arXiv subjects

J. Maíz Apellániz

Publications and source records attributed to J. Maíz Apellániz.

At least 19 recordsLinked to original sources

arXiv2026

Results on young stellar clusters with the WEAVE LIFU

We present the first results of two Spanish TAC programs using the WEAVE LIFU that have been obtaining data since October 2023. The first one is obtaining high-resolution multi-epoch spectroscopy of the nine stellar clusters that contain a minimum number of 3 O-type stars (and many more B stars) within the field of view of the WEAVE LIFU and that are accessible from La Palma with the purpose of studying the spectroscopic multiplicity of the OB stars. The second program is obtaining single-shot low-resolution spectroscopy of as many stellar clusters with OB stars as possible with the purpose of characterizing the OB-star population in those regions that are too crowded to be properly studied with the guaranteed time SCIP program. That program has already observed 54 clusters in a wide range of environments, from H II regions to gas-free clusters, and distances, from clusters in the solar neighbourhood to (nearby) extragalactic systems. We also present the tools developed for this program, which include a data cube processing and visualisation utility and UNWIND, a code that fits and subtracts the ISM signature in the observed spectra.

astro-ph.SR↗

arXiv2026

A new method to cleanly separate hot and cool populations using just Gaia and 2MASS photometry

We have developed a photometric method that produces clean hot (intrinsically blue) populations using Gaia and 2MASS photometry alone with [a] a very small (false positives < 1%) contamination from cool (intrinsically red) luminous sources, [b] independent of extinction (limited only by S/N), and [c] with only small losses (false negatives < 10%) of real OB stars. Applying the method to Gaia DR3 data we are able to recover extinguished OB stars down to E(G_BP-G_RP) = 5, producing a catalog of ~2x10^5 candidate OB stars that reaches beyond the Scutum-Centaurus arm. This method can potentially extend the sample of known OB stars by an order of magnitude, which would yield a large leap in our knowledge of the populations of compact-object progenitors, including gravitational-wave sources.

astro-ph.SR↗

arXiv2026

The IACOB project XVIII. Prevalence of short-period binaries among Galactic helium rich O-type stars

For decades, the origin of helium enrichment in O-type stars has remained an open question. In this study, we investigate the correlation between surface helium abundance and orbital parameters for a sample of 45 O-type SB1 systems --including Cyg X-1. We find seven He-rich systems, all of which are concentrated at short orbital periods (P$\lesssim 15$ days) and are classified as runaways. In addition, four of them present relatively high eccentricities, while the other three have ellipsoidal variations. We argue that these properties are the result of binary interaction. These findings provide strong observational evidence that binary interaction is the dominant origin of helium enrichment in O-type stars. This result has important implications for the treatment of chemical mixing and surface abundances in massive-star evolutionary models, and establishes helium enrichment as a promising observational tracer for identifying post-interaction binary systems.

astro-ph.SR↗

arXiv2026

Multiplicity of Massive Stars at Low Metallicity: Early Results from the BLOeM Campaign

Massive stars at low metallicity (Z) play a central role in shaping the high-redshift Universe, yet their multiplicity remains poorly constrained. The Binarity at Low Metallicity (BLOeM) campaign is a two-year survey of 929 stars in the Small Magellanic Cloud with the Fibre Large Array Multi Element Spectrograph (FLAMES) instrument at ESO's Very Large Telescope, providing the first large-scale spectroscopic monitoring of massive stars at low Z (1/5 solar). Analysis of the initial nine epochs reveals high intrinsic binary fractions (>70%) on the main sequence and a steep decline in evolved objects. Analysis of the full dataset will yield orbital solutions, identify black-hole companions, and allow a derivation of the initial mass function for single and binary stars at low Z.

physics.gen-ph↗

arXiv2026

Multiplicity of Massive stars in the Milky Way (M3W). I. Project description, UNWIND, application to GLS 11 448, and DIB catalog

