Bibcode
Landoni, M.; Falomo, R.; Treves, A.; Scarpa, R.; Reverte Payá, D.
Bibliographical reference
The Astronomical Journal, Volume 150, Issue 6, article id. 181, 4 pp. (2015).
Advertised on:
12
2015
Citations
27
Refereed citations
25
Description
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
Å. 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.
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