Through long-slit spectral observations of the early type disk galaxy ESO 119-055 and archival panoramic spectroscopy data, we studied the kinematics, excitation, and oxygen abundance of the ionized gas in the outer disk of the galaxy. We discovered the decoupled rotation of the gas and stars in the center so revealing the gas acquisition from outside after the stellar-disk formation. The inhomogeneous distribution of the gas metallicity over the disk gives the evidence in favor of a very recent accretion event, approximately 100 Myr ago. Among the H II regions that we detected in the disk of ESO 119-055, the probable source of the gas is identified—the remnant of a small metal-poor satellite accreted by the host galaxy.

Stellar counterrotating (CR) galaxies are systems hosting two large-scale stellar components rotating in opposite directions—a main, preexisting galaxy body with an older stellar population and a younger CR stellar disk likely formed from externally accreted gas. Such systems offer a unique opportunity to study disk assembly by analyzing the stellar populations of each component. Using integral field spectroscopic data from the SDSS-IV Mapping Nearby Galaxies at Apache Point Observatory survey, we identified a sample of 120 CR disk galaxies (65 reliable and 55 probable systems) by inspecting their kinematic maps and analyzing the shape of the stellar line-of-sight velocity distribution, which was recovered nonparametrically. Of these, 74 CR galaxies have not been reported in previous studies. For one-third of our sample, we further derived the ages and metallicities of stars for both disks via a spectral decomposition technique. We show that the observed spatial bimodality—where the CR disk either is concentrated in the central region (inner ​counterrotation) or dominates the outer part of the galaxy (outer counterrotation)—is driven by differences in the stellar mass and angular momentum of the CR disk. The wide range of stellar metallicities observed in CR disks suggests that no single source of external material is solely responsible for the formation of counterrotation in all galaxies; instead, proposed mechanisms such as merger with gas-rich satellites, accretion from cosmic filaments, and exchange of gas between neighboring galaxies can dominate in individual cases.

Aims . The purpose of this work is to spectroscopically analyse the classical Cepheid V708 Car. A preliminary check of the spectrum of V708 Car showed that this is a lithium-rich supergiant. We also found that V708 Car has an unusual chemical composition in that the abundances of various elements correlate with their condensation temperatures. We tried to find an explanation of this feature, which is unusual for classical Cepheids. Methods . For the spectroscopic analysis, we used methods based on the assumption of local and non-local thermodynamic equilibrium. Results . We determined the fundamental parameters of our program star V708 Car. This long-period Cepheid has a mass of about 12 M ⊙ . We derived the abundances of 27 chemical elements in this star. They are clearly correlated with their condensation temperature: the higher the condensation temperature, the lower the abundance (there are exceptions for sodium and barium, however). We explain this peculiar chemical composition of the V708 Car atmosphere by the gas–dust separation in the envelope of this star. A similar mechanism leads to the observed peculiarities of the chemical composition of λ Boo, W Vir, and asymptotic giant branch stars.

In the framework of the ongoing project, aimed at the systematical studying galaxies in nearby voids, we conducted spectroscopy with the Southern African Large Telescope (SALT) of 62 objects from the Nearby Void Galaxy (NVG) sample. They include 8 remaining objects of the 60 preselected candidates to eXtremely Metal-Poor (XMP) dwarfs, two known void XMP dwarfs and 52 void dwarfs residing within the Local Volume. For 47 galaxies residing in the nearby voids, we obtained spectra of the diverse quality. For 42 of them, we detected the Hydrogen and Oxygen lines that allowed us to get estimates of O/H in the observed HII regions. For 12 of the 42 objects, we detected the faint line [Oiii]4363, that allowed us to directly derive the electron temperature T_e and obtain their gas O/H by the direct method. 14 objects with the undetected [Oiii]4363 line fall to the lowest metallicities range (12+log(O/H) < 7.5 dex). For them, we use a carefully checked new empirical 'Strong line' method of Izotov et al. For 14 other objects with only strong lines detected and with 12+log(O/H) of 7.5-8.0 dex, we used the modified version of 'semi-empirical' method of Izotov and Thuan. It accounts for effect of the excitation parameter O32 on T_e. 16 new galaxies are found with parameter 12+log(O/H) < 7.39 dex. Of them, four have 12+log(O/H) = 7.07 - 7.20 dex. Of the 60 observed NVG objects, 15 have mistaken radial velocities in HyperLEDA. They do not reside in the nearby voids.

