arXiv subjects

A. Marco

Publications and source records attributed to A. Marco.

At least 19 recordsLinked to original sources

arXiv2026

Astro+ database. I. Description and first results

The vast amounts of spectroscopic data for massive stars provided by previous and existing instruments on ground-based and space-based telescopes have saturated our capability to process them by human inspection routines. Consequently, there is a pressing need for fully automatic machine-assisted tools to help handle incoming data. To this end, we present the development of a massive star spectroscopic interactive database, Astro+. We aim to provide users with a reliable, versatile, and user-friendly platform that will be significant for understanding massive stars and set an important precedent for future open-access astrophysical research. This tool allows authorized users to upload their own spectra and, by using the fully automated tool HiLineThere, a Python-based program, it can homogeneously derive basic stellar parameters, such as v_rad, v sin i, Teff and log g for massive OB-type stars, using a solar-metallicity grid of FASTWIND models, and v_rad, [Fe/H], Teff and log g for red supergiant stars, in a completely autonomous way. Here we present the first results of the tool HiLineThere on optical spectra for OB-type stars and red supergiants. We compare the output of our analysis for OB-type stars with literature values for a large sample of well-studied objects, finding differences within the expected error ranges: Teff ~ 800 K, log g ~ 0.1 dex, and v sin i ~ 10 km/s. Preliminary tests on early-B stars also show consistent results during the transition to lower temperatures. For red supergiants, we find differences within 7 km/s in v_rad and ~300 K in Teff for two test samples.

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arXiv2022

Web-based telluric correction made in Spain: spectral fitting of Vega-type telluric standards

Infrared spectroscopic observations from the ground must be corrected from telluric contamination to make them ready for scientific analyses. However, telluric correction is often a tedious process that requires significant expertise to yield accurate results in a reasonable time frame. To solve these inconveniences, we present a new method for telluric correction that employs a roughly simultaneous observation of a Vega analog to measure atmospheric transmission. After continuum reconstruction and spectral fitting, the stellar features are removed from the observed Vega-type spectrum and the result is used for cancelling telluric absorption features on science spectra. This method is implemented as TelCorAl (Telluric Correction from Alicante), a Python-based web application with a user-friendly interface, whose beta version will be released soon.

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arXiv2020

Three open clusters containing Cepheids: NGC 6649, NGC 6664 and Berkeley 55

Classical Cepheids in open clusters play an important role in benchmarking stellar evolution models, anchoring the cosmic distance scale, and invariably securing the Hubble constant. NGC 6649, NGC 6664 and Berkeley 55 are three pertinent clusters that host classical Cepheids and red (super)giants, and an analysis was consequently initiated to assess newly acquired spectra ($\approx$50), archival photometry, and $Gaia$ DR2 data. Importantly, for the first time chemical abundances are determined for the evolved members of NGC 6649 and NGC 6664. We find that they are slightly metal-poor relative to the mean Galactic gradient, and an overabundance of Ba is observed. Those clusters likely belong to the thin disc, and the latter finding supports D'Orazi et al. (2009) "$s$-enhanced" scenario. NGC 6664 and Berkeley 55 exhibit radial velocities consistent with Galactic rotation, while NGC 6649 displays a peculiar velocity. The resulting age estimates for the clusters ($\approx$70 Ma) imply masses for the (super)giant demographic of $\approx$6 M$_{sun}$. Lastly, the observed yellow-to-red (super)giant ratio is lower than expected, and the overall differences relative to models reflect outstanding theoretical uncertainties.

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arXiv2019

A comprehensive study of NGC 2345, a young open cluster with a low metallicity

NGC 2345 is a young open cluster hosting seven blue and red supergiants, low metallicity and a high fraction of Be stars which makes it a privileged laboratory to study stellar evolution. We aim to improve the determination of the cluster parameters and study the Be phenomenon. Our objective is also to characterise its seven evolved stars by deriving their atmospheric parameters and chemical abundances. We performed a complete analysis combining for the first time $ubvy$ photometry with spectroscopy as well as $Gaia$ Data Release 2. We obtained spectra with classification purposes for 76 stars and high-resolution spectroscopy for an in-depth analysis of the blue and red evolved stars. We identify a new red supergiant and 145 B-type likely members within a radius of 18.7$\pm$1.2 arcmin, which implies an initial mass, $M_{\textrm{cl}}\approx$5200 M$_{\odot}$. We find a distance of 2.5$\pm$0.2 kpc for NGC 2345, placing it at $R_{\textrm{GC}}$=10.2$\pm$0.2 kpc. Isochrone fitting supports an age of 56$\pm$13 Ma, implying masses around 6.5 M$_{\odot}$ for the supergiants. A high fraction of Be stars ($\approx$10$\%$) is found. From the spectral analysis we estimate for the cluster an average $v_{\textrm{rad}}$=$+58.6\pm0.5$ kms$^{-1}$ and a low metallicity, [Fe/H]=$-$0.28$\pm$0.07. We also have determined chemical abundances for Li, O, Na, Mg, Si, Ca, Ti, Ni, Rb, Y, and Ba for the evolved stars. The chemical composition of the cluster is consistent with that of the Galactic thin disc. One of the K supergiants, S50, is a Li-rich star, presenting an A(Li)$\approx$2.1. An overabundance of Ba is found, supporting the enhanced $s$-process. NGC 2345 has a low metallicity for its Galactocentric distance, comparable to typical LMC stars. It is massive enough to serve as a testbed for theoretical evolutionary models for massive intermediate-mass stars.

