In the period between 2009 and 2015, several very high-energy (VHE >100 GeV) gamma-ray flaring events from the BL Lac object PKS 1424+240 were observed by the Cerenkov telescopes VERITAS and MAGIC. It had uncertain redshift (z) and using spectroscopical measurement, Paiano et al. (2017) found it to be z=0.604. Using four different extragalactic background light (EBL) models and the photohadronic model, nine independently observed VHE gamma-ray spectra of PKS 1424+240 are analyzed and a global χ2 fit is performed on all observations to estimate the best-fit value for the redshift for each EBL model. Confidence levels (CL) intervals for the redshift are also estimated using all the EBL models. This method is tested by comparing our analysis with the observed value. It is shown that the photohadronic scenario provides an excellent description of all the observed spectra. It is found that the EBL model of Dom\'inguez et al. (2011) is the one that provides the most restrictive limits on the redshift of PKS 1424+240, but in our analysis, z=0.604 lies within the 3σ CL interval of the EBL model of Saldana-Lopez et al. (2021).
@article{arxiv.2407.19134,
title = {Redshift constrain of BL Lac PKS 1424+240},
author = {Sarira Sahu and D. I. Páez-Sánchez and B. Medina-Carrillo and R. de J. Pacheco-Aké and G. Sánchez-Colón and Subhash Rajpoot},
journal= {arXiv preprint arXiv:2407.19134},
year = {2024}
}