| Canonical Name: | W 28 |
| TeVCat Name: | TeV J1801-233 |
| Other Names: | HESS J1801-233
SNR G006.4-00.1
GRO J1801−2320 |
| Source Type: | SNR/Molec. Cloud |
| R.A.: | 18 01 42.2 (hh mm ss) |
| Dec.: | -23 20 06.0 (dd mm ss) |
| Gal Long: | 6.66 (deg) |
| Gal Lat: | -0.27 (deg) |
| Distance: | 2 kpc |
| Flux: | (Crab Units) |
| Energy Threshold: | 100 GeV |
| Spectral Index: | 2.66 |
| Extended: | Yes |
| Size (X): | 0.17 (deg) |
| Size (Y): | 0.17 (deg) |
| Discovery Date: | 2008-04 |
| Discovered By: | H.E.S.S. |
| Green's Catalog: | Link |
| 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 J1801-233 |
| Source Class: | SNR |
| Identified Object: | W 28 |
| R.A. (J2000): | 270.43 deg (18 01 42) |
| Dec. (J2000): | -23.34 deg (-23 20 06) |
| Positional uncertainty: | 0.031 deg |
| Spatial Model: | Gaussian |
| Size: | 0.170 +/- 0.030 deg |
| Spectral Model: | power law |
| Integral Flux > 1 TeV: | 4.52e-13 +/- 9.94e-14 cm-2 s-1 |
| Pivot Energy, E0: | 1.00 TeV |
| Diff. Flux at E0: | 7.50e-13 +/- 1.11e-13 cm-2 s-1 TeV-1 |
| Spectral Index: | 2.66 +/- 0.27 |
| HGPS Source Notes: | |
| | |
The authors note that: "In total, there are four previously published VHE gamma-ray sources that are not redetected with the current HGPS analysis. All of these are rather
faint sources which, for the HGPS analysis, yield significances close to the HGPS detection threshold of T S = 30. We consider these as real sources of gamma-rays; the
nondetection in the HGPS is primarily a result of differences between the HGPS analysis and specific analysis methods."
- In Aharonian et al. (2008) the emission in the region of W 28 was found to be split into two components:
- HESS J1801-233, which is not significant in the HGPS analysis and is coincident with the W 28 SNR itself, and
- a complex region HESS J1800-240 offset by 0.5deg to the south.
The latter was previously found to be resolved into three hotspots dubbed HESS J1800-240 A, HESS J1800-240 B,
and HESS J1840-240 C (Aharonian et al. 2008).
This source is part of the HESS J1800-240 (A, B
& C) and HESS J1801-233 source complex,
characterizing emission features of the SNR W 28 region (Aharonian et al. 2008).
The emission was found to be split into two components: HESS J1801-233, which is coincident with the northeastern boundary of W 28 where the shockwave is
interacting with a molecular cloud, and a complex region HESS J1800-240 (A, B
& C) offset by 0.5 deg to the south. HESS J1801-233 does not reach the TS = 30 threshold
and is therefore not found to be significant in the HGPS analysis. We note that the gamma-ray emission from W 28 is bright in the GeV range and is clearly detected
above 50 GeV (Ackermann et al. 2016). It has a steep spectral index of 2.7 +/- 0.3
at VHE (Aharonian et al. 2008). It is therefore not detected here because of our
higher analysis energy threshold (about 400 GeV at a longitude of 7 deg) and because of the inclusion of the large-scale emission model in our analysis, which
reduces the significance of such a faint source. Furthermore, we reiterate that HESS J1800-240 (A, B
& C) is detected in the HGPS as one large Gaussian source, rather than
three individual hotspots as in Aharonian et al. (2008). This potentially also contributes to a reduction of the significance of this previously established
source HESS J1801-233.
