The main goal of the Korean VLBI Network Calibrator Survey (KVNCS) is to expand the VLBI calibrators catalog for KVN, KaVA(KVN and VERA Array), EAVN(East-Asian VLBINetwork), and other extended regions. The secondKVNCS (KVNCS2) aimed to detect VLBI fringes of new candidates for calibrators in the K band. Out of the 1533 sources whose single-dish flux density in the K band was measured with KVN telescopes (Lee et al. 2017), 556 sources were observed with KVN in the K band. KVNCS2 confirmed the detection of VLBI fringes of 424 calibrator candidates over a single baseline. All detected sources had a high Signal-to-Noise Ratio (SNR) of >25. Finally, KVNCS2 confirmed 347 new candidates as VLBI calibrators in the K band, resulting in a 5% increase in the sky coverage compared to previous studies. The spatial distribution was quasi-uniform across the observable region (Dec. > −32.5◦). In addition, the possibility as calibrator candidates for the detected sources was checked, using an analysis of the flux-flux relationship. Ultimately, the KVNCS catalog will not only become the VLBI calibrator list but is also useful as a database of compact radio sources for astronomical studies.

Abstract
1. Introduction
2. Source Selection and Observation
3. Data Analysis
4. Results and Discussion
    4.1. Fringe Detection
    4.2. Spatial Distribution
    4.3. Flux-Flux Relationship
5. Summary
Acknowledgments
References

• Jeong Ae Lee(Korean Astronomy and Space Science Institute, 776, Daedeokdae-ro, Yuseong-gu, Daejeon, Republic of Korea) Corresponding Author
• Taehyun Jung(Korean Astronomy and Space Science Institute, University of Science ans Technology)
• Bong Won Sohn(Korean Astronomy and Space Science Institute, University of Science ans Technology)
• Do-Young Byun(Korean Astronomy and Space Science Institute, University of Science ans Technology)