Dear AAVSONet Telescope Allocation Committee,
As part of the PLATO benchmark eclipsing binaries initiative and also member of AAVSO, I would like to propose the observation of eclipses for the detached eclipsing binaries HD 4875, HD 22064, TYC 8547-22-1, CD-31 3271, and CD-27 2812, using the Optical Craftsman 0.61m Telescope (OC61), located at the Mount John University Observatory (MJUO), via the AAVSONet.
The PLATO (PLAnetary Transits and Oscillations of stars) is the third medium-class mission in ESA's Cosmic Vision program. PLATO was adopted by ESA Science Programme Committee in June 2017 and is due to be launched in 2026. Its objective is to find and study a large number of extrasolar planetary systems, with emphasis on the properties of terrestrial planets in the habitable zone around Sun like stars. PLATO has also been designed to investigate seismic activity in stars, enabling the precise characterization of the planet host stars, including its age.
The PLATO benchmark eclipsing binaries initiative, conducted by the PLATO Benchmark stars work package (WP 125 500) of the Determination of Stellar Parameters work package (WP 125 000), as part of the Stellar Science work package (WP12) (https://warwick.ac.uk/fac/sci/physics/research/astro/plato-science/resources/psmdocuments/plato-uwa-psm-wbs-0013_i4.0_wp120000_stellar_science_structure.pdf), has as one of its main objetives the coordination of benchmark observations for testing stellar models used by the PLATO mission, and for validation of the stellar parameters that will be provided in the PLATO mission data products (Gent et al. 2022).
The 20 detached eclipsing binary stars (DEBS) selected as targets for the benchmark show a total secondary eclipse with depths around 1 per cent and narrow eclipses (Maxted et al. 2023).
Observations in multiple filters of the secondary eclipse are needed to measure the flux ratio, in order to help improve the the accuracy and reliability of the effective temperature measurements for the two stars in the binary system. However, observations of the primary eclipse should also be useful for the analysis.
The observations of each eclipse must be conducted in high cadence using, using a par of photometric filters B and V (faint targets) or R and I (bright targets), in order to cover a complete ingress and/or egress of an eclipse plus some data before and after (~20 minutes) to measure the out-of-eclipse level and eclipse depth.
In addition, the 24" OC61 telescopes are particularly required for these observations due to the following factors:
- The 24" OC61 telescope is well suited for these targets in order to achieve the photometric precision required for HD 4875 at 11.08 ppt depth of the secondary eclipse and 8.97 V-mag star;
- The observability from the southern celestial hemisphere at the Mount John University Observatory is favorable for all these targets below +35° in declination, and its elevation at 1029 meters and Class 2 Bortle scale sky should be also helpful;
- The necessity for only ingress or egress observations of the eclipses, plus the required baseline observation of 20 minutes pre-ingress or post-egress, leads to minimum duration of 1.82 hours for the observing session of CD-31 3271 at best case. According to the Dr Karen Pollard (Director UC Mt John Observatory), this should provide a good match for the climate variations at the New Zealand site, and should also help minimize the conflict with other observation activities currently in place.
Finally, the observations would require a high cadence alternating between the most suitable pair of filters, and having the integration time adjusted accordingly in order to achieve a SNR~500 (or ~2 ppt RMS), not to exceed an interval of 2 minutes between exposures and also having the minimum dead time between them as low as possible, in order not to impact the precision of the eclipse model fit to the data.
