Likely IPs without a Known Orbital Peirod

Orbital period (P_orb) is a fundamental parameter for all CVs.

Just by knowing P_orb, the overall system size and the radius of the secondary can be constrained; the secular mass transfer rate and the evolutionary history of the system can be inferred; the optical brightness of an accretion disk can be estimated.

If a hydrogen-rich CV shows a coherent period well below the orbital period minimum (about 80 min) of CVs, the period is almost certainly related to the white dwarf spin, and we would infer that the system is likely an IP. However, there is too much one cannot study in a likely IP without a known orbital period, including the P_orb/P_spin ratio and the Disk Brightness Index (DBI; Mukai & Pretorius (2023)).

Therefore, starting in 2024 August, I have made it an explicit policiy to require P_orb to consider the IP nature to be confirmed.

Probable IPs without an orbital period

Swift J0525.6+2416: The spin period is 226.3 s as per X-ray observation, but the orbital period remains unknown.
Swift J0535.2+2830: There is an optical photometric period of 25.4 min, presumably the spin period; however, the orbital period remains unknown.
1RXS J080114.6-462324: The 1310 s X-ray period (probably also seen in the optical) is presumably the spin period. However, the orbital period is unknown.
Swift J0958.0-4208: The X-ray period of 296.22 s presumably is the spin period. There is no information on the orbital period.
IGR J14091-6108: There is a 9.6 min X-ray period, presumably the spin; the orbital period is unknown.
AX J1700.1-4157: The 714.5 s X-ray signal presumably reflects the spin period. The orbital period is unknown.
Suzaku J174035.6-301416: The 432 s X-ray signal presumably reflects the spin period. The orbital period is unknown.
SAX J1748.2-2808: The 593 s X-ray signal presumably reflects the spin period. The orbital period is unknown.
CXOPS J180354.3-300005: This Baade's window source has a 1028 s Chandra period, but the orbital period is unknown.
IGR J18048-1455: There is a ~25 min X-ray period, but the orbital period is unkown.
IGR J18151-1052: While the spin period has been detected in X-ray and optical observations, the orbital period is unknown. Classified as "confirmed" in IP Catalog Version 2021.
AX J1832.3-0840: While it now has a confirmed spin period from X-ray and optical observations, the orbital period remains unknown. Also, further optical photometry is also desirable, particularly to shed light on the (currently unexplained) 2303 and 4723 s modulations. Classified as "confirmed" in IP Catalog Version 2021.
IGR J18434-0508: The spin period is now known to be 304.4 s from X-ray observations, twice the optical photometric period. This system was temporarily listed as "confirmed" in IP Catalog Update No.7 between 2026 January and August.
ZTF J185139.81+171430.3: The 12.36953 min optical period presumably is the spin period; the orital period remains unknown.
2PBC J1911.4+1412: The 12.448 min optical period presumably is the spin period; the orital period remains unknown.