5 research outputs found
HD 183986: a high-contrast SB2 system with a pulsating component
There is a small group of peculiar early-type stars on the main sequence that
show different rotation velocities from different spectral lines. This
inconsistency might be due to the binary nature of these objects. We aim to
verify this hypothesis by a more detailed spectroscopic and photometric
investigation of one such object: HD 183986. We obtained 151 high and medium
resolution spectra that covered an anticipated long orbital period. There is
clear evidence of theorbital motion of the primary component. We uncovered a
very faint and broad spectrum of the secondary component. The corresponding SB2
orbital parameters, and the component spectra, were obtained by Fourier
disentangling using the KOREL code. The component spectra were further modeled
by iSpec code to arrive at the atmospheric quantities and the projected
rotational velocities. We have proven that this object is a binary star with
the period = 1268.2(11) d, eccentricity = 0.5728(20), and mass ratio
= 0.655. The primary component is a slowly rotating star (
km.s) while the cooler and less massive secondary rotates much faster
( km.s). Photometric observations obtained by the
TESS satellite were also investigated to shed more light on this object. A
multi-period photometric variability was detected in the TESS data ranging from
hours (the Sct-type variability) to a few days (spots/rotational
variability). The physical parameters of the components and the origin of the
photometric variability are discussed in more detail.Comment: Accepted to AJ. arXiv admin note: text overlap with arXiv:1307.2553
by other authors. text overlap with arXiv:1307.2553 by other author
BU Canis Minoris -- the Most Compact Known Flat Doubly Eclipsing Quadruple System
We have found that the 2+2 quadruple star system BU CMi is currently the most
compact quadruple system known, with an extremely short outer period of only
121 days. The previous record holder was TIC 219006972 (Kostov et al. 2023),
with a period of 168 days. The quadruple nature of BU CMi was established by
Volkov et al. (2021), but they misidentified the outer period as 6.6 years. BU
CMi contains two eclipsing binaries (EBs), each with a period near 3 days, and
a substantial eccentricity of about 0.22. All four stars are within about 0.1
solar mass of 2.4 solar masses. Both binaries exhibit dynamically driven
apsidal motion with fairly short apsidal periods of about 30 years, thanks to
the short outer orbital period. The outer period of 121 days is found both from
the dynamical perturbations, with this period imprinted on the eclipse timing
variations (ETV) curve of each EB by the other binary, and by modeling the
complex line profiles in a collection of spectra. We find that the three
orbital planes are all mutually aligned to within 1 degree, but the overall
system has an inclination angle near 83.5 degrees. We utilize a complex
spectro-photodynamical analysis to compute and tabulate all the interesting
stellar and orbital parameters of the system. Finally, we also find an
unexpected dynamical perturbation on a timescale of several years whose origin
we explore. This latter effect was misinterpreted by Volkov et al. (2021) and
led them to conclude that the outer period was 6.6 years rather than the 121
days that we establish here.Comment: 19 pages, 8 pages, accepted to MNRA
Rapidly rotating stars and their transiting planets: KELT-17b, KELT-19Ab, and KELT-21b in the CHEOPS and TESS era
Rapidly rotating early-type main-sequence stars with transiting planets are
interesting in many aspects. Unfortunately, several astrophysical effects in
such systems are not well understood yet. Therefore, we performed a photometric
mini-survey of three rapidly rotating stars with transiting planets, namely
KELT-17b, KELT-19Ab, and KELT-21b, using the Characterising Exoplanets
Satellite (CHEOPS), complemented with Transiting Exoplanet Survey Satellite
(TESS) data, and spectroscopic data. We aimed at investigating the spin-orbit
misalignment and its photometrical signs, therefore the high-quality light
curves of the selected objects were tested for transit asymmetry, transit
duration variations, and orbital precession. In addition, we performed transit
time variation analyses, obtained new stellar parameters, and refined the
system parameters. For KELT-17b and KELT-19Ab we obtained significantly smaller
planet radius as found before. The gravity-darkening effect is very small
compared to the precision of CHEOPS data. We can report only on a tentative
detection of the stellar inclination of KELT-21, which is about 60 deg. In
KELT-17b and KELT-19Ab we were able to exclude long-term transit duration
variations causing orbital precession. The shorter transit duration of
KELT-19Ab compared to the discovery paper is probably a consequence of a
smaller planet radius. KELT-21b is promising from this viewpoint, but further
precise observations are needed. We did not find any convincing evidence for
additional objects in the systems.Comment: Accepted for publication in MNRA