相关论文: The redshift of the BL Lac object TXS 0506+056
The determination of the redshift of extragalactic gamma ray sources is of fundamental importance for the interpretation of their emission models and extragalactic population studies, AGN classification schemes, and to study the interaction…
We present our follow-up observations to search for an electromagnetic counterpart of the IceCube high-energy neutrino, IceCube-170922A. Monitoring observations of a likely counterpart, TXS 0506+056, are also described. First, we quickly…
A neutrino with energy of $\sim$290 TeV, IceCube-170922A, was detected in coincidence with the BL Lac object TXS~0506+056 during enhanced gamma-ray activity, with chance coincidence being rejected at $\sim 3\sigma$ level. We monitored the…
The BL Lac object 4FGLJ0955.1+3551 has been suggested as a possible source of ultra energetic neutrinos detected by the Icecube observatory. The target was observed in January 2020 at the Large Binocular Telescope. Our spectroscopy…
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 MAGIC (TeV) and FERMI (GeV) telescopes during a…
We report results of a spectroscopic campaign carried out at the 10 m Gran Telescopio Canarias for a sample of 22 BL Lac objects detected (or candidates) at TeV energies, aimed to determine or constrain their redshift. This is of…
Following the high activity of the gamma-ray Fermi source 4FGL J0449.1+1121 (PKS 0446+112), possibly associated with a IceCube neutrino event IC-240105A, we obtained optical spectroscopy with the Gran Telescopio Canarias of the counterpart.…
We report on the redshift of the BL Lac object 3FGL J0909.0+2310 based on observations obtained with the OSIRIS Multi Object Spectrograph (MOS) mounted on the 10.4-m Gran Telescopio Canarias. A redshift of 0.432+/-0.002 was obtained by the…
The recent spatial and temporal coincidence of the blazar TXS 0506+056 with the IceCube detected neutrino event IC-170922A has opened up a realm of multi-messenger astronomy with blazar jets as a plausible site of cosmic-ray acceleration.…
Aims: The determination of elusive redshifts of bright BL Lac objects Methods: We use the capabilities of newly available spectrograph X-Shooter at European Southern Observatory (ESO) Very Large Telescope, that combines high resolution and…
A correlation between astrophysical high-energy neutrinos and blazars has been suggested by various authors. In particular, a likely association between IceCube events and intermediate and high-energy peaked BL Lac objects has led to a…
Aims. We aim to determine the redshift (or stringent lower limits) of a number of bright BL Lacs objects. Methods. We secured medium resolution optical and near-infrared spectra of 4 bright BL Lac objects of unknown redshift using the…
While blazars have long been one of the candidates in the search for the origin of ultra-high energy cosmic rays and astrophysical neutrinos, the BL Lac object TXS 0506+056 is the first extragalactic source that is correlated with some…
We are carrying out a program of high signal to noise optical spectroscopy of BL Lacs with unknown or tentative redshift. Here we report some preliminary results. New redshifts are measured for PKS0754+100 (z=0.266) and 1ES0715-259…
We are carrying out a multi-purpose program of high signal to noise optical spectroscopy at medium resolution of 30 BL Lac objects. Here we report the detection of three new redshifts, and the discovery of three misclassified sources. The…
The blazar TXS 0506+056 got into the spotlight of the astrophysical community in September 2017, when a high-energy neutrino detected by IceCube (IceCube-170922A) was associated at the 3 $\sigma$ level to a $\gamma$-ray flare from this…
On 2017 September 22, the IceCube Neutrino Observatory reported the detection of the high-energy neutrino event \icnu, of potential astrophysical origin. It was soon determined that the neutrino direction was consistent with the location of…
TXS 0506+056 is a blazar that has been recently identified as the counterpart of the neutrino event IceCube-170922A. Understanding blazar type of TXS 0506+056 is important to constrain the neutrino emission mechanism, but the blazar nature…
We report redshift measurements for 12 BL Lacertae objects from a program aimed at obtaining high signal to noise (up to ~ 500) optical spectroscopy of a mixed sample of objects. The new observations, gathered with the 8 m ESO Very Large…
The uncertainty region of the highly energetic neutrino IceCube200107A includes 3HSP J095507.9+355101 ($z$~=~0.557), an extreme blazar, which was detected in a high, very hard, and variable X-ray state shortly after the neutrino arrival.…