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Observation Date (UT) Observation Lat

Canonical Name:gamma Cygni
TeVCat Name:TeV J2021+404
Other Names:MAGIC J2019+408
SNR G78.2+2.1
Source Type:Composite SNR
R.A.:20 21 12 (hh mm ss)
Dec.:+40 25 48 (dd mm ss)
Gal Long: 78.18 (deg)
Gal Lat: 2.13 (deg)
Distance: 1.7 kpc
Flux: (Crab Units)
Energy Threshold: GeV
Spectral Index:2.55
Extended:Yes
Size (X):0.53 (deg)
Size (Y):0.53 (deg)
Discovery Date:2010-10
Discovered By: MAGIC
TeVCat SubCat:Default Catalog

Source Notes:

Source Position:

From MAGIC Collaboration (2023):
There are three emission components in this soucre. The position quoted
in TeVCat is that of the SNR interior.

SNR interior:
- R.A. (J2000): +20h 21m 12s
- Dec. (J2000): +40d 25m 48s

MAGIC J2019+408:
- R.A. (J2000): +20h 19m 43.25s
- Dec. (J2000): +40d 52m 12s

Arc (Gaussian model):
- R.A. (J2000): +20h 18m 02s
- Dec. (J2000): +40d 30m 36s

Source Extent:

From MAGIC Collaboration (2023):
There are three emission components in this source. The extension quoted
in TeVCat is that of the SNR interior.

SNR interior: 0.53 deg (radius of disc)
MAGIC J2019+408: 0.13 deg (sigma of Gaussian)
Arc (Gaussian model): 0.12 deg (sigma of Gaussian)

Spectral & Flux Parameters:

From MAGIC Collaboration (2023):
- All sources were best fit with a power-law function with flux
normalisation N0, spectral index A, and scaling energy E0:
SNR interior:
... N0: (10 +/ 2 (stat) +6.7 -3.5 (syst) ) x10e-13
... A: -2.55 +/- 0.16 (stat) +0.30 -0.25 (syst)
... EO: 1 TeV
... Detection significance: 6.1 sigma
MAGIC J2019+408:
... N0: (10.0 +/ 0.9 (stat) +6.0 -3.5 (syst) ) x10e-13
... A: -2.81 +/- 0.10 (stat) +0.21 -0.19 (syst)
... EO: 1 TeV
... Detection significance: 16.7 sigma
Arc (Gaussian model):
... N0: (5.2 +/ 0.8 (stat) +3.6 -2.2 (syst) ) x10e-13
... A: -2.99 +/- 0.16 (stat) +0.22 -0.22 (syst)
... EO: 1 TeV
... Detection significance: 10.3 sigma

Distance:

From MAGIC Collaboration (2023):
- "Based on radio observations and using Sigma-D relations, HI velocity
measurements, and the association with the Wolf-Rayet binary V444 Cyg,
the distance to gamma Cygni was determined to be 1.5-2.6 kpc."
- References given for the distance:
... Higgs et al. (1977);
... Landecker et al. (1980);
... Lozinskaya et al. (2000);
... Uchiyama et al. (2002);
... Leahy et al. (2013)
- The value used by MAGIC Collaboration (2023) is 1.7 kpc.

Source Association:

From MAGIC Collaboration (2023):
- "Combining MAGIC and Fermi-LAT data, we investigated the gamma-ray
emission in the vicinity of the gamma Cygni SNR G 78.2+2.1, and
identified three main source components: the SNR interior, an extended
emission located immediately outside the SNR that we call the arc, and
a Gaussian-shaped extended source MAGIC J2019+408 in the north-west of
the remnant. The brightness ratio between the source components is
energy dependent with the SNR shell dominating below approx. 60 GeV
and the arc only being observed by MAGIC above 250 GeV. The morphologies
and spectra of MAGIC J2019+408 and the arc suggest an association with
the SNR. The indices for a power-law model for MAGIC J2019+408 and the
shell are approx. 2 in the Fermi-LAT energy range and apprpox. 2.8 for
the three components in the MAGIC energy range (similar within
uncertainties, but explicitly 2.55 for the shell, 2.81 for the MAGIC
J2019+408, and 3.02 for the arc)."


Seen by: MAGIC
  • An ultrahigh-energy gamma-ray bubble powered by a super PeVatron
    Lhaaso Collaboration, Science Bulletin 69 p449-457 (2024) [LINK]
  • Study of the GeV to TeV morphology of the gamma Cygni SNR (G 78.2+2.1) with MAGIC and Fermi-LAT. Evidence for cosmic ray escape
    MAGIC Collaboration et al., A&A 670 pA8 (2023) [LINK]

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