| Canonical Name: | HESS J1857+026 |
| TeVCat Name: | TeV J1857+026 |
| Other Names: | MAGIC J1857.2+0263
MAGIC J1857.6+0297
1HWC J1857+023
2HWC J1857+027 |
| Source Type: | UNID |
| R.A.: | 18 57 11 (hh mm ss) |
| Dec.: | +02 40 00 (dd mm ss) |
| Gal Long: | 35.96 (deg) |
| Gal Lat: | -0.06 (deg) |
| Distance: | |
| Flux: | (Crab Units) |
| Energy Threshold: | GeV |
| Spectral Index: | 2.39 |
| Extended: | Yes |
| Size (X): | 0.11 (deg) |
| Size (Y): | 0.08 (deg) |
| Discovery Date: | 2007-07 |
| Discovered By: | H.E.S.S. |
| 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 J1857+026 |
| Source Class: | Unid |
| Identified Object: | None |
| R.A. (J2000): | 284.34 deg (18 57 21) |
| Dec. (J2000): | 2.76 deg (02 45 24) |
| Positional uncertainty: | 0.060 deg |
| Spatial Model: | 2-Gaussian |
| Size: | 0.259 +/- 0.056 deg |
| Spectral Model: | power law |
| Integral Flux > 1 TeV: | 4.00e-12 +/- 2.93e-13 cm-2 s-1 |
| Pivot Energy, E0: | 0.95 TeV |
| Diff. Flux at E0: | 7.08e-12 +/- 4.16e-13 cm-2 s-1 TeV-1 |
| Spectral Index: | 2.57 +/- 0.06 |
| HGPS Source Notes: | |
| | |
From the HGPS paper:
The size of the source HESS J1857+026 is significantly larger in this analysis than previously published in
Aharonian et al. (2008a). In the
latter, the source is fit with an asymmetric Gaussian (0.11 deg +/- 0.08 deg x 0.08 deg +/- 0.03 deg), whereas the HGPS analysis best models the source with
two Gaussian components for an approximate size of 0.26 deg +/- 0.06 deg. The difference in size is explained by the multicomponent approach of the
HGPS that better takes into account the larger scale emission underneath the central bright core.
Four 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":
- J1856+0245 (PSR)
- MAGIC J1857.2+0263 (EXTRA)
- MAGIC J1857.6+0297 (EXTRA)
- 2FHL J1856.8+0256 (2FHL)
"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."
The sources
MAGIC J1857.2+0263 and
MAGIC J1857.6+0297
form part of a two-source scenario that the MAGIC data favour for this source.
Source position and its uncertainty:
The position from
Aharonian et al. (2008) is used in TeVCat.
From
Aleksic et al. (2014):
- R.A. (J2000): 18 57 15.7 +/- 15.7s(stat) +/- 5.8s(syst)
- Dec. (J2000): 02 42 17 +/- 1'26''(stat) +/- 1'48''(syst)
From
Aharonian et al. (2008):
- R.A.: (J2000): 18 57 11
- Dec. (J2000): +02 40 00
- The fit position has a statistical error of 0.05 deg
- This is the position reported in TeVCat
From
Klepser et al. (2011):
- R.A.: (J2000): 18.953 +/- 0.002(stat) +/- 0.002(sys) hrs (18h 57m 10.8s)
- Dec. (J2000): 2.70 +/- 0.02(stat) +/- 0.03(sys) deg (02d 42m)
Source Extent:
From
Aleksic et al. (2014):
- intrinsic source extension of 0.20 +/- 0.03(stat) +/- 0.02(syst) deg
From
Aharonian et al. (2008):
- semi-major axis: 0.11 +/- 0.08 deg
- semi-minor axis: 0.08 +/- 0.03 deg
- angle: -3 +/- 49 deg
...measured counter-clk relative to RA axis
From
Klepser et al. (2011):
- source extension: 0.22 +/- 0.02(stat) +/- 0.02(sys) deg (radius?)