(ABRIDGED BUT NOT TOO FAR) Multiplicity is ubiquitous among massive stars and its understanding is constrained by the sample of well-determined orbits. The immediate goal of M3W is to significantly increase the number of massive multiple systems with well-determined orbits and masses. We will address issues such as multiplicity statistics, the mass function in clusters and the field, the properties of binaries with compact companions and gravitational-wave progenitors, the origin and characteristics of runaways and their 3-D motions, the use of apsidal motion as a probe of stellar interiors, and the mass discrepancy between different methods (evolutionary, spectroscopic, and Keplerian). In this first paper, we present the project; describe the data and tools that will be used, including the disentangling UNWIND tool; analyse the very massive twin binary system GLS 11 448; and briefly introduce some of the following papers of the series. We present a new orbit for GLS 11 448, using UNWIND to obtain for the first time disentangled spectra for the full 3820-11 000 $\mathring{A}$ range for an OB spectroscopic binary. We derive the stellar parameters, making new stellar lines available for the study of O stars. The Aa and Ab components of GLS 11 448, both classified as O3.5 II(f*), are the two most massive O stars ever detected according to the evolutionary masses of 70$\pm$10 M$_\odot$ and 76$\pm$11 M$_\odot$ determined in this paper. We also report the first-ever detection of the interstellar He I 10 830 triplet in absorption in an OB-star sightline. As a by-product of the ISM model derived for UNWIND using GLS 11 448 and five other standard stars, we present the most detailed diffuse-interstellar-band (DIB) library ever built, with a total of 631 DIBs in the 4000-17 100 $\mathring{A}$ range, of which 37 are fitted with multiple-Gaussian profiles and 119 had never been identified before.

astro-ph.SR↗

arXiv2026

The World Cup in space: Finding ionised buckyballs in the ISM with CARMENES

Over a century after the discovery of the first diffuse interstellar bands (DIBs) in absorption in stellar spectra (Heger et al 1922), their origin is still mostly unknown. The exception are four DIBs (out of 600+ known) in the 9300-9700 Angstrom region, for which a possible ascription to C_60^+ (ionised buckminsterfullerene, shaped liked a football, hence buckyballs) has been made. However, those DIBs are located in a spectral region heavily contaminated by telluric H_2O absorption, hampering their detection and study from the ground. I present the results of a study with the CARMENES spectrograph that uses a novel technique with multi-epoch spectroscopy at different times of the year to shift the relative position of the DIBs and the surrounding telluric lines, hence facilitating the analysis of the DIBs. The technique has been applied to 41 sightlines of diverse extinctions and environments, with positive detections in all of them. Our results are consistent with three of those DIBs having C_60^+ as the carrier.

astro-ph.GA↗

arXiv2026

New Observations of the Strongly Magnetic O-star NGC 1624-2 Reveal Its Magnetic South Pole

NCG 1624-2 has the strongest detected magnetic field of all known main-sequence O-type stars. It was originally found that its magnetospheric emission lines followed a $\sim$5 month periodicity, and the existing line-of-sight magnetic measurements were predominantly of strong positive (north) polarity. As such, the field's geometric interpretation has been a mildly tilted (with respect to the rotational axis) dipole, such that only the magnetic north pole is visible during a rotation cycle. However, S. Seadrow et al. (2026) recently reported that new magnetospheric observations no longer phased with the established ephemeris and that the period had to be decreased by a few days. S. Seadrow et al. (2026) also found that existing magnetic measurements did not rule out a period twice as long (306.56 d). This period suggests a different magnetic configuration with a larger dipolar tilt, making both magnetic poles visible over a single rotation. Because previous spectropolarimetric observations did not have sufficient phase coverage to distinguish between the geometries, both were equally viable. In this paper, we present new spectropolarimetric observations obtained specifically to resolve this ambiguity. Our new magnetic measurements have a strong negative (south) polarity, confirming that the rotational period of NGC 1624-2 is indeed nearly twice as long as previously thought. Our measurements show that both poles come within a similar angle to our line of sight and likely have roughly the same local magnetic field strength (with a dipolar strength of 15-20 kG or more depending on the inclination angle).

astro-ph.SR↗

arXiv2026

New Insights from Revisiting the Rotation Period of the Strongly Magnetic O Star, NGC 1624-2

NGC 1624-2 hosts the strongest surface magnetic field found on an O star thus far. When applied across several epochs of observations, the star's currently accepted rotation period (157.99 d) does not coherently characterize the variations of spectral lines of magnetospheric origin. We analyze Lomb-Scargle periodograms produced with new and archival, multi-instrument spectroscopic time series of Balmer H and He spectral lines. We find that 153.17 $\pm$ 0.42 d and 306.56 $\pm$ 1.19 d are both equally suitable periods at phasing the spectral and magnetic time series data in a manner consistent with the Oblique Rotator Model. The 306.56 d period implies a magnetic geometry for NGC 1624-2 that is quite different from the previously accepted one, for which both magnetic poles should be observed during a full rotational cycle. If this is the case, the star's magnetic South pole has yet to be observed, and additional spectropolarimetric observations should be acquired in order to confirm whether or not the south pole is in fact observable.

