A New X-Ray Census of Rotation Powered Pulsars

Abstract

To date, over 4000 pulsars have been detected. In this study, we identify 231 X-ray counterparts of Australia Telescope National Facility (ATNF) pulsars by performing a spatial cross match across the Chandra, XMM-Newton observational catalogs. This data set represents the largest sample of X-ray counterparts ever compiled, including 98 normal pulsars (NPs) and 133 millisecond pulsars (MSPs). Based on this significantly expanded sample, we re-establish the correlation between X-ray luminosity and spin-down power, given by L X ∝ E ̇ 0.85 ± 0.05 across the whole X-ray band. The strong correlation is also observed in hard X-ray band, while in soft X-ray band there is no significant correlation. Furthermore, L X shows a strong correlation with spin period and characteristic age for NPs. For the first time, we observe a strongly positive correlation between L X and the light cylinder magnetic field ( B lc ) for MSPs, with both NPs and MSPs following the relationship L X ∝ B lc 1.14 , consistent with the outer-gap model of pulsars that explains the mechanism of X-ray emission. Additionally, we investigate potential X-ray counterparts for Galactic Plane Pulsar Snapshot pulsars, finding a lower likelihood of detection compared to ATNF pulsars.

Full text

A New X-Ray Census of Rotation Powered Pulsars
Yu-Jing Xu (徐雨婧)
1,2,5
, Han-Long Peng (彭寒龙)
2,5
, Shan-Shan Weng (翁山杉)
2,3
, Xiao Zhang (张潇)
2,3
, and
Ming-Yu Ge (葛明玉)
4
1
Department of Astronomy, Xiamen University, Xiamen, 361005, Fujian, People’s Republic of China
2
School of Physics and Technology, Nanjing Normal University, Nanjing, 210023, Jiangsu, People’s Republic of China; wengss@njnu.edu.cn
3
Institute of Physics Frontiers and Interdisciplinary Sciences, Nanjing Normal University, Nanjing, 210023, Jiangsu, People’s Republic of China
4
Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
Received 2024 October 22; revised 2024 December 16; accepted 2025 January 18; published 2025 March 3
Abstract
To date, over 4000 pulsars have been detected. In this study, we identify 231 X-ray counterparts of Australia
Telescope National Facility (ATNF)pulsars by performing a spatial cross match across the Chandra, XMM-
Newton observational catalogs. This data set represents the largest sample of X-ray counterparts ever compiled,
including 98 normal pulsars (NPs)and 133 millisecond pulsars (MSPs). Based on this significantly expanded
sample, we re-establish the correlation between X-ray luminosity and spin-down power, given by 
µ
L
E
X
0.85 0.0
5
across the whole X-ray band. The strong correlation is also observed in hard X-ray band, while in soft X-ray band
there is no significant correlation. Furthermore, L
X
shows a strong correlation with spin period and characteristic
age for NPs. For the first time, we observe a strongly positive correlation between L
X
and the light cylinder
magnetic field (B
lc
)for MSPs, with both NPs and MSPs following the relationship µ
L
B
Xlc
1.14, consistent with the
outer-gap model of pulsars that explains the mechanism of X-ray emission. Additionally, we investigate potential
X-ray counterparts for Galactic Plane Pulsar Snapshot pulsars, finding a lower likelihood of detection compared to
ATNF pulsars.
Unified Astronomy Thesaurus concepts: Pulsars (1306);Rotation powered pulsars (1408);Neutron stars (1108)
Materials only available in the online version of record: machine-readable tables
1. Introduction
In the 1930s, stellar evolution theories predicted that a
neutron star (NS)could form when a massive star exhausts its
fuel and undergoes gravitational collapse (W. Baade &
F. Zwicky 1934). Many years later, the existence of NSs was
confirmed by the discovery of radio pulsars in 1967 August
(A. Hewish et al. 1968). NSs can be powered either by
rotational kinetic energy, magnetic energy, or accretion, and
they manifest in various ways. Rotation-powered pulsars
(RPPs)account for over 90% of the population, emitting
beams of electromagnetic radiation due to high-energy
processes occurring at the magnetic poles or in the surrounding
region (A. Lyne & F. Graham-Smith 2012).
There are currently ∼3630 RPPs in the Australia Telescope
National Facility (ATNF)Pulsar Catalogue (version 2.3.0,
R. N. Manchester et al. 2005).
6
The Fermi/LAT mission has
revealed that about 10% of the known RPPs are visible in the
gamma-ray band (D. A. Smith et al. 2023). Furthermore, over a
hundred X-ray RPPs have been reported (W. Becker &
J. Truemper 1997; W. Becker 1999; H.-K. Chang et al.
2023). In contrast, the optical and IR emissions have been
poorly studied (R. P. Mignani 2011,2018), and optical
pulsations have been revealed for less than 1% of NSs
(A. Lyne & F. Graham-Smith 2012; F. Ambrosino et al. 2017).
The radiation mechanisms of broadband emissions from RPPs
are not yet completely clarified, especially for photon energies
lower than the gamma-ray band. In this context, much effort
has been devoted to statistical studies. A notable positive
correlation between X-ray luminosity (L
X
)and pulsar spin-
down power (
E
)has been documented (e.g., W. Becker &
J. Truemper 1997; N. Rea et al. 2012; H.-K. Chang et al. 2023).
However, for some pulsars, their distances still have large
uncertainties and X-ray emission may arise from a mix of
components. As a result, the scatter in this relation is large
(e.g., A. Possenti et al. 2002; X.-H. Li et al. 2008), highlighting
the need for more data to better understand X-ray emission
from RPPs.
The Five-hundred-meter Aperture Spherical radio Telescope
(FAST)is the most sensitive radio telescope used for
discovering pulsars (R. Nan et al. 2011; P. Jiang et al. 2019).
FAST has discovered more than 1000 pulsars (D. Li et al.
2018; L. Qian et al. 2019; S.-S. Weng et al. 2022; J. L. Han
et al. 2021,2025), particularly with two key science projects:
the Commensal Radio Astronomy FAST Survey (D. Li et al.
2018)and the Galactic Plane Pulsar Snapshot (GPPS)survey
(J. L. Han et al. 2021,2025). Until 2024 November, the GPPS
program had discovered 751 pulsars,
7
including some very
faint sources. Detailed studies of these sources are progressing
steadily (W. Q. Su et al. 2023; D. J. Zhou et al. 2023).
In this paper, we use all available archived X-ray observa-
tions from the Chandra and XMM-Newton missions to explore
potential associations between X-ray point sources and pulsars
identified in the ATNF and GPPS catalogs. In Section 2,we
present a spatial matching analysis to construct the pulsar
sample, and examine the correlation between X-ray luminosity
and timing parameters for ATNF pulsars. In Section 3,we
The Astrophysical Journal, 981:100 (10pp), 2025 March 10 https://doi.org/10.3847/1538-4357/adaebc
© 2025. The Author(s). Published by the American Astronomical Society.
5
Yu-Jing Xu and Han-Long Peng contributed equally to this work.
Original content from this work may be used under the terms
of the Creative Commons Attribution 4.0 licence. Any further
distribution of this work must maintain attribution to the author(s)and the title
of the work, journal citation and DOI.
6
https://www.atnf.csiro.au/people/pulsar/psrcat/
7
http://zmtt.bao.ac.cn/GPPS/GPPSnewPSR.html
1

