Trust, Otto ; Joshi, Santosh ; Nsamba, Benard ; Aol, Sharon ; Vermeulen, Owen ; Ssembatya, Ronald ; De Cat, Peter ; Lampens, Patricia ; Barnes, Sydney A. ; Goswami, Partha P. ; Dileep, Athul ; Ghosh, Surath C. ; Kumar, Pramod S. ; Jurua, Edward ; Sarkar, Mrinmoy ; Bedi, Sarabjeet S.

submitted to Monthly Notices of the Royal Astronomical Society (2026)

Abstract: We present the first homogeneous photometric and spectroscopic study of four bright field stars (HD 73135, BD +19◦ 2045, BD +19◦ 2046, and TYC 1395-855-1) that lie close to the variable HD 73045. These were monitored, but never fully analysed, by the Nainital–Cape Survey. Johnson-BV CCD time series from four 0.4–1.3 m telescopes show all four stars to be constant at the ≲ 0.12 mag level. Space-based K2 Campaigns 5 and 18 reveal low-amplitude variability only in HD 73135 and BD +19◦ 2045, and we additionally analyse TESS photometry from Sectors 45 and/or 72. HD 73135 shows a persistent 1.4–1.6 d doublet consistent with rotational modulation, although an orbital (ellipsoidal) interpretation cannot be excluded without time-series radial velocities; in TESS the dominant low-frequency power shifts to longer timescales (P ≃ 3–4.5 d), inconsistent with the vsini-R constraint, and we therefore adopt the K2 timescale. BD +19◦ 2045 exhibits a 0.08–0.40 d−1 γ-Doradus g-mode spectrum also detected in TESS Sector 72. BD +19◦ 2046 and TYC 1395-855-1 are non-variable or only marginally variable in K2 but show coherent low-frequency signals in TESS, which we conservatively classify as uncertain. In addition, high-resolution HERMES spectra confirm HD 73135’s Am nature (kA7 hF1 mF2) and show Sr–Ba overabundances of ∼ +1 dex. BD +19◦ 2045 is a chemically normal F8 V star, while BD +19◦ 2046 and TYC 1395-855-1 are K1–K2 sub-giants. Using spectroscopic constraints, we performed the first-step towards precise characterisation of these stars, yielding the masses, radii, and ages. These stars are located just 6◦ from the planned PLATO North-Ecliptic Ridge field, hence furnish benchmark targets for forthcoming asteroseismic and exoplanet surveys.

Keyword(s): Stars: chemically peculiar ; Stars: rotation ; Stars: starspots ; Stars: general