Context. The oldest stars in the Milky Way are metal-poor with [Fe/H] < -1.0, displaying peculiar elemental abundances compared to solar values. The relative variations in the chemical compositions among stars is also increasing with decreasing stellar metallicity, allowing for the pure signature of unique nucleosynthesis processes to be revealed. The study of the r-process is, for instance, one of the main goals of stellar archaeology and metal-poor stars exhibit an unexpected complexity in the stellar production of the r-process elements in the early Galaxy. Aims. In this work, we report the atmospheric parameters, main dynamic properties, and the abundances of four metal-poor stars: HE 1523-0901, HD 6268, HD 121135, and HD 195636 (-1.5 > [Fe/H] > -3.0). Methods. The abundances were derived from spectra obtained with the HRS echelle spectrograph at the Southern African Large Telescope, using both local and non-local thermodynamic equilibrium (LTE and NLTE) approaches, with the average error between 0.10 and 0.20 dex. Results. Based on their kinematical properties, we show that HE 1523-0901 and HD 195636 are halo stars with typical high velocities. In particular, HD 121135 displays a peculiar kinematical behaviour, making it unclear whether it is a halo or an accreted star. Furthermore, HD 6268 is possibly a rare prototype of very metal-poor thick disk stars. The abundances derived for our stars are compared with theoretical stellar models and with other stars with similar metallicity values from the literature. Conclusions. HD 121135 is Al-poor and Sc-poor, compared to stars observed in the same metallicity range (-1.62 > [Fe/H] > -1.12). The most metal-poor stars in our sample, HE 1523-0901, HD 6268, and HD 195636, exhibit anomalies that are better explained by supernova models from fast-rotating stellar progenitors for elements up to the Fe group. Compared to other stars in the same metal-licity range, their common biggest anomaly is represented by the low Sc abundances. If we consider the elements beyond Zn, HE 1523-0901 can be classified as an r-II star, HD 6268 as an r-I candidate, and HD 195636 and HD 121135 exhibiting a borderline r-process enrichment between limited-r and r-I star. Significant relative differences are observed between the r-process signatures in these stars.

ABSTRACT This paper presents the results of analysing the integrated light (IL) low-resolution spectra of globular clusters (GCs) in the M31 and Centaurus A groups of galaxies. The sample consists of eight very metal-poor GCs ($\rm [Fe/H]\le -2$ dex) with high signal-to-noise ratio spectra acquired with the telescopes: the 6-m SAO RAS (BTA), the Southern African Large (SALT), and the 6.5-m Magellan (MMT). We study the influence of contribution of the horizontal branch stars on the hydrogen Balmer line profiles in the IL spectra. By modelling the Balmer lines, as well as the metal lines in the observed spectra, we determine the optimum parameters of stellar evolution isochrones and, consequently, the parameters of the atmospheres of the cluster stars. For all the studied GCs, the parameters of horizontal branch stars set by the selected isochrones, the corresponding ages, and carbon abundances are presented for the first time. The abundances of several other elements (Mg, Ca, Ti, Cr, and Mn) were determined for five GCs for the first time. All the studied GCs have blue horizontal branches and are older than 10 Gyr. Their chemical abundances, with the exception of Mg and Mn, are in good agreement with the abundances of stars in the Galactic field. The reasons of low [Mg/Fe] and of high [Mn/Fe] are discussed. Study of the fundamental properties of stellar populations in old GCs facilitates a better understanding of the formation processes of their parent galaxies and nucleosynthesis in the early Universe.

