arXiv subjects

F. Anders

Publications and source records attributed to F. Anders.

At least 19 recordsLinked to original sources

arXiv2026

XP-TEAL: Gaia XP Tool for Emission and Absorption Lines II. Gaia-HELIX catalogue of H$\alpha$ emitters in Gaia BP/RP spectra

Context: With Gaia's third Data Release (DR3), low-resolution BP/RP (XP) spectra became available for more than 219 million sources. In previous work, we developed a fast method for detecting absorption and emission lines while measuring their equivalent widths directly from the XP spectral coefficients. Aims: We conduct a systematic search for H$\alpha$ emitters in the Gaia DR3 XP spectra. Methods: We measured the equivalent width of the Balmer H$\alpha$ line for all sources with Gaia XP spectra and selected an initial sample of 556100 sources depicting an H$\alpha$ emission-like feature at $2\sigma$ level or above. Using a semi-supervised classifier complemented by manual spectral labelling, we removed sources that merely masqueraded as emission-line stars. Results: We find that 95% of the initial candidates are most likely cool M-type stars, where a molecular absorption band gives rise to a local maximum that can mimic H$\alpha$ emission. Subsequently, 28394 sources were flagged as bona fide H$\alpha$ emitters using the Gaia DR3 XP spectra. The majority are Be-like candidates (26287), M-type emission-line stars (717), Herbig Ae/Be candidates (525), quasi-stellar objects (204), Wolf-Rayet stars (177), cataclysmic variables (51), and carbon stars (18), among other sources. Our equivalent widths and stellar classifications agree well with results from higher-resolution studies and recent Gaia XP spectra-based catalogues. Ground-based spectroscopic follow-up for some of the newly found H$\alpha$ emitters reinforces our confidence in the catalogue.

astro-ph.SR↗

arXiv2026

XP-TEAL: Gaia XP tool for emission and absorption lines. I. Balmer lines in open clusters

Context. The third Gaia data release (Gaia DR3) includes blue and red low-resolution spectrophotometry for more than 200 million sources. These Gaia XP spectra are represented by sets of coefficients multiplying linear combinations of basis functions related to Hermite functions. In a previous work we introduced a method that maximally exploits the information encoded in the Gaia spectrophotometric coefficients in order to identify absorption and emission lines. Aims. Our aim is to detect hydrogen Balmer emission and absorption lines in stars belonging to open clusters included in the released Gaia DR3 blue and red spectrophotometry, and to characterise the Balmer line strengths as a function of colour. Methods. We refined our XP tool for emission and absorption lines (XP-TEAL), using derivatives of the internal spectral coefficients to analyse hydrogen Balmer lines in the Gaia DR3 XP spectra. We tested our results using stars in open clusters, considering both absorption and emission features. Results. The analysis of the hydrogen lines in the spectra of open cluster stars allows us to assess the performance and limitations of the method. We find an empirical dependence of the absorption-line equivalent widths on the intrinsic colour of the stars, which allows us to derive precise colour excesses caused by interstellar extinction. We also identify 1256 stars with emission lines, 356 of which have not previously been reported in the literature. Conclusions. We successfully tested our XP-TEAL code on stars in clusters and have made both the source code and the online version available to the community. Despite the low resolution of Gaia spectrophotometry, our code is able to extract useful line information.

astro-ph.SR↗

arXiv2025

Analysis of mass-transferring binary candidates in the Milky Way

Mass transfer between stars in binary systems profoundly impacts their evolution, yet many aspects of this process (especially the stability, mass loss, and eventual fate of such systems) remain poorly understood. One promising avenue to constrain these processes is through the identification and characterisation of systems undergoing active mass transfer. Inspired by the slow brightening preceding stellar merger transients, we worked on a method to identify Galactic mass-transferring binaries in which the donor is a Hertzsprung gap (HG) star. We constructed an initial sample of HG stars using the Gaia EDR3 contribution Starhorse catalogue, and we identified candidate mass-transferring systems by selecting sources that exhibit Balmer emission features (using the low-resolution Gaia XP spectra), mid-infrared excess (from WISE photometry), and photometric variability (inferred from the error in the Gaia G-band magnitude). This multi-criteria selection yielded a sample of 67 candidates, which we further analysed using complementary photometric and spectroscopic data. Among our candidates, we identified at least nine eclipsing binaries and some sources that are potential binaries as well. Three sources in our sample are strong candidates for mass-transferring binaries with a yellow component, and three more are binaries with a Be star. Notably, four sources in our sample are strong candidates for hosting a compact companion, based on their ultraviolet or X-ray signatures. The main sources of contamination in our search are hot but highly reddened stars (primarily Oe and Be stars). As an additional outcome of this work, we present a refined catalogue of 308 bona fide HG stars, selected using improved extinction corrections and stricter emission-line criteria. This enhanced sample is expected to contain a significantly higher fraction of scientifically valuable mass-transferring binaries.

