Abstract:
We present a study based on the high-resolution spectroscopy and K2 space photometry of five chemically peculiar stars in
the region of the open cluster M44. The analysis of the high-precision photometric K2 data reveals that the light variations in
HD 73045 and HD 76310 are rotational in nature and caused by spots or cloud-like co-rotating structures, which are non-stationary
and short-lived. The time-resolved radial velocity measurements, in combination with the K2 photometry, confirm that HD 73045
does not show any periodic variability on time-scales shorter than 1.3 d, contrary to previous reports in the literature. In addition
to these new rotational variables, we discovered a new heartbeat system, HD 73619, where no pulsational signatures are seen.
The spectroscopic and spectropolarimetric analyses indicate that HD 73619 belongs to the peculiar Am class, with either a weak
or no magnetic field, considering the 200-G detection limit of our study. The least-squares deconvolution profiles for HD 76310
indicate a complex structure in its spectra, suggesting that this star is either part of a binary system or surrounded by a cloud shell.
When placed in the Hertzsprung–Russell diagram, all studied stars are evolved from the main sequence and situated in the δ Scuti
instability strip. This work is relevant for further detailed studies of chemically peculiar stars, for example on inhomogeneities
(including spots) in the absence of magnetic fields and the origin of the pulsational variability in heartbeat systems.