New time series photometry of WISE J152614.95-111326.4, an eclipsing binary candidate, has been obtained. Full cycles of variation were covered in five filters, ranging from B to z. Archival time series photometry is also available from several sources. The phased light curve shape changes from a double wave form in the red, to a single wave at shorter wavelengths. Analysis of the spectral energy distribution and SALT spectra shows the presence of a cool (similar to 7 250-7 900 K) white dwarf and an M6 star. The light curves can be explained by a hot spot on the opposing hemisphere of the white dwarf. The star may be in a pre-cataclysmic variable phase with a very low rate of mass flow from the red dwarf to the white dwarf, such that no flickering is evident. Evidence in favour of this hypothesis is that the period of the system (2.25 h) is in the cataclysmic variable period gap. It is speculated that a weak magnetic field associated with the white dwarf funnels accreted material onto a magnetic pole. Amplitudes of the W1 and W2 WISE light curves are anomalously large. The possibility is discussed that variability in this spectral region is primarily driven by electron cyclotron radiation.

We have completed our observational program to search for wide binary systems with non-coeval components in the southern sky and report our results here. The final set of four systems was spectroscopically investigated in this paper. No binary systems with components of different ages were found among them. Taking into account our previous studies, we estimate the fraction of such binaries (i.e., binaries formed, presumably, by capture) to be not higher than 0.06%. The study will be continued on the northern sky.

Stellar counterrotation in disk galaxies directly relates to the complex phenomenon of the disk mass assembly believed to be driven by external processes, such as accretion and mergers. The study of such systems makes it possible to reveal the source of external accretion and establish the details of this process. In this paper, we investigate the galaxy PGC 66551 (MaNGA ID 1-179561), which hosts two large-scale counterrotating (CR) stellar disks identified in the Sloan Digital Sky Survey MaNGA data and then confirmed using deep follow-up spectroscopy with the 10 m Southern African Large Telescope. We measured the properties of ionized gas and stellar populations of both CR disks in PGC 66551. We found that the CR disk is compact, contains young stars with subsolar metallicity, and has a stellar mass of 5 × 10 ^9 M _⊙ , which amounts to ≈20% of the galaxy’s total. Surprisingly, the main 8 Gyr old disk has a significantly lower metallicity of −0.8 dex than other CR galaxies. We developed a simple analytic model of the history of the metal enrichment, which we applied to PGC 66551 and constrained the parameters of the galactic outflow wind, and estimated the metallicity of the infalling gas that formed the CR disk to be −0.9... −0.5 dex. Our interpretation prefers a merger with a gas-rich satellite over cold accretion from a cosmic filament as a source of gas, which then formed the CR disk in PGC 66551.

ABSTRACT We investigated the ionized and atomic gas kinematics and excitation state in the central region of ongoing star formation of the nearby low-metallicity dwarf galaxy Sextans B. The analysis is based on the new observations performed in the H α emission line with high resolution (R ∼ 16 000) scanning Fabry–Perot interferometer at the 6-m BTA Special Astrophysical Observatory of the Russian Academy of Sciences telescope, and on the long-slit spectral observations at the 9.2-m SALT and 2.5-m Caucasian Mountain Observatory of Sternberg Astronomical Institute of Moscow State University telescopes. Strong non-circular gas motions detected in the studied regions probably resulted from the off-plane gas motions and impact of stellar feedback. We identified six regions of elevated H α velocity dispersion, five of which exhibit asymmetric or two-component H α line profiles. Three of these regions are young (<1.1 Myr) expanding ($V_\mathrm{exp} \sim 25-50 \, \mbox{km}\, \mbox{s}^{-1}$) superbubbles. We argue that at least three regions in the galaxy could be supernova remnants. We conclude that supernovae feedback is the dominant source of energy for superbubbles in Sextans B, which is expected for such a low metallicity, although we cannot rule out a strong impact of pre-supernova feedback for one superbubble.