astro-ph.SR↗

arXiv2025

Abundances of P, S, and K in 58 bulge spheroid stars from APOGEE

We have previously studied several elements in 58 selected bulge spheroid stars, based on spectral lines in the H-band. We now derive the abundances of the less-studied elements phosphorus (P; Z=15), sulphur (S; Z=16), and potassium (K; Z=19). The abundances of P, S, and K in 58 bulge spheroid stars are compared both with the results of a previous analysis of the data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE), and with a few available studies of these elements. We derive the individual abundances through spectral synthesis, using the stellar physical parameters available for our sample from the DR17 release of the APOGEE project. We provide recommendations for the best lines to be used for the studied elements among those in the H-band. We also compare the present results, together with literature data, with chemical-evolution models. Finally, the neutrino-process was taken into account for the suitable fit to the odd-Z elements P and K. We confirm that the H-band has useful lines for the derivation of the elements P, S, and K in moderately metal-poor stars. The abundances, plotted together with literature results from high-resolution spectroscopy, indicate that: moderately enhanced phosphorus stars are found, reminiscent results obtained for thick disk and halo stars of metallicity [Fe/H]~-1.0. Therefore, for the first time, we identify this effect to occur in the old stars from the bulge spheroid. Sulphur is an alpha-element and behaves as such. Potassium and sulphur both exhibit some star-to-star scatter, but fit within the expectations from chemical evolution models.

astro-ph.SR↗

arXiv2025

Open clusters in the outer disc studied with MEGARA@GTC Auner 1 and Berkeley 102

Open clusters offer crucial insights into stellar nucleosynthesis and the chemical evolution of the Galactic disc, as their ages and distances can be determined with higher accuracy compared to field stars. In this study, we investigate the outermost regions of the Milky Way disc using two previously unstudied open clusters -Auner 1 and Berkeley 102- located at Galactocentric distances of approximately 14 kpc in largely uncharted areas of the Galaxy. We obtained medium-resolution spectra (R > 18,700) using the MEGARA integral-field unit (IFU) spectrograph on the 10.4 m Gran Telescopio Canarias (GTC), targeting red giant member stars in both clusters. From these spectra, we derived radial velocities, stellar atmospheric parameters, and chemical abundances for six elements: Fe, Ca, Co, Ni, Ba, and Eu. Additionally, we provide updated estimates of the clusters' ages and distances. Both clusters are old (3.2 +- 0.7 Ga), distant (d ~ 8 kpc), and lie below the Galactic plane (Z Gal ~ -0.7 kpc), with moderate extinction (AV ~ 1.3 mag). We find that Auner 1 has a metallicity of [Fe/H] = -0.30 +- 0.09 and Berkeley 102 of [Fe/H] = -0.35 +- 0.06, consistent with other clusters at similar Galactocentric radii and indicating minimal azimuthal variation in metallicity. The [X/Fe] abundance ratios align with expected trends, although [Ca/Fe] is slightly higher in both clusters, and [Eu/Fe] is notably enhanced in Berkeley 102 ([Eu/Fe] = 0.64 +- 0.05). Our findings highlight the effectiveness of GTC/MEGARA in IFU mode for Galactic archaeology and emphasize the need for further medium-to-high resolution spectroscopic studies of remote open clusters to refine models of the outer Galactic disc's chemical evolution.

astro-ph.GA↗

arXiv2024

New stellar age estimates using SPInS based on Gaia DR3 photometry and LAMOST DR8 abundances

Reliable stellar age estimates are fundamental for testing several problems in modern astrophysics, in particular since they set the time scales of Galactic dynamical and chemical evolution. In this study, we determine ages using only Gaia DR3 photometry and parallaxes, in combination with interstellar extinction maps, spectroscopic metallicities and $\alpha$ abundances from the latest data release (DR8) of the LAMOST survey. In contrast with previous age estimates, we do not use spectroscopic effective temperatures or surface gravities, thus relying on the excellent precision and accuracy of the Gaia photometry. We use a new version of the publicly available SPInS code with improved features, including the on-the-fly computation of the autocorrelation time and the automatic convergence evaluation. We determine reliable age estimates for 35,096 and 243,768 sub-giant and main-sequence turn-off stars in the LAMOST DR8 low- and medium-resolution surveys with typical uncertainties smaller than 10%. In addition, we successfully test our method on more than 4,000 stars of 14 well-studied open and globular star clusters covering a wide range of ages, confirming the reliability of our age and uncertainty estimates.

