Resolving SLX 1744−299 and SLX 1744−300 in the hard X-ray band: Implications for their ultracompact nature

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Table 1.

Best-fit spectral results for SLX 1744−299 and SLX 1744−300.

Component	Parameter	SLX 1744−299		SLX 1744−300
		NTHCOMP	NTHCOMP+BBODYRAD	NTHCOMP	NTHCOMP+BBODYRAD
CONST	C_AB	1.03 ± 0.01	1.03 ± 0.01	1.03 ± 0.01	1.03 ± 0.01

TBABS	N_H (10²² cm⁻²)	3.3^†	3.3^†	3.7^†	3.7^†

NTHCOMP	Γ	2.33 ± 0.01	2.32 ± 0.01	2.28 ± 0.02	2.28 ± 0.02
	kT_e (keV)	$38_{- 12}^{+ 53}$ $Mathematical equation: $ 38_{-12}^{+53} $$	$37_{- 12}^{+ 19}$ $Mathematical equation: $ 37_{-12}^{+19} $$	8.7 ± 0.8	8.7 ± 0.5
	kT_seed (keV)	0.58 ± 0.02	=kT_bb	0.63 ± 0.03	=kT_bb
	norm_compt (×10⁻²)	1.3 ± 0.1	1.3 ± 0.1	1.4 ± 0.1	1.4 ± 0.1

BBODYRAD	kT_bb (keV)	–	0.57 ± 0.04	—	0.64 ± 0.03
	norm_bb	–	< 3.3	–	< 1.4
	R_bb [km] ^b	–	< 1.3	–	< 1.2

$F_{X}^{a}$ $Mathematical equation: $ \mathit{F}_{\mathrm{X}}^{a} $$ [0.5–10 keV]		1.49 ± 0.01	1.54 ± 0.01	1.93 ± 0.01	1.93 ± 0.01
$F_{X}^{a}$ $Mathematical equation: $ \mathit{F}_{\mathrm{X}}^{a} $$ [2–10 keV]		1.33 ± 0.01	1.36 ± 0.01	1.73 ± 0.01	1.73 ± 0.01
$F_{X}^{a}$ $Mathematical equation: $ \mathit{F}_{\mathrm{X}}^{a} $$ [3–78 keV]		1.77 ± 0.01	1.77 ± 0.01	2.02 ± 0.01	2.02 ± 0.01

$L_{X}^{b}$ $Mathematical equation: $ \mathit{L}_{\mathrm{X}}^{b} $$ [10³⁶ erg s⁻¹]		< 1.06 ± 0.51	< 1.06 ± 0.51	< 2.56 ± 0.43	< 2.56 ± 0.43

$χ_{ν}^{2} / d . o . f .$ $Mathematical equation: $ \chi^{2}_{\nu}/\mathrm{d.o.f.} $$		1.04/856	1.04/855	1.03/797	1.03/796

Notes. We used a thermal Comptonisation model, const×TBabs×(nthComp), with inp_Type = 0 and free kT_seed. We also used a combined model, const×TBabs×(nthComp+bbodyrad), in which kT_seed is tied to the BB temperature (kT_bb). All parameter uncertainties are reported at the 90 per cent confidence level. ^† Corresponding parameter frozen during the fit. ^a Unabsorbed X-ray flux in units of 10⁻¹⁰ erg cm⁻² s⁻¹. ^b Calculated in the 3–78 keV range, assuming an upper limit of 7.2 ± 1.4 kpc for SLX 1744−299 and 10.3 ± 0.8 kpc for SLX 1744−300.

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