**Table 3:** X-ray flux limits for H₂O maser sources without good X-ray spectra, observed and corrected for galactic absorption (see Sect. 4.2). With the exception of the kilomaser galaxy NGC 4293, all sources host megamasers.
Source	Observed	Corrected
	upper	upper
	limit	limit
	(10^-13 erg cm^-2 s^-1)
NGC 235A^a	2.91	4.50
NGC 449^b	3.07	6.55
NGC 591^b	3.73	7.63
NGC 613^a	2.14	3.38
IC 184^a	2.51	4.19
UGC 3255^a	3.66	10.34
VII ZW 73^a	4.02	9.35
Mrk 78^a	5.88	11.55
J0804+3607^a	2.06	3.19
NGC 2824^a	3.02	5.50
NGC 2960^a	3.41	6.51
NGC 2979^a	2.93	5.75
Mrk 34^b	1.60	2.16
NGC 3735^a	1.64	2.52
NGC 4293^a	2.74	4.78
NGC 5495^a	4.58	9.22
NGC5793^b	9.41	22.8
NGC 6323^a	1.61	2.67
IRAS F19370-0131^a	5.11	15.00
NGC 6926^a	3.20	7.49
AM2158-380NED02^a	2.77	4.20
TXS 2226-184^b	4.31	7.84
IC 1481^b	3.61	7.73

^a Upper limits to 0.1-2.4 keV fluxes, obtained from the ROSAT X-Ray All-Sky Survey with HEASARC (High Energy Astrophysics Science Archive Research Center).
^b Tentative or negative detections by ASCA (0.3-12 keV) from TARTARUS version 3.0 at formal 3.19, 9.34, 4.72, 7.36, 0.12, and 2.89 $\sigma$ levels for NGC 449, NGC 591 Mrk 34, NGC 5793, TXS 2226-184 and IC 1481, respectively. For the way the given flux limits were derived, see also footnote a.

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