astro-ph.GA↗

arXiv2024

Abundances of iron-peak elements in 58 bulge spheroid stars from APOGEE

Stars presently identified in the bulge spheroid are probably very old, and their abundances can be interpreted as due to the fast chemical enrichment of the early Galactic bulge. The abundances of the iron-peak elements are important tracers of nucleosynthesis processes, in particular oxygen burning, silicon burning, the weak s-process, and alpha-rich freeze-out. Aims. The aim of this work is to derive the abundances of V, Cr, Mn, Co, Ni, and Cu in 58 bulge spheroid stars and to compare them with the results of a previous analysis of data from APOGEE. We selected the best lines for V, Cr, Mn, Co, Ni, and Cu located within the H-band of the spectrum, identifying the most suitable ones for abundance determination, and discarding severe blends. Using the stellar physical parameters available for our sample from the DR17 release of the APOGEE project, we derived the individual abundances through spectrum synthesis. We then complemented these measurements with similar results from different bulge field and globular cluster stars, in order to define the trends of the individual elements and compare with the results of chemical-evolution models. We verify that the H-band has useful lines for the derivation of the elements V, Cr, Mn, Co, Ni, and Cu in moderately metal-poor stars. The resulting abundances indicate that: V, Cr, and Ni vary in lockstep with Fe; Co tends to vary in lockstep with Fe, but could be showing a slight decrease with decreasing metallicity; and Mn and Cu decrease with decreasing metallicity. These behaviours are well reproduced by chemical-evolution models except for Cu, which appears to drop faster than the models predict for moderate metallicities. Finally, abundance indicators combined with kinematical and dynamical criteria appear to show that our 58 sample stars are likely to have originated in situ.

astro-ph.SR↗

arXiv2024

Transferring spectroscopic stellar labels to 217 million Gaia DR3 XP stars with SHBoost

In this paper, we explore the feasibility of using machine learning regression as a method of extracting basic stellar parameters and line-of-sight extinctions from spectro-photometric data. We built a stable gradient-boosted random-forest regressor (xgboost), trained on spectroscopic data, capable of producing output parameters with reliable uncertainties from Gaia DR3 data (most notably the low-resolution XP spectra), without ground-based spectroscopic observations. Using Shapley additive explanations, we interpret how the predictions for each star are influenced by each data feature. For the training and testing of the network, we used high-quality parameters obtained from the StarHorse code for a sample of around eight million stars observed by major spectroscopic stellar surveys, complemented by curated samples of hot stars, very metal-poor stars, white dwarfs, and hot sub-dwarfs. The training data cover the whole sky, all Galactic components, and almost the full magnitude range of the Gaia DR3 XP sample of more than 217 million objects that also have reported parallaxes. We have achieved median uncertainties of 0.20 mag in V-band extinction, 0.01 dex in logarithmic effective temperature, 0.20 dex in surface gravity, 0.18 dex in metallicity, and $12\%$ in mass (over the full Gaia DR3 XP sample, with considerable variations in precision as a function of magnitude and stellar type). We succeeded in predicting competitive results based on Gaia DR3 XP spectra compared to classical isochrone or spectral-energy distribution fitting methods we employed in earlier works, especially for parameters $A_V$ and $T_{\rm eff}$, along with the metallicity values. Finally, we showcase some potential applications of this new catalogue, including extinction maps, metallicity trends in the Milky Way, and extended maps of young massive stars, metal-poor stars, and metal-rich stars). [abridged]

