An Updated Search of Steady TeV $\gamma-$Ray Point Sources in Northern Hemisphere Using the Tibet Air Shower Array

TL;DR

This study updates a northern sky survey for TeV gamma-ray point sources using Tibet Air Shower Array data, finding no new sources but setting improved flux upper limits and confirming known sources like Crab Nebula and Mrk421.

Contribution

The paper provides an updated analysis with nearly three times more data, improving flux limits and confirming known sources in the northern hemisphere.

Findings

No new TeV gamma-ray sources detected.

Flux upper limits improved by 1.7 times.

Crab Nebula and Mrk421 remain the brightest sources.

Abstract

Using the data taken from Tibet II High Density (HD) Array (1997 February-1999 September) and Tibet-III array (1999 November-2005 November), our previous northern sky survey for TeV $\gamma-$ray point sources has now been updated by a factor of 2.8 improved statistics. From $0.0^{\circ}$ to $60.0^{\circ}$ in declination (Dec) range, no new TeV $\gamma-$ray point sources with sufficiently high significance were identified while the well-known Crab Nebula and Mrk421 remain to be the brightest TeV $\gamma-$ray sources within the field of view of the Tibet air shower array. Based on the currently available data and at the 90% confidence level (C.L.), the flux upper limits for different power law index assumption are re-derived, which are approximately improved by 1.7 times as compared with our previous reported limits.