This is one of the 31 firmly-identified objects among the HGPS sources. Two 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":
- 2FHL J1801.3-2326e (2FHL)
- 3FGL J1801.3-2326e (3FGL)
- W28 (EXTRA)
"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
Aharonian et al. (2008):
- R.A. (J2000): 270.426 +/- 0.031 (deg) (Converts to R.A. (J2000): 18 01 42.24)
- Dec. (J2000): -23.335 +/- 0.032 (deg) (Converts to Dec. (J2000): -23 20 06.0)
From HESS
Online Catalog:
- R.A. (J2000): 18:01:42.2
- Dec. (J2000): -23:20:06
Source Extent:
From
Aharonian et al. (2008):
- radius: 0.17 +/- 0.03 deg
Source Associations:
From
Maxted et al. (2016):
"We present 12 mm Mopra observations of the dense (>10e3 cm e-3 )
molecular gas towards the north-east (NE) of the W28 supernova remnant
(SNR). This cloud is spatially well-matched to the TeV gamma-ray
source HESS J1801-233 and is known to be a SNR-molecular cloud
interaction region."
Fermi sources associated with this object:
- 1FGL J1801.3-2322c and 1FGL J1800.5-2359c
Source Morphology:
This SNR has a mixed-morphology.
Fermi Data:
From
Neronov et al. (2013):
- The Fermi data were subjected to a variability analysis.
- "The strongest excess of variability is centered at the supernova
remnant W28"
- "... It is possible that the variability is produced by one or
several pulsars in this region of the Galaxy. Otherwise, the source
of variability could be gamma-ray-loud binaries that are below the
sensitivity of LAT."
Seen by: H.E.S.S.
-
Shock and Cosmic-Ray Chemistry Associated with the Supernova Remnant W28
Tu, Tian-yu et al., ApJ 966 p178 (2024) [LINK]
-
Initial state of the recombining plasma in supernova remnant W 28
Himono, Rui et al., PASJ 75 p373-383 (2023) [LINK]
-
Absorption Line Observations of H3+ and CO in Sight Lines Toward the Vela and W28 Supernova Remnants
Indriolo, Nick, arXiv e-prints parXiv:2303.13689 (2023) [LINK]
-
High-velocity interstellar absorption associated with the supernova remnant W28
Ritchey, Adam M., arXiv e-prints parXiv:2005.09818 (2020) [LINK]
-
Constraining the cosmic ray spectrum in the vicinity of the supernova remnant W28: from sub-GeV to multi-TeV energies
Phan, V.H.M. et al., arXiv e-prints parXiv:1910.09987 (2019) [LINK]
-
Interaction between Molecular Clouds and MeV-TeV Cosmic-ray Protons Escaped from Supernova Remnants
Makino, K. et al., arXiv e-prints p (2019) [LINK]
-
Probing maximum energy of cosmic rays in SNR through gamma rays and neutrinos from the molecular clouds around SNR W28
Banik, Prabir and Bhadra, Arunava, Astroparticle Physics 103 p7-15 (2018) [LINK]
-
Leaked GeV CRs from a broken shell: Explaining 9 years Fermi-LAT data of SNR W28
Cui, Y. et al., ArXiv e-prints p (2018) [LINK]
-
The Origin of Recombining Plasma and the Detection of the Fe-K Line in the Supernova Remnant W28
Okon, H. et al., ArXiv e-prints p (2018) [LINK]
-
Evidence for a neutral iron line generated by MeV protons from supernova remnants interacting with molecular clouds
Nobukawa, K.K. et al., ArXiv e-prints p (2018) [LINK]
-
Similarity of gamma-ray spectrum in middle aged supernova remnants (SNRs) interacting with molecular clouds (MC): what can we learn?