Spectral Information:
From
Abeysekara et al. (2017):
- "The energy spectrum measured by HAWC is compatible with the ones
reported by H.E.S.S. (HESS J1857+026) and MAGIC (the latter being
measured on a 0.4 deg region encompassing both MAGIC sources
(
MAGIC J1857.2+0263 and
MAGIC J1857.6+0297)), supporting the
identification of 2HWC J1857+027 with these sources."
From
Aleksic et al. (2014):
- Index: 2.16 +/- 0.07(stat) +/- 0.15(syst)
- Flux normalisation: 5.37 +/- 0.44(stat) +/- 1.5(qyqt) at 1 TeV
- Energy range: 100 GeV - 13 TeV
From
Aharonian et al. (2008):
- Index: 2.39 +/- 0.08
- Flux normalisation: 6.1 +/- 0.7 e-12 (cm-2 s-1 TeV-1)
- Energy range: 0.6 - 80 TeV
From
Klepser et al. (2011):
- Index: 2.27 +/- 0.08(stat) +/- 0.1(sys)
- Normalisation: 4.7 +/- 0.6(stat) +/- 1.4(sys)
- Energy range: ~0.1 - 10 TeV
Source Classification and Association:
From
Petriella, Duvidovich & Giacani (2021):
- "We provide new insights into the nature of HESS J1857+026, a
very-high-energy gamma}-ray source whose complex morphology in the
TeV band was attributed to the superposition of two distinct sources."
- "We performed radio continuum observations to look for the pulsar
wind nebula and the supernova remnant associated with the pulsar PSR
J1856+0245, which might be powering part of the gamma-ray emission."
- "The new observations at 1.5GHz do not show evidence of emission above
the noise level that could be associated with either HESS J1857+026
or PSR J1856+0245. Also, in the new image at 6.0GHz we do not detect
radio emission from a pulsar wind nebula powered by PSR J1856+0245."
- "The neutral gas analysis shows the existence of a superbubble in
the direction of the gamma-ray source. We suggest that this structure
is located at approx. 5.5kpc, compatible with the distance to the
pulsar PSR J1856+0245."
- "We conclude that TeV emission from HESS J1857+026 originates in a
superbubble, arguing in favour of a single gamma-ray source rather
than the superposition of two distinct sources. The pulsar PSR
J1856+0245 could also be contributing as a source of gamma-rays within
the bubble."
From
Abeysekara et al. (2017):
- "Source 2HWC J1857+027 has been previously reported by HAWC as 1HWC J1857+023.
It is associated with TeV source HESS J1857+026 (approx. 0.1 deg away)."
- "The H.E.S.S. source was considered a PWN candidate (e.g.,
Tibolla et al. 2011),
associated with PSR J1856+0245 (E-dot = 4.6 x10e36 erg s−1 d = 6.3 kpc,
age = 20.6 kyr). Recent MAGIC observations revealed that the VHE
emission above 1 TeV can be spatially separated into two sources:
MAGIC J1857.2+0263 and
MAGIC J1857.6+0297 (
Aleksic et al. 2014). They
also confirmed the PWN nature of the first source, and a molecular
cloud association was suggested for the second source. These two MAGIC
sources are too close to be distinguishable in the HAWC analysis
reported here."
From
Abeysekara et al. (2015):
- "The source 1HWC J1857+023* is detected at 6.2sigma post trials and
is approx. 0.4deg away from both HESS J1857+026 and
HESS J1858+020.
... The flux of HESS J1857+026 is approximately an order of
magnitude higher than
HESS J1858+020, and the differential flux
normalization from 1HWC J1857+023 is compatible with the combined flux
of HESS J1857+026 and
HESS J1858+020"
*1HWC J1857+023 is not listed under a separate entry in TeVCat. It is
listed as an associated source for HESS J1857+026,
HESS J1858+020,
MAGIC J1857.2+0263 and
MAGIC J1857.6+0297.
