Observations of Five Southern-Hemisphere Cataclysmic Binary Stars

Abstract

We present observations and analyses of five little-studied cataclysmic binary stars in the southern celestial hemisphere. Our new observations are from the South African Astronomical Observatory. The objects and salient results are as follows: (i) 6dF0752-54 is a dwarf nova with an orbital period Porb = 5.05 hr that shows a contribution from a mid-M type secondary in its mean spectrum. (ii) J0916-26 had been suspected of being a magnetic CV with an eclipse period of 3.37 hr. Our spectrum corroborates this classification. (iii) GSC 08944 is a novalike variable with Porb = 3.80 hr. Archival photometry also shows a persistent photometric period near 4.03 hr, apparently from a positive super- hump. Its emission line behavior is consistent with an SW Sextantis-type novalike. (iv) MGAB-V253, also Gaia20eys, had been identified as a short-period eclipsing novalike with Porb = 1.44 hr. Our spectrum shows shows broad emission lines consistent with this, and the extensive TESS data show a persistent modulation near 1.35 hr, evidently a negative superhump. It is less luminous than most novalikes, but significantly brighter than quiescent dwarf novae with comparably short periods. (v) Finally, DDE 45 shows a complicated variability history, cycling rapidly between high and low states for a time and more recently showing outbursts resembling a U Gem-type dwarf nova. We find a 2.07 hr radial velocity period, which also appears in archival TESS photometry. The emission lines are double-peaked, with an orbital S-wave similar to low-inclination dwarf novae. To be published in Astronomical Journal.