astro-ph.SR↗

arXiv2025

Why the northern hemisphere needs a 30-40 m telescope and the science at stake: Massive stars in spiral galaxies

This document discusses the three main lines expected to dominate massive-star research in the 2040s, namely: (1) The role of metallicity in stellar evolution, especially in determining the end products such as gravitational-wave progenitors. (2) The initial mass function from the most massive stars to substellar objects. (3) The role of the environment in the different modes of star formation from compact star clusters to born-this-way associations and from massive clusters to small stellar groups. More specifically, we present the contributions to such science that would be enabled by a 30~m type telescope in the northern hemisphere studying spiral galaxies. Those can be grouped in three: our own Galaxy, the Milky Way; the other two spiral galaxies in the Local Group, M31 and M33; and other galaxies within 25 Mpc, such as M101, M51, and NGC~6946. This work is based on the fact that, as of today, no construction of a 30~m telescope has yet started in the northern hemisphere, so even in the best case scenario of such a hypothetical telescope, its full operation would not start until the late 2030s or early 2040s. It makes no assumptions about its location but supposes an instrumentation development similar to that of ELT.

astro-ph.IM↗

arXiv2025

Alma Luminous Star catalogue IV: A Massive star census in the Magellanic Clouds

The fourth part of the Alma Luminous Star catalogue (ALS IV) aims to create the most comprehensive sample of massive stars in the Magellanic Clouds (MCs). By combining Gaia DR3 with Simbad and complementing this information with other photometric and spectroscopic catalogues, we select the massive stars in this region. To achieve this, we apply filters in photometry, combining different bands, as well as in variability and spectral types from the literature. With this approach, we will obtain one of the most complete samples of massive stars in the MCs, which can be used both to study the Clouds and the Magellanic Bridge, as well as the massive stars they contain.

astro-ph.GA↗

arXiv2025

Gaia and massive stars in 2025

I present some of the highlights of the Gaia mission on massive stars and discuss what the fourth data release (DR4) will bring in late 2026. In the first part of the contribution I describe the different types of Gaia products available now and for DR4 and their caveats. In the second part I present the most significant results on massive stars regarding parameter determination, binaries, photometric variability, stellar groups, and the sample and spatial distribution.

astro-ph.SR↗

arXiv2025

Binarity at LOw Metallicity (BLOeM): a spectroscopic VLT monitoring survey of massive stars in the SMC

Surveys in the Milky Way and Large Magellanic Cloud revealed that the majority of massive stars will interact with companions during their lives. However, knowledge of the binary properties of massive stars at low metallicity, which approaches the conditions of the Early Universe, remains sparse. We present the Binarity at LOw Metallicity (BLOeM) campaign - an ESO large programme designed to obtain 25 epochs of spectroscopy for 929 massive stars in the SMC - the lowest metallicity conditions in which multiplicity is probed to date (Z = 0.2 Zsun). BLOeM will provide (i) the binary fraction, (ii) the orbital configurations of systems with periods P < 3 yr, (iii) dormant OB+BH binaries, and (iv) a legacy database of physical parameters of massive stars at low metallicity. The stars are observed with the LR02 setup of the giraffe instrument of the Very Large Telescope (3960-4570A, resolving power R=6200; typical signal-to-noise ratio S/N=70-100). This paper utilises the first 9 epochs obtained over a three-month time. We describe the survey and data reduction, perform a spectral classification of the stacked spectra, and construct a Hertzsprung-Russell diagram of the sample via spectral-type and photometric calibrations. The sample covers spectral types from O4 to F5, spanning the effective temperature and luminosity ranges 6.5<Teff/kK<45 and 3.7<log L/Lsun<6.1 and initial masses 8<Mini/Msun<80. It comprises 159 O-type stars, 331 early B-type (B0-3) dwarfs and giants (luminosity classes V-III), 303 early B-type supergiants (II-I), and 136 late-type supergiants. At least 82 stars are Oe/Be stars: 20 O-type and 62 B-type (13% and 11% of the respective samples). In addition, it includes 4 high-mass X-ray binaries, 3 stars resembling luminous blue variables, 2 bloated stripped-star candidates, 2 candidate magnetic stars, and 74 eclipsing binaries.

astro-ph.SR↗

arXiv2025

The Alma catalogue of OB stars. III. A cross-match with Gaia DR3 and an extension based on new spectral classifications

