SIMBAD references

We report BeppoSAX observations of five transient black hole candidates during their quiescent phase. We confirm that these sources are X-ray faint, improving on and complementing existing upper limits. We derive 1-10keV upper limits for GRO J0422+32, GRS 1009-45, 4U 1630-47 and XTE J1748-288, which range from 2x10³²erg/s to 5x10³⁴erg/s. We positively detect GS 2023+338. Its X-ray spectrum can be fit by a power law (photon index Γ=1.9) or a thermal bremsstrahlung (with kT_br=7keV), converting in both cases to a 1-10keV unabsorbed luminosity of ∼10³³erg/s. These values are comparable to the ones derived during an ASCA observation in 1994, indicating that the source remains stable over a ∼5 yr baseline.