On the Nature of Long-Period Dwarf Novae with Rare and Low-Amplitude Outbursts

摘要: There are several peculiar long-period dwarf-nova like objects, which show rare, low-amplitude outbursts with highly ionized emission lines. 1SWASP J162117$+$441254, BD Pav, and V364 Lib belong to this kind of objects. Some researchers even doubt whether J1621 have the same nature as normal dwarf novae. We studied in these three objects via our optical photometry spectroscopy, performed numerical modeling their orbital variations investigate properties. found that lasted for a long interval (a few tens days), slow rises brightness were commonly observed during early stage outbursts. Our analyses suggest has very high inclination, close 90 deg, plus faint hot spot. Although Pav seems slightly lower inclination ($\sim$75 deg), other properties similar those J1621. On hand, appears massive white dwarf, companion star, low ($\sim$35 deg). In addition, possibly transfer rate and/or large disks originating from periods. find can explain infrequent within context disk instability model novae without strong magnetic field. we highly-ionized lines outburst due dwarf. More instances class object may be unrecognized, since unremarkable easily overlooked.