2019ApJ...882...93H

Double neutron star (DNS) systems are produced from massive binaries. A supernova (SN) explosion of an extremely stripped star is expected to occur at the final stage of DNS formation. This type of SN is called an ultra-stripped SN (USSN). Recent research revealed that a type Ic SN, iPTF 14gqr (SN 2014ft), has low ejecta mass (≃0.2 M_☉) and its progenitor has a helium envelope with mass ∼0.01 M_☉. This SN is interpreted as a USSN, and thus this is the first discovery of a USSN. Furthermore, the observation of iPTF 14gqr provides us with some information about its formation history. Here, we perform rapid population synthesis calculations so as to estimate the detection rate of iPTF 14gqr like USSNe with optical transient surveys: the intermediate Palomar Transient Factory (iPTF), the Zwicky Transient Facility (ZTF), and the Large Synoptic Survey Telescope (LSST). We find that iPTF, ZTF, and LSST can observe iPTF 14gqr like USSNe at rates of 0.3, 10, and 1 yr^–1, respectively. The iPTF can detect 1 iPTF 14gqr like USSN during its four year observation. We also investigate effects of mass-loss efficiency during Roche-lobe overflow on formation channels.