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Observation Date (UT) Observation Lat

Canonical Name:SNR G327.1-01.1
TeVCat Name:TeV J1554-550
Other Names:HESS J1554-550
Source Type:PWN
R.A.:15 54 37 (hh mm ss)
Dec.:-55 05 27 (dd mm ss)
Gal Long: 327.16 (deg)
Gal Lat: -1.08 (deg)
Distance: 9 kpc
Flux:0.015 (Crab Units)
Energy Threshold:1000 GeV
Spectral Index:2.19
Extended:No
Discovery Date:2012-01
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 J1554-550
Source Class: PWN
Identified Object: G327.1-01.1
R.A. (J2000): 238.65 deg (15 54 37)
Dec. (J2000): -55.09 deg (-55 05 27)
Positional uncertainty: 0.020 deg
Spatial Model: Gaussian
Size: N/A
Spectral Model: power law
Integral Flux > 1 TeV: 2.91e-13 +/- 5.73e-14 cm-2 s-1
Pivot Energy, E0: 2.26 TeV
Diff. Flux at E0: 5.79e-14 +/- 1.14e-14 cm-2 s-1 TeV-1
Spectral Index: 2.19 +/- 0.17
HGPS Source Notes:
This is one of the 31 firmly-identified objects among the HGPS sources. One possible association is 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":
- G327.1−1.1 (COMP)

"Composite SNRs have both a shell and an interior PWN detected at lower energies and can be more complex to identify correctly. If the angular size of the shell emission is larger than the size of the VHE emission, we can identify the VHE emission as coming from the PWN filling the SNR. This is the case for HESS J1554−550 (PWN in SNR G327.1−1.1)."

"VHE gamma-ray emission from HESS J1554−550 is firmly identified with the PWN G327.15−1.04 within the composite SNR G327.1−1.1, on the basis of both a spatial coincidence with the PWN and the size of the VHE emission region, which can be constrained to less than 0.035deg. Preliminary H.E.S.S. morphological and spectral properties of the VHE source were first published by Acero et al. (2012) and are compatible with the HGPS results. However, while previously the source size was given as 0.03deg +/- 0.01deg, the more conservative HGPS analysis procedure used here finds the source to be compatible with being point-like, and there is a limit on the size that is nonetheless compatible."

"The VHE size limit rules out significant emission from the outer shell of the SNR and is compatible with the compact, nonthermal PWN, which is observed in both radio and X-rays (Temim et al. 2009, 2015) but not HE gamma rays (Acero et al. 2013; Ackermann et al. 2016). Furthermore, the VHE centroid is compatible with the peak of the radio emission from the PWN and the tail of X-ray PWN. Although pulsed emission from the putative pulsar at the heart of the composite SNR has not been detected in radio, X-ray, nor HE gamma-ray bands, the X-ray data provide evidence for the existence of a powerful pulsar, that has an estimated Edot = 3.1 x 10e36 erg s-1 (Temim et al. 2015). The distance to the SNR is not well determined, but has been estimated to be roughly 9 kpc (Sun et al. 1999). Assuming this distance, the VHE luminosity of HESS J1554−550 is L_gamma(1−10 TeV) = 1.0 x 10e34(d/9 kpc)^2 erg s−1 and the apparent efficiency is 0.3%, which is compatible with the efficiencies (<~10%) of other VHE sources that have been identified as PWNe (Kargaltsev et al. 2013)."

Source Position:
The source position was updated from that of Acero et al. (2012) to
that of H.E.S.S. Collaboration (2018) on 191023.
From H.E.S.S. Collaboration (2018):
- R.A. (J2000): 15 54 37
- Dec. (J2000): -55 05 27
- Positional uncertainty: 0.020 deg
From Acero et al. (2012):
- R.A. (J2000): 15h 54m 36s +/- 1' (stat)
- Dec. (J2000): -55d 05m 05s +/- 1' (stat)

Spectral Properties:
The index was updated from that of Acero et al. (2012) to
that of H.E.S.S. Collaboration (2018) on 191023.
From H.E.S.S. Collaboration (2018):
- Spectral index: 2.19 +/- 0.17
From Acero et al. (2012):
- Spectral index: 2.1 +/- 0.2(stat) +/- 0.2(syst)

Source Extent:
The source position was updated from that of Acero et al. (2012) to
that of H.E.S.S. Collaboration (2018) on 191023.
From H.E.S.S. Collaboration (2018):
- " while previously the source size was given as 0.03deg +/- 0.01deg,
the more conservative HGPS analysis procedure used here finds the
source to be compatible with being point-like, and there is a limit on
the size that is nonetheless compatible."
- the VHE emission region is "constrained to less than 0.035deg"
From Acero et al. (2012):
- 1.8' +/- 0.6'(stat)

Source Association:
From H.E.S.S. Collaboration (2018):
- "VHE gamma-ray emission from HESS J1554−550 is firmly identified
with the PWN G327.15−1.04 within the composite SNR G327.1−1.1, on the
basis of both a spatial coincidence with the PWN and the size of the
VHE emission region, which can be constrained to less than 0.035deg."
From Acero et al. (2012):
- "... the gamma-ray emission is contained in the interior of the remnant,
where the bright PWN is observed both in the radio and the X-ray band. It is
also interesting to note that no gamma-ray emission is detected from the shell
of the remnant."

Distance:
From H.E.S.S. Collaboration (2018):
- The distance to the SNR is not well determined, but has been estimated
to be roughly 9 kpc ( Sun et al. 1999).


Seen by: H.E.S.S.
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