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arXiv2019

MONOS: Multiplicity Of Northern O-type Spectroscopic systems. I. Project description and spectral classifications and visual multiplicity of previously known objects

[ABRIDGED] AIMS. MONOS is collecting information and studying O-type spectroscopic binaries with delta > -20 deg. In this 1st paper we describe the sample and provide spectral classifications and additional information for objects with previous SB or EB orbits. In the future we will test the validity of previous solutions and calculate new SB orbits. METHODS.The spectra in this paper have 2 sources: GOSSS, which is obtaining blue-violet R~2500 spectroscopy of thousands of massive stars, and LiLiMaRlin, a library of libraries of high-resolution spectroscopy of massive stars obtained from 4 different surveys and additional data from our own observing programs and public archives. We also use lucky images from AstraLux. RESULTS. We present homogeneous spectral classifications for 92 O-type spectroscopic multiple systems and 10 optical companions. We discuss the visual multiplicity of each system with the support of AstraLux images and additional sources. For 11 O-type objects and for 6 B-type objects we present their first GOSSS spectral classifications. For 2 known EBs we detect SB2/SB1 lines for the first time, to which we add a third system already reported by us recently. For 2 previous SB1 systems we detect their SB2 nature for the first time and give their first separate spectral classifications, something we also do for a 3rd object just recently identified as a SB2. We also detect 9 new astrometric companions and provide updated information on several others. For sigma Ori AaAbB we provide spectral classifications for the 3 components with a single observation for the first time thanks to a lucky spectroscopy observation obtained close to the Aa,Ab periastron and for theta^1 Ori CaCb we add it to the class of Galactic Of?p stars, raising the number of its members to 6. Our sample of O-type spectroscopic binaries contains more triple/higher-order systems than double systems.

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arXiv2018

NGC 3105: a young open cluster with low metallicity

NGC 3105 is a young open cluster hosting blue, yellow and red supergiants. This rare combination makes it an excellent laboratory to constrain evolutionary models of high-mass stars. It is poorly studied and fundamental parameters such as its age or distance are not well defined. We intend to characterize in an accurate way the cluster as well as its evolved stars, for which we derive for the first time atmospheric parameters and chemical abundances. We identify 126 B-type likely members within a radius of 2.7$\pm$0.6 arcmin, which implies an initial mass, $M_{cl}\approx$4100 M$_{\odot}$. We find a distance of 7.2$\pm$0.7 kpc for NGC 3105, placing it at $R_{GC}$=10.0$\pm$1.2 kpc. Isochrone fitting supports an age of 28$\pm$6 Ma, implying masses around 9.5 M$_{\odot}$ for the supergiants. A high fraction of Be stars ($\approx$25 %) is found at the top of the main sequence down to spectral type b3. From the spectral analysis we estimate for the cluster a $v_{rad}$=+46.9$\pm$0.9 km s$^{-1}$ and a low metallicity, [Fe/H]=-0.29$\pm$0.22. We also have determined, for the first time, chemical abundances for Li, O, Na, Mg, Si, Ca, Ti, Ni, Rb, Y, and Ba for the evolved stars. The chemical composition of the cluster is consistent with that of the Galactic thin disc. An overabundance of Ba is found, supporting the enhanced $s$-process. NGC 3105 has a low metallicity for its Galactocentric distance, comparable to typical LMC stars. It is a valuable spiral tracer in a very distant region of the Carina-Sagittarius spiral arm, a poorly known part of the Galaxy. As one of the few Galactic clusters containing blue, yellow and red supergiants, it is massive enough to serve as a testbed for theoretical evolutionary models close to the boundary between intermediate and high-mass stars.

