Ground and space-based study of two globular cluster CVs: M22 CV1 and M5 V101

TL;DR

This study confirms the nature of two globular cluster cataclysmic variables, CV1 in M22 and V101 in M5, through multi-wavelength observations, highlighting their role in cluster dynamics.

Contribution

It provides detailed observational evidence of CVs in globular clusters, including light curves, spectra, and photometry, advancing understanding of their properties and evolution.

Findings

Confirmed CV1 as a dwarf nova through outburst analysis.

Detected emission lines indicating active accretion in V101.

Provided multi-band photometry and spectroscopy data for both CVs.

Abstract

As a class of compact binaries with large binding energy, cataclysmic variables formed through close encounters play an important role in the dynamical evolution of globular clusters. As part of a systematic search for CVs undergoing dwarf nova eruptions in globular clusters, our 2004 monitoring programme of M22 detected an outburst of the dwarf nova candidate CV1 during May. We implement the ISIS image subtraction routine to obtain a light curve for an outburst of CV1. We present the outburst light curve as well as HST/WFPC2 photometry in the V, U and near ultra-violet (nUV) bands and a Chandra/ACIS-S spectrum of the object. Our results confirm the DN nature of the outburst and the CV status of the object. We also present the results of a ground-based study of another globular cluster CV, M5 V101 - including quiescent medium-resolution WHT/ISIS spectroscopy in the B and R bands, displaying prominent Balmer and HeI emission, and R-band photometry.