Proposal #310

Target:
RT Cru

Magnitude range (according to VSX):
>11.1 - 13.3 V

Requested filters:
B, V, R, I

Exposition times:
The best possible in telescope owner's opinion. I request two (2x) images per filter to be made during every run (and uploaded to my VPhot account).

Observation cadence:
Daily (if time is available).

Observations start date:
As soon as possible.

Expiration date (YYYY-MM-DD format):
2023-06-01 (Of course, I am open to any changes if such are necessary.)

RT Cru is a ZAND type variable star with orbital period of 325 days and pulsation period of 63 days. According to Enhanced LCG, last observation of RT Cru was made on 2022-08-31. In total, there are 33590 observations of this star in AAVSO database (29123 in V-band and 2893 in B-band). RT Cru's case was included and described in scientific publications. Here are few examples:

- "The Nature of the Hard X-Ray-Emitting Symbiotic Star RT Cru" - G. J. M. Luna ; J. L. Sokoloski,

- "Light curves of symbiotic stars in massive photomeric surveys II: S and D’-type systems" - M. Gromadzki ; J. Mikołajewska ; I. Soszyński,

- "Observations of suspected symbiotic stars" - D. Cieslinski ; F. Elizalde ; J. E. Steiner.

There have been 4 notices for RT Cru in the AAVSO Alert Notice over several years:
- Special Notice #411: RT Cru observations need to be continued,
- Special Notice #409: Chandra observations scheduled for RT Cru,
- Alert Notice 503: Request for regular monitoring of the symbiotic variable RT Cru,
- Alert Notice 451: Monitoring of the Symbiotic Variable RT Cru Requested.

Therefore, I would like to provide continuity of photometric measurements. BSM-Berry (Bolt) is probably the best suited site for this proposal.
However, because R filter is not available there I would request only BVI images to be made if the proposal is accepted and allocated to BSM-Berry.

The star is said to be flickering in a 10-30 min. time scale.

All data would be submitted to AAVSO database after VPhot analysis.

Krzysztof Zieliński (ZKRA)