We present the third installment of the Alma Luminous Star (ALS) catalogue, aimed at creating the most comprehensive and clean sample of Galactic massive stars. This update extends the sample by adding approximately 2000 OB stars, incorporating astrometric and photometric data from the Gaia Data Release 3 (DR3) alongside spectroscopic information from the Galactic O-Star Catalog based on recent ground-based spectroscopic surveys. Rigorous astrometric corrections are applied to Gaia DR3 parallaxes, proper motions, and photometry, ensuring accurate distance estimates through a Bayesian method suited to this stellar population's spatial distribution in the Milky Way. We perform some comparative analyses highlighting the improved distance accuracy over previous versions, underscore the importance of precise spectral classifications with competing catalogues, and identify areas for improvement in Gaia DR3 effective temperature and extinction estimates for massive stars. We also address the challenges of having robust definitions for these objects. In addition, we explore the catalogue's ability to trace Galactic features such as spiral arms, spurs and OB associations (with some insights on the nature of Gould's Belt). Finally, we discuss the potential for further expanding the sample with upcoming surveys. This effort marks a significant advancement in the creation of a reliable census of Galactic massive stars, contributing to our understanding of the Milky Way's structure and star formation history. This catalogue should serve as a valuable reference for the massive star community, supporting research on stellar interiors, winds, stellar feedback, and other processes that make OB stars key to the evolution of galaxies.

astro-ph.SR↗

arXiv2025

MONOS: Multiplicity Of Northern O-type Spectroscopic systems. III. New orbits and Gaia TESS analysis for 10 SB2E systems

The MONOS project (Multiplicity Of Northern O-type Spectroscopic systems) aims to characterize O-type spectroscopic binaries in the northern hemisphere (dec > -20 deg) using high-resolution spectroscopy and multi-epoch photometry. This study uses Gaia DR3 epoch photometry and TESS light curves to detect periodic variability and refine orbital solutions. We analyze ten O-type binaries with quality Gaia and TESS data and available high-resolution spectra, complemented by Hipparcos or MUDEHaR photometry. Periods are derived using three techniques and combined with radial velocities to model each system with the phoebe code, yielding orbital and stellar parameters. We present eight previously unpublished orbits-two with new periods-and refine two others. In several cases, our periods match Gaia's, though we highlight issues such as half-period aliases. Among our key results, we report the first known Oe+O spectroscopic binary (BD +61 487) and a system of overcontact O-type supergiants in an eccentric orbit with evidence of past mass transfer (HD 169 727). The solutions are consistent with spectral classifications and theory, including short periods (< 3 days), high mass ratios, and semi-detached or overcontact configurations. These results expand the sample of O-type binaries with robust orbital characterization, especially in the short-period regime where tidal effects and mass transfer dominate. The combined use of Gaia, TESS, and spectroscopy proves effective and scalable, supporting future surveys and aiding our understanding of massive multiple-star evolution.

astro-ph.SR↗

arXiv2025

Binarity at LOw Metallicity (BLOeM): Enhanced multiplicity of early B-type dwarfs and giants at $Z=0.2\,{\rm Z}_\odot$

Early B-type stars ($M_i=8-15$ M$_\odot$) are frequently in multiple systems, as evidenced by spectroscopic campaigns in the Milky Way (MW) and the Large Magellanic Cloud (LMC). Previous studies have shown no strong metallicity dependence in the close-binary (a>10 au) fraction or orbital-period distributions between the MW's solar metallicity (Z$_\odot$) and that of the LMC (Z=0.5 Z$_\odot$). However, similar analyses in more metal-poor environments are still scarce. We focus on 309 early B-type stars (luminosity classes III-V) from the Binarity at LOw Metallicity campaign in the Small Magellanic Cloud (SMC, Z=0.2 Z$_\odot$) using VLT/FLAMES multi-epoch spectroscopy. By applying binary detection criteria consistent with previous works, we identify 153 stars (91 SB1, 59 SB2, 3 SB3) exhibiting significant radial-velocity (RV) variations, resulting in an observed multiplicity fraction of $f^{obs}_{mult}=50\pm3\%$. Using Monte Carlo simulations to account for observational biases, we infer an intrinsic close-binary fraction of $f_{mult}=80\pm8\%$. A Markov chain Monte Carlo analysis of the peak-to-peak RV distribution ($Δ{\rm RV}_{\rm max}$) confirms a high multiplicity fraction of $f_{mult}=78\pm5\%$. These findings suggest a possible anti-correlation between metallicity and the fraction of close B-type binaries, with the SMC multiplicity fraction significantly exceeding previous measurements in the LMC and MW. The enhanced fraction of close binaries at SMC's low metallicity may have broad implications for massive-star evolution in the early Universe. More frequent mass transfer and envelope stripping could boost the production of exotic transients, stripped supernovae, gravitational-wave progenitors, and sustained UV ionising flux, potentially affecting cosmic reionisation. Theoretical predictions of binary evolution under metal-poor conditions will provide a key test of our results.