employ the results of the 
-
L
E
Xcorrelation to constrain
possible counterparts for GPPS pulsars. Finally, a discussion
and our conclusions are presented in Section 4.
2. ATNF Pulsars
2.1. Sample Construction
Various mechanisms have been proposed to explain the
generation of X-ray emissions from pulsars. For some young
pulsars, surface thermal radiation (e.g., “Magnificent Seven”
and “Central Compact Objects”)or magnetic field decay (e.g.,
“Rotating Radio Transient”and Magnetars)may contribute to
the X-ray emission (K. Torii et al. 1998; E. V. Gotthelf et al.
2013; H.-K. Chang et al. 2023). In certain cases, this results
in X-ray luminosity that exceeds the pulsar’s spin-down
luminosity. X-ray emission from Be/gamma-ray binaries is
thought to arise from the shock between the stellar wind and
the pulsar wind (S. Johnston et al. 1992; J. J. Miller et al. 2013;
S.-S. Weng et al. 2022). Alternatively, in this study, we focus
exclusively on RPPs where rotational energy is the dominant
source of X-ray emission. The nonthermal power-law comp-
onent of their emission can be interpreted as magnetospheric
radiation. The origin of the thermal emission, however, remains
debated and is likely due to the bombardment of charged
particles returning from the magnetosphere onto the polar cap
region.
As a leading international facility in radio astronomy, the
ATNF catalog offers a comprehensive sample of pulsars,
encompassing all published RPPs while excluding accretion-
powered pulsars. In this work, we search for X-ray counterparts of
3630 pulsars listed in the ATNF pulsar catalog v2.3.0
8
(R. N. Manchester et al. 2005)by using the XMM-Newton
Serendipitous Source Catalog
9
(4XMM-DR13 Version;
N. A. Webb et al. 2020), the Chandra Source Catalog
Release 2.0
10
(CSC 2.0; I. N. Evans et al. 2010,2024). If the
angular separation between a pulsar and an X-ray source,
with a detection confidence level greater than 3σ, satisfies the
condition ()()()
d
=- +-R.A. R.A. cos decl. decl. decl.
XR
22 XXR
2
<R
X
−R
R
, we consider the X-ray source to be the counterpart
of the pulsar. R.A. and decl. denote the R.A. and decl. of a
source, R
X
and R
R
represent the positional uncertainties at the
2σconfidence level for the X-ray source and the pulsar,
respectively. For most radio-loud pulsars, the timing procedure
can help us to achieve positional accuracy down to milli-
arcseconds, and we use the Third Fermi/LAT Catalog of
Gamma-ray Pulsars Catalog (3PC)
11
(D. A. Smith et al. 2023)
to obtain more precise positions for radio-quiet and radio-faint
pulsars. The typical positional accuracy of XMM-Newton
serendipitous point source detections is generally less than
1

.
57, and the on-axis spatial resolution of Chandra data is
subarcsecond. However, the X-ray positional accuracy can
sometimes be overestimated, leading to some counterparts
being missed. We verified the results by cross-referencing with
compiled literature tables, identifying 19 counterparts for eight
normal pulsars (NPs)and 11 millisecond pulsars (MSPs;
X.-H. Li et al. 2008; J. Lee et al. 2018; F. Coti Zelati et al.
2020; H.-K. Chang et al. 2023). In summary, by positional
cross-matching, we identify 121 counterparts of pulsars,
comprising 65 MSPs and 56 NPs.
In some cases, the positions of X-ray sources in the
two X-ray catalogs are imprecise. For sources located in
supernova remnants (SNRs)or pulsar-wind nebulae (PWNe),
Figure 1. 
E
vs. luminosities of pulsars. Panels (a)–(e)reveal correlation in X-ray band, SX band (<2 keV), HX band (>2 keV), gamma-ray band and radio band,
respectively. MSPs and NPs are plotted by violet dots and orange squares, respectively. Blue, violet, and orange lines are best fit of all, millisecond and NPs,
respectively. The inverted triangles are upper limits of luminosity. The correlation trend is revealed by Pearson correlation coefficient (r)and Spearman tests (r
s
and
p
s
), listed in Table 2. Gray dotted lines represent different values of 
/
L
E
X. The orchid dashed line and black dashed–dotted line are fitting results of W. Becker &
J. Truemper (1997)and H.-K. Chang et al. (2023), respectively.
8
https://www.atnf.csiro.au/people/pulsar/psrcat/
9
https://heasarc.gsfc.nasa.gov/W3Browse/xmm-newton/xmmssc.html
10
https://cxc.cfa.harvard.edu/csc2.1/index.html
11
https://fermi.gsfc.nasa.gov/ssc/data/access/lat/3rd_PSR_catalog/
2
The Astrophysical Journal, 981:100 (10pp), 2025 March 10 Xu et al.