astro-ph.SR↗

arXiv2024

OCCASO V. Chemical-abundance trends with Galactocentric distance and age

Context. Open clusters provide valuable information on stellar nucleosynthesis and the chemical evolution of the Galactic disc, as their age and distances can be measured more precisely with photometry than for field stars. Aims. Our aim is to study the chemical distribution of the Galactic disc using open clusters by analysing the existence of gradients with Galactocentric distance, azimuth or height from the plane and dependency with age. Methods. High-resolution spectra (R>60 000) of 194 stars belonging to 36 open clusters are used to determine atmospheric parameters and chemical abundances with two independent methods: equivalent widths and spectral synthesis. The sample has been complemented with 63 clusters with high-resolution spectroscopy from literature. Results. We measure local thermodynamic equilibrium abundances for 21 elements: {\alpha} (Mg, Si, Ca, and Ti), odd-Z (Na and Al), Fe-peak (Fe, Sc, V, Cr, Mn, Co, Ni, Cu, and Zn), and neutron-capture (Sr, Y, Zr, Ba, Ce, and Nd). We also provide non-local thermodynamic equilibrium abundances for elements when corrections are available. We find inner disc young clusters enhanced in [Mg/Fe] and [Si/Fe] compared to other clusters of their age. For [Ba/Fe] we report an age trend flattening for older clusters (age<2.5 Ga). The studied elements follow the expected radial gradients as a function of their nucleosynthesis groups, which are significantly steeper for the oldest systems. For the first time, we investigate the existence of an azimuthal gradient, finding some hints of its existence among the old clusters (age>2 Ga).

astro-ph.GA↗

arXiv2023

Strong terahertz third-harmonic generation by kinetic heavy quasiparticles in CaRuO$_3$

We report on time-resolved nonlinear terahertz spectroscopy of a strongly correlated ruthenate, CaRuO$_3$, as a function of temperature, frequency and terahertz field strength. Third-harmonic radiation for frequencies up to 2.1 THz is observed evidently at low temperatures below 80 K, where the low-frequency linear dynamical response deviates from the Drude model and a coherent heavy quasiparticle band emerges by strong correlations associated with the Hund's coupling.Phenomenologically, by taking an experimentally observed frequency-dependent scattering rate, the deviation of the field driven kinetics from the Drude behavior is reconciled in a time-dependent Boltzmann description, which allows an attribution of the observed third-harmonic generation to the terahertz field driven nonlinear kinetics of the heavy quasiparticles.

cond-mat.str-el↗

arXiv2023

Spectroscopic age estimates for APOGEE red-giant stars: Precise spatial and kinematic trends with age in the Galactic disc

Over the last few years, many studies have found an empirical relationship between the abundance of a star and its age. Here we estimate spectroscopic stellar ages for 178 825 red-giant stars observed by the APOGEE survey with a median statistical uncertainty of 17%. To this end, we use the supervised machine learning technique XGBoost, trained on a high-quality dataset of 3060 red-giant and red-clump stars with asteroseismic ages observed by both APOGEE and Kepler. After verifying the obtained age estimates with independent catalogues, we investigate some of the classical chemical, positional, and kinematic relationships of the stars as a function of their age. We find a very clear imprint of the outer-disc flare in the age maps and confirm the recently found split in the local age-metallicity relation. We present new and precise measurements of the Galactic radial metallicity gradient in small age bins between 0.5 and 12 Gyr, confirming a steeper metallicity gradient for $\sim2-5$ Gyr old populations and a subsequent flattening for older populations mostly produced by radial migration. In addition, we analyse the dispersion about the abundance gradient as a function of age. We find a clear power-law trend (with an exponent $\beta\approx0.15$) for this relation, indicating a relatively smooth radial migration history in the Galactic disc over the past $7-9$ Gyr. Departures from this power law may possibly be related to the Gaia Enceladus merger and passages of the Sagittarius dSph galaxy. Finally, we confirm previous measurements showing a steepening in the age-velocity dispersion relation at around $\sim9$ Gyr, but now extending it over a large extent of the Galactic disc (5 kpc $<R_{\rm Gal}<13$ kpc). [Abridged]

astro-ph.GA↗

arXiv2023

Parameters for > 300 million Gaia stars: Bayesian inference vs. machine learning

The Gaia Data Release 3 (DR3), published in June 2022, delivers a diverse set of astrometric, photometric, and spectroscopic measurements for more than a billion stars. The wealth and complexity of the data makes traditional approaches for estimating stellar parameters for the full Gaia dataset almost prohibitive. We have explored different supervised learning methods for extracting basic stellar parameters as well as distances and line-of-sight extinctions, given spectro-photo-astrometric data (including also the new Gaia XP spectra). For training we use an enhanced high-quality dataset compiled from Gaia DR3 and ground-based spectroscopic survey data covering the whole sky and all Galactic components. We show that even with a simple neural-network architecture or tree-based algorithm (and in the absence of Gaia XP spectra), we succeed in predicting competitive results (compared to Bayesian isochrone fitting) down to faint magnitudes. We will present a new Gaia DR3 stellar-parameter catalogue obtained using the currently best-performing machine-learning algorithm for tabular data, XGBoost, in the near future.

