Papers › A Study of the Magnetic Activity and Variability of GJ 436
A Study of the Magnetic Activity and Variability of GJ 436
M. Kumar, R. Fares
The archive published only this paper's code-link row. Authors, date and abstract are from arXiv's metadata (CC0), read from the Kaggle arXiv metadata snapshot of 2026-09-12 where its title matched the archive's; the title is the archive's.
We present a magnetic activity study of GJ 436 using spectroscopic data from HARPS, spanning over 14 years, and additional data from NARVAL, falling within the HARPS observations. We study the CaII H&K, HeID3, NaI doublet, Hα and CaII IRT triplets lines and explore linear correlations between them. Using the full HARPS dataset, we found indices Hα vs CaII H&K & Hα vs HeI to correlate positively. From the NARVAL dataset, covering one observing epoch, we found CaII IRT₃ vs CaII IRT₂ & CaII IRT₃ vs Hα index to correlate negatively. We investigate long and short-term periodicity in these index variations using the Generalised Lomb-Scargle periodogram. For CaII H&K, NaI and Hα indices, we detect long-term periods of 2470.7d (~ 6.8 years), 1861.6d (~ 5.1 years) and 2160.9d (~ 5.9 years) respectively, consistent with GJ 436's photometric cycle of ~ 7.4 years. Applying the "Pooled Variance" technique to Hα & NaI indices, we found ~ 2500d to be the period of an activity cycle mechanism, in good agreement with the detected 2470.7d period. For CaII H&K and Hα indices, we detect short-term periods of $39.47^{+0.11}_{-0.15}$d and $40.46^{+0.44}_{-0.52}$d respectively, identified as the stellar rotation period. The stellar rotation is detected after prewhitening the long-term periodicity. It is detected as well in the analysis of individual observing epochs.
Code
Repository list and official/mentioned flags are the archive's, frozen 2025-07-28. Reachability, where shown, is from one Syntology probe window (2026-09-16 to 2026-09-18); repositories not probed show nothing. GitHub stars are not tracked.
Code Syntology ran Syntology
Not run by Syntology. Nothing on this page verifies that the listed code works.
Results from the paper archive 2025-07-28
No leaderboard rows for this paper in the archive.
Report a problem or propose a change · a person checks every report against the paper or source before anything changes; decisions are listed on /corrections