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Observation Date (UT) Observation Lat

Canonical Name:SS 433
TeVCat Name:TeV J1911+049
Other Names:1LHAASO J1910+0516*
1LHAASO J1913+0501
Source Type:Binary
R.A.:19 11 49.6 (hh mm ss)
Dec.:+04 58 57.8 (dd mm ss)
Gal Long: 39.69 (deg)
Gal Lat: -2.24 (deg)
Distance: 5.5 kpc
Flux: (Crab Units)
Energy Threshold: GeV
Spectral Index:2
Extended:Yes
Size (X):0.35 (deg)
Size (Y):0.00 (deg)
Discovery Date:2018-10
Discovered By: HAWC
TeVCat SubCat:Default Catalog

Source Notes:

This source was formally two entries in TeVCat (SS 433 e1 & SS 433 w1).
They were combined to one entry on 20241021.

Source Position:

Since the gamma-ray emission is localised to multiple regions in
SS 433, the source position quoted in TeVCat is that given in SIMBAD.
That position is taken from Gaia Collaboration (2020):
- R.A. (J2000): 19h 11m 49.6s
- Dec. (J2000): +04d 58' 57.8''

From HAWC Collaboration (2018):
- "The gamma-ray emission is spatially coincident with the X-ray
hotspots w1 and e1; no significant emission is observed at the
location of the central binary where the jets are produced"
Position of e1 from the simultaneous fit to the E+W hotspots:
- R.A. (J2000): 19h 13m 37s
- Dec. (J2000): +04d 55' 48''
Position of w1 from the simultaneous fit to the E+W hotspots:
- R.A. (J2000): 19h 10m 37s
- Dec. (J2000): +05d 02' 13''

Source Properties:

From HAWC Collaboration (2018):
- "SS 433 is a binary system containing a supergiant star that is
overflowing its Roche lobe with matter accreting onto a compact object
(either a black hole or neutron star) 1-3. Two jets of ionized matter
with a bulk velocity of approx. 0.26c extend from the binary,
perpendicular to the line of sight, and terminate inside W50, a
supernova remnant that is being distorted by the jets."
- "The lobes of W50 in which the jets terminate, about 40 pc from the
central source, are expected to accelerate charged particles, and
indeed radio and X-ray emission consistent with electron synchrotron
emission in a magnetic field have been observed. At higher energies
(> 100 GeV), the particle fluxes of γ rays from X-ray hotspots around
SS 433 have been reported as flux upper limits"
- "The TeV emission is localized to structures in the lobes, far from
the center of the system where the jets are formed. We have measured
photon energies of at least 25 TeV, and these are certainly not
Doppler boosted, because of the viewing geometry. We conclude that the
emission from radio to TeV energies is consistent with a single
population of electrons with energies extending to at least hundreds
of TeV in a magnetic field of approx. 16 micro-Gauss."

Source Extent:

From HAWC Collaboration (2018):
- "Upper limits on the angular size of the emission regions are 0.25 deg
for the east hotspot and 0.35 deg for the west hotspot at 90% confidence."
-"Given the distance to the source of 5.5 kpc, this corresponds to a
physical size of 24 pc and 34 pc, respectively. The constraint is
tighter on the eastern hotspot due to its higher statistical
significance."

Distance:

From HAWC Collaboration (2018):
- a distance of 5.5 kpc is quoted.

Spectral Information:

From HAWC Collaboration (2018):
- "The VHE gamma-ray flux is consistent with a hard E -2 spectrum,
though current data from HAWC are not of sufficient significance to
constrain the spectral index."
- "Therefore we report the flux of both hotspots at 20 TeV, where
systematic uncertainties due to the choice of spectral model are
minimized and the sensitivity of HAWC is maximized."
- VHE flux at e1: 2.4 +0.6 -0.5 (stat) +1.3 -1.3 (syst) e10-16 TeV-1 cm-2 s-1
- VHE flux at w1: 2.1 +0.6 −0.5 (stat) +1.2 -1.2 (syst) e10-16 TeV-1 cm-2 s-1

Gamma-ray emission:

From Xiao-Naet al. (2019):
- the authors analyse 10 years of Fermi-LAT data detecting it with a
significance of 5.5 sigma between 500 MeV and 10 GeV.
- "Our analysis indicates that an extended flat disk morphology is
preferred over a point-source description, suggesting that the GeV
emission region is much larger than that of the TeV emission detected
by HAWC."
- "The size of the GeV emission is instead consistent with the extent
of the radio nebula W50, a supernova remnant being distorted by the
jets, so we suggest that the GeV emission may originate from this
supernova remnant. The spectral result of the GeV emission is also
consistent with an supernova remnant origin."
- "We also derive the GeV flux upper limits on the TeV emission
region, which put moderate constrains on the leptonic models to
explain the multiwavelength data."

From HAWC Collaboration (2018):
- "In 1017 days of measurements with HAWC, an excess of gamma rays
with a post-trials significance of 5.4 sigma has been observed in a
joint fit of the eastern and western interaction regions of the jets
of SS 433."
- "The gamma-ray emission is spatially coincident with the X-ray
hotspots w1 and e1; no significant emission is observed at the
location of the central binary where the jets are produced"
- "HAWC detects gamma rays from the interaction regions up to at least
25 TeV. The energies of these gamma rays are a factor of three to ten
higher than previous measurements from microquasars (Albert et al. 2006,
Archambault et al. 2016). Since most gamma-ray telescopes are
optimized for measurements below 10 TeV, this may explain why these
photons were not observed in previous observational campaigns."

From MAGIC and H.E.S.S. Collaborations (2018):
- "We made use of dedicated observations from the Major Atmospheric
Gamma Imaging Cherenkov telescopes (MAGIC) and High Energy
Spectroscopic System (H.E.S.S.) of SS 433 taken from 2006 to
2011. These observation were combined for the first time and accounted
for a total effective observation time of 16.5 h, which were scheduled
considering the expected phases of minimum absorption of the putative
VHE emission."
- "No evidence of VHE gamma-ray emission either from the central
binary system or from the eastern/western interaction regions was
found."
- "Upper limits were computed for the combined data set. Differential
fluxes from the central system are found to be:
... =< 10e-12 - 10e-13 TeV-1 cm-2 s-1
in an energy range from few x 100 GeV to few TeV.
Integral flux limits down to
... 10e-12 - 10e-13 ph cm-2 s-1 and 10e-13 - 10e-14 ph cm-2 s-1 are obtained
at 300 and 800 GeV, respectively. "


Seen by: HAWC, LHAASO
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