astro-ph.GA↗

arXiv2023

The multiplicity fraction in 202 open clusters from Gaia

In this study, we estimate the fraction of binaries with high mass ratios for 202 open clusters in the extended solar neighbourhood (closer than 1.5 kpc from the Sun). This is one of the largest homogeneous catalogues of multiplicity fractions in open clusters to date, including the unresolved and total (close-binary) multiplicity fractions of main-sequence systems with mass ratio larger than $0.6_{-0.15}^{+0.05}$. The unresolved multiplicity fractions are estimated applying a flexible mixture model to the observed Gaia colour-magnitude diagrams of the open clusters. Then we use custom Gaia simulations to account for the resolved systems and derive the total multiplicity fractions. The studied open clusters have ages between 6.6 Myr and 3.0 Gyr and total high-mass-ratio multiplicity fractions between 6% and 80%, with a median of 18%. The multiplicity fractions increase with the mass of the primary star, as expected. The average multiplicity fraction per cluster displays an overall decreasing trend with the open cluster age up to ages about 100 Myr, above which the trend increases. Our simulations show that most of this trend is caused by complex selection effects (introduced by the mass dependence of the multiplicity fraction and the magnitude limit of our sample). Furthermore, the multiplicity fraction is not significantly correlated with the clusters' position in the Galaxy. The spread in multiplicity fraction decreases significantly with the number of cluster members (used as a proxy for cluster mass). We also find that the multiplicity fraction decreases with metallicity, in line with recent studies using field stars.

astro-ph.GA↗

arXiv2022

Abundance analysis of APOGEE spectra for 58 metal-poor stars from the bulge spheroid

The central part of the Galaxy host a multitude of stellar populations, including the spheroidal bulge stars, stars moved to the bulge through secular evolution of the bar, inner halo, inner thick disk, inner thin disk, as well as debris from past accretion events. We identified a sample of 58 candidate stars belonging to the stellar population of the spheroidal bulge, and analyse their abundances. The present calculations of Mg, Ca, and Si lines are in agreement with the APOGEE-ASPCAP abundances, whereas abundances of C, N, O, and Ce are re-examined. We find normal $α$-element enhancements in oxygen, similar to magnesium, Si, and Ca abundances, which are typical of other bulge stars surveyed in the optical in Baade's Window. The enhancement of [O/Fe] in these stars suggests that they do not belong to accreted debris. No spread in N abundances is found, and none of the sample stars is N-rich, indicating that these stars are not second generation stars originated in globular clusters. Ce instead is enhanced in the sample stars, which points to an s-process origin such as due to enrichment from early generations of massive fast rotating stars, the so-called spinstars

astro-ph.SR↗

arXiv2022

Tidally induced spiral arm wraps encoded in phase space

We study the dynamics of tidally induced spiral arms in our Galaxy in the context of its encounters with Sagittarius. We built toy models of the interaction between a host and a satellite galaxy using orbital integrations after a tidal encounter. We derived analytically the shape of the structures in phase space as a function of time for simple power-law potential models. We compared these models to a more realistic N-body simulation of the MW Sagittarius-like interaction and to data from Gaia DR3. As found before, an impulsive distant tidal approach of a galactic satellite leads to a two-armed spiral structure made of orbits in between their apocentres and pericentres, thus, with average negative galactocentric radial velocity. The two-arm pattern rotates at an angular speed of $ω-1/2κ$ which depends on radius, thus causing a wind-up with time. This produces ridges in the $R$-$V_ϕ$ projection with alternating signs of $V_R$ and oscillations of $V_R$ in the $L_Z$-$ϕ$ space, like those observed in the Gaia data. The frequency of these kinematic features increases with time, offering a powerful means to infer the potential and the perturbation's onset time and azimuthal phase. Fourier analysis allows us to date the impact times of simple models and even to date perturbations from various pericentric passages. For the MW, the Fourier analysis indicates a superposition of two different frequencies, as in previous studies. Assuming that both are due to impulsive and distant pericentre passages, we find perturbation times <0.6 Gyr and in the range of 0.8-2.1 Gyr. The latter is compatible with a previous pericentre of Sagittarius and would be related to four wraps of the spiral arms in the observed radial range. Further work on the self-gravitating response of galactic discs and possible degeneracies with secular processes by the bar is necessary. (ABR)

