SDSS J0018+3454: An Extremely Long Orbital Period CV

TL;DR

This study identifies SDSS J0018+3454 as an asynchronous magnetic cataclysmic variable with an extremely long orbital period of approximately 14.5 hours, based on optical spectroscopic analysis.

Contribution

The paper provides the first detailed spectroscopic analysis and orbital period determination of SDSS J0018+3454, revealing its classification as an asynchronous magnetic CV with a notably long orbital period.

Findings

Orbital period is approximately 14.5 hours based on absorption features.

Emission line radial velocities suggest a slightly shorter period of about 13.78 hours.

SDSS J0018+3454 is classified as an asynchronous magnetic CV (Polar).

Abstract

We present here results of an optical spectroscopic study of a new Cataclysmic Variable SDSS J001856.93+345444.3. We demonstrate that the most probable value of the orbital period of the system is Porb = 0.6051 \pm 0.022 days (=14.5226 hours), based on the measurements of radial velocity of a complex of absorption features emanating from the K2-K4V type secondary component. However, the radial velocity measurements from the emission lines are best folded with the period Pem = 0.5743day (=13.78 hours). The gamma-velocity of the emission lines varies significantly from epoch to epoch. There is an underlying broader and weaker component to the emission lines, which we could not resolve. Based on the appearance of the emission lines, the presence of very strong He II lines and the moderate polarization detected by Dillon et al. (2008), we conclude that SDSS J0018+3454 is an asynchronous magnetic CV (Polar).