X-rays in Cepheids: XMM-Newton Observations of $\eta$ Aql

TL;DR

This study used XMM-Newton to observe the Cepheid $ta$ Aql at maximum radius phase, finding no X-ray emission, and also investigated its stellar environment, providing insights into Cepheid atmospheres and surroundings.

Contribution

First X-ray observation of $ta$ Aql at maximum radius phase, testing for X-ray bursts similar to other Cepheids, and analysis of its stellar neighborhood.

Findings

No X-ray emission detected from $ta$ Aql at the observed phase.

No stellar grouping found around $ta$ Aql based on Gaia and 2MASS data.

Implications discussed for Cepheid upper atmosphere activity.

Abstract

X-ray bursts have recently been discovered in the Cepheids $\delta$ Cep and $\beta$ Dor modulated by the pulsation cycle. We have obtained an observation of the Cepheid $\eta$ Aql with the XMM-Newton satellite at the phase of maximum radius, the phase at which there is a burst of X-rays in $\delta$ Cep. No X-rays were seen from the Cepheid $\eta$ Aql at this phase, and the implications for Cepheid upper atmospheres are discussed. We have also used the combination of X-ray sources and Gaia and 2MASS data to search for a possible grouping around the young intermediate mass Cepheid. No indication of such a group was found.