astro-ph.GA↗

arXiv2022

Gaia Data Release 3: Catalogue Validation

The third gaia data release (DR3) provides a wealth of new data products. The early part of the release, Gaia EDR3, already provided the astrometric and photometric data for nearly two billion sources. The full release now adds improved parameters compared to Gaia DR2 for radial velocities, astrophysical parameters, variability information, light curves, and orbits for Solar System objects. The improvements are in terms of the number of sources, the variety of parameter information, precision, and accuracy. For the first time, Gaia DR3 also provides a sample of spectrophotometry and spectra obtained with the Radial Velocity Spectrometer, binary star solutions, and a characterisation of extragalactic object candidates. Before the publication of the catalogue, these data have undergone a dedicated transversal validation process. The aim of this paper is to highlight limitations of the data that were found during this process and to provide recommendations for the usage of the catalogue. The validation was obtained through a statistical analysis of the data, a confirmation of the internal consistency of different products, and a comparison of the values to external data or models. Gaia DR3 is a new major step forward in terms of the number, diversity, precision, and accuracy of the Gaia products. As always in such a large and complex catalogue, however, issues and limitations have also been found. Detailed examples of the scientific quality of the Gaia DR3 release can be found in the accompanying data-processing papers as well as in the performance verification papers. Here we focus only on the caveats that the user should be aware of to scientifically exploit the data.

astro-ph.SR↗

arXiv2022

Hunting for open clusters in Gaia EDR3: $628$ new open clusters found with OCfinder

The improvements in the precision of the published data in \textit{Gaia} EDR3 with respect to \textit{Gaia} DR2, particularly for parallaxes and proper motions, offer the opportunity to increase the number of known open clusters in the Milky Way by detecting farther and fainter objects that have so far go unnoticed. Our aim is to keep completing the open cluster census in the Milky Way with the detection of new stellar groups in the Galactic disc. We use \textit{Gaia} EDR3 up to magnitude $G = 18$ mag, increasing in one unit the magnitude limit and therefore the search volume explored in our previous studies. We use the \texttt{OCfinder} method to search for new open clusters in \textit{Gaia} EDR3 using a Big Data environment. As a first step, \texttt{OCfinder} identifies stellar statistical overdensities in the five dimensional astrometric space (position, parallax and proper motions) using the \texttt{DBSCAN} clustering algorithm. Then, these overdensities are classified into random statistical overdensities or real physical open clusters using a deep artificial neural network trained on well-characterised $G$, $G_{\rm BP} - G_{\rm RP}$ colour-magnitude diagrams. We report the discovery of $664$ new open clusters within the Galactic disc, most of them located beyond $1$ kpc from the Sun. From the estimation of ages, distances and line-of-sight extinctions of these open clusters, we see that young clusters align following the Galactic spiral arms while older ones are dispersed in the Galactic disc. Furthermore, we find that most open clusters are located at low Galactic altitudes with the exception of a few groups older than $1$ Gyr. We show the success of the \texttt{OCfinder} method leading to the discovery of a total of $1\,310$ open clusters (joining the discoveries here with the previous ones based on \textit{Gaia} DR2)[abridged]

astro-ph.GA↗

arXiv2021

Femtosecond phononic coupling to both spins and charges in a room temperature antiferromagnetic semiconductor

Spintronics is postulated on the possibility to employ the magnetic degree of freedom of electrons for computation and couple it to charges. In this view, the combination of the high-frequency of spin manipulations offered by antiferromagnets, with the wide tunability of the electronic properties peculiar of semiconductors provides a promising and intriguing platform. Here we explore this scenario in $α$-MnTe, which is a semiconductor antiferromagnetically ordered at room temperature. Relying on a Raman mechanism and femtosecond laser pulses, we drive degenerate modes of coherent optical phonons, which modulate the chemical bonds involved in the super-exchange interaction. The spectrally-resolved measurements of the transient reflectivity reveal a coherent modulation of the band-gap at the frequency of 5.3 THz. The detection of the rotation of the polarisation, typically associated with magneto-optical effects, shows coherent and incoherent contributions. Modelling how the ionic motion induced by the phonons affects the exchange interaction in the material, we calculate the photoinduced THz spin dynamics: the results predict both a coherent and incoherent response, the latter of which is consistent with the experimental observation. Our work demonstrates that the same phonon modes modulate both the charge and magnetic degree of freedom, suggesting the resonant pumping of phonons as a viable way to link spin and charge dynamics even in nonlinear regimes.

physics.optics↗