Back to Main Page
Observation Date (UT) Observation Lat

Canonical Name:MGRO J1908+06
TeVCat Name:TeV J1907+062
Other Names:HESS J1908+063
0FGL J1907.5+0602
1AGL J1908+0613
GEV J1907+557
G40.5-0.5
ARGO J1907+0627
ARGO J1910+0720
VER J1907+062
1HWC J1907+062c
2HWC J1908+063
eHWC J1907+063
Source Type:UNID
R.A.:19 07 54 (hh mm ss)
Dec.:+06 16 07 (dd mm ss)
Gal Long: 40.39 (deg)
Gal Lat: -0.79 (deg)
Distance:
Flux:0.17 (Crab Units)
Energy Threshold:1000 GeV
Spectral Index:2.1
Extended:Yes
Size (X):0.34 (deg)
Size (Y):0.34 (deg)
Discovery Date:2007-08
Discovered By: Milagro
TeVCat SubCat:Default Catalog

Source Notes:

H.E.S.S. Galactic Plane Survey (HGPS, 2018):
A selection of information for each of the 78 sources in the HGPS is provided in TeVCat. For full details, visit the HGPS website.

Name: HESS J1908+063
Source Class: Unid
Identified Object: None
R.A. (J2000): 287.10 deg (19 08 23)
Dec. (J2000): 6.39 deg (06 23 16)
Positional uncertainty: 0.083 deg
Spatial Model: Gaussian
Size: 0.486 +/- 0.027 deg
Spectral Model: power law
Integral Flux > 1 TeV: 8.35e-12 +/- 5.67e-13 cm-2 s-1
Pivot Energy, E0: 2.06 TeV
Diff. Flux at E0: 2.06e-12 +/- 1.40e-13 cm-2 s-1 TeV-1
Spectral Index: 2.26 +/- 0.06
HGPS Source Notes:
From the HGPS paper:

The position and size published in Aharonian et al. (2009) are significantly different from those obtained in the HGPS analysis. The position is offset by 0.17 deg and the size is found to be 0.48 deg +/- 0.04 deg, which is 0.14 deg larger. We note that the size we find is consistent with that measured by the VERITAS Collaboration (Aliu et al. 2014b), even though the positions differ by 0.3 deg. A plausible cause for these discrepancies is that this is a large source likely composed of multiple components, where results are expected to be sensitive to the morphology assumptions and to details in background modeling techniques, in particular, if those tend to absorb large-scale features.

Five possible associations are listed in Table A.9. "This is a list of astronomical objects, extracted from catalogs of plausible counterparts, which are are found to be spatially coincident with the HGPS source":
- ARGO J1907+0627 (EXTRA)
- MGRO J1908+06 (EXTRA)
- G40.5-0.5 (SNR)
- 3FGL J1907.9+0602 (3FGL)
- J1907+0602 (PSR)
"EXTRA associations: For completeness, in addition to the associations obtained through the catalog-based, automatic procedure, we add a list of 20 extra associated objects that are plausible counterparts for some HGPS sources and are not covered by the limited set of catalogs we use."

Source position and its uncertainty:

From Abeysekara et al. (2017):
- R.A. (J2000): 287.05 +/- 0.06 deg (stat) (= 19h 08m 12s)
- Dec. (J2000): 6.39 +/- 0.06 deg (stat) (= 06d 23' 24''4)

From Aliu et al. (2014):
- R.A. (J2000): 286.64 +/- 0.02 deg (= 19h 07m 21.6s)
- Dec. (J2000): 6.22 +/- 0.02 deg (= 06d 13' 12")
"Our best fitted position differs from the position reported for HESS
J1908+063 by 0.15deg . This is larger than the quoted statistical
uncertainties, but a relatively small fraction of the Gaussian
width. The shift may arise due to systematic effects, e.g., the fact
that the emission is not well described by a symmetric two-dimensional
Gaussian or a difference in energy bands between the two
measurements."

From Bartoli et al. (2013):
- R.A. (J2000): 19h 07m 48s
- Dec. (J2000): +06d 27'
Source position and its uncertainty:

From Bartoli et al. (2012)
- R.A. (J2000): 19h 08m 01s
- Dec. (J2000): +06d 24'
- with a statistical error of 12' and a systematic error of 6' per axis

From Abdo et al. (2009):
- R.A.: 19h 06m 44s
- Dec.: -05d 50m
... with a 1 sigma error circle of 0.27deg

From Aharonian et al. (2009):
- l: 40d 23' 09.2'' +/- 2.4' (stat) (= 19h 07m 54.30s R.A.)
- b: -0d 47' 10.1'' +/- 2.4' (stat) (= 06d 16m 07.2s Dec.)
... with a systematic error of 20" per axis

From HESS: online catalog:
- R.A.: 19h 07m 54s
- Dec.: 06d 16m 07s

Source Extent:

From Aliu et al. (2014):
- intrinsic extension of 0.44 +/- 0.02 deg

From Bartoli et al. (2012)
- 0.49 +/- 0.22 degrees

From Abdo et al.(2007):
- The upper limit on the angular extent is 2.6 deg (90% CL)

From Aharonian et al. (2009):
- angular size of 0.34 deg (no error quoted)

From HESS online catalog:
- radius: 0.34 +0.04 -0.03 deg

Spectral Properties:

From Abeysekara et al. (2017):
- Spectral index: 2.52 +/- 0.05(stat) +/- 0.02(syst) assuming a point source
- Spectral index: 2.33 +/- 0.03(stat) +/- 0.02(syst) assuming a radius of 0.8 deg

From Aliu et al. (2014):
- Spectral index: 2.20 +/- 0.10(stat) +/- 0.20(syst)

From ARGO-YBJ Collaboration (2012):
- Spectral index: 2.54 +/- 0.36 (stat)

From Aharonian et al. (2009):
- Spectral index: 2.10 +/- 0.07(stat) +/- 0.2(syst)

Flux:

From Abeysekara et al. (2017):
- the flux normalisation at 7 TeV was calculated to be:
- 34.1 +/- 2.2(stat) +/- 17.05(syst) x10e15 TeV-1 cm-2 s-1 assuming a point source
- 85.1 +/- 4.2(stat) +/- 42.55(syst) x10e15 TeV-1 cm-2 s-1 assuming a radius of 0.8 deg

From ARGO-YBJ Collaboration (2013):
- "The flux determined by ARGO-YBJ was consistent with that of Milagro
but higher than that of HESS by a factor of ∼3."

From ARGO-YBJ Collaboration (2012):
- an integrated luminosity above 1 TeV of about 1.8 times the Crab Nebula luminosity

From Aharonian et al. (2009):
- 0.17 Crab > 1 TeV

From Abdo et al. (2009):
- 0.72 Crab > 35 TeV
- The Milagro flux is based on a comparison of the quoted flux
at 35 TeV of 116.7e-17 /TeV /s /cm2 with that from the Crab
(162.6e-17 /TeV /s /cm2) also quoted at 35 TeV

Source Association:

From Kostunin et al. (2021):
- "In this work we revisit the unidentified source MGRO J1908+06,
initially detected by Milagro, using an updated H.E.S.S. dataset and
analysis pipeline. The vicinity of the source contains a supernova
remnant and pulsars as well as molecular clouds"
- In addition to fitting the entire region with a power law spectrum,
the authors also fit three different regions.
- "In the present analysis we pre-defined three regions based on
possible origins of the gamma-ray emission with astrophysical
associations. ... There is indication of spectral difference across
the region, but this remains to be confirmed with further tests."

From Cao et al. (2021):
- MGRO J1908+06 / HESS J1908+063 / ARGO J907+0627 / VER J1907+062 / 2HWC 1908+063 may
be associated with LHAASO J1908+0621

From Li et al. (2021):
- "The unidentified TeV source MGRO J1908+06, with emission extending
from hundreds of GeV to beyond 100 TeV, is one of the most intriguing
sources in the Galactic plane. MGRO J1908+06 spatially associates with
an IceCube hotspot of neutrino emission, though not significant yet,
indicating a possible hadronic origin of the observed gamma-ray
radiation."
- "Here we describe a multiwavelength analysis on MGRO J1908+06 to
determine its nature. We identify, for the first time, an extended GeV
source as the counterpart of MGRO J1908+06, discovering possibly
associated molecular clouds (MCs)."
- "The GeV spectrum shows two well-differentiated components: a soft
spectral component below ∼ 10 GeV, and a hard one (index 1.6) above
these energies. The lower-energy part is likely associated with the
dense MCs surrounding the supernova remnant SNR G40.5-0.5, whereas the
higher-energy component, which connects smoothly with the spectrum
observed in TeV range, resembles the inverse Compton emission observed
in relic pulsar wind nebulae."
- "This simple scenario seems to describe the data satisfactorily, but
raises questions about the interpretation of the emission at hundreds
of TeV. In this scenario, no detectable neutrino flux would be
expected."

From Duvidovich, Petriella & Giacani (2019):
- "This paper aims to provide new insights on the origin of the TeV
source VER J1907+062 through new high-quality radio observations"
- "The new radio observations do not show any evidence of a pulsar
wind nebula (PWN) driven by the pulsars present in the field and no
radio counterpart to the proposed X-ray PWN powered by PSR J1907+0602
is seen in the new VLA image at 6 GHz down to a noise level of 10
microJy beam-1."
- "Molecular clouds were discovered over the eastern, southern, and
western borders of the radio shell of G40.5-0.5, suggesting an
association with the SNR."
- "We explored several scenarios for the origin of VER J1907+062. We
propose as the most probable scenario one in which the TeV emission is
produced by two separated gamma-ray sources located at different
distances: one of leptonic origin and associated with a PWN powered by
PSR J1907+0602 at approx. 3.2 kpc and another of hadronic origin and
produced by the interaction between G40.5-0.5 and the surrounding
molecular gas at approx. 8.7 kpc."

