J/A+A/706/A168 STONKS XMM transient/variable X-ray sources (Webbe+, 2026)
STONKS first results: Long-term transients in the XMM-Newton Galactic plane
survey.
Webbe R., Quintin E., Webb N., Ponti G., Bao T., Maitra C., Mandel S.,
Mondal S.
<Astron. Astrophys. 706, A168 (2026)>
=2026A&A...706A.168W 2026A&A...706A.168W (SIMBAD/NED BibCode)
ADC_Keywords: X-ray sources ; Transient ; Positional data ; Spectroscopy ;
Photometry ; Cross identifications ; Optical ; Infrared
Keywords: methods: data analysis - X-rays: general
Abstract:
The study of astronomical transients at high energies provides
insights into some of the most extreme physical events in the
universe; however, carrying out their detection and fast follow-up
studies are limited by instrumental constraints. Search for Transient
Object in New observations using Known Sources (STONKS) is a
near-real-time transient detection system for XMM-Newton offering the
capability to detect transients in XMM-Newton observations at fainter
fluxes than can be achieved with wide survey instruments. We present
the transients detected with the STONKS pipeline found in an
XMM-Newton multi- year heritage survey of the Galactic plane to
identify and classify highly variable X-ray sources that have recently
been reported in this region. We examined the alerts created by the
STONKS pipeline from over 200 XMM observations of the Galactic plane,
screening for instrumental effects. The 78 alerts associated with 70
real astrophysical sources were then subjected to further temporal and
spectral analysis. From the 70 sources we identified, we were able to
classify 32 with a high degree of confidence, including 7 X-ray
binaries, 1 gamma-Cas analogue, and 1 magnetar candidate. Of the 70
sources, 23 were detected for the first time in X-rays. This
systematic analysis of publicly available data has shown the value and
potential of STONKS in the application to XMM-Newton observations. It
will enable the community to detect transient and highly variable
sources at fainter fluxes than with any other X-ray transient
detection systems.
Description:
These tables contain the supplementary data tables B1, B2, B3, and C1
as referenced in DOI:10.1051/0004-6361/202557789. The tables contain
x-ray properties, astrometric positions, fluxes, cross-identifications
with Gaia, 2MASS, AllWISE and Simbad, spectral models fitting
properties, source classifications, source NHs and temperatures.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablec1.dat 75 78 X-ray properties of STONKS alert sources
tablec2.dat 113 70 Multi-wavelength properties of counterparts
tablec3.dat 84 78 Classifications of STONKS alert sources
tabled1.dat 125 342 Results of spectral fitting to STONKS alert
sources
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
II/328 : AllWISE Data Release (Cutri+ 2013)
IX/69 : XMM-Newton Serendipitous Source Catalogue 4XMM-DR13 (Webb+, 2023)
IX/68 : XMM-Newton Serendipitous Source Catalogue 4XMM-DR12 (Webb+, 2023)
Byte-by-byte Description of file: tablec1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Alert Alert sources number (Alert)
4- 12 I9 --- XMM XMM observation identifier (OBSID)
14- 16 I3 --- Source Source number within the observation
(Source)
18- 19 I2 h RAh Right ascension (J2000)
21- 22 I2 min RAm Right ascension (J2000)
24- 28 F5.2 s RAs Right ascension (J2000)
30 A1 --- DE- Declination sign (J2000)
31- 32 I2 deg DEd Declination (J2000)
34- 35 I2 arcmin DEm Declination (J2000)
37- 40 F4.1 arcsec DEs Declination (J2000)
42- 45 F4.2 arcsec ePos Error in right ascension and declination
(Error)
47- 62 A16 --- 4XMM Identifier in the 4XMM DR14 catalogue
(4XMM)
