High-cadence GW astrometry in the μHz gap

@misc{mentasti2026highcadence,
  title = {{High-cadence GW astrometry in the $μ$Hz gap}},
  author = {Giorgio Mentasti and Carlo Contaldi},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.27221},
  eprint = {2610.27221},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.27221},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - High-cadence GW astrometry in the μHz gap
AU  - Giorgio Mentasti
AU  - Carlo Contaldi
PY  - 2026
DA  - 2026/10/19
PB  - arXiv
DO  - 10.48550/arxiv.2610.27221
UR  - https://arxiv.org/abs/2610.27221
AB  - We forecast the sensitivity of a dedicated, fast-spinning astrometric survey to a stochastic gravitational-wave background (SGWB) in the microhertz gap between pulsar timing arrays (PTAs) and LISA. Spinning the satellite faster samples each star more often, raising the Nyquist frequency and opening higher frequencies at no cost in noise: the shorter, noisier exposures are exactly compensated by their number, so the white-noise floor of each position stream is independent of cadence. High frequencies are where astrometry is most competitive, because the deflection measures the strain directly: its strain noise is white, whereas the equivalent noise of pulsar timing grows as f^2. With a cross-correlation estimator over N reference stars and the astrometric overlap computed in the distant-source limit, we find that a Gaia-like satellite scanning the ecliptic poles, with N∼10^4 bright stars over $10$~yr, falls short of the background measured by PTAs by a factor ∼ 60. A larger, $8$-m-class aperture, or a constellation of satellites covering the whole sky, reaches it, while extending the reach continuously across the μHz band.
ER  -