Time-resolved photometric and spectroscopic analysis of a luminous Ap star HD103498

TL;DR

This study investigates the photometric and spectroscopic variability of the luminous Ap star HD103498, revealing transient 15-minute periodicity and detailed chemical composition, suggesting it is an evolved star with unique properties.

Contribution

First detailed time-series photometric and spectroscopic analysis of HD103498, identifying transient pulsations and characterizing its chemical abundances and evolutionary status.

Findings

Detected 15-minute periodicity in 2007 photometry

No radial velocity variations observed in spectroscopic data

Star shows chemical abundances similar to evolved Ap stars

Abstract

We present the results on the photometric and spectroscopic monitoring of a luminous Ap star HD103498. The time-series photometric observations were carried out on 17 nights using three-channel fast photometer attached to the 1.04-m optical telescope at ARIES, Nainital. The photometric data of five nights of year 2007 show clear signature of 15-min periodicity. However, the follow-up observations during 2007--2009 could not repeated any such periodicity. To confirm the photometric light variations, the time-series spectroscopic observations were carried out with the 2.56-m Nordic Optical Telescope (NOT) at La Palma on February 2, 2009. Any radial velocity variations were absent in this data set which is in full agreement with the photometric observations taken near the same night. Model atmosphere and abundance analysis of HD103498 show that the star is evolved from the Main Sequence and its atmospheric abundances are similar to two other evolved Ap stars HD133792 and HD204411: large overabundances of Si, Cr, and Fe and moderate overabundances of the rare-earth elements. These chemical properties and a higher effective temperature distinguish HD103498 from any known roAp star.