X-ray Emission from the FU Orionis Star V1735 Cygni

TL;DR

This study reports the first X-ray detections of the FU Orionis star V1735 Cygni and a nearby embedded protostar, revealing high-temperature plasma indicative of magnetic activity rather than accretion shocks.

Contribution

It provides the first X-ray spectra of V1735 Cygni, showing high-temperature plasma and magnetic activity signatures in FU Orionis objects.

Findings

High-temperature plasma (kT > 5 keV) detected in V1735 Cygni and a nearby protostar.

No large X-ray flares observed during the study.

Hard X-ray emission suggests magnetic processes, not accretion shocks.

Abstract

The variable star V1735 Cyg (= Elias 1-12) lies in the IC 5146 dark cloud and is a member of the class of FU Orionis objects whose dramatic optical brightenings are thought to be linked to episodic accretion. We report the first X-ray detections of V1735 Cyg and a deeply-embedded class I protostar lying 24 arcsecs to its northeast. X-ray spectra obtained with EPIC on XMM-Newton reveal very high-temperature plasma (kT > 5 keV) in both objects, but no large flares. Such hard X-ray emission is not anticipated from accretion shocks and is a signature of magnetic processes. We place these new results into the context of what is presently known about the X-ray properties of FU Orionis stars and other accreting young stellar objects.