PV Cep and V350 Cep: stars on the way between FUors AND EXors

TL;DR

This study analyzes the eruptive behaviors of PV Cep and V350 Cep, revealing their transitional nature between FUor and EXor classes through new observations and spectral analysis.

Contribution

It provides new observational data and spectral analysis showing that PV Cep and V350 Cep are intermediate objects between FUor and EXor classes.

Findings

PV Cep experienced a regular outburst with a prolonged deep minimum.

V350 Cep remained at maximum brightness with an unaltered spectrum.

Both stars likely represent intermediate objects between FUor and EXor classes.

Abstract

Based on new observations during 2015-2020 and published data, the unusual eruptive variables PV Cep and V350 Cep are examined. It is shown that PV Cep underwent a regular outburst followed by a drop in brightness that lasted overall from 2011 to 2019 and is still in a deep minimum. The outburst was accompanied by substantial changes in the intensity and profiles of a number of lines, including Ha, [SII], and [OI]. The forbidden lines generally have negative radial velocities and can be divided into four components, with variable velocities and relative intensities. V350 Cep essentially is at a maximum brightness level over the entire time and its spectrum is practically unaltered. The available data suggest that the pronounced P Cyg profile of the Ha line in the spectrum of V350 Cep appeared several years after the luminosity rise, in 1986. The luminosities of the stars in the current state are estimated to be 20 L(sun) and 3.3 L(sun), respectively. It is concluded that both stars may represent a so-called intermediate objects between the FUor and EXor classes.