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This notation is often used for a dominant chord which resolves to a minor chord afterwards. It's the same as a dominant 7 chord, but with a b9 near the top of the voicing: 1-3-5-b7-b9
Standard scale choice
There are (at least) two options here. You could use the 5th mode of the harmonic minor scale, which gives you: 1 b2 3 4 5 b6 b7 or you could use the 'reversed' diminished scale, which alternates semitone-wholetone-semitone-wholetone-... for the whole octave. 1 b2 #2 3 #4 5 6 b7
Soloist or accompanist might play 7alt instead. But if you stick with the diminished scale, notice that it is possible to build a major or a minor triad on every other note of the scale. Lines made up from these triads can sound very modern.