Search Publications
Ages and metallicities of globular clusters in M81 using GTC/OSIRIS spectra
Cortesi, Arianna; Gómez-González, V. M. A.; Alzate, Jairo A. +8 more
We here present the results of an analysis of the optical spectroscopy of 42 globular cluster (GC) candidates in the nearby spiral galaxy M81 (3.61 Mpc). The spectra were obtained using the long-slit and multi-object spectroscopic modes of the OSIRIS instrument at the 10.4-m Gran Telescopio Canarias at a spectral resolution of ~1000. We used the c…
BAL outflow in quasar B0254-3327B: analysis and comparison with other extreme UV outflows
Kriss, Gerard A.; Arav, Nahum; Dehghanian, Maryam +2 more
We have identified a broad absorption line (BAL) outflow in the HST/STIS spectrum of the quasar QSO B0254-3327B at velocity v = -3200 km s-1. The outflow has absorption troughs from ions such as Ne VIII, Na IX, Si XII, and Ne V. We also report the first detection of S XIV absorption troughs, implying very high ionization. Via measuremen…
The distribution, kinematics, and luminosities of extreme helium stars as probes of their origin and evolution
Jeffery, C. S.; Martin, P.; Philip Monai, A.
Hydrogen-deficient stars include the cool R CrB variable (RCBs) and hydrogen-deficient carbon (HdCs) giants through extreme helium stars (EHes) to the very hot helium-rich subdwarfs (He-sdO and O(He) stars) and white dwarfs. With surfaces rich in helium, nitrogen, and carbon, their origins have been identified with the merger of two white dwarfs. …
A Statistical, Photometric, and SED Analysis to Characterize the BSS Populations in Old Open Cluster: Berkeley 39
Medhi, Biman J.; Sheikh, A. H.
We present a statistical, photometric, and spectral energy distribution (SED) analysis to characterize the blue straggler stars (BSSs) populations in the Galactic old open cluster Berkeley 39. Berkeley 39 is a 6.16 Gyr old open cluster located at a distance of 3.99 Kpc.Gaia DR3 astrometry data have been used to estimate the membership probabilitie…
The debris disc of HD 131488: bringing together thermal emission and scattered light
Henning, Thomas; Hughes, A. Meredith; Kirchschlager, Florian +9 more
We show the first SPHERE/IRDIS and IFS data of the CO-rich debris disc around HD 131488. We use N-body simulations to model both the scattered light images and the spectral energy distribution of the disc in a self-consistent way. We apply the Henyey-Greenstein approximation, Mie theory, and the Discrete Dipole Approximation to model the emission …
The extremely young planetary nebula M 3-27: an analysis of its evolution, physical conditions, and abundances
Peña, Miriam; Ruiz-Escobedo, Francisco; Beltrán-Sánchez, Ana Valeria
Spectrophotometric data of the young planetary nebula M 3-27, from 2004 to 2021, are presented and discussed. We corroborate that the H I Balmer lines present features indicating they are emitted by the central star, therefore He I lines were used to correct line fluxes by effects of reddening. Important variability on the nebular emission lines b…
HD 12098: a highly distorted dipole mode in an obliquely pulsating roAp star
Saio, H.; Kurtz, D. W.; Joshi, Santosh +2 more
HD 12098 is a rapidly oscillating Ap star pulsating in the most distorted dipole mode yet observed in this class of star. Using Transiting Exoplanet Survey Satellite (TESS) Sector 58 observations, we show that there are photometric spots at both the magnetic poles of this star. It pulsates obliquely primarily in a strongly distorted dipole mode wi…
Very metal-poor stars I: a catalogue derived from LAMOST DR9
Zhao, Gang; Li, Haining; Hou, Xiaokun
In this paper, a semisupervised machining learning technique had been utilized to analyse low-resolution stellar spectra from Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST) Data Release 9 (DR9). We identified approximately 111 000 potential very metal-poor stars. Estimation of their stellar parameters ($T_{\rm eff}$, ${\rm log}…
Stellar properties of an actively accreting Algol-type eclipsing binary 2M16212643+2136590
Stassun, Keivan G.; Kounkel, Marina; Sun, Meng +2 more
Interacting binary stars undergo evolution that is significantly different from single stars, thus, a larger sample of such systems with precisely determined stellar parameters is needed to understand the complexities of this process. We present an analysis of a hierarchical triple containing a spectroscopically double-lined eclipsing binary, 2M16…
EC 19529-4430: SALT identifies the most carbon- and metal-poor extreme helium star
Jeffery, C. S.; Woolf, V. M.; Miszalski, B. +2 more
EC 19529-4430 was identified as a helium-rich star in the Edinburgh-Cape (EC) Survey of faint-blue objects and subsequently resolved as a metal-poor extreme helium (EHe) star in the Southern African Large Telescope (SALT) survey of chemically peculiar hot subdwarfs. This paper presents a fine analysis of the SALT high-resolution spectrum. EC 19529…