V455 And
V515 And
AE Aqr
FO Aqr
V349 Aqr
XY Ari
V405 Aur
V647 Aur
HT Cam
MU Cam
DW Cnc
V709 Cas
V1025 Cen
V1033 Cas
TV Col
TX Col
UU Col
V2069 Cyg
V2306 Cyg
DO Dra
PQ Gem
V418 Gem
DQ Her
V1323 Her
V1460 Her
V1674 Her
EX Hya
NY Lup
V2400 Oph
V2731 Oph
V3037 Oph
V598 Peg
GK Per
AO Psc
HZ Pup
V667 Pup
WX Pyx
V1223 Sgr
V4743 Sgr
CC Scl
V1062 Tau
AX J1740.1
AX J1832.3
AX J1853.3
CTCV J2056
CXO J174954
IGR J04571
IGR J08390
IGR J15094
IGR J16500
IGR J16547
IGR J17014
IGR J17195
IGR J18151
IGR J18173
IGR J18308
IGR J19267
PBC J0927.8
PBC J1841.1
RX J1804
RX J2015
RX J2113
RX J2133
RX J2306
Swift J0717
Swift J1839
Swift J2006
Swift J2138

Full Catalog

Related Systems

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Criteria for IP Classification

On this site, I have the absolute power to decide which systems I include as IPs, which as candidates. Now I have started a 5-tier system from "ironclad" to "doubtful." "Ironclad" is used for systems that so obviously belong to the class, there are no arguments (e.g., AO Psc), while "confirmed" systems may not have as many independent lines of evidence, or one or more of the periods may not be known, or known accurately. "Probable" and "possible" indicate the lack of hard evidence either way, but that I have my personal guesses as to whether they are IPs ("probable") or not ("possible").

"Doubtful" usually means there are later papers that disagree with the IP classification. My philosophy for this catalog is to never remove an object if it was once proposed to be an IP in refereed journal, even if there is a new consensus that it is not (including objects that are not even CVs).

Joe's 1994 review contains a section titled "The Cast: Rules of the Audition." Of his 6 criteria, I would not be bothered by a lack of circular polarization or a relatively soft X-ray spectrum - there are confirmed IPs with neither. However, I place a stronger emphasis on optical emission lines. Penning's pioneering work as well as many papers by Coel Hellier and company show that IPs have radial velocity (or its proxy, V/R ratio) modulation on the spin period. This is easy to underatsnd: a significant fraction of optical emission lines in IPs come from the "accretion curtain." So, if time-resolved optical spectroscopy with a sufficient sensitivity fails to show such a behavior, I would take that as a strong negative.

Of course, the usual criteria for IP classification is optical and X-ray spin modulations.

When the classification depends on the optical periodicity, it should be coherent and persistent to a high degree. It has to be repeatedly observed, ideally over several years; If you see apparent modulations for a few cycles --- don't get too excited. I think every CV observer should read Warner's Warning (or see th PDF version of the same) before attempting to identify periodicities in CVs. If I were writing my papers on KO Vel now, with the same data, I would probably write a very different paper.

When X-ray pulses are involved, I would relax the requirement --- two independent X-ray pulse period determinations would be sufficient for me (assuming it is known to be a CV and the periods agree). It is not sufficient for a sub-orbital X-ray periodicity to be seen once. Such one-time-only X-ray periodicities have been seen in many non-magnetic CVs. Usually in such systems, different periods are seen in different X-ray observations, proving that these X-ray modulations are not tied directly to the spin period of the white dwarf.

I would also happily accept somewhat weak optical detection (in terms of establishing persistence and coherence) combined with a single X-ray detection of the same period.

Koji Mukai, originally written in 2002 February, last substantive update in 2014 September; the link to Warner's Warning updated in 2022 January.

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Please send your comments, suggestions etc. to Koji.Mukai@nasa.gov and/or Koji.Mukai@umbc.edu
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