Mysteries Department
Sign inRequest access
MethodsGround-based photometry / multi-observer time seriesObserver-offset ensemble reduction of the AAVSO record
Method · ground-based photometry / multi-observer time series

Observer-offset ensemble reduction of the AAVSO record

Measure the star's year-scale brightness history from 2015 to the present, where observer-to-observer zero-points of a few hundredths of a magnitude would otherwise dominate.

Ground-based photometry / multi-observer time seriesVersion 1.0Licence MIT1 runUsed on 1 mystery

Questions it answers

Code Python

Download module (.py)aavso_reduce.pyView source

Runs and results 1 run

RunMysteryMeasuredResultAgainstDate
RUN0DED7WSPR1ENTabby'sSeasonal median relative to 2019; least-squares slope in mmag per year within 2015.7-2018.2 and 2018.5-2026.9; changepoint BIC gain{'B': {'n_obs': 31245, 'nights': 2680, 'observers': 17, 'slope_2015.7_2018.2': [2.41, 2.56], 'slope_2018.5_2026.9': [1.79, 0.45]}, 'V': {'n_obs': 80214, 'nights': 3117, 'seasonal': {'2015': -0.0037, '2016': 0.0024, '2017': 0.0132, '2018': 0.004, '2019': 0, '2020': 0.0025, '2021': 0.002, '2022': 0.0074, '2023': 0.001, '2024': -0.003, '2025': 0.006, '2026': 0.0009}, 'observers': 24, 'slope_2015.7_2018.2': [8.51, 2.58], 'slope_2018.5_2026.9': [-0.04, 0.32], 'changepoint_bic_gain': -3.2}}simon2018 +6.3 +/- 1.4 mmag/yr (2015-2017, ASAS-SN bd) · schaefer2018 0.023 mag in B over 2015.75-2018.18 (about 9.6 mmag/yr), V 0.77 x B · asassn_catalogue_v1 -0.5 +/- 1.2 mmag/yr 2015-2018 (this department, Session 2)

Applied to

Tabby's star (KIC 8462852)
2 datasetsAAVSO International Database export for KIC 8462852, 1 July 2018 to 29 October 2026 (77,195 observations, with comparison stars), AAVSO International Database export for KIC 8462852, October 2015 to June 2018 (66,875 observations, with comparison stars)

References

  1. Schaefer, B., Bentley, R., Boyajian, T. et al. 2018. The KIC 8462852 light curve from 2015.75 to 2018.18 shows a variable secular decline. Monthly Notices of the Royal Astronomical Society 481(2), 2235–2248.
  2. ASAS-SN 2015-2017: fade of 6.3 +/- 1.4 mmag per year, more extreme than 99.4 per cent of 1,078 comparison stars; ASAS V 2006-2017 shows brightening 2006-07, dimming 2009-13 (15.8 +/- 1.5 mmag/yr) and brightening around 2014, so a straight line is a poor description. The modern-era reference for the fade's non-monotonic history.
Private beta Downloads are for beta members

We're in a private beta while we get things right. Everything here is free to read; downloading datasets, sources and code is open to members for now.

Apply to the betaSign in
It takes a couple of minutes. We'll reply by email.