From Abeysekara et al. (2017):
- "Source 2HWC J1908+063 is associated with the PWN MGRO J1908+06."
- "This source was considered unidentified until the advent of
Fermi-LAT, which shed light on the nature of MGRO J1908+06 and
strengthened the PWN scenario to explain its VHE gamma-ray emission
(Abdo et al. 2010; Acero et al. 2013). The spectrum measured in this
work under the extended hypothesis is consistent with the spectra
obtained by H.E.S.S., VERITAS, and MILAGRO, and lower than the
ARGO-YBJ results"

From Abeysekara et al. (2015):
- "1HWC J1907+062c is 4.6sigma post trials with a best-fit position that
is compatible with previously reported positions of MGROJ1908+06. The
differential flux normalization is consistent with the flux measured
by H.E.S.S. and VERITAS and in agreement with Milagro given the
statistical uncertainties of both instruments."

From Aliu et al. (2014):
- "The TeV emission from J1908 is strong in the region near PSR
J1907+0602 and also extends toward SNR G40.5–0.5. A key question
regarding the nature of the emission is whether it is solely due to a
PWN associated with PSR J1907+0602 or whether there are additional
sources of TeV emission."
- "In conclusion, J1908 appears to be physically somewhat larger than
other TeV PWNe of similar age and the TeV spectrum does not appear to
soften with distance from the pulsar, as observed in similar TeV PWNe
and expected from electron cooling. There is no strong TeV emission
associated with the radio-bright shell of SNR G40.5-0.5. Interaction
of the pulsar wind with nearby molecular clouds or the SNR shock could
explain the large size and lack of spectral softening in J1908. It is
also possible that another PWN, associated with an undetected second
pulsar located near the southern edge of SNR G40.5-0.5, could
contribute to the VHE emission, but this would require the presence of
a second, and as yet undetected, pulsar."

From Bartoli et al. (2013):
- ARGO J1907+0627 is consistent in position with HESS J1908+063
(Aharonian et al. 2009), while ARGO J1910+0720 is completely outside
the extended region of HESS J1908+063. In a previous work, these two
sources have been considered as a single unique source, identified as
the extended source MGRO J1908+06"
- they suggest that MGRO J1909+06 "could be
a blend of the two sources" (ARGO J1907+0627 and ARGO J1910+0720).

From Acero et al. (2013):
- This LAT emission from this source below 10 GeV is likely from a
pulsar

From Abdo et al. (2009):
- " The peak of the signal is found at a position consistent with the
pulsar PSR J1907+0602"
- "The continuity of the Milagro and ARGO-YBJ observations and the
stable excess rate observed by ARGO-YBJ and recorded in four years of
data support the identification of MGRO J1908+06 as the steady
powerful TeV pulsar wind nebula of PSR J1907+0602, with an integrated
luminosity over 1 TeV ∼ 1.8 times the luminosity of the Crab Nebula."

From Abdo et al.(2007):
- Possible associations: GEV J1907+0557, SNR G40.5-0.5

From Abdo et al. (2009):
- Possible associations: 0FGL J1907.5+0617, 1AGL J1908+0613, GEV 1907+557

Emission above 56 GeV and above 100 TeV:

From HAWC Collaboration (2019):
- This source overlaps with eHWC J1907+063 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 J1907+063
... R.A. (deg): 286.91 +/- 0.10
... Dec. (deg): 6.32 +/- 0.09
... Extension > 56 TeV (deg): 0.52 +/- 0.09
... F (10e-14 ph cm-2 s-1): 2.8 +/- 0.4
... sqrt(TS) > 56 TeV: 10.4
... Nearest 2HWC source: J1908+063
... Distance to 2HWC source (deg): 0.16
... sqrt(TS) > 100 TeV: 7.30
- This source also exhibits significant emission above 100 TeV and is fit with a spectral
model of a log parabola:
... sqrt(TS) of the spectral fit: 37.8
... Extension > 100 TeV (deg): 0.67 +/- 0.03
... Flux normalisation at 10 TeV (10e-13 TeV-1 cm-2 s-1): 0.95 +/- 0.05
... Spectral parameter alpha: 2.46 +/- 0.03
... Spectral parameter beta: 0.11 +/- 0.02

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: H.E.S.S., Milagro, ARGO-YBJ, VERITAS, HAWC
Want a reference added? Send a bibtex entry to the TeVCat Team
Try TevCat 2.0 Beta!