  We use TESS 10-minute Full Frame Images (Sectors 27-55) to study a sample of
1708 stars within 500 pc of the Sun that lie in a narrow colour range in the
centre of the delta Scuti instability strip (0.29 < BP-RP < 0.31). Based on the
Fourier amplitude spectra, we identify 848 delta Scuti stars, as well as 47
eclipsing or contact binaries. The strongest pulsation modes of some delta
Scuti stars fall on the period-luminosity relation of the fundamental radial
mode but many correspond to overtones that are approximately a factor of two
higher in frequency. Many of the low-luminosity delta Scuti stars show a series
of high-frequency modes with very regular spacings. The fraction of stars in
our sample that show delta Scuti pulsations is about 70% for the brightest
stars (G<8), consistent with results from Kepler. However, the fraction drops
to about 45% for fainter stars and we find that a single sector of TESS data
only detects the lowest-amplitude delta Scuti pulsations (around 50 ppm) in
stars down to about G=9. Finally, we have found four new high-frequency delta
Scuti stars with very regular mode patterns, and have detected pulsations in
lambda Mus that make it the fourth-brightest delta Scuti in the sky (G=3.63).
Overall, these results confirm the power of TESS and Gaia for studying
pulsating stars.
