UltraCompCAT A Catalogue of Ultra-Compact and Short Orbital Period X-ray Binaries

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ID# 6

M15 X-2

CXOU J212958.1+121002, NGC 7078 X-2

Confirmed UCXB

RA                 Dec    

[hh:mm:ss.ss]          [dd:mm:ss.ss]

21:29:58.14   +12:10:01.52

                     [ICRS]

ℓ                      b

[deg]                            [deg]

065.012156  -27.311977

Year of discovery: 2000

(White2001)

Basic data
Location in Globular Cluster M15/NGC 7078
Type of accretor NS Persistent
Distance [kpc]
(other distances)
 		10.709 -0.096+0.095
Baumgardt2021
Harris2010Kuulkers2003Watkins2015
z [kpc] -4.91 Baumgardt2021
Orbital period (Porb) [min] 22.5806±0.0002 Dieball2005
Porb determination method UV modulation
Thermonuclear X-ray burst Short-B
IB 		vanParadijs1990bSmale2001
Galloway2020
Peak X-ray flux [erg s-1 cm-2]
(2 - 10 keV)		 6.71E-11 White2001
NH [x1022 cm-2] <0.034 White2001
E(B-V) [mag] 0.1±0.01 Harris2010
Magnitude U=18.6 DeMarchi1994White2001
Proposed companion C, He WD
(UV SED modelling) 		Dieball2005


NOTES
M15 X-2 could only be separated from AC211 by Chandra. The combined unresolved emission is known as 4U 2129+12 or 4U 2127+119.
Although it is not clear which of the sources is the burster, it is believed to be M15 X-2 (White2001, Kuulkers2003).
Although M15 X-2 is a persistent source, it has shown episodes of increased activity (Sivakoff2011, Pooley2013, Homan2022).
The source was detected at 5 and 7 GHz during its 2011 increased activity period (Miller-Jones2011).

Spectral data
UV Excess of flux (C IV λ1550 and He II λ1640 emission lines ?) Dieball2005
Optical
X-ray Featureless White2001Koliopanos2021

Peak Optical/NIR magnitudes
If the system is transient, quiescent magnitudes are indicated with a "q" superindex
DeMarchi1994White2001 Díaz-Sánchez2012
U=18.6, I < 20.5
Aladin finding chart
Scroll to zoom. Set survey image in "Manage layers"
Default image: DSS2 Red
M15 X-2 in Simbad

Pan-STARRS1 finding chart

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PS1 Finding chart

References to finding charts

Dieball2005White2001


This research has made use of NASA's Astrophysics Data System (ADS) and the SIMBAD database operated at CDS (Strasbourg, France)
Please acknowledge the use of this catalogue in any published work you derive from it.
Last modified: 09 May 2023.