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Observation Date (UT) Observation Lat

Canonical Name:H 1722+119
TeVCat Name:TeV J1725+118
Other Names:
Source Type:HBL
R.A.:17 25 04.3 (hh mm ss)
Dec.:+11 52 15 (dd mm ss)
Gal Long: 34.12 (deg)
Gal Lat: 24.48 (deg)
Flux:0.02 (Crab Units)
Energy Threshold:150 GeV
Spectral Index:
Discovery Date:2013-05
Discovered By: MAGIC
TeVCat SubCat:Default Catalog

Source Notes:

160322: The source was moved from "Newly Announced" to "Default" catalogue.

Source Position:

No source position or positional uncertainty is provided.
From NED:
- R.A. (J2000): 17h 25m 04.3s
- Dec. (J2000): +11d 52m 15s


From Zahoor et al. (2021):
- In this work, the effect of the absorption of the extragalactic
galactic background light was used to place constraints on the
redshifts of gamma-ray sources.
- "The very high energy (VHE) gamma-ray spectral indices of blazars
show strong correlation with the source redshift. Absence of any such
correlation in low energy gamma rays and X-rays indicate the presence
of Extragalactic Background Light (EBL) induced absorption of VHE
gamma rays. By employing a linear regression analysis, this
observational feature of blazars is used to constrain the redshift of
BL Lac objects which was unknown/uncertain earlier."
- Two different regression relations were used to constrain the source
redshift and the following values were found for H 1722+119:
- z = 0.15 +/- 0.07
- z = 0.13 +/- 0.06

From Ahnen et al. (2016):
- "We used contemporaneous high energy gamma-ray observations from
Fermi-LAT to estimate the redshift of the source. Within the framework
of the current extragalactic background light models, we estimate the
redshift to be z = 0.34 +/- 0.15"

From Landoni et al. (2014):
- "We secured optical and near-infrared medium-resolution spectra of
four bright BL Lac objects of unknown redshift using the spectrograph
X-Shooter at the ESO-VLT. "
- "In spite of the high quality of the spectra and the extended
spectral range of the observations, we have not detected intrisic
spectral features for these sources. However, we are able to provide
strigent lower limits to their redshift." (For two TeV sources: PG
1553+113 and H 1722+119)
- For H 1722+119 they inferred z > 0.35

From Cortina for the MAGIC Collaboration (2013):
- " Its redshift is uncertain; Sbarufatti et al. 2006 give z>0.17."

Spectral information:

From Ahnen et al. (2016):
- Spectral index: 3.3 +/- 0.3(stat) +/- 0.2(syst)


From Ahnen et al. (2016):
- a flux at the level of 2.5 +/- 0.5 per cent of that from the Crab
Nebula above 150 GeV was detected
- no evidence for flux variability on a night-by-night basis was found


Ahnen et al. (2016) note that this source was classified as an IBL
by Nieppola et al. (2006). The source is classified as
a HSP in the Fermi-LAT 3LAC so we classify it as a HBL here.

Additional Information:

From Ahnen et al. (2016):
- "The results reported here are based on the observa- tions performed
during six nights between 2013 May 17 and 22, triggered by the high
optical state detected by the KVA (Kungliga Vetenskaps
Akademientelescope) located at the Observatorio del Roque de los
Muchachos, La Palma (Canary Islands, Spain), and operated by the
Tuorla Observatory, Finland"
From Cortina for the MAGIC Collaboration (2013):
- "The MAGIC observations were triggered by the extended optical high
state of the source, reported by the Tuorla blazar monitoring program"

Seen by: MAGIC
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