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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Low Luminosity IPs

Pretorius & Mukai (2014) pointed out that, while the hard X-ray luminosity of most IPs are at about 1033 ergs s-1 or above, there is a hint of a separate population of low-luminosity IPs (LLIPs). Note that the bolometric X-ray luminosity is a factor of a few higher than the values tabulated by Pretorius & Mukai (2014), who used the Swift BAT 14-195 keV luminosity.

The table below is the list of confirmed or ironclad IPs with X-ray (in the traditional band, measured mostly with XMM-Newton or with Swift XRT) below 2.5x1032 ergs s-1. This is based on the Gaia EDR3 distance estimate, as well as the cataloged X-ray fluxes. In the vast majority of cases, these objects are undetected in the Swift BAT hard X-ray survey; in the few cases with BAT detection, the hard X-ray luminosity is also given.

I chose 2.5x1032 ergs s-1 as the cut-off here, because that's just allows DO Dra, with BAT luminosity of 8.2x1031 ergs s-1 and was one of the original LLIPs of Pretorius & Mukai (2014), to be included. First IP to be excluded by this criterion is 1RXS J211336.1+542226 at 4.5x1032 (with a BAT-band luminosity of 3.4x1032).

Several objects in this table deserve special comments:

  • AE Aqr is a known propeller system, of course.
  • The lowest X-ray luminosity systems, V455 And (with a spin period of 67.619685 s) and V1460 Her (38.87126 s), may well be unrecognized propellers.
  • DQ Her is a deeply eclipsing system in which the direct line of sight to the white dwarf proper is blocked by the accretion disk. Thus, the intrinsic X-ray luminosity is potentially much higher than the observed value. It is therefore not clear if DQ Her should be classified as an LLIP.
The rest of the systems listed definitly qualify as LLIPs.

The X-ray luminosities of 6 confirmed or ironclad IPs are unknown, either because the X-ray fluxes are unknown, or because there are no Gaia EDR3 parallaxes. Of these, XY Ari may well qualify as an LLIP. Although there is no Gaia parallax (because of the intervening molecular cloud), Littlefair, Dhillon & Marsh 2001 used IR data to estimate a distance of 270+/-100 pc. Using 270 pc, its X-ray luminosity is 1.2x1032 ergs s-1 (hard X-ray luminosity: 2.6x1032 ergs s-1).

A List of Low-Luminosity IPs

RankName LXLHS GabsPo
1V455 And 5.4x1028  11.61.351421
2V1460 Her 1.6x1030  7.94.9884535
3DQ Her 3.5x1030  6.14.646902
4EX Hya 6.6x10301.0x1031 9.41.6376123
5V1025 Cen 1.1x10314.2x1031 10.71.410
6AE Aqr 1.4x1031  6.19.8797346
7CTCV J2056-3014 1.8x1031  9.91.76
8AX J1853.3-0128 3.7x1031  10.71.45
9V598 Peg 4.9x1031  9.81.3854
10CC Scl 7.9x1031  10.31.4056136
11HT Cam 8.7x1031  8.81.43309
12DW Cnc 8.9x1031  9.01.435024
13DO Dra 2.4x10328.2x1031 8.83.96898

A List of Regular IPs

For comparison, I continue the above table with the rest of (regular) IPs. Note that the listed X-ray luminosities are not corrected for intrinsic absorption. While this is probably not a major issue for LLIPs (with low intrinsic absorption), it may have a major effect on these, regular, IPs. The true, intrinsic, unabsorbed luminosities are higher than those listed in this table. This is not an issue with the BAT-band hard X-ray luminosity, where any absorption correction is likely to be minimal. I find that 46 of the 71 confirmed or ironclad IPs have X-ray luminosity in the range 9.6x1032 to 9.6x1033 ergs s-1, with three outliers with even higher X-ray luminosity.

RankName LXLHS GabsPo
141RXS J211336.1+542226 4.5x10323.4x1032 9.14.17
15GK Per 7.1x10321.3x1033 4.447.9249
16V1323 Her 8.0x1032  6.14.4021
17PBC J0927.8-6945 9.7x10321.5x1033 5.24.790
18FO Aqr 9.8x10321.8x1033 5.34.849430
19RX J2015.6+3711 1.0x1033<4.9x1033 6.712.7611
20tWX Pyx 1.1x1033  5.7~5.3
20tIGR J17014-4306 1.1x10331.3x1033 5.612.8166
20tIGR J19267+1325 1.1x1033  8.33.449
20tMU Cam 1.1x10331.7x1033 5.04.7186
24tV405 Aur 1.2x10331.8x1033 4.84.143012
24tAO Psc 1.2x10337.9x1032 4.93.591012
26V349 Aqr 1.3x1033  5.53.23
27Swift J183920.1-045350 1.4x1033  6.6~5.6
28V2069 Cyg 1.5x10332.9x1033 5.37.48039
29IGR J16500-3307 1.7x10333.3x1033 5.73.617
30tTX Col 1.8x10331.2x1033 5.85.691
30tV3037 Oph 1.8x1033  7.25.722
30tPQ Gem 1.8x10332.1x1033 4.85.1926
30tTV Col 1.8x10331.8x1033 5.55.486398
34IGR J17195-4100 1.9x10331.9x1033 6.24.006
35IGR J15094-6649 2.1x10333.4x1033 4.55.88
36tBG CMi 2.2x10332.2x1033 5.23.2339650
36tAX J1832.3-0840 2.2x10335.0x1033 8.3 
36tUU Col 2.2x1033  5.63.45
36tHZ Pup 2.2x1033  4.65.09
36tIGR J16547-1916 2.2x10332.9x1033 5.53.715
41tV1033 Cas 2.3x10334.1x1033 5.64.033
41tAX J1740.1-2847 2.3x1033  7.52.1 ?
43V709 Cas 2.5x10334.8x1033 5.15.332898
44tV515 And 2.7x10332.0x1033 5.02.731087
44tIGR J08390-4833 2.7x1033  5.8~8
46V2306 Cyg 2.8x10332.6x1033 5.24.371490
47V2400 Oph 2.9x10332.8x1033 4.93.43
48IGR J04571+4527 3.0x10335.1x1033 6.26.2 ? 4.8?
49Swift J0717.8-2156 3.3x10335.1x1033 5.95.515
50V1223 Sgr 3.4x10334.9x1033 4.33.365856
511RXS J230645.0+550816 3.6x1033  4.83.26
52V647 Aur 3.7x10336.0x1033 4.53.46565
53Swift J2138.8+5544 4.1x1033  5.64.426
54tIGR J18308-1232 4.6x10331.0x1034 5.95.374
54tV1062 Tau 4.6x10334.5x1033 5.79.98119
56V4743 Sgr 4.8x1033  3.66.7176
57V667 Pup 5.1x10331.0x1034 3.05.611
58EI UMa 5.4x10334.4x1033 4.66.434
591RXS J213344.1+510725 6.1x10331.2x1034 4.37.13834
60V418 Gem 6.2x10338.0x1033 4.54.36925
61NY Lup 7.8x10331,8x1034 2.89.87
62Swift J2006.4+3645 9.5x10333.3x1034 4.617.2842
63V2731 Oph 1.1x10343.1x1034 4.415.421
64IGR J18173-2509 2.9x10343.9x1034 3.51.53
651RXS J180431.1-273932 4.4x1034  2.94.99

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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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