ABSTRACT Just 10 recurrent novae (RNe) – which erupt repeatedly on time-scales shorter than one century – are known in our Galaxy. The most extreme RN known (located in the Andromeda galaxy), M31N 2008-12a, undergoes a nova eruption every year, and is surrounded by a vast nova ‘super-remnant’, 134 pc in extent. Simulations predict that all RNe should be surrounded by similar vast shells, but previous searches have failed to detect them. KT Eri has recently been suggested to be a RN, and we have used the Condor Array Telescope to image its environs through multiple narrow-band filters. We report the existence of a large (∼50-pc diameter), H $\, \alpha$-bright shell centred on KT Eri, exactly as predicted. This strongly supports the claim that KT Eri is the 11th Galactic recurrent nova, and only the second nova known to be surrounded by a super-remnant. SALT spectra of the super-remnant demonstrate that its velocity width is consistent with that of M31-2008-12a.

SALT is a 10-m class optical telescope located in Sutherland, South Africa, owned by an international consortium and operated in fully queue-scheduled mode by the South African Astronomical Observatory. In this paper we present an update on all observatory performance metrics since the start of full science operations in late 2011, including science time, weather and technical downtime, and time used for planned engineering activities and our new instruments commissioning. We analyze key statistics describing the science output of SALT, the completion fractions of scheduled observations per priority class, and analyze the more than 500 refereed papers to date since first light based on SALT data. We discuss our latest telescope metrics and the results of our analysis of our acquisition times, what steps we are taking to make significant improvements to our metrics, our metrics dashboard and hiring of a new 'salt efficiency software developer'. Some of these projects, along with the latest developments in software, instrumentation and engineering projects, are presented in detail in other SPIE papers. We also highlight that significant effort has also been placed on the improvement of our data reduction pipelines. The SALT refereed paper output has continued to increase steadily at a pace comparable to other large telescopes when counted from the start of science operations and when scaled by the number of telescopes. When scaled by operations costs (where known), SALT is still clearly very cost-effective compared to most other large telescope operations. We also highlight that in terms of citations and impact, SALT again at a comparable level to other large telescopes. We also discuss the exciting arrival of the Near IR spectrograph, which expands the telescope's wavelength range into the NIR, and the addition of a laser frequency comb to calibrate the High Stability mode of our High Resolution Spectrograph, in line with strategic vision for exoplanet science. We also briefly discuss our plans for SALT as an important component of the SAAO in an "Intelligent Observatory" framework aiming to network a suite of telescopes and instruments on the observing site.

ABSTRACT We have fulfilled a detailed long-slit spectroscopic analysis for two SB0 galaxies – NGC 1533 and NGC 1543, – belonging to the Dorado group. Our spectral data reveal asymmetric decoupled kinematics of the stars and ionized gas in these barred lenticular galaxies that give evidences for external origin of the gas in the rings. We have calculated the star formation rates in the rings by using the ultraviolet fluxes of the rings corrected for the foreground and intrinsic absorption; and we have estimated parameters of the stellar populations in the inner parts of the galaxies confirming that they are old – except the nucleus of NGC 1543, which demonstrates signatures of rejuvenation less than 5 Gyr ago.