Table 1
X-Ray Counterpart of RPPs
Name X-ray Source P
P
DL
X
L
SX
L
HX
L
G
References
(s)(s/s)(kpc)(erg s
−1
)(erg s
−1
)(erg s
−1
)(erg s
−1
)
NP
J0002+6216 2CXO J000258.1+621609 0.115364 5.97 ×10
−15
6.357 1.50 ×10
32
1.08 ×10
32
3.58 ×10
31
9.01 ×10
33
(T)
J0007+7303 2CXO J000701.5+730308
e
0.315873 3.60 ×10
−13
1.4 1.75 ×10
31
5.63 ×10
30
9.74 ×10
30
1.01 ×10
35
(T, 1)
J0058-7218 2CXO J005816.8-721805
e
0.021766 2.89 ×10
−14
59.7 6.54 ×10
34
1.76 ×10
34
4.90 ×10
34
L(T, 2)
J0108-1431 4XMM J010808.3-143150 0.807565 7.70 ×10
−17
0.21 6.99 ×10
28
4.03 ×10
28
2.79 ×10
28
L(T)
KLLLLLLLLL
J2055+2539 4XMM J205548.9+253958
e
0.319561 4.10 ×10
−15
0.62 9.89 ×10
29
4.06 ×10
29
5.82 ×10
29
2.44 ×10
33
(T, 35)
J2139+4716
c
2CXO J213955.9+471613 0.282849 1.79 ×10
−15
<0.8 <5.7 ×10
29
<1.1 ×10
29
<4.88 ×10
29
<4.65 ×10
35
(36)
J2225+6535
b
2CXO J222552.8+653536 0.682542 9.66 ×10
−15
0.9 1.45 ×10
30
LL L(3)
J2229+6114
b
2CXO J222905.2+611409
e
0.051648 7.74 ×10
−14
3 3.82 ×10
32
LL2.59 ×10
35
(3, 4)
MSP
J0023+0923 2CXO J002316.8+092323 0.00305 1.14 ×10
−20
1.818 6.87 ×10
30
6.09 ×10
30
7.71 ×10
29
3.03 ×10
33
(T)
J0024-7204C
a,d
L0.005757 −4.99 ×10
−20
4.52 1.70 ×10
30
LL L(38)
J0024-7204D
a,d
L0.005358 −3.42 ×10
−21
4.52 3.30 ×10
30
LL L(38)
J0024-7204E
a
L0.003536 9.85 ×10
−20
4.52 5.00 ×10
30
LL L(38)
KLLLLLLLLL
J2241-5236 4XMM J224142.0-523635
e
0.002187 6.90 ×10
−21
1.042 6.30 ×10
30
5.00 ×10
30
1.23 ×10
30
3.25 ×10
33
(T, 4)
J2256-1024 2CXO J225656.3-102434 0.002295 1.14 ×10
−20
2.083 2.09 ×10
31
1.40 ×10
31
6.98 ×10
30
4.25 ×10
33
(T)
J2302+4442 4XMM J230246.9+444222 0.005192 1.39 ×10
−20
0.863 2.75 ×10
30
2.10 ×10
30
4.85 ×10
29
3.47 ×10
33
(T)
J2339-0533 4XMM J233938.7-053305 0.002884 1.41 ×10
−20
1.1 3.77 ×10
31
1.00 ×10
31
2.77 ×10
31
5.90 ×10
33
(T)
Notes. L
X
: X-ray luminosity in 0.3–10.0 keV for XMM-Newton and in 0.5–7.0 keV for Chandra. L
SX
: SX luminosity in 0.3–2.0 keV for XMM-Newton and in 0.5–2.0 keV for Chandra. L
HX
: HX luminosity in
2.0–10.0 keV for XMM-Newton and in 2.0–7.0 keV for Chandra. L
G
: Gamma-ray luminosity in 100 MeV. L: The luminosity error is derived from the flux error in the catalogs, which ranges between 10% and 30%.
However, the error introduced by the DM is dominant but not included in the table.
a
The pulsars are MSP in GCs, and their X-ray luminosities are taken from J. Zhao & C. O. Heinke (2022).
b
The pulsars are associated with PWNe or SNRs, and their X-ray luminosities are obtained from the references listed in the “References”column.
c
The upper limits of these distance are inferred from the spin-down power 
E
and the energy flux G
100
above 100 MeV, with references listed in column “References.”The distances of other pulsars are acquired from he
ATNF catalog, using the YMW16 electron distribution model (J. M. Yao et al. 2017).
d
The 
Pis either unavailable or negative, according to the ATNF catalog. These pulsars are excluded from the following correlation analysis.
e
These pulsars have been reported to exhibit X-ray pulsations.
References. The data source for the distance or luminosity of the pulsar. If two references are provided, the second one refers to the study reporting the X-ray pulsations. (T)This work; (1)M. Marelli (2012);(2)
W. C. G. Ho et al. (2022);(3)J.-Y. Hsiang & H.-K. Chang (2021);(4)D. A. Smith et al. (2023);(5)K. E. McGowan et al. (2006);(6)R. Ding et al. (2024);(7)C. Y. Ng et al. (2007);(8)A. S. Tanashkin et al. (2022);(9)
M. Rigoselli & S. Mereghetti (2018);(10)A. Danilenko et al. (2020);(11)W. Hermsen et al. (2018);(12)M. Rigoselli et al. (2019);(13)W. Becker et al. (2004);(14)M. Renaud et al. (2010);(15)W. C. G. Ho et al.
(2022);(16)J. Park et al. (2023);(17)J. Hare et al. (2021);(18)E. Gotthelf & NuSTAR Observatory Team (2014);(19)H.-K. Chang et al. (2023);(20)M. Rigoselli et al. (2022);(21)F. Camilo et al. (2009);(22)A. Van
Etten et al. (2012);(23)D. Zheng et al. (2023);(24)M. Marelli et al. (2014);(25)L. Duvidovich et al. (2019);(26)L. C. C. Lin et al. (2014);(27)L. C.-C. Lin et al. (2009);(28)D. Pandel & R. Scott (2012);(29)F. Lu
et al. (2007);(30)S. I. Kim et al. (2020);(31)D. A. Zyuzin et al. (2021);(32)D. A. Zyuzin et al. (2018);(33)J. W. T. Hessels et al. (2004);(34)M. Razzano et al. (2023);(35)M. Marelli et al. (2016);(36)H. J. Pletsch
et al. (2012);(37)J. Zhao & C. O. Heinke (2022);(38)S. Guillot et al. (2019);(39)A. M. Archibald et al. (2010);(40)A. Papitto et al. (2015).
(This table is available in its entirety in machine-readable form in the online article.)
3
The Astrophysical Journal, 981:100 (10pp), 2025 March 10 Xu et al.

