Predicting the self-lensing population in optical surveys

Abstract

The vast majority of binaries containing a compact object and a regular star spend most of their time in a quiescent state where no strong interactions occur between components. Detection of these binaries is extremely challenging and only few candidates have been detected through optical spectroscopy. Self-lensing represents a new means of detecting compact objects in binaries, where gravitational lensing of the light from the visible component by the compact object produces periodic optical flares. Here we show that current and planned large-area optical surveys can detect a significant number (∼100–10,000s) of these self-lensing binaries and provide insights into the properties of the compact lenses. We show that many of the predicted population of observable self-lensing binaries will be observed with multiple self-lensing flares; this both improves the chances of detection and also immediately distinguishes them from chance-alignment micro-lensing events. Through self-lensing we can investigate long – but previously hidden – stages of binary evolution and consequently provide new constraints on evolutionary models which impact on the number and nature of double compact object mergers.

Astrometric excess noise in Gaia EDR3 and the search for X-ray binaries

“…Several recent theoretical works have highlighted the feasibility of large surv e ys, including astrometric missions (Gould & Salim 2002 ;Barsto w et al 2014 ;Brei vik, Chatterjee & Larson 2017 ;Mashian & Loeb 2017 ;Yalinewich et al 2018 ;Andre ws, Brei vik & Chatterjee 2019 ;Chawla et al 2021 ) and microlensing searches (Masuda & Hotokezaka 2019 ;Wiktorowicz et al 2021 ), to unco v er large new populations of black holes in binary orbits. Massive spectroscopic surv e ys are also beginning to probe this territory through brute force blind searches for radial velocity variations characteristic of massive compact objects (Yi, Sun & Gu 2019 ;Wiktorowicz et al 2020 ;Price-Whelan et al 2020 ).…”

Modeling Long-term Variability in Stellar-compact Object Binary Systems for Mass Determinations

“…Recent population synthesis studies by Wiktorowicz et al (2021) have estimated the amount of self-lensing systems that will be observed by upcoming surveys such as LSST, TESS, and Zwicky Transient Facility to be of the order of 10 3 -10 4 . A large fraction of these systems will undergo self-lensing events that would result in amplifications smaller than a millimagnitude difference, thus, the pulses would be indistinguishable from noise.…”

“…A large fraction of these systems will undergo self-lensing events that would result in amplifications smaller than a millimagnitude difference, thus, the pulses would be indistinguishable from noise. However, Wiktorowicz et al (2021) estimate up to 200 of such systems that will create self-lensing pulses that will be detectable and distinguishable by the surveys. This would put the amount of discovered self-lensing systems on the same order as that of known X-ray binary (XRB) systems.…”

“…For simplicity, we assume circular orbits for these cases. To find the minimum acceptable inclination i min , we adopt the methodology of Wiktorowicz et al (2021); for the maximum impact parameter, the minimum inclination is determined by the equation i arccos…”

Astrometric excess noise in Gaia EDR3 and the search for X-ray binaries

“…Several recent theoretical works have highlighted the feasibility of large surveys, including astrometric missions (Gould & Salim 2002;Barstow et al 2014;Breivik et al 2017;Mashian & Loeb 2017;Yalinewich et al 2018;Andrews et al 2019;Chawla et al 2021) and microlensing searches (Masuda & Hotokezaka 2019;Wiktorowicz et al 2021), to uncover large new populations of black holes in binary orbits. Massive spectroscopic surveys are also beginning to probe this territory through brute force blind searches for radial velocity variations characteristic of massive compact objects (Yi et al 2019;Wiktorowicz et al 2020;Price-Whelan et al 2020).…”