Tang, X., ArXiv e-prints p (2018) [LINK]
-
Dense molecular gas at 12 mm towards Galactic TeV gamma-ray sources
de Wilt, P. et al., MNRAS 468 p2093-2113 (2017) [LINK]
-
CTIO, ROSAT HRI and Chandra ACIS Observations of the Archetypical Mixed-Morphology Supernova Remnant W28 (G6.4-0.1)
Pannuti, T.G. et al., ArXiv e-prints p (2017) [LINK]
-
SNRs W28 and W44: old cosmic ray accelerators in molecular clouds
Zirakashvili, V.N. and Ptuskin, V.S., ArXiv e-prints p (2017) [LINK]
-
Molecular Shocks and the Gamma-ray Clouds of the W28 Supernova Remnant
Maxted, N. et al., ArXiv e-prints p (2016) [LINK]
-
Ammonia excitation imaging of shocked gas towards the W28 gamma-ray source HESS J1801-233
Maxted, N.I. et al., ArXiv e-prints p (2016) [LINK]
-
Irradiated shocks in the W28 A2 massive star-forming region: a site for cosmic rays acceleration?
Gusdorf, A. et al., ArXiv e-prints p (2015) [LINK]
-
A statistical study of Galactic SNR source spectra detected at >GeV energies
Mandelartz, M. et al., ArXiv e-prints p (2013) [LINK]
-
Search for variable gamma-ray emission from the Galactic plane in the Fermi data
Neronov, A. et al., A&A 543 pL9 (2012) [LINK]
-
Unified model for the gamma-ray emission of supernova remnants
Yuan, Q. et al., ArXiv e-prints p (2012) [LINK]
-
Anisotropic CR diffusion and gamma-ray production close to supernova remnants, with an application to W28
Nava, L. and Gabici, S., ArXiv e-prints p (2012) [LINK]
-
Gamma Rays from Cosmic Rays in Supernova Remnants
Dermer, C.D. and Powale, G., ArXiv e-prints p (2012) [LINK]
-
A 7 mm line survey of the shocked and disrupted molecular gas towards the W28 field TeV gamma-ray sources
Nicholas, B.P. et al., MNRAS 419 p251-266 (2012) [LINK]
-
Gamma-rays from molecular clouds illuminated by accumulated diffusive protons. II: interacting supernova remnants
Li, H. and Chen, Y., ArXiv e-prints p (2011) [LINK]
-
12 mm line survey of the dense molecular gas towards the W28 field TeV gamma-ray sources
Nicholas, B. et al., MNRAS 411 p1367-1385 (2011) [LINK]
-
Imaging of Four Galactic Supernovae Remnants in the Mid-Infrared, and their Interaction with the Interstellar Medium
Marquez-Lugo, R.A. and Phillips, J.P., ArXiv e-prints p (2010) [LINK]
-
Fermi LAT Observations of the Supernova Remnant W28 (G6.4-0.1)
The Fermi-LAT Collaboration: A.A. Abdo, ArXiv e-prints p (2010) [LINK]
-
AGILE detection of GeV gamma-ray emission from the SNR W28
Giuliani, A. et al., ArXiv e-prints p (2010) [LINK]
-
Molecular Clouds as a Probe of Cosmic-Ray Acceleration in a Supernova Remnant
Fujita, Y. et al., ApJ 707 pL179-L183 (2009) [LINK]
-
Discovery of very high energy gamma-ray emission coincident with molecular clouds in the W 28 (G6.4-0.1) field
Aharonian, F. et al., A&A 481 p401-410 (2008) [LINK]
-
Sub-mm/mm studies of the molecular gas in the Galactic disk; the TeV gamma ray SNR RXJ1713.7-3946 and the W28 high mass star forming region
Fukui, Y., ArXiv e-prints p (2008) [LINK]
-
Physical properties of molecular clouds as revealed by NANTEN CO survey: from the galactic center to the galactic warp
Mizuno, A. and Fukui, Y., 317 p59-+ (2004) [LINK]
-
Polarization Observations of 1720 MHz OH Masers toward the Three Supernova Remnants W28, W44, and IC 443
Claussen, M.J. et al., ApJ 489 p143-+ (1997) [LINK]
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