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Call for Proposals for the East Asian VLBI Network (EAVN) for the 2025A semester Proposal submission deadline: 2024 November 1 (Fri.), 8:00 UT EAVN website: https://eavn.kasi.re.kr/

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--- Major revisions from the 2024B semester ---

* Telescope time provided by Sejong is changed tentatively in the 2025A semester (100 hours --> 50 hours; See also Section 3).

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*** 1. Overview ***

We invite proposals for open-use observations with the East Asian VLBI Network (EAVN), which is the international collaborative VLBI array between China, Korea, and Japan. In the 2025A semester, 15 telescopes (KaVA (VERA 4 x 20 m and KVN 4 x 21 m), Tianma 65 m, Sheshan 25 m, Nanshan 26 m, Takahagi 32 m, Hitachi 32 m, Yamaguchi 32 m, and Sejong 22 m) participate in the EAVN open-use program. Note that two partner telescopes of EAVN, Nobeyama 45 m and Kunming 40 m, do not join the open-use program in the 2025A semester.

*** 2. Observing mode ***

EAVN provides opportunities of VLBI observations with a data recording rate of 1 Gbps (total bandwidth of 256 MHz) and with single polarization at 6.7, 22, and 43 GHz. Dual-polarization mode is also opened on a shared-risk basis (KaVA 8 telescopes, Tianma, Nanshan, and Takahagi). Dual-frequency (22 and 43 GHz) simultaneous observation system can also be used for EAVN observations at KaVA and Sejong, while the observing term in which the system is available will be determined later. Note that only the single-polarization mode is operational for dual-frequency simultaneous observation. Details of available observing mode can be found in the EAVN Status Report on the EAVN website.

*** 3. Telescope time and array configuration *** The total available observation time for EAVN is up to 500 hours in the 2025A semester, while the available observing time for individual EAVN telescopes are different. Please refer to the EAVN status report on the EAVN website for more details. All EAVN observations will be allocated from 2025 January 16 – June 15, while note that Sejong’s telescope time will be available from 2025 March 1 for replacement of the receiver.

EAVN accepts a request for usage of sub-array configuration (KaVA 8 telescopes and additional telescopes from non-KaVA stations). There are several conditions of the antenna combination depending on the observing frequency. Further details about the sub-array configuration are shown in the EAVN status report.

*** 4. Maximum total request time ***

In the 2025A semester, no limitation of the maximum request time for a single proposal is determined in case of usage of only KaVA 8 telescopes, while one can request for the maximum total telescope time of 50 hours for Tianma and Nanshan, and 24 hours for Takahagi, Hitachi, Yamaguchi, and Sejong.

EAVN accepts a proposal which requests observations across two successive semesters (2025A (2025 January 16 – June 15) and 2025B (2025 September 1 – 2026 January 15)). In this case, one can request for the maximum total telescope time of 100 hours for Tianma and Nanshan, and 48 hours for Takahagi, Hitachi, Yamaguchi, and Sejong.

*** 5. Target of opportunity ***

EAVN accepts target of opportunity (ToO) proposals. Note that Sejong cannot be included for ToO proposals. It is strongly recommended that ToO proposals (especially expected ToO) are submitted during the regular CfP, while unexpected or urgent ToO can be submitted as Director's Discretionary Time (DDT) proposals at any time. Note that the total approved time for ToO observation in the 2025A semester is limited to be 100 hours for ToO proposals for both expected and unexpected events.

ToO proposals must address clear triggering criteria to initiate an observation. ToOs are valid for one year after it is approved. ToO proposals for DDT should follow the same way of regular call and should be submitted via the EAVN website.

*** 6. Proposal submission ***

Proposals should be submitted via the EAVN website. Proposers are asked to sign up with the EAVN website prior to submitting a proposal. Proposal submission deadline is 2024 November 1 (Fri.), 8:00 UT. Please refer to the EAVN status report for detailed information about the proposal format. The designated cover sheet form can be downloaded from the EAVN websites.

*** 7. Acknowledgment ***

All EAVN users are asked to specify the acknowledgment to EAVN in their publications. A template for the acknowledgment can be found in the EAVN website.

Sincerely,

Mareki Honma

Director of Mizusawa VLBI Observatory, NAOJ

Kee-Tae Kim

Director of Radio Astronomy Division, KASI

Zhi-Qiang Shen

Director of Shanghai Astronomical Observatory, CAS

and

Na Wang

Director of Xinjiang Astronomical Observatory, CAS