MACHO Mass Determination Based on Space Telescope Observation

Abstract

We investigate the possibility of lens mass determination for a caustic crossing microlensing event based on a space telescope observation. We demonstrate that the parallax due to the orbital motion of a space telescope causes a periodic fluctuation of the light curve, from which the lens distance can be derived. Since the proper motion of the lens relative to the source is also measurable for a caustic crossing event, one can find a full solution for microlensing properties of the event, including the lens mass. To determine the lens mass with sufficient accuracy, the light curve near the caustic crossing should be observed within uncertainty of ∼1%. We argue that the Hubble Space Telescope observation of the caustic crossing supplied with ground-based observations of the full light curve will enable us to determine the mass of MACHOs, which is crucial for understanding the nature of MACHOs.

Mass Measurements of Isolated Objects From Space-Based Microlensing

“…Therefore, if that magnification pattern has a non-zero second derivative, such as when the source crosses a caustic (where the magnification diverges to infinity), the physical size of the source limits the observed magnification, leading to a rounded feature in the light curve whose width directly reflects the source size (Gould 1994a;Witt & Mao 1994). The microlens parallax p E is measured through observations from either a single accelerating platform (Gould 1992(Gould , 2013Honma 1999) or two wellseparated observatories (Refsdal 1966;Gould 1994bGould , 1997.…”

Geosynchronous Microlens Parallaxes

“…Hence, the oscillations would typically be minuscule. To overcome this obstacle, Honma (1999) proposed that the observations should be made during caustic crossings, which he showed dramatically increase the strength of the signal. However, alerting HST to imminent caustic crossings is extremely difficult, more so for planetary events, and in fact such measurements have never been carried out, nor even attempted.…”

Microlensing: Exploring the Dark Corners of the Galaxy with a Thousand Tiny Flashlights

“…The Earth and various space telescopes are all accelerating platforms. This acceleration can be seen in the light curve of the microlensing event, provided the event timescale is a significant fraction of the orbit [38,39,40]. Second, a microlensing event from two different locations will have a different observed light curve for each location because of the parallax effect [41,42,43,44].…”