The following list of predicted eclipse observations are suggested for the next 180 days for HD 4875 (OC61 - pre/post-baseline(s) already considered):
- 2024-08-08 14:59 (Session start time in UTC) to 18:33 (Session end time in UTC): secondary eclipse with 16% Moon illumination at 159˚ distance;
- 2024-08-29 11:18 (Session start time in UTC) to 18:07 (Session end time in UTC): primary eclipse with 18% Moon illumination at 104˚ distance;
- 2024-10-09 09:03 (Session start time in UTC) to 16:50 (Session end time in UTC): primary eclipse with 37% Moon illumination at 91˚ distance;
- 2024-10-29 10:29 (Session start time in UTC) to 14:03 (Session end time in UTC): secondary eclipse with 8% Moon illumination at 159˚ distance;
The following list of predicted eclipse observations are suggested for the next 180 days for TYC 8547-22-1 (OC61 - pre/post-baseline(s) already considered):
- 2024-09-02 11:40 (Session start time in UTC) to 14:37 (Session end time in UTC): primary eclipse with 0% Moon illumination at 85˚ distance;
- 2024-09-04 11:46 (Session start time in UTC) to 17:50 (Session end time in UTC): secondary eclipse with 2% Moon illumination at 86˚ distance;
- 2024-09-06 14:59 (Session start time in UTC) to 17:53 (Session end time in UTC): primary eclipse with 12% Moon illumination at 88˚ distance;
- 2024-09-21 10:59 (Session start time in UTC) to 17:02 (Session end time in UTC): secondary eclipse with 83% Moon illumination at 92˚ distance;
- 2024-09-23 14:11 (Session start time in UTC) to 17:21 (Session end time in UTC): primary eclipse with 61% Moon illumination at 89˚ distance;
- 2024-10-06 09:27 (Session start time in UTC) to 13:02 (Session end time in UTC): primary eclipse with 11% Moon illumination at 90˚ distance;
- 2024-10-08 10:11 (Session start time in UTC) to 16:15 (Session end time in UTC): secondary eclipse with 27% Moon illumination at 92˚ distance;
- 2024-10-10 13:24 (Session start time in UTC) to 16:48 (Session end time in UTC): primary eclipse with 48% Moon illumination at 94˚ distance;
- 2024-10-23 08:21 (Session start time in UTC) to 12:15 (Session end time in UTC): primary eclipse with 59% Moon illumination at 87˚ distance;
- 2024-10-25 09:24 (Session start time in UTC) to 15:27 (Session end time in UTC): secondary eclipse with 38% Moon illumination at 86˚ distance;
- 2024-10-27 12:36 (Session start time in UTC) to 16:16 (Session end time in UTC): primary eclipse with 20% Moon illumination at 86˚ distance;
- 2024-11-11 08:52 (Session start time in UTC) to 14:40 (Session end time in UTC): secondary eclipse with 74% Moon illumination at 96˚ distance;
- 2024-11-28 09:20 (Session start time in UTC) to 13:52 (Session end time in UTC): secondary eclipse with 7% Moon illumination at 89˚ distance;
- 2024-11-28 09:20 (Session start time in UTC) to 13:52 (Session end time in UTC): secondary eclipse with 7% Moon illumination at 89˚ distance;
- 2024-11-30 11:01 (Session start time in UTC) to 15:30 (Session end time in UTC): primary eclipse with 1% Moon illumination at 91˚ distance;
The following list of predicted eclipse observations are suggested for the next 180 days for CD-31 3271 (OC61 - pre/post-baseline(s) already considered):
- 2024-09-11 15:28 (Session start time in UTC) to 17:44 (Session end time in UTC): secondary eclipse with 55% Moon illumination at 119˚ distance;
- 2024-09-28 12:24 (Session start time in UTC) to 15:42 (Session end time in UTC): secondary eclipse with 15% Moon illumination at 68˚ distance;
- 2024-10-12 12:44 (Session start time in UTC) to 16:44 (Session end time in UTC): primary eclipse with 69% Moon illumination at 116˚ distance;
- 2024-10-29 10:22 (Session start time in UTC) to 14:06 (Session end time in UTC): primary eclipse with 8% Moon illumination at 87˚ distance;
- 2024-11-12 11:11 (Session start time in UTC) to 14:46 (Session end time in UTC): secondary eclipse with 84% Moon illumination at 94˚ distance;
- 2024-11-26 11:49 (Session start time in UTC) to 15:34 (Session end time in UTC): primary eclipse with 19% Moon illumination at 92˚ distance;
- 2024-11-29 09:22 (Session start time in UTC) to 11:26 (Session end time in UTC): secondary eclipse with 4% Moon illumination at 108˚ distance;
- 2024-12-10 13:37 (Session start time in UTC) to 15:26 (Session end time in UTC): secondary eclipse with 72% Moon illumination at 89˚ distance;
- 2024-12-27 10:17 (Session start time in UTC) to 13:52 (Session end time in UTC): secondary eclipse with 12% Moon illumination at 112˚ distance;
The following list of predicted eclipse observations are suggested for the next 180 days for CD-27 2812 (OC61 - pre/post-baseline(s) already considered):
- 2024-10-21 12:28 (Session start time in UTC) to 16:27 (Session end time in UTC): secondary eclipse with 77% Moon illumination at 58˚ distance;
- 2024-10-29 10:25 (Session start time in UTC) to 13:56 (Session end time in UTC): secondary eclipse with 8% Moon illumination at 90˚ distance;
The following list of predicted eclipse observations are suggested for the next 180 days for HD 22064 (OC61 - pre/post-baseline(s) already considered):
- 2024-10-26 13:06 (Session start time in UTC) to 16:18 (Session end time in UTC): secondary eclipse with 28% Moon illumination at 100˚ distance;
- 2024-12-20 09:45 (Session start time in UTC) to 12:49 (Session end time in UTC): secondary eclipse with 73% Moon illumination at 101˚ distance;
Cordially,
Andre Kovacs | 