Radial velocities and metallicities of red giant stars in the old open cluster NGC 7762

We present and discuss radial velocity and the very first metallicity measurements for nine evolved stars in the poorly known old open cluster NGC 7762. We isolated eight radial velocity cluster members and one interloper. Radial velocities are in good agreement with previous studies. NGC 7762 turns out to be of solar metallicity within the uncertainties ([Fe/H]=0.04$\pm$0.12). For this metallicity, the cluster age is 2.5$\pm$0.2 Gyr, and falls in a age range where only a few old open clusters are known. With respect to previous studies, we find a larger distance, implying the cluster to be located at 900$^{+70}_{-50}$ pc from the Sun. For most of the elements we measure solar-scaled abundance ratios. We searched the literature for open clusters of similar age in the solar vicinity and found that NGC 7762 can be considered a twin of Ruprecht 147, a similar age cluster located at only 300 pc from the Sun. In fact, beside age, also metallicity and abundance ratios are very close to Ruprecht 147 values within the observational uncertainties.Comment: 8 pages, 5 figures, accepted for publication in the Astronomical Journa

Summary of the 3rd BINA Workshop

BINA-3 has been the third workshop of this series involving scientists from India and Belgium aimed at fostering future joint research in the view of cutting-edge observatories and advances in theory. BINA-3 was held at the Graphic Era Hill University, 22-24 March 2023 at Bhimtal (near Nainital), Uttarakhand, India. A major event was the inauguration of the International Liquid-Mirror Telescope (ILMT), the first liquid mirror telescope devoted exclusively to astronomy. BINA-3 provided impressive highlights encompassing topics of both general astrophysics and solar physics. Research results and future projects have been featured through invited and contributed talks, and poster presentations.Comment: This paper was submitted as a contribution to the proceedings of the third Belgo-Indian Network for Astronomy and Astrophysics (BINA) workshop, which was held in Bhimtal, Uttarakhand (India) on 22-24 March 2023. The final, peer-reviewed version will be published in Bulletin de la Soci\'et\'e Royale des Sciences de Li\`ege. The manuscript contains ten page

Spectroscopic Devices for Asteroseismology With Small Telescopes in NARIT

The National Astronomical Research Institute of Thailand (NARIT) has a manifold network of small telescopes installed worldwide. These telescopes serve educational and research purposes and are equipped mainly with CCD detectors for direct imaging and photometry. To extend the possible field of applications, several telescopes were fitted with commercially available medium-resolution spectrographs eShel from Shelyak. With these devices, researchers in NARIT obtained a versatile tool for stellar spectroscopy. Here we describe the current status of available equipment, possible ways of upgrading, and briefly introduce the achieved results of the asteroseismologic study of fast-rotating stars.Comment: This paper was submitted as a contribution to the proceedings of the third Belgo-Indian Network for Astronomy and Astrophysics (BINA) workshop, which was held in Bhimtal, Uttarakhand (India) on 22-24 March 2023. The final, peer-reviewed version will be published in Bulletin de la Soci\'et\'e Royale des Sciences de Li\`ege. The manuscript contains 5 pages, 3 figures, and 4 reference

Spectropolarimetry of Magnetic Chemically Peculiar Stars in the Orion OB1 Association

We summarise the results of a spectropolarimetric survey of 56 chemically peculiar (CP) stars in the association of Orion OB1. We uniformly collected the observational material with the 6-m telescope BTA of the Special Astrophysical Observatory in 2013-2021. We identify 14 new magnetic CP stars with a longitudinal magnetic field exceeding approximately 500 G. The studied sample contains 31 magnetic stars or 55% of the whole CP population in Orion OB1. We show that the percentage of the magnetic CP stars and the field strength drops sharply with age. The mean longitudinal magnetic field in the young subgroup OB1b ($\log t=6.23$) is confidently almost three times stronger than in the older subgroups OB1a ($\log t=7.05$) and OB1c ($\log t=6.66$). In the Orion Nebula, a place with the youngest stellar population ($\log t < 6.0$), we detect the magnetic field only in 20% of CP stars. Such occurrence drastically differs from 83% of magnetic CP stars in the nearby subgroup OB1c. We consider this effect an observational bias caused by a significant portion of a very young population with the signatures of Herbig Ae/Be stars. The technique we used for magnetic measurements, and the quality of available data do not allow us to detect weak fields in the case of stars with a limited number of lines and emissions in spectra.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journal. Contains 14 pages, 11 figure

HiFLEx – a highly flexible package to reduce cross-dispersed Echelle spectra

© 2020 The Astronomical Society of the Pacific. Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence (https://creativecommons.org/licenses/by/3.0/). Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.We describe a flexible data reduction package for high resolution cross-dispersed echelle data. This open-source package is developed in Python and includes optional GUIs for most of the steps. It does not require any pre-knowledge about the form or position of the echelle-orders. It has been tested on cross-dispersed echelle spectrographs between 13k and 115k resolution (bifurcated fiber-fed spectrogaph ESO-HARPS and single fiber-fed spectrograph TNT-MRES). HiFLEx can be used to determine radial velocities and is designed to use the TERRA package but can also control the radial velocity packages such as CERES and SERVAL to perform the radial velocity analysis. Tests on HARPS data indicates radial velocities results within ±3ms−1 of the literature pipelines without any fine tuning of extraction parameters.Peer reviewe

Hot Magnetic Stars in Exotic Multiple Systems

A strong and stable magnetic field covering the whole surface is a landmark of chemically peculiar or CP stars. To explain the origin of mag- netic stars, several hypotheses were proposed, which depending on the mech- anism and time of formation can be grouped into three main. The magnetic field may originate in the protostellar medium (“fossil field”), turbulent layers of a star (“dynamo” mechanism) or in the other environment. In either scenario, binary stars appear as a merit of its reliability. Recent advances in observational astrophysics uncovered a bunch of new binary magnetic stars that were considered as rare before. We outline the results of studies of exotic binary and multiple systems with magnetic CP components: HD 6757, HD 34736, and HD 40759

Radial Velocity and Chemical Composition of Evolved Stars in the Open Clusters NGC 6940 and Tombaugh 5

We present and discuss medium resolution (R 3c 13000), high signal-to-noise ({{S}}/{{N}} 3c 100), spectroscopic observations in the field of the open clusters NGC 6940 and Tombaugh 5. Spectra were recorded for seven candidate red giant stars in both clusters. For the latter, we present the very first chemical abundance analysis. We derive radial velocities for all the stars in NGC 6940, confirming membership to the cluster for all of them, while on the same ground, we exclude two stars in To 5. We perform a chemical abundance analysis of different atomic species, in particular Fe I, Si I, Ca I, Ti I, and Ni I. The mean metallicity of NGC 6940 is [Fe/H] = +0.09 \ub1 0.06 dex, in good agreement with previous works, while for To 5 is [Fe/H] = +0.06 \ub1 0.11 dex. Therefore, both clusters exhibit a chemical composition close to the solar value and do not deviate from the [Fe/H] Galactic radial abundance gradient. With these new values, we estimate the fundamental cluster parameters, after having derived clusters\u2019 distances from the Gaia DR2 database. By adopting these distances, we derive updated estimated for the clusters ages: 1.0 \ub1 0.1 Gyr of NGC 6940 and 0.25 \ub1 0.05 Gyr for Tombaugh 5