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arXiv2017

NGC 6067: a young and massive open cluster with high metallicity

NGC 6067 is a young open cluster hosting the largest population of evolved stars among known Milky Way clusters in the 50-150 Ma age range. It thus represents the best laboratory in our Galaxy to constrain the evolutionary tracks of 5-7 M$_{\odot}$ stars. We have used high-resolution spectra of a large sample of bright cluster members (45), combined with archival photometry, to obtain accurate parameters for the cluster as well as stellar atmospheric parameters. We derive a distance of 1.78$\pm$0.12 kpc, an age of 90$\pm$20 Ma and a tidal radius of 14.8$^{6.8}_{3.2}$ arcmin. We estimate an initial mass above 5700 M$_{\odot}$, for a present-day evolved population of two Cepheids, two A supergiants and 12 red giants with masses $\approx$6 M$_{\odot}$. We also determine chemical abundances of Li, O, Na, Mg, Si, Ca, Ti, Ni, Rb, Y and Ba for the red clump stars. We find a supersolar metallicity, [Fe/H]=+0.19$\pm$0.05, and a homogeneus chemical composition, consistent with the Galactic metallicity gradient. The presence of a Li-rich red giant, star 276 with A(Li)=2.41, is also detected. An over-abundance of Ba is found, supporting the enhanced $s$-process. The ratio of yellow to red giants is much smaller than one, in agreement with models with moderate overshooting, but the properties of the cluster Cepheids do not seem consistent with current Padova models for supersolar metallicity.

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arXiv2017

Confirmation of six Be X-ray binaries in the Small Magellanic Cloud

The X-ray binary population of the Small Magellanic Cloud (SMC) contains a large number of massive X-ray binaries and the recent survey of the SMC by XMM-Newton has resulted in almost 50 more tentative high mass X-ray binary candidates. Using probability parameters from Haberl & Sturm (2016) together with the optical spectra and timing in this work, we confirm six new massive X-ray binaries in the SMC. We also report two very probable binary periods; of 36.4d in XMM 1859 and of 72.2 d in XMM 2300. These Be X-ray binaries are likely part of the general SMC population which rarely undergoes an X-ray outburst.

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arXiv2016

The young open cluster NGC 7067 using Strömgren photometry

NGC 7067 is a young open cluster located in the direction between the first and the second Galactic quadrants and close to the Perseus spiral arm. This makes it useful for studies of the nature of the Milky Way spiral arms. Stromgren photometry taken with the Wide Field Camera at the Isaac Newton Telescope allowed us to compute individual physical parameters for the observed stars and hence to derive cluster's physical parameters. Spectra from the 1.93-m telescope at the Observatoire de Haute-Provence helped to check and improve the results. We obtained photometry for 1233 stars, individual physical parameters for 515 and spectra for 9 of them. The 139 selected cluster members lead to a cluster distance of 4.4+/-0.4 kpc, with an age below log10(t(yr))=7.3 and a present Mass of 1260+/-160Msun. The morphology of the data reveals that the centre of the cluster is at (ra,dec)=(21:24:13.69,+48:00:39.2) J2000, with a radius of 6.1arcsec. Stromgren and spectroscopic data allowed us to improve the previous parameters available for the cluster in the literature.

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arXiv2016

Open clusters in AurOB2

We study the area around the HII region Sh 2-234, including the young open cluster Stock 8, to investigate the extent and definition of the association Aur OB2 and the possible role of triggering in massive cluster formation. We obtained Str\"omgren and J,H,Ks photometry for Stock 8 and Str\"omgren photometry for two other cluster candidates in the area, which we confirm as young open clusters and name Alicante 11 and Alicante 12. We took spectroscopy of 33 early-type stars in the area, including the brightest cluster members. We calculate a common distance of $2.80^{+0.27}_{-0.24}$ kpc for the three open clusters and surrounding association. We derive an age 4-6 Ma for Stock 8, and do not find a significantly different age for the other clusters or the association. The star LSV +34 23, with spectral type O8 II(f), is likely the main source of ionization of Sh 2-234. We observe an important population of pre-main sequence stars, some of them with disks, associated with the B-type members lying on the main-sequence. We interpret the region as an area of recent star formation with some residual and very localized ongoing star formation. We do not find evidence for sequential star formation on a large scale. The classical definition of Aur OB2 has to be reconsidered, because its two main open clusters, Stock 8 and NGC 1893, are not at the same distance. Stock 8 is probably located in the Perseus arm, but other nearby HII regions whose distances also place them in this arm show quite different distances and radial velocities and, therefore, are not connected.

