51 Pegasi - a planet-bearing Maunder minimum candidate

TL;DR

This study observed 51 Pegasi with X-ray telescopes, finding it exhibits very low X-ray activity consistent with a Maunder minimum star, and provides insights into its coronal temperature and activity state.

Contribution

First X-ray observations of 51 Pegasi indicating its very low activity level, supporting its classification as a Maunder minimum candidate and challenging the hot Jupiter activity enhancement hypothesis.

Findings

51 Peg has a coronal temperature below 1 million Kelvin.

The star shows very low X-ray flux consistent with Maunder minimum activity.

No evidence of activity enhancement from a Hot Jupiter was detected.

Abstract

We observed 51 Peg, the first detected planet-bearing star, in a 55 ks XMM-Newton pointing and in 5 ks pointings each with Chandra HRC-I and ACIS-S. The star has a very low count rate in the XMM observation, but is clearly visible in the Chandra images due to the detectors' different sensitivity at low X-ray energies. This allows a temperature estimate for 51 Peg's corona of T<1MK; the detected ACIS-S photons can be plausibly explained by emission lines of a very cool plasma near 200eV. The constantly low X-ray surface flux and the flat-activity profile seen in optical CaII data suggest that 51 Peg is a Maunder minimum star; an activity enhancement due to a Hot Jupiter, as proposed by recent studies, seems to be absent. The star's X-ray fluxes in different instruments are consistent with the exception of the HRC Imager, which might have a larger effective area below 200eV than given in the calibration.