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

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ID# 17

Swift J1756.9-2508

Confirmed UCXB

RA                 Dec     [hh:mm:ss.ss]          [dd:mm:ss.ss] 17:56:57.43  -25:06:27.4                      [ICRS]

ℓ                      b [deg]                            [deg] 004.580765  -00.212396

Year of discovery: 2007

(Krimm2007)

Basic data

Location in Globular Cluster
Type of accretor	NS AMXP (182.06 Hz / 5.49 ms)	Transient Krimm2007
Distance [kpc] (other distances)	assumed 8	Krimm2007 Sanna2018a
z [kpc]	-0.03	Krimm2007
Orbital period (Porb) [min]	54.7017±0.0013	Krimm2007
Porb determination method	X-ray pulsation
Thermonuclear X-ray burst
Peak X-ray flux [erg s-1 cm-2] (2 - 10 keV)	1.54E-09	Sanna2018a
NH [x1022 cm-2]	8.14+0.14-0.15	Sanna2018a
E(B-V) [mag]
Magnitude
Proposed companion	(likely a He-dominated WD) (donor mass-radius constraint)	Krimm2007

NOTES

No radio detection during the 2007 outburst (continuum emission at 8.7 Ghz: Possenti2007, pulsations at 1.4 GHz: Hessels2007) and 2009 outburst (5.5 and 9 GHz; Tudose2009a). A NIR Ks counterpart, exhibiting variability of about 1.3 mag in two observations taken close to the end of the 2007 outburst and during quiescence, was proposed by Burderi2007. The source was not detected in quiescence after the 2007 outburst with an upper limit of 4.3E-4 counts/s (95% c.l., 0.3-8 keV; Papitto2007). Li2021 obtained a value for the orbital period derivative of (7.9±9.5)E-13 s/s. This implies that the binary system had a constant orbital period since the first outburst in 2007.

Spectral data

UV
Optical
X-ray	Fe Kα (6-7 keV)	Koliopanos2021

Peak Optical/NIR magnitudes

If the system is transient, quiescent magnitudes are indicated with a "q" superindex

Aladin finding chart

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Swift J1756.9-2508 in Simbad

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Pan-STARRS1 finding chart

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