the extended X-ray emission complicates accurate positioning.
Because MSPs in globular clusters (GCs)are relatively
dense and faint, they are challenging to resolve using the
pipelined processing methods applied in the Chandra CSC 2.0
catalog. However, some studies have conducted more detailed
analyses of these sources, yielding additional X-ray counter-
parts (e.g., J.-Y. Hsiang & H.-K. Chang 2021; J. Zhao &
C. O. Heinke 2022). We collected data from the literature on
68 MSPs in 29 GCs and 42 NPs associated with SNRs or
PWNe, incorporating these into our sample as a significant
supplement. However, their luminosities are reported across the
entire X-ray band because detailed spectral analyses are
lacking.
In total, we identify 231 X-ray counterparts of pulsars,
including 98 NPs and 133 MSPs. Their properties, spanning
radio, X-ray, and gamma-ray bands, are listed in Table 1.
2.2. Probability of Spatial Coincidence
In principle, an association can only be unambiguously
confirmed as a real counterpart when X-ray pulsations are
detected. However, in most cases, the time resolution of
imaging X-ray observations is insufficient for pulsation
searches. The time resolution of Chandra data is ∼3.2 s,
12
and the time resolution of XMM-Newton EPIC-pn’s full frame
mode observation data is 73.4 ms.
13
Nevertheless, X-ray
pulsations have been reported for 51 NPs and 18 MSPs in
the literature (see Table 1).
We also estimate the probability of positional coincidence
using the logN–logSdistribution at the Galactic center
(M. P. Muno et al. 2003). According to the discussion in
Section 4.1 of M. P. Muno et al. (2003)(see also Figure 10 in
their paper), the surface density of sources is extremely high,
∼15,000 sources deg
−2
above the flux limit of 3 ×
10
−15
erg cm
−2
s
−1
in the 2.0–8.0 keV range. This corresponds
to ∼0.009 contaminating sources within the 1

.
57 location error
circle (the typical XMM-Newton positional resolution). How-
ever, we argue that the chance coincidence probability is likely
much lower for the following reasons: first, the fluxes of
pulsars analyzed in this work are mostly greater than
3×10
−15
erg cm
−2
s
−1
, with a median value of 7 ×
10
−14
/9×10
−15
erg cm
−2
s
−1
for NPs and MSPs; second,
the surface density at the pulsar position should be much
smaller than at the Galactic center; finally, Chandra sources
exhibit even smaller positional uncertainties and a lower
likelihood of coincidence. Moreover, more refined analyses
have been performed on a large proportion of MSPs in
GCs (e.g., J.-Y. Hsiang & H.-K. Chang 2021; J. Zhao &
C. O. Heinke 2022, Section 2.1)and sources detected within
PWNe can also be considered secure associations. Therefore,
we conclude that the probability of positional coincidence is
very low, even if there is an absence of X-ray pulsations.
2.3. Pulsar Parameters
According to the magnetic dipole radiation model for
pulsars, rotation power is assumed to be transformed into
dipole radiation loss energy. The energy loss rate 
E
can be
expressed as 
=p
E
IP
P
42
3, where a typical moment of
I=10
45
gcm
2
is assumed. Other parameters can be derived
from the observed rotational period Pand its derivative 
P
,as
described by the following relations: the characteristic age

t=P
P2, the surface magnetic field strength
=´
B
3.2
surf

()PP1019 0.5 G, and the magnetic field at light cylinder

=´ -
B
PP2.9 10
lc 8 2.5 0.
5
G.
In this work, distances are estimated using the dispersion
measure (DM)based on the YMW16 electron distribution
model (J. M. Yao et al. 2017). For radio-quiet or radio-faint
gamma-ray pulsars, we adopt pseudodistances inferred from
the spin-down power 
E
and the energy flux G
100
above
100 MeV. As a result, upper limits on luminosities across all
bands are provided for these sources, with relevant references
listed in Table 1. The luminosities of radio-loud pulsars in the
radio and gamma-ray bands are taken from the ATNF catalog
and Fermi Pulsar catalog. However, it is important to note that
the uncertainty in luminosity is typically dominated by the
uncertainty in the DM distance, and could deviate significantly
from the actual value. For example, the distance of 93 pc for
PSR J1057-5226 is derived using the YMW16 model
(J. M. Yao et al. 2017), while NE2001 model places it at
720 pc (J. M. Cordes & T. J. W. Lazio 2002), showing an
order-of-magnitude difference (M. Kerr et al. 2018). Moreover,
it has been cautioned that the DM distances for some pulsars
are overestimated and questionable, especially for the pulsars in
the direction of the Local Arm or the tangential direction of
spiral arms (J. L. Han et al. 2021). Following H.-K. Chang
et al. (2023), we adopt an uncertainty of 40% in distances in
this work. The X-ray luminosity is derived from flux and
distance, and its error is calculated based on the error transfer
formula.
2.4. Correlation of Parameters
It has been reported that, the X-ray luminosity of RPPs is
strongly correlated with 
E
, but is orders of magnitude lower
than 
E
(
/~-
--
L
E10 10
X61
, Z. Arzoumanian et al. 2011;
N. Rea et al. 2012; A. Vahdat et al. 2022; H.-K. Chang et al.
2023). The correlation was first explored in the soft X-ray (SX)
band (0.1–2.4 keV)by W. Becker & J. Truemper (1997)using
ROSAT data, leading to the relation 
µ-
LE
10
X3. A. Possenti
et al. (2002)later extended this analysis to the 2–10 keV band,
obtaining 
µ
L
E
X
1.34. X.-H. Li et al. (2008)made a significant
advancement by separating the X-ray luminosity contributions
from pulsars and their associated PWNe, reporting

µ
L
E
X,psr
0.92 0.04 and 
µ
L
E
X,pwn
1.45 0.08 in 2–10 keV.
Recently, H.-K. Chang et al. (2023)used the nonthermal
X-ray luminosity in 0.5–8 keV band for 68 RPPs, finding

µ
L
E
X
0.88 0.06.
In this work, we use X-ray luminosities in 0.3–10.0 keV
range for XMM-Newton and in 0.5–7.0 keV range for Chandra,
further categorizing the data into SX band (<2 keV), hard
X-ray (HX)band (>2 keV). To avoid unscientific results, we
exclude pulsars with unavailable or negative values for 
P
from
the analysis. The upper limits of luminosities for radio-quite or
radio-faint gamma-ray pulsars are shown in Figures 1–3, but
are not included in the correlation analysis. We plot 
E
versus
luminosities in the X-ray, gamma-ray, and radio bands in
Figure 1, employing Pearson and Spearman correlation tests to
assess the strength of linear and monotonic correlations,
respectively. The results, summarized in Table 2, show that
the X-ray and gamma-ray bands exhibit a strong correlation
between 
E
and luminosity, approximating 
µ´ -
L
E210
X4.
12
https://cxc.harvard.edu/cdo/about_chandra/
13
https://heasarc.gsfc.nasa.gov/docs/xmm/uhb/epicmode.html
4
The Astrophysical Journal, 981:100 (10pp), 2025 March 10 Xu et al.

