
- The authors show "the spectral energy distributions of three
luminous sources with fluxes exceeding 1 CU (at 100 TeV): LHAASO
J1825-1326, LHAASO J1908+0621 and LHAASO J2226+6057. Above 100 TeV,
the spectra of these sources are steep, characterized by a power-law
photon index of approx. 3. However, a closer look reveals that
between 10 TeV and 500 TeV, the spectra experience gradual
steepening with energy. To explore this tendency, the spectra were
fitted by the so-called log-parabola function dN/dE ∝ E-A(E), where
the local photon index A(E) = a + blogE (a and b are free
parameters) characterizes the slope of the tangent. For all three
spectra, the log-parabola fits are preferred over simple power-law
fits. The gradual steepening of multi-hundred-teraelectronvolt gamma
rays is partly due to the photon-photon absorption that occurs
during their interactions with the diffuse far-infrared and
microwave radiation fields."
- For LHAASO J2226+6057 the parameters of the fit are:
... a: 1.56
... b: 0.88
... A: 3.01

Possible Origin:

From De Sarker et al. (2022):
- the authors "study a pulsar wind nebula interpretation of LHAASO J2226+6057,
which has a relatively well covered multi-frequency spectrum."
- "We have considered different values of braking index and true age
for the fitting of the multi-wavelength (MWL) spectral energy
distribution (SED) of LHAASO J2226+6057. The best-fit PWN model
parameters and their 1 sigma confidence intervals were evaluated. We
have also demonstrated the impact of reverberation on the MWL SED with
increasing time. Additionally, we have discussed the resultant large
radius and low magnetic field associated with the PWN in question, as
caveats for the possible physical connection of the pulsar as the
origin of this high energy source."

From Cao et al. (2021):
- This list contains sources potentially at the origin of the LHAASO source, together with their class, their distance, age and luminosity
- SNR G106.3+2.7, Supernova Renmant, Distance: 0.8 kpc, Age: approx. 10 kyr
- PSR J2229+6614, Pulsar, Distance: 0.8 kpc, Age: approx. 10 kyr, L_s: 2.2 x10e37

Potential TeV Counterparts:

From Cao et al. (2021):
- This list contains "Nearby teraelectronvolt sources within 1deg of the centre of the LHAASO source"
- VER J2227+608
- Boomerang Nebula


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: LHAASO
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