64- 65 A2 --- Class STONKS alert classification (Alert_Class)
67 A1 --- Spectral STONKS spectral alert flag (Spectral)
69- 73 F5.2 10-13mW/m2 Flux Observed X-ray flux (Flux)
75 A1 --- Var True variability flag (True_Alert)
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Byte-by-byte Description of file: tablec2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Alert Alert sources number (Alert)
4- 26 A23 --- SIMBAD SIMBAD identified counterpart (SIMBAD)
28- 46 I19 --- GaiaDR3 ? Gaia DR3 source identified counterpart
(Gaia)
48- 51 F4.1 mag Gmag ? G-band mean magnitude (m_G)
53- 55 F3.1 arcsec SepGaia ? Angular separation to Gaia counterpart
(Sep_Opt)
57- 72 A16 --- 2MASS ? 2MASS identified counterpart (2MASS)
74 A1 --- l_Jmag Lower limit flag
76- 80 F5.2 mag Jmag ? Observed 2MASS J magnitude (m_J)
82- 84 F3.1 arcsec SepNIR ? Separation to 2MASS counterpart (Sep_NIR)
86- 104 A19 --- AllWISE AllWISE identified counterpart (AllWISE)
106- 109 F4.1 mag W1mag ? Observed AllWISE W1 magnitude (m_W1)
111- 113 F3.1 arcsec SepMIR ? Separation to AllWISE counterpart (Sep_MIR)
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Byte-by-byte Description of file: tablec3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Alert Alert sources number (Number)
4- 5 A2 --- Class STONKS alert class (Alert_Class)
7- 11 A5 --- MW Multi-wavelength counterparts (MW)
13- 16 F4.2 kpc D ? Distance estimates (d)
18- 22 F5.2 [10-7W] log(LX) Estimated X-ray luminosity (logL_X)
24 A1 --- l_log(FX/FOpt) Lower limit flag
26- 30 F5.2 [-] log(FX/FOpt) X-ray-to-optical flux ratio
(logFX/FOpt)
32 A1 --- Var Intra-observation variability flag
(Short_Variable)
34- 44 A11 --- Spect Spectral model (Spectrum)
46- 51 F6.2 keV kBT1 ? Temperature of first component (kT)
53- 58 F6.2 keV kBT2 ? Temperature of second component (kT_2)
60- 63 F4.2 keV kBT3 ? Temperature of third component (kT_3)
65- 67 F3.1 --- Abund ? Elemental abundance for apec/ray
(Abund)
69- 72 F4.2 --- alpha ? Power Law index (alpha)
74- 82 A9 --- ObjClass Source classification (Src_Class)
84 A1 --- Q Source classification quality flag
(Quality)
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Byte-by-byte Description of file: tabled1.dat
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Bytes Format Units Label Explanations
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1- 4 F4.1 --- Alert Alert sources number (Alert)
6- 19 A14 --- Spect Spectral Model (Model)
21- 26 F6.2 10+20cm-2 NH Neutral H Column Density (N_H)
28- 33 A6 10+20cm-2 e_NH ? Lower limit of NH (NHlower)
35- 40 F6.2 10+20cm-2 E_NH ? Upper limit of NH (NHupper)
42- 47 F6.2 keV kBT ? Temperature of first component (kT)
49- 53 A5 keV e_kBT ? Lower limit of kT (kT_lower)
55- 60 F6.2 keV E_kBT ? Upper limit of kT (kT_upper)
62- 67 F6.2 keV kBT2 ? Temperature of second component (kT2)
69- 72 F4.2 keV e_kBT2 ? Lower uncertainty of kBT2 (kT2_lower)
74- 78 F5.2 keV E_kBT2 ? Upper uncertainty of kBT2 (kT2_upper)
80- 84 F5.2 keV kBT3 ? Temperature of third component (kT3)
86- 89 F4.2 keV e_kBT3 ? Lower uncertainty of kBT3 (kT3_lower)
91- 94 F4.2 keV E_kBT3 ? Upper uncertainty of kBT3 (kT3_upper)
96- 98 F3.1 --- Abund ? Elemental abundance for apec/ray (Abund)
100- 104 F5.2 --- alpha ? Photon index (alpha)
106- 110 F5.2 --- e_alpha ? Lower uncertainty on alpha (alpha_lower)
112- 115 F4.2 --- E_alpha ? Upper uncertainty on alpha (alpha_upper)
117- 119 I3 --- dof ? Degrees of Freedom (dof)
121- 125 F5.2 --- Chi2 Model Reduced Chi-squared (Chi2_nu)
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Acknowledgements:
Robbie Webbe, robbie.webbe(at)irap.omp.eu
(End) Luc Trabelsi [CDS] 07-Jan-2026