The explicit linear fit across the entire band yields
µ
L
X

E
0.85 0.05, consistent with the findings of H.-K. Chang et al.
(2023). The data align with the broken power-law fitting results
in their study.
In general, the thermal component primarily contributes to
the SXs, while the nonthermal component dominates HXs and
could also contribute significantly to the SXs. Consequently,
the correlation in the SX band becomes noticeably weaker (the
Figure 2. X-ray luminosity vs. timing parameters. Panels (a)–(c)reveal a correlation between L
X
with P,
P
and B
surf
. Panel (d)is a correlation between X-ray
luminosity and τ. The gray regions are theoretical lines for =Blog 6, 7, 8, ...,1
4
surf G under the precondition that 
µ
L
E
X0.85. Dots and legends are the same as
Figure 1. Linear fitting lines are plotted for Pearson correlation coefficient r>0.6.
Figure 3. X-ray luminosity vs. B
lc
and τ. Dots and legends are the same as Figure 1. Panel (a)is correlation between X-ray luminosity and B
lc
. Panel (b)is correlation
with best fitofB
lc
and τin two dimensions.
5
The Astrophysical Journal, 981:100 (10pp), 2025 March 10 Xu et al.

Table 2
Results of Linear Fitting and Spearman Tests
a. Correlation Between 
E
and Luminosities in Different Bands
L
X
ALL MSP NP
αrr
s
p
s
αrr
s
p
s
αrr
s
p
s
L
X
0.85 ±0.05 0.83 0.83 1.18 ×10
−46
0.87 ±0.17 0.62 0.64 7.8 ×10
−11
0.83 ±0.06 0.83 0.86 6.2 ×10
−29
(176 sources)(83 sources)(93 sources)
L
SX
0.39 ±0.08 0.51 0.55 1.8 ×10
−10
0.78 ±0.24 0.56 0.57 2.7 ×10
−06
0.34 ±0.09 0.54 0.47 4.4 ×10
−04
(110 sources)(58 sources)(52 sources)
L
HX
0.79 ±0.08 0.73 0.75 1.6 ×10
−21
1.48 ±0.25 0.65 0.61 1.4 ×10
−06
0.68 ±0.09 0.83 0.85 1.5 ×10
−15
(114 sources)(53 sources)(51 sources)
L
G
0.64 ±0.08 0.77 0.76 2.7 ×10
−22
0.77 ±0.24 0.72 0.75 3.8 ×10
−10
0.62 ±0.11 0.79 0.76 7.0 ×10
−12
(106 sources)(50 sources)(56 sources)
L
R
0.30 ±0.05 0.49 0.46 4.9 ×10
−07
0.38 ±0.14 0.37 0.15 3.0 ×10
−01
0.22 ±0.07 0.40 0.33 1.2 ×10
−02
(110 sources)(52 sources)(58 sources)
b. Correlation Between X-ray Luminosity and Timing Parameters
L
X
MSP NP
αrr
s
p
s
αrr
s
p
s
P−1.26 ±0.39 −0.33 −0.36 1.8 ×10
−05
−2.95 ±0.27 −0.72 −0.73 1.2 ×10
−16
(132 sources) (93 sources)

P
0.13 ±0.16 0.10 0.09 4.0 ×10
−01
1.08 ±0.12 0.58 0.60 2.0 ×10
−10
(83 sources) (93 sources)
B
surf
−0.10 ±0.26 −0.05 −0.05 6.7 ×10
−01
0.96 ±0.24 0.26 0.27 8.8 ×10
−03
(83 sources) (93 sources)
τ−0.47 ±0.19 −0.30 −0.31 4.0 ×10
−03
−1.18 ±0.10 −0.76 −0.78 2.2 ×10
−20
(83 sources) (93 sources)
B
lc
1.20 ±0.23 0.64 0.69 5.0 ×10
−13
1.14 ±0.09 0.82 0.85 1.8 ×10
−27
(83 sources) (93 sources)
c. Correlation Between Gamma-ray Luminosity and Timing Parameters
L
G
MSP NP
αrr
s
p
s
αrr
s
p
s
P−2.12 ±0.53 −0.53 −0.57 5.0 ×10
−05
−2.22 ±0.30 −0.71 −0.70 2.0 ×10
−09
(52 sources) (56 sources)

P
0.56 ±0.20 0.41 0.24 1.2 ×10
−01
0.61 ±0.17 0.44 0.46 3.8 ×10
−04
(50 sources) (56 sources)
B
surf
0.50 ±0.38 0.20 0.06 6.8 ×10
−01
0.32 ±0.36 0.12 0.17 2.0 ×10
−01
(50 sources) (56 sources)
τ−0.81 ±0.17 −0.58 −0.55 1.5 ×10
−04
−0.80 ±0.12 −0.66 −0.68 6.5 ×10
−09
(50 sources) (56 sources)
B
lc
1.06 ±0.16 0.71 0.75 7.1 ×10
−09
0.87 ±0.09 0.79 0.79 5.6 ×10
−13
(50 sources) (56 sources)
Note. αis the index of a power function by a linear fitting and the error is given at 1σconfidence level, such as 
µas
L
Er.
Xis the Pearson correlation coefficient measuring the linear correlation. r
s
and p
s
are the
Spearman correlation coefficient and significance level measuring monotone correlation.
6
The Astrophysical Journal, 981:100 (10pp), 2025 March 10 Xu et al.

