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Observation Date (UT) Observation Lat

Canonical Name:Geminga
TeVCat Name:TeV J0632+173
Other Names:0FGL J0634.0+1745
MGRO C3
MGRO J0632+17
2HWC J0631+169
2HWC J0635+180
PSR J0633+1746
Source Type:PWN/TeV Halo
R.A.:06 32 28 (hh mm ss)
Dec.:+17 22 00 (dd mm ss)
Gal Long: 195.34 (deg)
Gal Lat: 3.78 (deg)
Distance: 0.25 kpc
Flux:0.23 (Crab Units)
Energy Threshold:3500 GeV
Spectral Index:
Extended:Yes
Size (X):2.60 (deg)
Size (Y):2.60 (deg)
Discovery Date:2009-04
Discovered By: Milagro
TeVCat SubCat:Default Catalog

Source Notes:

Source position and its uncertainty:

From Milagro Abdo et al. (2009):
- R.A. (J2000): 06h 32m 28s
- Dec. (J2000): +17d 22'
- Uncertainty (from Abdo et al., 2007): 0.4deg (stat); 0.3deg (syst)

From Abeysekara et al.(2017):
Two 2HWC sources are associated with Geminga; their locations are:
2HWC J0631+169
- R.A. (J2000): 98.00
- Dec. (J2000): +17.00
- Statistical uncertainty: 0.11 deg
2HWC J0635+180
- R.A. (J2000): 98.83
- Dec. (J2000): +18.05
- Statistical uncertainty: 0.13 deg

Special Notes:

HAWC Abeysekara et al.(2017):
- Energy range: hundreds of GeV to tens of TeV
- "2HWC J0631+169 and 2HWC J0635+180 are both found in the point
source search, each above the TS threshold value of 25. The
corresponding TS maximum in the 2-deg extended search is 126. They
appear to be associated with Geminga, a known GeV (Abdo et al. 2010b)
gamma-ray pulsar. Prior to HAWC, Milagro was the only TeV instrument
to have detected it. Milagro reported an extended source of full width
at half maximum around 2.6 deg and a hard spectrum (Abdo et al. 2009).
The large extent of the source makes it difficult for IACTs to observe
it. To date none have reported a detection of Geminga"
- 2HWC J0631+169 is located at 0.39 deg from Geminga
- 2HWC J0635+180 is located at 0.97 deg from Geminga

MAGIC Ahnen et al. (2016):
- Energy range: 50 - 200 GeV
- The MAGIC Collaboration performed deep observations of Geminga,
which yielded 63 hours of good-quality data. They searched for
emission from the pulsar and pulsar wind nebula:
- "We did not find any significant detection, and derived 95%
confidence level upper limits. The resulting upper limits ... for the
Geminga pulsar and for the surrounding nebula at 50 GeV are the most
constraining ones obtained so far at VHE."

HAWC Baughman et al.(2015):
- Energy range: HAWC's energy threshold is significantly lower than
Milagro's for these data
- HAWC’s preliminary results show an extended region of emission
consistent with that observed with Milagro.
- the authors note that "Imaging Atmospheric Cherenkov Telescopes
(IACTs) have observed Geminga without significant detection for over
two decades. An extended, hard TeV source is extremely difficult to
observe with the IACT technique. Milagro’s observation implies an
extended, hard spectrum source."

Milagro Abdo et al. (2009):
- Energy: approx. 35 TeV
- Milagro report a source associated with 0FGL J0634.0+1745 with a
statistical significance of 3.5 sigma when the region around this
source is smoothed by the PSF of the Milagro detector. Since this
source seems to be extended however, the region is smoothed instead
with an additional 1 degree Gaussian to reveal the extension of the
source. This results in a significance of 6.3 sigma.

Source Location (J2000):

Milagro: ATel 2172
- R.A.: 06h 32m 28s
- Dec.: 17d 22m

Source Extent:

From Mitchell et al. (2021):
- "H.E.S.S. confirms the detection of extended gamma-ray emission
around the Geminga pulsar in an independent dataset from that of the
previously announced detection"
- "we can state that the true radial extent of the emission is
definitely >= 2 deg and highly likely to be >= 3.2 deg. A forthcoming
publication will describe this analysis in detail, including the tests
made with different background approaches."

From Mitchell & Caroff for the H.E.S.S. Collaboration (2019):
- an extension of >1 deg was reported for the region of the Geminga Pulsar
HAWC Abeysekara et al.(2017):
- "When fitted with a uniform disk source model, the extent observed
in HAWC is around 2 deg in radius"
Milagro Abdo et al. (2009):
- radius: 2.6 +0.7 -0.9 deg

Spectral Information:

HAWC Abeysekara et al.(2017):
- the measured spectrum is relatively hard at 2.2
- the measured spectrum depends on the assumed morphology

Flux:

Milagro Abdo et al. (2009):
- The flux quoted here is based on a comparison of the flux at 35 TeV
of 37.7e-17 /TeV /s /cm2 with that from the Crab (162.6e-17 /TeV /s /cm2)
also quoted at 35 TeV.

Distance:

From Faherty et al. (2007):
- "We find the parallax pi = 4.0 +/- 1.3 mas, corresponding to a
distance to Geminga of (250 -62 +120) pc, a result 60% larger than the
previously published value. The proper motion is 178.2 +/- 1.8 mas/year."

Source Classification:

From Di Mauro et al. (2019):
- "We detect a gamma-ray halo around Geminga with a significance in
the range 7.8-11.8 sigma depending on the interstellar emission model
considered. This measurement is compatible with e+ and e- emitted by
the PWN, which inverse-Compton scatter with photon fields located
within a distance of about 100 pc from the pulsar, where the diffusion
coefficient is estimated to be around 1.1 x 10e27 cm2/s at 100 GeV."

From Abeysekara et al.(2017):
- "Compared to other TeV PWNe, the associated pulsar PSR J0633+1746 is
relatively old (342 kyr), nearby (250 +120 -62 pc) and has a low
spindown power (3.2 10e34 erg s-1 ). Geminga (together with PSR
B0656+14) has been proposed as the dominant source of the local
population of TeV electrons and positrons, and thus a possible
explanation for the PAMELA positron excess (Aharonian et al. 1995;
Yuksel et al. 2009)."

From Linden et al. (2017):
- the authors propose that this object is a member of a new class of
TeV emitters - "extrended TeV halos"
- "Observations by HAWC and Milagro have detected bright and spatially
extended TeV gamma-ray sources surrounding the Geminga and Monogem
pulsars. We argue that these observations, along with a substantial
population of other extended TeV sources coincident with pulsar wind
nebulae, constitute a new morphological class of spatially extended
TeV halos."

From Acero et al. (2013):
- This LAT emission from this source below 10 GeV is likely from a
pulsar
Milagro Abdo et al. (2009):
- This source is extended and associated with Geminga and is
therefore postulated to be the PWN of this pulsar


Emission components:

- no variability is reported by Abdo et al. (2009) and, due to
its extent, the emission is assumed to arise from the nebula
- a pulsed component above 1 TeV has also been reported (4.4 sigma)
by Neshpor et al. (2001); this has not been confirmed by other instruments


Seen by: Milagro, HAWC
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