Limiting the accretion disk light in two mass transferring hot subdwarf binaries by Kunal Deshmukh et al. on Thursday 24 November

We report the results from follow-up observations of two Roche-lobe filling

hot subdwarf binaries with white dwarf companions predicted to have accretion

disks. ZTF J213056.71+442046.5 (ZTF J2130) with a 39-minute period and ZTF

J205515.98+465106.5 (ZTF J2055) with a 56-minute period were both discovered as

subdwarf binaries with light curves that could only be explained well by

including an accretion disk in their models. We performed a detailed

high-resolution spectral analysis using Keck/ESI to search for possible

accretion features for both objects. We also employed polarimetric analysis

using the Nordic Optical Telescope (NOT) for ZTF J2130. We did not find any

signatures of an accretion disk in either object, and placed upper limits on

the flux contribution and variation in degree of polarisation due to the disk.

Owing to the short 39-minute period and availability of photometric data over

six years for ZTF J2130, we conducted an extensive $O - C$ timing analysis in

an attempt to look for orbital decay due to gravitational wave radiation. No

such decay was detected conclusively, and a few more years of data paired with

precise and consistent timing measurements were deemed necessary to constrain

$\dot P$ observationally.

arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.12502v1