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

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ID# 3

2S 0918-549

4U 0919-54

Confirmed UCXB

RA                 Dec     [hh:mm:ss.ss]          [dd:mm:ss.ss] 09:20:26.95  -55:12:24.7                      [ICRS]

ℓ                      b [deg]                            [deg] 275.852936  -03.844515

Year of discovery: 1974

(Giacconi1974)

Basic data

Location in Globular Cluster
Type of accretor	NS	Persistent
Distance [kpc] (other distances) Gaia [kpc]	3.0±0.2 (H), 3.9±0.2 (He) 4.0 5.77+2.77-1.60	Galloway2020 Jonker2004IntZand2005b VanDenEijnden2021 BailerJones2018
z [kpc]	-0.26	Galloway2020
Orbital period (Porb) [min]	17.4±0.1	Zhong2011
Porb determination method	Optical modulation
Thermonuclear X-ray burst	Short-B IB	Jonker2001b IntZand2005
Peak X-ray flux [erg s-1 cm-2] (2 - 10 keV)	1.12E-10	Juett2003b
NH [x1022 cm-2]	0.3	Juett2003b
E(B-V) [mag]
Magnitude	V = 20.98±0.07	Chevalier1987
Proposed companion	He WD; CO WD; ONe WD (Burst modelling; optical spectrum; X-ray spectral modelling)	IntZand2005b Nelemans2004Nelemans2006 Juett2001

NOTES

Radio flux density < 20 μJy (5.5 GHz; VanDenEijnden2021. According to the authors, the source was not detected at radio frequencies; the radio luminosity < ~3E27 erg/s). Fradio < 6 mJy (2 cm (14.7GHz); Duldig1979).

Spectral data

UV
Optical	Featureless (see, however, Nelemans2004 and Nelemans2006 for a marginal CO detection).	Nelemans2004Nelemans2006
X-ray	Ne (0.7 keV)	Juett2001

Peak Optical/NIR magnitudes

If the system is transient, quiescent magnitudes are indicated with a "q" superindex Chevalier1987 Zhong2011
V = 20.98±0.07, B = 21.29±0.07, r' = 20.95±0.16

Aladin finding chart

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Default image: DSS2 Red

2S 0918-549 in Simbad

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References to finding charts

Zhong2011Chevalier1987