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Observation Date (UT) Observation Lat

Canonical Name:W Comae
TeVCat Name:TeV J1221+282
Other Names:VTS J1221+281,
ON 231,
B2 1219+28
Source Type:IBL
R.A.:12 21 31.7 (hh mm ss)
Dec.:+28 13 59 (dd mm ss)
Gal Long: 201.73 (deg)
Gal Lat: 83.29 (deg)
Distance: z=0.102
Flux:0.09 (Crab Units)
Energy Threshold:200 GeV
Spectral Index:3.81
Extended:No
Discovery Date:2008-08
Discovered By: VERITAS
TeVCat SubCat:Default Catalog

Source Notes:

Source position and its uncertainty:
From Acciari et al. (2008):
"The mean position of the W Com excess is derived by fitting a 2D Gaussian
function to the uncorrelated excess sky map and is found to be compatible
within errors with the nominal position of W Com"
- no information on the magnitude of the positional uncertainty is provided
- the source position provided by NED is used here
From Acciari et al. (2009):
- "The position of the peak of the gamma-ray excess, reconstructed by
fitting a two-dimensional Gaussian function to the uncorrelated excess
sky map, is in agreement with the position of the radio source
associated with W Com (Fey et al. (2004)): Difference in
RA=40"+/-31"(stat); Difference in Dec=-55"+/-41.4"(stat). The
systematic uncertainty on the . pointing, verified with optical
pointing monitors, is less than 50". The morphology of the excess is
compatible with the distribution expected from a point source."

Spectral Properties:
From Acciari et al. (2008):
- Spectral index: 3.81 +/- 0.35(stat) +/- 0.34(syst)
From Acciari et al. (2009):
- Spectral index (flare): 3.68 +/- 0.22(stat) +/- 0.3(syst)

Flux:
The flux from this source has been found to be variable (see references).
From Acciari et al. (2008):
- a flux at a level of 9% that of the Crab was reported
From Acciari et al. (2009):
- a flare with a flux at a level of ~25% that of the Crab was reported


Seen by: VERITAS
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