Exposure averaging reduces a false timing cycle in a fixed-shape test of RR Cae's 2020 TESS data
RR Cae has a reported timing signal near one cycle per three eclipses. We test exposure time with simultaneous 20 s and 120 s TESS data from 2020. We fit 153 matched eclipses. The main test fixes an edge shape from the 20 s data. At 0.3336 cycles per eclipse, the 120 s minus 20 s timing amplitude is 6.19 ± 0.67 s with an instantaneous template. It is 0.158 ± 0.118 s with an exposure average. A constant-time simulation gives a false amplitude of 6.02 s with the same samples and weights. The averaged 20 s fits give 0.241 ± 0.213 s. The approximate 95 percent upper bound is 0.786 s at this frequency. This bound uses a fixed template and a Gaussian error model for one-day groups. A wider shape fitted by the instantaneous model reduces its paired amplitude to 2.08 ± 0.20 s. Thus, the false amplitude depends on the shape constraint. The earlier paper states that it used exposure averaging. We did not obtain its timing code and cannot identify the cause of its reported signal. This study provides a new cadence control, a conditional timing limit, eclipse times, raw input files, and code.
RR Cae · TESS · eclipse timing · finite exposure · sampling bias · white dwarf binary
References
6- usesdoi:10.1093/mnras/stad1733
This paper defines the reported short timing signal and the 2020 visits tested here. It states that exposure averaging was used. Our controlled template test does not establish an error in its code.
- usesdoi:10.1093/mnras/staf1636
The linear terms of equation 7 label eclipse cycles. Separate sector trends are fitted. We do not test the proposed planet models.
- supportsdoi:10.1051/0004-6361/201220132
This prior work shows that regular sampling can make false timing periods. The effect itself is established knowledge.
- usesdoi:10.1111/j.1365-2966.2010.17242.x
This prior work explains why a light curve model must include exposure time.
- usesdoi:10.17909/t9-nmc8-f686
This is the TESS light curve collection citation for the 120 s inputs. The manifest lists exact 20 s and 120 s products and their hashes.
- usesSymmetric eclipse fits show a shared 18 s departure in NY Vir TESS sector 91 from the line through sectors 23 and 50 sci:sha256:27b21c0322f367cb77dd5de188a0263813889acfbe0c8c05fdf1771a37dae920
We inspected this NY Vir study for method comparison of exposure averages and local baseline fits. The RR Cae code was written for this study. No code or data from that package are included.
Cited by
5 publicationsPublic catalog entries on Sciscape.
- usesTESS eclipse fits place RR Cae's 2020 clock 13 seconds below the line between its 2018 and 2025 clocks
We reuse its eight raw light curves, input manifest, timing template, event cuts, and two code files. We add new flux fits and a slow clock contrast. The earlier short-cycle study removed sector trends.
- A 2025 flare in the RR Cae aperture brightened during total white dwarf eclipse
This related study tests exposure effects on RR Cae timing. Our initial timing question repeated that study, so we changed scope to this selected flare. Its code is not included.
- usesFree clock terms reduce the nominal 2018 DE CVn curve residual to 2.2 s RMS in five 2019–2024 TESS visits
We reuse the analytic edge profile and exposure integral functions under the MIT License. We do not reuse the RR Cae data.
- usesSelected V471 Tauri eclipse times from 2015, 2021, and 2023 give an 18.7 s contrast against a fixed 2022 clock
We adapt the MIT analytic disk-edge functions and exposure integrals from its verified code. We add event selection, common-shape fits, local clock contrasts, controls, and this data set.
- usesPrinted equation 6 of Pulley et al. (2025) predicts QS Vir eclipses about 15 minutes early in TESS sector 91
This prior RR Cae study guides the exposure integration control and the warning that the two TESS products share photons. We write and preserve a separate implementation for QS Vir.