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arXiv2016

The Galactic O-Star Spectroscopic Survey (GOSSS). III. 142 additional O-type systems

This is the third installment of GOSSS, a massive spectroscopic survey of Galactic O stars, based on new homogeneous, high signal-to-noise ratio, R~2500 digital observations selected from the Galactic O-Star Catalog (GOSC). In this paper we present 142 additional stellar systems with O stars from both hemispheres, bringing the total of O-type systems published within the project to 590. Among the new objects there are 20 new O stars. We also identify 11 new double-lined spectroscopic binaries (SB2s), of which 6 are of O+O type and 5 of O+B type, and an additional new tripled-lined spectroscopic binary (SB3) of O+O+B type. We also revise some of the previous GOSSS classifications, present some egregious examples of stars erroneously classified as O-type in the past, introduce the use of luminosity class IV at spectral types O4-O5.5, and adapt the classification scheme to the work of Arias et al. (2016).

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arXiv2015

The little-studied cluster Berkeley 90. I. LS III +46 11: a very massive O3.5 If* + O3.5 If* binary

Context: It appears that most (if not all) massive stars are born in multiple systems. At the same time, the most massive binaries are hard to find due to their low numbers throughout the Galaxy and the implied large distances and extinctions. AIMS: We want to study: [a] LS III +46 11, identified in this paper as a very massive binary; [b] another nearby massive system, LS III +46 12; and [c] the surrounding stellar cluster, Berkeley 90. Methods: Most of the data used in this paper are multi-epoch high-S/N optical spectra though we also use Lucky Imaging and archival photometry. The spectra are reduced with devoted pipelines and processed with our own software, such as a spectroscopic-orbit code, CHORIZOS, and MGB. Results: LS III +46 11 is identified as a new very-early-O-type spectroscopic binary [O3.5 If* + O3.5 If*] and LS III +46 12 as another early O-type system [O4.5 V((f))]. We measure a 97.2-day period for LS III +46 12 and derive minimum masses of 38.80$\pm$0.83 M_Sol and 35.60$\pm$0.77 M_Sol for its two stars. We measure the extinction to both stars, estimate the distance, search for optical companions, and study the surrounding cluster. In doing so, a variable extinction is found as well as discrepant results for the distance. We discuss possible explanations and suggest that LS III +46 12 may be a hidden binary system, where the companion is currently undetected.

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arXiv2014

CAF\'E-BEANS: An exhaustive hunt for high-mass binaries

CAF\'E-BEANS is an on-going survey running on the 2.2 m telescope at Calar Alto. For more than two years, CAF\'E-BEANS has been collecting high-resolution spectra of early-type stars with the aim of detecting and characterising spectroscopic binaries. The main goal of this project is a thorough characterisation of multiplicity in high-mass stars by detecting all spectroscopic and visual binaries in a large sample of Galactic O-type stars, and solving their orbits. Our final objective is eliminating all biases in the high-mass-star IMF created by undetected binaries.

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arXiv2014

Orbital and physical properties of the $σ$ Ori Aa,Ab,B triple system

We provide a complete characterization of the astrophysical properties of the $σ$ Ori Aa,Ab,B hierarchical triple system, and an improved set of orbital parameters for the highly eccentric $σ$ Ori Aa,Ab spectroscopic binary. We compiled a spectroscopic dataset comprising 90 high-resolution spectra covering a total time span of 1963 days. We applied the Lehman-Filhés method for a detailed orbital analysis of the radial velocity curves and performed a combined quantitative spectroscopic analysis of the {$σ$ Ori Aa,Ab,B} system by means of the stellar atmosphere code FASTWIND. We used our own plus other available information on photometry and distance to the system for measuring the radii, luminosities, and spectroscopic masses of the three components. We also inferred evolutionary masses and stellar ages using the Bayesian code BONNSAI. The orbital analysis of the new radial velocity curves led to a very accurate orbital solution of the $σ$ Ori Aa,Ab pair. We provided indirect arguments indicating that $σ$ Ori B is a fast rotating early-B dwarf. The FASTWIND+BONNSAI analysis showed that the Aa,Ab pair contains the hottest and most massive components of the triple system while $σ$ Ori B is a bit cooler and less massive. The derived stellar ages of the inner pair are intriguingly younger than the one widely accepted for the $σ$ Orionis cluster, at 3$\pm$1 Ma. The outcome of this study will be of key importance for a precise determination of the distance to the $σ$ Orionis cluster, the interpretation of the strong X-ray emission detected for $σ$ Ori Aa,Ab,B, and the investigation of the formation and evolution of multiple massive stellar systems and substellar objects.