Pearson correlation coefficient r=0.51)compared to that of
W. Becker & J. Truemper (1997)due to the mixture of thermal
and nonthermal emissions (Figure 1and Table 2). The
correlation in the HX band remains strong (r=0.73),
suggesting that harder X-ray emission may provide valuable
insights into the process of rotational energy loss being
converted into X-rays (A. Possenti et al. 2002).
Because additional unpulsed X-ray emission may originate
from young PWNe or from intrabinary shocks in MSPs
(W. Becker & J. Truemper 1997; W. Becker 1999; L. Zhang &
Table 3
Possible X-ray Counterparts of GPPS Pulsars
Pulsar
a
Gpps No. Period
b
(s)D
YMW16
(kpc)X-ray sources R.A. Decl. L
X
(erg s
−1
)Var
Flag
4XMM
J2022+3845g gpps0076 1.0089 17.2 J202205.4+384518 20:22:05.46 +38:45:18.83 9.07 ×10
32
FALSE
J202211.1+384423 20:22:11.19 +38:44:23.53 6.30 ×10
32
FALSE
J2021+4024g gpps0087 0.37054 25.0 J202112.9+402403 20:21:12.94 +40:24:03.61 6.22 ×10
32
FALSE
J202114.3+402319 20:21:14.35 +40:23:19.57 1.27 ×10
33
FALSE
J202118.8+402431 20:21:18.83 +40:24:31.82 4.93 ×10
32
FALSE
J1852-0002g gpps0098 0.2451 5.6 J185204.5-000155 18:52:04.48 −00:01:57.00 1.90 ×10
32
FALSE
J1907+0709g gpps0120 0.3441 5.4 J190756.2+070832 19:07:56.29 +07:08:32.14 9.58 ×10
31
FALSE
J1913+0458g gpps0222 0.44479 4.1 J191337.0+045826 19:13:37.05 +04:58:26.06 4.86 ×10
32
FALSE
J2024+3751g gpps0256 0.21164 15.4 J202429.1+374953 20:24:29.19 +37:49:53.82 3.41 ×10
32
FALSE
J1911+0906g gpps0285 16.9259 1.1 J191135.8+090724 19:11:35.86 +09:07:24.25 3.60 ×10
29
FALSE
J1912+1000g gpps0321 3.0528 4.1 J191244.9+095954 19:12:44.90 +09:59:54.67 2.17 ×10
31
FALSE
J1843-0127g gpps0363 2.16489 7.2 J184332.7-012851 18:43:32.75 −01:28:51.35 3.48 ×10
32
FALSE
J1852-0834g gpps0378 0.249315 6.7 J185218.9-083500 18:52:19.00 −08:35:00.21 5.84 ×10
32
TRUE
J1913+0453g gpps0400 0.006086 15.0 J191346.7+045151 19:13:46.78 +04:51:52.09 5.05 ×10
32
FALSE
J191346.7+045151 19:13:46.71 +04:51:51.63 7.84 ×10
32
FALSE
J1846-0252g gpps0563 2.209439 6.4 J184627.1-025230 18:46:27.12 −02:52:30.17 3.10 ×10
32
FALSE
J1819-0050g gpps0581 0.006602 4.5 J181933.9-005006 18:19:33.96 −00:50:05.91 2.76 ×10
32
FALSE
J1845-0254g gpps0582 0.492655 5.8 J184532.8-025411 18:45:32.89 −02:54:12.14 1.94 ×10
32
FALSE
J2032+4055g gpps0623 0.048739 10.1 J203237.2+405556 20:32:36.99 +40:55:56.62 6.85 ×10
33
FALSE
J1818-0051g gpps0666 2.20669 2.7 J181836.3-005225 18:18:36.37 −0:52:25.74 5.65 ×10
31
FALSE
J1847-0308g gpps0735 29.76927 3.4 J184701.6-030753 18:47:01.65 18:47:01.65 6.57 ×10
31
FALSE
J1851+0037g gpps0744 2.52373 5.2 J185146.7+003533 18:51:46.39 18:51:46.39 2.09 ×10
33
FALSE
2CXO
J1852+0056g gpps0014 1.177793 7.2 J185215.4+005743 18:52:15.40 +00:57:43.30 6.29 ×10
31
FALSE
J1855+0139g gpps0026 0.44414 5.2 J185512.5+013807 18:55:12.57 +01:38:07.90 4.31 ×10
31
TRUE
J185518.9+013844 18:55:18.94 +01:38:44.38 7.63 ×10
31
FALSE
J1904+0519g gpps0037 1.68053 2.5 J190403.8+052014 19:04:03.81 +05:20:14.02 1.71 ×10
31
FALSE
J190404.8+052006 19:04:04.83 +05:20:06.68 6.35 ×10
30
FALSE
J2022+3845g gpps0076 1.0089 17.2 J202205.4+384519 20:22:05.46 +38:45:19.55 3.57 ×10
32
FALSE
J202209.5+384413 20:22:09.53 +38:44:13.95 9.90 ×10
30
TRUE
J202209.9+384348 20:22:09.90 +38:43:48.03 8.58 ×10
31
FALSE
J202210.8+384341 20:22:10.82 +38:43:41.97 9.08 ×10
30
FALSE
J202211.2+384423 20:22:11.27 +38:44:23.58 2.35 ×10
31
FALSE
J2021+4024g gpps0087 0.37054 25.0 J202106.0+402319 20:21:06.04 +40:23:19.68 4.14 ×10
32
FALSE
J202111.7+402335 20:21:11.71 +40:23:35.29 4.65 ×10
32
FALSE
J202112.8+402405 20:21:12.91 +40:24:05.48 6.84 ×10
31
TRUE
J202114.3+402520 20:21:14.35 +40:25:20.41 8.58 ×10
31
FALSE
J1907+0658g gpps0127 0.21834 7.7 J190737.8+065841 19:07:37.84 +06:58:41.02 4.78 ×10
31
FALSE
J1909+0905g gpps0178 1.49488 5.4 J190935.9+090600 19:09:35.92 +09:06:00.44 5.88 ×10
31
FALSE
J1953+1844 gpps0190 0.004441 4.3 J195337.9+184454 19:53:37.96 +18:44:54.40 1.25 ×10
30
FALSE
J1931+1841g gpps0233 2.59411 5.4 J193111.2+183934 19:31:11.22 +18:39:34.27 3.53 ×10
31
FALSE
J2030+3833g gpps0295 L15.2 J203024.9+383322 20:30:25.00 +38:33:22.98 9.17 ×10
32
FALSE
J1844-0223g gpps0493 0.65772 6.3 J184516.7-022929 18:45:16.78 −02:29:29.63 3.63 ×10
32
FALSE
J1929+1337g gpps0495 0.203318 7.8 J192924.8+133637 19:29:24.83 +13:36:37.19 3.73 ×10
32
FALSE
J1915+1045g gpps0518 1.54588 3.7 J191531.5+104333 19:15:31.54 +10:43:33.80 1.03 ×10
30
FALSE
J2032+4055g gpps0623 0.048739 10.1 J203234.8+405617 20:32:34.87 +40:56:17.23 1.76 ×10
32
TRUE
J203236.3+405529 20:32:36.33 +40:55:29.62 2.23 ×10
32
FALSE
J203240.2+405348 20:32:40.21 +40:53:48.85 2.56 ×10
31
FALSE
J1843-0310g gpps0672 0.285151 8.5 J184305.3-030954 18:43:05.31 −03:09:54.86 2.92 ×10
32
FALSE
Notes.
a
Pulsar names with a suffix“g”indicate the temporary nature, due to position uncertainty of about 1
¢
.5.
b
Several pulsars are discovered due to single pulses and their spin periods are currently unavailable (D. J. Zhou et al. 2023).D
YMW16
: Distance estimated based on
the YMW16 electron distribution model (J. M. Yao et al. 2017). Var
Flag
: The flag is set to “True”if the source displayed flux variability within one or between
observations or to “False”if the source was tested for variability but did not qualify.
(This table is available in machine-readable form in the online article.)
7
The Astrophysical Journal, 981:100 (10pp), 2025 March 10 Xu et al.