astro-ph.SR↗

arXiv2025

Gaia-ESO Survey: massive stars in the Carina Nebula. II. The spectroscopic analysis of the O-star population

The new census of massive stars in the Carina nebula reveals the presence of 54 apparently single O-type stars in the Car OB1 association, an extremely active star-forming region which hosts some of the most luminous stars of the Milky Way. A detailed spectroscopic analysis of the currently most complete sample of O-type stars in the association can be used to inspect the main physical properties of cluster members and test evolutionary and stellar atmospheres models. We perform quantitative spectroscopic analysis for the most complete sample of apparently single O-type stars in Car OB1 with available spectroscopic data. From the high-resolution GES and OWN spectra we obtain a reliable distribution of rotational velocities for a sample of 37 O-type stars. It shows a bimodal structure with a low velocity peak at 60 km s$^{-1}$ and a short tail of fast rotators reaching 320 km s$^{-1}$. We also perform quantitative spectroscopic analysis and derive effective temperature, surface gravity and He abundance for a sample of 47 O-type stars, now including further stars from GOSSS database. Radii, luminosities, and spectroscopic masses were also determined using $Gaia$ astrometry. We create the Hertzsprung-Russell Diagram to inspect the evolutionary status of the region and confirm the lack of stars close to the Zero Age Main Sequence (ZAMS) between $\sim$35 -- 55 M$_\odot$. We confirm a very young population with an age distribution peaking at 1 Myr, some stars close or even on the ZAMS, and a secondary peak at 4 -- 5 Myr in the age distribution. We confirm the youth of Trumpler 14, which is also the only cluster not showing the secondary peak. We also find a clear trend to evolutionary masses higher than derived spectroscopic masses for stars with evolutionary mass below 40 M$_{\odot}$.

astro-ph.SR↗

arXiv2024

Multi-Epoch precise photometry from the ground: MUDEHaR, magnetic stars and everything around

MUDEHaR is an on-going multi-epoch photometric survey with two narrow filters in H$α$ and the calcium triplet window that uses the T80Cam wide-field imager at the JAST/T80 telescope at Spanish Javalambre astronomical observatory. It is obtaining 100 epochs/year per field for 20 fields in the Galactic disk, each of 2\,deg$^2$, for a total of 40\,deg$^2$. Focused on stellar clusters and HII regions including bright stars, its main objective is to detect tens of thousands OB stars that present emission variability in H$α$ on days-months-years scale. The observed targets include magnetic massive stars, pulsating stars, and all kinds of variable stars. Among our driving scientific objectives of MUDEHaR observations is to identify potential magnetic candidates in massive stars. Only 10--20\,\% of OB stars display a measurable magnetic field, and its origin is still in debate. We outline here the multi-step process involved in identifying OB magnetic stars, highlighting the significance of MUDEHaR observations in this process.

astro-ph.SR↗

arXiv2024

Spectral classification

Spectral classification is the division of stars into classes based on their spectral characteristics. Different classification systems have existed since the 19th century but the term is used nowadays mostly to refer to the Morgan-Keenan (MK) system, which was established in the 1940s and has been developed since then. The MK classification has three components: a spectral type, a luminosity class, and (possibly) suffixes or qualifiers. The first two components represent temperature and luminosity sequences (a 2-D grid), respectively, and the third one includes additional information. The MK system is an Aristotelian morphological classification system that uses the MK process, an inductive approach based on specimens (standard stars) that define the system. In that respect, it is different from and a required preliminary step for quantitative spectroscopy, whose goal is to extract the physical properties and chemical composition of the stars. In this entry we provide a brief history of spectral classification, describe the general properties of the classification criteria of the MK system, analyze the specific spectral type and luminosity class criteria used for each spectral class, and introduce the different peculiar types that can be found within the 2-D classification grid and at its edges.

astro-ph.SR↗