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arXiv2014

MGB and the new Galactic O-Star Spectroscopic Survey spectral classification standard grid

In this poster we present three developments related to the Galactic O-Star Spectroscopic Survey (GOSSS). First, we are making public the first version of MGB, an IDL code that allows the user to compare oberved spectra to a grid of spectroscopic standards to measure spectral types, luminosity classes, rotation indexes, and spectral qualifiers. Second, we present the associated grid of standard stars for the spectral types O2 to O9.7, with several improvements over the original GOSSS grid of Sota et al. (2011). Third, we present a list of egregious classification errors in SIMBAD: stars that are or have been listed there as being of O type but that in reality are late-type stars.

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arXiv2014

New galactic star clusters discovered in the VVV survey. Candidates projected on the inner disk and bulge

VISTA Variables in the Vía Láctea (VVV) is one of six ESO Public Surveys using the 4 meter Visible and Infrared Survey Telescope for Astronomy (VISTA). The VVV survey covers the Milky Way bulge and an adjacent section of the disk, and one of the principal objectives is to search for new star clusters within previously unreachable obscured parts of the Galaxy. The primary motivation behind this work is to discover and analyze obscured star clusters in the direction of the inner Galactic disk and bulge. Regions of the inner disk and bulge covered by the VVV survey were visually inspected using composite JHKs color images to select new cluster candidates on the basis of apparent overdensities. DR1, DR2, CASU, and PSF photometry of 10x10 arcmin fields centered on each candidate cluster were used to construct color-magnitude and color-color diagrams. Follow-up spectroscopy of the brightest members of several cluster candidates was obtained in order to clarify their nature. We report the discovery of 58 new infrared cluster candidates. Fundamental parameters such as age, distance, and metallicity were determined for 20 of the most populous clusters.

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arXiv2014

VdBH 222: a starburst cluster in the inner Milky Way

It has been suggested that the compact open cluster VdBH 222 is a young massive distant object. We set out to characterise VdBH 222 using a comprehensive set of multi-wavelength observations. We obtained multi-band optical (UBVR) and near-infrared (JHK) photometry of the cluster field, as well as multi-object and long-slit optical spectroscopy for a large sample of stars in the field. We applied classical photometric analysis, as well as more sophisticated methods using the CHORIZOS code, to determine the reddening to the cluster. We then plotted dereddened HR diagrams and determined cluster parameters via isochrone fitting. We have identified a large population of luminous supergiants confirmed as cluster members via radial velocity measurements. We find nine red supergiants (plus one other candidate) and two yellow supergiants. We also identify a large population of OB stars. Ten of them are bright enough to be blue supergiants. The cluster lies behind 7.5 mag of extinction for the preferred value of Rv of 2.9. Isochrone fitting allows for a narrow range of ages between 12 and 16 Ma. The cluster radial velocity is compatible with distances of 6 and 10 kpc. The shorter distance is inconsistent with the age range and Galactic structure. The longer distance implies an age of 12 Ma and a location not far from the position where some Galactic models place the far end of the Galactic Bar. VdBH 222 is a young massive cluster with a likely mass greater than 20000 Msolar . Its population of massive evolved stars is comparable to that of large associations, such as Per OB1. Its location in the inner Galaxy, presumably close to the end of the Galactic bar, adds to the increasing evidence for vigorous star formation in the inner regions of the Milky Way.

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arXiv2014

Massive open star clusters using the VVV survey III: A young massive cluster at the far edge of the Galactic bar

Context: Young massive clusters are key to map the Milky Way's structure, and near-IR large area sky surveys have contributed strongly to the discovery of new obscured massive stellar clusters. Aims: We present the third article in a series of papers focused on young and massive clusters discovered in the VVV survey. This article is dedicated to the physical characterization of VVV CL086, using part of its OB-stellar population. Methods: We physically characterized the cluster using $JHK_S$ near-infrared photometry from ESO public survey VVV images, using the VVV-SkZ pipeline, and near-infrared $K$-band spectroscopy, following the methodology presented in the first article of the series. Results: Individual distances for two observed stars indicate that the cluster is located at the far edge of the Galactic bar. These stars, which are probable cluster members from the statistically field-star decontaminated CMD, have spectral types between O9 and B0V. According to our analysis, this young cluster ($1.0$ Myr $<$ age $< 5.0$ Myr) is located at a distance of $11^{+5}_{-6}$ kpc, and we estimate a lower limit for the cluster total mass of $(2.8^{+1.6}_{-1.4})\cdot10^3 {M}_{\odot}$. It is likely that the cluster contains even earlier and more massive stars.

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