K. S. Cheng 2003; H.-K. Chang et al. 2023), the correlation
coefficient for MSPs (r=0.62)is generally smaller than that of
NPs (r=0.83), as shown in Table 2. In our sample, 110
sources (MSPs in GCs or NPs associated with PWNe)are
adopted from the literature, which only provided the luminos-
ities in the whole X-ray band (J.-Y. Hsiang & H.-K. Chang
2021; J. Zhao & C. O. Heinke 2022). Fitting across the entire
X-ray band yields a best-fit slope (α=0.85 ±0.05)higher
than those in the SX (α=0.39 ±0.08)and HX
(α=0.79 ±0.08)bands (Figure 1and Table 2), indicating
a discrepancy between the sources from literature and those
derived from spatial matching. However, we cannot determine
whether this small discrepancy is intrinsic or due to systematic
differences in flux calculations. The numbers of pulsars
involved in each fitting are also listed in Table 2.
The linear correlation between X-ray luminosity and spin-
down power strongly supports the magnetic dipole model, in
which magnetic dipole radiation extracts rotational kinetic
energy and causes the spin-down. We further investigate the
correlation between X-ray luminosity and five timing para-
meters, as shown in Figures 2and 3, and Table 2. For
correlations where the Pearson correlation coefficients r>0.6,
we use curve_fit module in Scipy package to plot fitting
lines showing the trend, and provide fitting errors at 1σ
confidence level. In Figure 2panels (a)and (b), the best fits for
Pand 
P
of NPs are L
X
∝P
−2.95±0.27
and L
X

µ
P1.08 0.12,
respectively. Since pulsar timing parameters are functions of P
and 
P
, the best fit in two dimensions is found to be L
X

µ- 
PP
2.55 0.16 0.85 0.04 . In panel (c), the surface magnetic
strength (B
surf
)shows no significant correlation with L
X
,
consistent with the result from H.-K. Chang et al. (2023).In
panel (d), the gray regions represent theoretical lines for
=Blog 6, 7, 8, ...,1
4
surf G under the assumption that

µ
L
E
X
0.8
5
. The distribution ranges for MSPs and NPs fall
between 6–10 and 10–14, consistent with the values calculated
from detected Pand 
P
. It is worth noting that MSPs are old
neutron stars “recycled”by the accretion of mass and angular
momentum from a companion star in a mass-transfer binary
(D. Bhattacharya & E. P. J van den Heuvel 1991), so the
characteristic age τmight deviate from the real age for MSPs.
In Figure 3panel (a), we report for the first time a strong
correlation between B
lc
and L
X
for MSPs. The fitting line
reveals a consistent relationship for both NPs and MSPs,
approximately µ
L
B
Xlc
1.14. This strong correlation is also found
in the gamma-ray band, with Pearson correlation coefficients
r=0.71 for MSPs and r=0.79 for NPs (Table 2(c)). This
result provides valuable constraints for high-energy emission
models of pulsars. The outer-gap model offers an explanation
for these emissions, suggesting that gamma-rays are produced
in the outer-gap by electron-positron pairs (e
±
)through inverse
Compton scattering or curvature radiation processes
(K. S. Cheng et al. 1986). As these gamma-rays travel back
toward the neutron star surface, they convert into secondary
electron-positron pairs via photon-photon pair creation. These
secondary pairs then emit nonthermal X-rays through synchro-
tron radiation near the light cylinder (K. S. Cheng et al. 1998;
J. Takata et al. 2012).
We also note that with the same B
lc
, X-ray luminosity of NPs
tends to exceed that of MSPs. Therefore, two-dimensional
fitting is also performed, as shown in panel (b)of Figure 3. The
best fitting between L
X
and B
lc
,τis L
X
tµ-
Blc
0.86 0.06 0.42 0.03.
This result is consistent with the 
-
L
E
Xcorrelation, as

tµµµ
--
L
BPPE
Xlc0.5 3 .
3. GPPS Pulsars
3.1. Sample Construction and Data Collection
To discover pulsars within the Galactic latitude of ±10°
from the Galactic plane, the GPPS survey team designed the
snapshot observation mode. In this mode, a sky patch of
approximately 0.1575 square degrees is surveyed by four
pointings using three-beam switching of the 19 beams from the
L-band 19-beam receiver on FAST (see J. L. Han et al. 2021,
for more details). The L-band resolution is about 2¢
.9(P. Jiang
et al. 2019), so the initial position of a pulsar detected from one
beam has an accuracy of

1¢
.5. This accuracy can be
significantly improved (0

.
1)with a long-term timing
campaign (W. Q. Su et al. 2023). We search for candidate
X-ray counterparts within a circle centered on the position of
GPPS pulsars with a radius of 1¢
.5. Only point-like X-ray
sources are selected by setting the extent flag EP_Extent =0
for XMM-Newton sources and extent_flag =FALSE for
Chandra sources. The spatial match between the GPPS pulsars
and the XMM-Newton and Chandra catalogs yields 48
associations (Table 3).
3.2. Parameters Analysis
We convert the fluxes listed in the catalogs to the isotropic X-ray
luminosities in the 0.3–10 keV and 0.5–7 keV bands for XMM-
Newton and Chandra catalogs, respectively. The X-ray point
sources exhibit X-ray luminosities ranging from 3.6 ×10
29
erg s
−1
to 6.8 ×10
33
erg s
−1
. Assuming that the GPPS pulsars share the
same 
µ
L
E
X
0.85 (Figure 1)correlation with the ATNF pulsars, the
spin-down power can be calculated with the observed X-ray
luminosity. The period Pof GPPS pulsars is provided in the
catalog, and the period derivative 
P
can be derived using the
formula 
=p
PEP
I4
3
2. For most sources, the 
E
and 
P
derived from the