From
Aleksic et al. (2014):
- "... we present a detailed analysis of the energy-dependent
morphology of this region. We couple these results with archival
multiwavelength data and outline evidence in favor of a two-source
scenario, whereby one source is associated with a PWN, while the other
could be linked with a molecular cloud complex containing an HII
region and a possible gas cavity."
- "Above 1 TeV we found that the VHE emission is due to two spatially
distinct statistically significant components, which we denote
MAGIC J1857.2+0263 and
MAGIC J1857.6+0297"
From
Acero et al. (2013):
- Analysis of the LAT data from this source leads to its
classification as a PWN candidate
From
Rousseau et al. (2012):
- Their calculated gamma-ray efficiency of ~5% for Edot = 4.6 × 1036
erg s-1 puts this object in the range expected for pulsar wind nebulae.
- "HESS J1857+026 is a spatially extended gamma-ray source detected by
H.E.S.S. and classified as a possible pulsar wind nebula candidate
powered by PSR J1856+0245."
- "Conclusion: The nature of HESS J1857+026 remains unclear. From the
observations presented here, we know that the GeV source is positionally
and spectrally consistent with the TeV source, suggesting a physical relationship."
From
Tibolla et al. (2011):
- this source is identified as a PWN
From
Klepser et al. (2011):
- "the morphology and overall spectral shape of the main emission zone
supports the concept of a PWN nature of HESS J1857+026. (...) However,
the wide-range, flat TeV spectrum and the apparently different
spectral behaviour of the northern tail of the source might still
indicate a more complex scenario for this object."
Seen by: H.E.S.S., MAGIC, HAWC
-
Using Interstellar Clouds to Search for Galactic PeVatrons: Gamma-ray Signatures from Supernova Remnants
Mitchell, A.M.W. et al., arXiv e-prints parXiv:2103.01787 (2021) [LINK]
-
Radio study of HESS J1857+026. Gamma-rays from a superbubble?
Petriella, Alberto et al., arXiv e-prints parXiv:2107.12849 (2021) [LINK]
-
The H.E.S.S. Galactic plane survey
H.E.S.S. Collaboration et al., A&A 612 pA1 (2018) [LINK]
-
The 2HWC HAWC Observatory Gamma-Ray Catalog
Abeysekara, A.U. et al., ApJ 843 p40 (2017) [LINK]
-
Search for TeV Gamma-Ray Emission from Point-like Sources in the Inner Galactic Plane with a Partial Configuration of the HAWC Observatory
Abeysekara, A.U. et al., ArXiv e-prints p (2015) [LINK]
-
MAGIC reveals a complex morphology within the unidentified gamma-ray source HESS J1857+026
MAGIC Collaboration et al., ArXiv e-prints p (2014) [LINK]
-
Constraints on the Galactic Population of TEV Pulsar Wind Nebulae Using Fermi Large Area Telescope Observations
Acero, F. et al., ArXiv e-prints p (2013) [LINK]
-
Recent Results from the MAGIC Telescopes
Tibolla, O. and for the MAGIC collaboration, ArXiv e-prints p (2012) [LINK]
-
Fermi-LAT constraints on the pulsar wind nebula nature of HESS J1857+026
Rousseau, R. et al., A&A 544 pA3 (2012) [LINK]
-
New developments in the ancient PulsarWind Nebulae scenario
Tibolla, O. et al., ArXiv e-prints p (2011) [LINK]
-
Mapping the extended TeV source HESS J1857+026 down to Fermi-LAT energies with the MAGIC telescopes
Klepser, S. et al., ArXiv e-prints p (2011) [LINK]
-
Ancient Pulsar Wind Nebulae in light of recent GeV and TeV observations
Tibolla, O. et al., ArXiv e-prints p (2011) [LINK]
-
HESS very-high-energy gamma-ray sources without identified counterparts
Aharonian, F. et al., A&A 477 p353-363 (2008) [LINK]
-
PSR J1856+0245: Arecibo Discovery of a Young, Energetic Pulsar Coincident with the TeV Gamma-ray Source HESS J1857+026
Hessels, J.W.T. et al., ApJ 682 pL41-L44 (2008) [LINK]
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