WHAT IS THE REDSHIFT OF THE GAMMA-RAY BL LAC SOURCE S4 0954+65?

ABSTRACT High signal-to-noise ratio spectroscopic observations of the BL Lac object S4 0954+65 at the alleged redshift z = 0.367 are presented. This source was detected at gamma frequencies by the MAGIC (TeV) and FERMI (GeV) telescopes during a remarkable outburst that occurred in 2015 February, mak...

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Bibliographic Details
Published in:The Astronomical journal 2015-12, Vol.150 (6), p.1-4
Main Authors: Landoni, M., Falomo, R., Treves, A., Scarpa, R., Payá, D. Reverte
Format: Article
Language:English
Subjects:
ABSORPTION SPECTROSCOPY
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BL LACERTAE OBJECTS
BL Lacertae objects: individual (S4 0954+65)
COSMIC PHOTONS
EMISSION SPECTROSCOPY
Equivalence
Estimates
Gamma rays
gamma rays: general
GEV RANGE
Outbursts
RED SHIFT
SIGNAL-TO-NOISE RATIO
Spectroscopy
TELESCOPES
TEV RANGE
VISIBLE RADIATION
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Summary:ABSTRACT High signal-to-noise ratio spectroscopic observations of the BL Lac object S4 0954+65 at the alleged redshift z = 0.367 are presented. This source was detected at gamma frequencies by the MAGIC (TeV) and FERMI (GeV) telescopes during a remarkable outburst that occurred in 2015 February, making the determination of its distance particularly relevant for our understanding of the properties of the extragalactic background light. Contrary to previous reports on the redshift, we found that the optical spectrum is featureless at an equivalent width limit of ∼0.1 . A critical analysis of the existing observations indicates that the redshift is still unknown. Based on the new data we estimate a lower limit to the redshift at z ≥ 0.45.
ISSN:0004-6256
1538-3881
1538-3881
DOI:10.1088/0004-6256/150/6/181