Revisiting Andromeda's Parachute

TL;DR

This study provides precise time delays, microlensing analysis, and spectral measurements of the gravitational lens system PS J0147+4630, improving its utility for cosmological research and revealing quasar properties.

Contribution

The paper offers new time delay measurements, detailed spectral analysis, and an updated lens model for Andromeda's Parachute, enhancing its application in cosmology.

Findings

One accurate time delay with 4% uncertainty was measured.

Detected significant microlensing variations over several years.

Estimated quasar black hole mass as log(M_BH/M_sun)=9.34 ± 0.30.

Abstract

The gravitational lens system PS J0147+4630 (Andromeda's Parachute) consists of four quasar images ABCD and a lensing galaxy. We obtained $r$-band light curves of ABCD in the 2017$-$2021 period from a monitoring with two 2-m class telescopes. These curves and state-of-the-art curve-shifting algorithms led to three independent time delays relative to image A, one of which is accurate enough (uncertainty of about 4%) to be used in cosmological studies. Our finely sampled light curves and some additional fluxes in the years 2010$-$2013 also demonstrated the presence of significant microlensing variations. This paper also focused on new near-IR spectra of ABCD in 2018$-$2019 that were derived from archive data of two 10-m class telescopes. We analysed the spectral region including the MgII, H$\beta$, [OIII], and H$\alpha$ emission lines (0.9$-$2.4 $\mu$m), measuring image flux ratios and a reliable quasar redshift of 2.357 $\pm$ 0.002, and finding evidence of an outflow in the H$\alpha$ emission. In addition, we updated the lens mass model of the system and estimated a quasar black-hole logarithmic mass ${\log \left[ M_{\rm{BH}}/\rm{M_{\odot}} \right]}$ = 9.34 $\pm$ 0.30.