Swift Follow-up Observations of MAXI Discovered Galactic Transients

TL;DR

This paper reports on the first year of follow-up observations of Galactic transients discovered by MAXI using NASA's Swift, achieving precise localizations and optical identifications to study their nature.

Contribution

It introduces a systematic follow-up program with Swift for MAXI transients, improving localization accuracy and enabling optical/IR counterpart identification.

Findings

Localization accuracy up to 1.5 arc-seconds

Successful monitoring of specific sources like MAXI J1659-152 and MAXI J1409-619

Enhanced ability to identify optical counterparts of X-ray transients

Abstract

We describe the results of the first year of a program to localize new Galactic Transient sources discovered by MAXI with NASA's Swift mission. Swift is ideally suited for follow-up of MAXI discovered transients as its X-ray Telescope (XRT) field of view (~0.2 degrees radius) is closely matched to the typical MAXI error circle. The XRT is capable of localizing new sources to an accuracy of up to 1.5 arc-seconds radius (90% confidence), and the Swift Optical/UV Telescope also provides optical imaging of any optical counterpart of the X-ray source. If no optical counterpart is found with Swift (usually due to absorption), the XRT position is good enough to allow for ground based IR telescopes to positively identify the optical counterpart. Although localization and identification of MAXI transients is the main aim of the program, these are often followed up by long term monitoring of the source. We present here results from 2 of these monitoring programs: the black-hole candidate MAXI J1659-152, and the Be/X-ray binary candidate MAXI J1409-619.