The Southern African Large Telescope (SALT) is a 10-m class fixed-elevation telescope with a primary mirror composed of 91 spherically figured one metre segments. A prime focus tracker assembly carries the spherical aberration corrector (SAC) and two of SALT's instruments, SALTICAM (the acquisition and imaging camera) and the multi-purpose Robert Stobie spectrograph (RSS). Included in the tracker payload is a fibre-instrument feed, that positions similar to 45m long fibre cables coupled to the spectrographs in thermal enclosures beneath the telescope. These are the High-Resolution Spectrograph (HRS) and NIRWALS (Near InfraRed Washburn Astronomical Laboratories Spectrograph). The other major undertaking is a custom-built laser frequency comb and precision radial velocity data pipeline for the HRS, due in 2025. A novel RSS slit-mask IFU was recently commissioned, adding optical IFU spectroscopy to SALT's capabilities. Work is also underway to develop a new red channel to turn the RSS into a dual-beam spectrograph. A study done in 2021 investigated the feasibility of building deployable robotic arms equipped with mini SACs to take advantage of SALT's huge uncorrected field of view. Lastly, a pre-study is now underway to explore options for replacing the SAC and prime focus payload on the tracker to improve telescope performance and make provision for future instrument development.

ABSTRACT The dwarf irregular galaxy HIPASS J1131-31 was discovered as a source of HI emission at low redshift in such close proximity of a bright star that we call it Peekaboo. The galaxy resolves into stars in images with Hubble Space Telescope, leading to a distance estimate of 6.8 ± 0.7 Mpc. Spectral optical observations with the Southern African Large Telescope reveal HIPASS J1131-31 to be one of the most extremely metal-poor galaxies known with the gas-phase oxygen abundance 12 + log(O/H) = 6.99 ± 0.16 dex via the direct [O iii] 4363 line method and 6.87 ± 0.07 dex from the two strong line empirical methods. The red giant branch of the system is tenuous compared with the prominence of the features of young populations in the colour-magnitude diagram, inviting speculation that star formation in the galaxy only began in the last few Gyr.

We present the results of spectral observations and consequent analysis of six long-period double-lined eclipsing binaries (DLEBs) with main-sequence (MS) components from a sample formed with the aim of testing the ‘‘mass–luminosity’’ relation (MLR) for stars in the M/M_⊙>1.5 mass range. We analyzed all the obtained spectra using a technique that allows one to reveal the binary nature of the system and determine T_eff and log g for each component, as well as the system metallicity [Fe/H] and line-of-sight extinction E(B-V) . We computed the absolute parameters of the systems under consideration. An analysis of the obtained spectra shows that for three of the six objects (V1156 Cyg, EU Gem and V733 Per) we can clearly establish their binary nature and determine the spectral type and class for each component. Both components of the V733 Per system have already left the MS, and therefore the system must be excluded from our sample, whereas studies of V1156 Cyg and EU Gem should continue. OT And did not demonstrate a binary spectrum, however, the main component of the system is a hot A6 V star, and therefore, OT And should remain in our sample. We also revealed no binarity in the IM Del and LX Gem systems. Their brighter components turned out to be a cool giant and a supergiant, and these systems should be excluded from the sample based on the results of our analysis. We used the same technique to analyze the two spectra obtained for systems EU Gem and LX Gem using LAMOST. We have shown that the parameters determined from LAMOST spectra are in good agreement with the parameters determined for spectra obtained at the Caucasian Mountain Observatory (CMO) of SAI MSU. Our analysis allowed us to plot a first approximation of the V1156 Cyg velocity curves and show that the cool component in this system has a larger mass.

ABSTRACT We report the results of optical échelle spectroscopy with the Southern African Large Telescope (SALT) of the mass donor star BSDL923 in the neutron star (NS) high-mass X-ray binary XMMU J051342.6−672412 associated with the LMC supernova remnant (SNR) MCSNR J0513−6724. We found that BSDL923 is a B0.7 III star with double peaked emission lines originating in a circumbinary disc-like structure. Modelling with the stellar atmosphere code fastwind was used to derive Teff = 27 000 K, log g = 3.22, $v\sin i\approx 100\, {\rm \, km\, s^{-1}}$ and $\log (L_*/\rm \, L_\odot)=5.46$ of BSDL923, as well as to show that the surface of this star is polluted with α-elements from the supernova ejecta. We found also that the NS is orbiting BSDL923 in an eccentric orbit with the orbital period of 1.280 d and the semimajor axis of $17\pm 3 \,R_\odot$, which is less than or equal to the radius of BSDL923 of $25\pm 5 \,R_\odot$. We speculate that the NS is embedded in the atmosphere of BSDL923 either because it was kicked at birth towards this star or because of inflation of BSDL923 caused by the energy input from the supernova blast wave. Using long-slit spectroscopy with SALT, we searched for possible signs of the SNR shell in the 2D spectrum, but did not find them. This lack of detection is consistent with the young age of this SNR, implying that it is still in the adiabatic phase.