-
L
E
Xrelation appear excessively high. It is illogical for many
sources to have τvalues smaller than 1 kyr or magnetic fields
greater than the critical value of 4.4 ×10
13
G(Figure 4). Excluding
these suspicious sources, there remain 27 X-ray point sources
located within 16 pulsars’positional error circles. However, it is
important to note that a large proportion of these X-ray point
sources are not actual X-ray counterparts of the GPPS pulsars. Due
to FAST’s angular resolution of 2¢
.9, the probability to find an
unrelated X-ray source within a positional error circle is 10
3
–10
4
times higher than that for the ATNF pulsars. Hence, there may be
multiple X-ray sources surrounding the GPPS pulsars within 1¢
.5
(e.g., J1855+0139g and J2021+4024g).
As discussed above, X-ray luminosity of RPPs is positively
correlated with their rotational energy loss (W. Becker &
J. Truemper 1997; X.-H. Li et al. 2008; Z. Arzoumanian et al.
2011; J. Vink et al. 2011; N. Rea et al. 2012; A. Vahdat et al.
2022; H.-K. Chang et al. 2023). Assuming 
~´ -
L
E210
X4
(Figure 1), the derived values of 
E
are larger than 10
34
erg s
−1
when L
X
>2×10
30
erg s
−1
. In contrast, more than 60 newly
discovered pulsars by FAST have timing solutions, and their
spin-down powers are mostly less than 10
34
erg s
−1
(D. Li et al.
2018; W. Q. Su et al. 2023; Q. D. Wu et al. 2023). We estimate
the fluxes of these pulsars using the detected Pand 
P
,finding
that almost 87% are lower than 10
−15
erg cm
−2
s
−1
. However,
most sources detected by XMM-Newton and Chandra have
8
The Astrophysical Journal, 981:100 (10pp), 2025 March 10 Xu et al.

fluxes over 10
−14
erg cm
−2
s
−1
and 10
−15
erg cm
−2
s
−1
,
respectively (N. A. Webb et al. 2020; F. A. Primini et al.
2011). Only the MSP, PSR J1953+1844, is found to be
associated with a faint X-ray point source, 2CXO J195337.9
+184454 (R.A. =19:53:38.0, decl. =+18:44:54.4)with a
separation of less than 0

.
2(Z. Pan et al. 2023). Thus, we
conclude that the X-ray counterparts of FAST newly
discovered pulsars are less likely to be found in the mentioned
XMM-Newton and Chandra catalogs compared to ATNF
pulsars, and the point sources with high X-ray luminosity are
likely to be coincidences with GPPS pulsars.
4. Discussion and Summary
In this work, we search for the X-ray counterparts of ATNF
pulsars by cross-correlating their positions with the XMM-
Newton, Chandra catalogs. A total of 231 X-ray counterparts
are identified, including 98 NPs and 133 MSPs, making this the
largest and most comprehensive catalog to date.
1. X-ray luminosity of pulsars shows a strong correlation
with spin-down power across the entire X-ray band for
both NPs and MSPs, following the relation

µ
L
E
X
0.85 0.0
5
, which is consistent with the findings of
H.-K. Chang et al. (2023)within the error margins. The
positive correlation is particularly strong in the HX band,
while in the soft band the correlation weakens compared
to W. Becker & J. Truemper (1997), likely due to the
presence of mixed thermal and nonthermal components.
2. In traditional RPP theories, magnetic dipole radiation
extracts rotational kinetic energy from neutron star and
translates it into electromagnetic radiation, including
X-ray emissions. This suggests an expected positive
correlation between the magnetic field and electro-
magnetic radiation. However, no significant correlation
is observed between L
X
and B
surf
. On the other hand, we
observe strong correlations between X-ray luminosity and
the pulsar parameters P,τ, and B
lc
for NPs. Notably, this
study is the first to report a strong correlation between B
lc
and luminosities in the X-ray and gamma-ray bands of
both NPs and MSPs. These findings suggest that the
high-energy emission from RPPs can be more effectively
explained by the outer-gap model. The best fit for L
X
as a
function of B
lc
and τin two dimensions is L
X
tµ-
Blc
0.86 0.06 0.42 0.03.
3. For all detected pulsars, luminosities in the radio and
gamma-ray bands do not show significant correlations with
timing parameters. However, when examining the correla-
tion for pulsars with X-ray counterparts listed in Table 1and
calculating the Pearson and Spearman correlation coeffi-
cients (see Table 2),wefind that gamma-ray luminosity
shows a strong correlation with P,τ,andB
lc
, similar to the
correlations seen in the X-ray band. In contrast, we still find
no significant correlations in the radio band.
4. We identify 27 putative associations around the 16 GPPS
pulsars. However, by examining the properties of GPPS
pulsars with available timing solutions, we find that their

E
tend to be below 10
34
erg s
−1
, and most estimated
fluxes are below the detection thresholds of current X-ray
telescopes, unless long-term exposure is available.
Consequently, we conclude that the likelihood of
discovering the actual X-ray counterparts is lower
compared to the ATNF pulsars. A portion of the X-ray
point sources selected in this work are likely coincidental
and unrelated to the GPPS pulsars.
Acknowledgments
We would like to thank the referee for their valuable suggestions
and comments that improved the clarity of the paper. This research
has made use of data collected by ATNF, FAST, and two X-ray
missions, Chandra, and XMM-Newton. FAST is a Chinese
national mega-science facility, operated by National Astronomical
Observatories, Chinese Academy of Sciences. S.S.W. thank
Professors Jin-Lin Han, Hao Tong, and Ren-Xin Xu for many
valuable discussions. The authors give their thanks for support
from the National Natural Science Foundation of China under
Grants 12473041, 12033006, 12373051, and 12393852.
Facilities: CXO, XMM, FAST:500m, Fermi.
Data Availability
The XMM-Newton and Chandra point source catalogs used
in this work are available from https://heasarc.gsfc.nasa.gov/
W3Browse/xmm-newton/xmmssc.html and https://cxc.cfa.
harvard.edu/csc2.1/index.html, respectively. The information
of ATNF and FAST GPPS pulsars are available on the
webpage of https://www.atnf.csiro.au/people/pulsar/psrcat/
and the GPPS survey http://zmtt.bao.ac.cn/GPPS/
GPPSnewPSR.html, respectively.
Table 1will be updated regularly online: https://xray-
pulsar.github.io/counterparts/.
ORCID iDs
Yu-Jing Xu (徐雨婧)https://orcid.org/0009-0000-3830-9650
Han-Long Peng (彭寒龙)https://orcid.org/0009-0009-
8477-8744
Shan-Shan Weng (翁山杉)https://orcid.org/0000-0001-
7595-1458
Xiao Zhang (张潇)https://orcid.org/0000-0002-9392-547X
Ming-Yu Ge (葛明玉)https://orcid.org/0000-0002-
2749-6638
Figure 4. 
-P
P
diagrams. The values of 
P
are derived by the relationship
that 
µ
L
E
X0.85.
9
The Astrophysical Journal, 981:100 (10pp), 2025 March 10 Xu et al.

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