Prospects of Finding Detached Black Hole-Star Binaries with TESS. (arXiv:1808.10856v5 [astro-ph.HE] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Masuda_K/0/1/0/all/0/1">Kento Masuda</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hotokezaka_K/0/1/0/all/0/1">Kenta Hotokezaka</a>
We discuss prospects of identifying and characterizing black hole (BH)
companions to normal stars on tight but detached orbits, using photometric data
from the Transiting Exoplanet Survey Satellite (TESS). We focus on the
following two periodic signals from the visible stellar component: (i)
in-eclipse brightening of the star due to gravitational microlensing by the BH
(self-lensing), and (ii) a combination of ellipsoidal variations due to tidal
distortion of the star and relativistic beaming due to its orbital motion
(phase-curve variation). We evaluate the detectability of each signal in the
light curves of stars in the TESS input catalog, based on a pre-launch noise
model of TESS photometry as well as the actual light curves of spotted stars
from the prime Kepler mission to gauge the potential impact of stellar activity
arising from the tidally spun-up stellar components. We estimate that the
self-lensing and phase-curve signals from BH companions, if exist, will be
detectable in the light curves of effectively $mathcal{O}(10^5)$ and
$mathcal{O}(10^6)$ low-mass stars, respectively, taking into account orbital
inclination dependence of the signals. These numbers could be large enough to
actually detect signals from BHs: simple population models predict some 10 and
100 detectable BHs among these “searchable” stars, although the latter may be
associated with a comparable number of false-positives due to stellar
variabilities and additional vetting with radial velocity measurements would be
essential. Thus the TESS data could serve as a resource to study nearby BHs
with stellar companions on shorter-period orbits than will potentially be
probed with Gaia.
We discuss prospects of identifying and characterizing black hole (BH)
companions to normal stars on tight but detached orbits, using photometric data
from the Transiting Exoplanet Survey Satellite (TESS). We focus on the
following two periodic signals from the visible stellar component: (i)
in-eclipse brightening of the star due to gravitational microlensing by the BH
(self-lensing), and (ii) a combination of ellipsoidal variations due to tidal
distortion of the star and relativistic beaming due to its orbital motion
(phase-curve variation). We evaluate the detectability of each signal in the
light curves of stars in the TESS input catalog, based on a pre-launch noise
model of TESS photometry as well as the actual light curves of spotted stars
from the prime Kepler mission to gauge the potential impact of stellar activity
arising from the tidally spun-up stellar components. We estimate that the
self-lensing and phase-curve signals from BH companions, if exist, will be
detectable in the light curves of effectively $mathcal{O}(10^5)$ and
$mathcal{O}(10^6)$ low-mass stars, respectively, taking into account orbital
inclination dependence of the signals. These numbers could be large enough to
actually detect signals from BHs: simple population models predict some 10 and
100 detectable BHs among these “searchable” stars, although the latter may be
associated with a comparable number of false-positives due to stellar
variabilities and additional vetting with radial velocity measurements would be
essential. Thus the TESS data could serve as a resource to study nearby BHs
with stellar companions on shorter-period orbits than will potentially be
probed with Gaia.
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