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

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ID# 1

4U 1820-303

X Sgr X-4

Confirmed UCXB

RA                 Dec     [hh:mm:ss.ss]          [dd:mm:ss.ss] 18:23:40.50  -30:21:40.09                      [ICRS]

ℓ                      b [deg]                            [deg] 002.788211  -07.913491

Year of discovery: 1972

(Giacconi1972)

Basic data

Location in Globular Cluster	NGC 6624
Type of accretor	NS	Persistent
Distance [kpc] (other distances)	8.019 +0.108-0.108	Baumgardt2021 Heasley2000Kuulkers2003Harris2010Galloway2020
z [kpc]	-1.10	Baumgardt2021
Orbital period (Porb) [min]	11.42	Stella1987
Porb determination method	X-ray modulation
Thermonuclear X-ray burst	Short-B SB	Clark1977 Strohmayer2002a
Peak X-ray flux [erg s-1 cm-2] (2 - 10 keV)	5.02E-09	Costantini2012
NH [x1022 cm-2]	0.16±0.003	Sidoli2001
E(B-V) [mag]	0.28 ± 0.03	Harris2010
Magnitude	B=18.7	King1993a
Proposed companion	He WD (Burst modelling)	Cumming2003

NOTES

Wang2010 detected an UV modulation at 693.5±1.3 s, ~1% longer than the orbital period, interpreted as a superhump period. Moreover, the source shows a long term modulation at ~171 d in X-rays (e.g., Priedhorsky1984, Zdziarski2007,Chou2001b) Chou2001b measured an orbital period derivative of (-7.54±3.21)E-13 s/s. The source is detected in radio (Russell2021)

Spectral data

UV
Optical
X-ray	O VII, O VIII and Ne IX absorption lines (hot interstellar medium?)	Futamoto2004Cackett2008

Peak Optical/NIR magnitudes

If the system is transient, quiescent magnitudes are indicated with a "q" superindex King1993a
B=18.7

Aladin finding chart

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4U 1820-303 in Simbad

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Pan-STARRS1 finding chart

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References to finding charts

King1993a