Abstract:
We present the results of the photometric and spectroscopic monitoring of the luminous Ap
star HD103498. The time-series photometric observations were carried out on 17 nights using
a three-channel fast photometer attached to the 1.04-m optical telescope at the Aryabhatta
Research Institute of Observational Sciences (ARIES), Nainital. The photometric data from
five nights in 2007 show a clear signature of 15-min periodicity. However, the follow-up
observations during 2007–2009 did not reproduce any such periodicity. To confirm the photometric
light variations, time-series spectroscopic observations were carried out with the 2.56-m
Nordic Optical Telescope (NOT) at La Palma on 2009 February 2. No radial velocity variations
were present in this data set, which is in full agreement with the photometric observations
taken around the same date. Model atmosphere and abundance analysis of HD103498 show
that the star is evolved from the main sequence and its atmospheric abundances are similar to
those of 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.