Metal-poor stars allow us to establish the early history of the Milky Way, furthermore the stars on advanced evolution stage (e.g. giants, AGB stars etc.) give the opportunity to research the peculiarities of stellar evolution at low metallicity. On the base of the 11-m Southern African Large Telescope (SALT) spectra obtained using HRS fibre-fed echelle-spectrograph during 2018–2020, the atmospheric parameters and elemental abundances of four metal-poor stars HE 1523-0901, HD 6268, HD 121135, and HD 195636 ( [Fe/H] ~ -1.5 – -3.0) have been obtained. The iron abundance was determined based on the equivalent widths of absorption lines. The carbon abundance was obtained using the molecular synthesis fitting for the CH (4300-4330 ÅÅ) region, nitrogen from CN at 3883 Å, oxygen from [O] line at 6300 Å and IR triplet at 7770 Å The relationship between the chemical enrichment of stars and their stellar evolution is considered. It may be associated with the processes of mixing inside the stars, and the mechanisms of matter transfer during stellar evolution.

Luminous Blue Variables (LBVs) are massive stars that show strong spectral and photometric variability. The question of what evolutionary stages they represent and what exactly drives their instability is still open, and thus is it important to understand whether LBVs without significant ongoing activity exist, and for how long such dormant LBVs may ``sleep''. In this article we investigate the long-term variability properties of the LBV candidate MN112, by combining its optical and infrared spectral data covering 12 years with photometric data covering nearly a century acquired by both modern time-domain sky surveys and historical photographic plates. We analyze the spectra, derive physical properties of the star by modelling its atmosphere and use a new distance estimate from Gaia data release 3 (DR3) to determine the position of MN112 both inside the Galaxy and in the Hertzsprung--Russell diagram. Distance estimation increased in almost two times in comparison with Gaia DR2. Due to that MN112 moved in upper part of the diagram and according to our modeling it lies on evolutionary track for star with initial mass $M_*=70 M_\odot$ near Humphreys--Davidson limit. Given the absence of any significant variability we conclude that the star is a dormant LBV that has been inactive for at least a century now.

Although S0 galaxies are usually considered"red and dead", they often demonstrate star formation organized into ring structures. We aim to clarify the nature of this phenomenon and how it differs from star formation in spiral galaxies. We investigated the nearby, moderate-luminosity S0 galaxy NGC 254 using long-slit spectroscopy taken with the South African Large Telescope and publicly available imaging data. Applying a full spectral fitting, we analyzed gaseous and stellar kinematics as well as ionized gas excitation and metallicity and stellar population properties resolved by radius. An advanced approach of simultaneously fitting spectra and photometric data allowed us to quantify the fraction of hidden counter-rotating stars in this galaxy. We find that the ionized gas is counter-rotating with respect to the stars throughout NGC 254 disk, indicating an external origin of the gas. We argue the gas-rich galaxy merger from retrograde orbit as a main source of counter-rotating material. The star formation fed by this counter-rotating gas occurs within two rings: an outer ring at R=55 - 70 arcsec and an inner ring at R=18 arcsec. The star formation rate is weak, 0.02 solar mass per year in total, and the gas metallicity is slightly subsolar. We estimated that the accretion of the gas occurred about 1 Gyr ago, and about 1% of all stars have formed in situ from counter-rotating gas.