Papers by Ignacio Negueruela
and other research outputs The identification of the optical/IR counterpart of the 15.8-s transie... more and other research outputs The identification of the optical/IR counterpart of the 15.8-s transient X-ray pulsar XTE J1946+274 Journal Article
Astronomy & Astrophysics, 2018
Context.The IACOB and OWN surveys are two ambitious, complementary observational projects which h... more Context.The IACOB and OWN surveys are two ambitious, complementary observational projects which have made available a large multi-epoch spectroscopic database of optical high resolution spectra of Galactic massive O-type stars.Aims.Our aim is to study the full sample of (more than 350) O stars surveyed by the IACOB and OWN projects. As a first step towards this aim, we have performed the quantitative spectroscopic analysis of a subsample of 128 stars included in the modern grid of O-type standards for spectral classification. The sample comprises stars with spectral types in the range O3–O9.7 and covers all luminosity classes.Methods.We used the semi-automatizedIACOB-BROADandIACOB-GBAT/FASTWINDtools to determine the complete set of spectroscopic parameters that can be obtained from the optical spectrum of O-type stars. A quality flag was assigned to the outcome of theIACOB-GBAT/FASTWINDanalysis for each star, based on a visual evaluation of how the synthetic spectrum of the best fit...
Monthly Notices of the Royal Astronomical Society, 2017
NGC 6067 is a young open cluster hosting the largest population of evolved stars among known Milk... more 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 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 ± 0.12 kpc, an age of 90 ± 20 Ma and a tidal radius of 14.8 +6.8 −3.2 arcmin. We estimate an initial mass above 5700 M , for a present-day evolved population of two Cepheids, two A supergiants and 12 red giants with masses ≈6 M. 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 ± 0.05, and a homogeneous 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 overabundance of Ba is found, supporting the enhanced s-process. The ratio of yellow to red giants is much smaller than 1, 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.
Astronomy & Astrophysics, 2014
The Gaia-ESO Survey is a large public spectroscopic survey that aims to derive radial velocities ... more The Gaia-ESO Survey is a large public spectroscopic survey that aims to derive radial velocities and fundamental parameters of about 10 5 Milky Way stars in the field and in clusters. Observations are carried out with the multi-object optical spectrograph FLAMES, using simultaneously the medium-resolution (R ∼ 20 000) GIRAFFE spectrograph and the high-resolution (R ∼ 47 000) UVES spectrograph. In this paper we describe the methods and the software used for the data reduction, the derivation of the radial velocities, and the quality control of the FLAMES-UVES spectra. Data reduction has been performed using a workflow specifically developed for this project. This workflow runs the ESO public pipeline optimizing the data reduction for the Gaia-ESO Survey, automatically performs sky subtraction, barycentric correction and normalisation, and calculates radial velocities and a first guess of the rotational velocities. The quality control is performed using the output parameters from the ESO pipeline, by a visual inspection of the spectra and by the analysis of the signal-to-noise ratio of the spectra. Using the observations of the first 18 months, specifically targets observed multiple times at different epochs, stars observed with both GIRAFFE and UVES, and observations of radial velocity standards, we estimated the precision and the accuracy of the radial velocities. The statistical error on the radial velocities is σ ∼ 0.4 km s −1 and is mainly due to uncertainties in the zero point of the wavelength calibration. However, we found a systematic bias with respect to the GIRAFFE spectra (∼0.9 km s −1) and to the radial velocities of the standard stars (∼0.5 km s −1) retrieved from the literature. This bias will be corrected in the future data releases, when a common zero point for all the setups and instruments used for the survey is be established.
Research Notes of the AAS, 2020
Monthly Notices of the Royal Astronomical Society, 2018
As part of a wider investigation of evolved massive stars in Galactic open clusters, we have spec... more As part of a wider investigation of evolved massive stars in Galactic open clusters, we have spectroscopically identified three candidate classical Cepheids in the little-studied clusters Berkeley 51, Berkeley 55, and NGC 6603. Using new multi-epoch photometry, we confirm that Be 51 #162 and Be 55 #107 are bona fide Cepheids, with pulsation periods of 9.83 ± 0.01 d and 5.850 ± 0.005 d respectively, while NGC 6603 star W2249 does not show significant photometric variability. Using the period-luminosity relationship for Cepheid variables, we determine a distance to Be 51 of 5.3 +1.0 −0.8 kpc and an age of 44 +9 −8 Myr, placing it in a sparsely attested region of the Perseus arm. For Be 55, we find a distance of 2.2 ± 0.3 kpc and age of 63 +12 −11 Myr, locating the cluster in the Local arm. Taken together with our recent discovery of a long-period Cepheid in the starburst cluster VdBH222, these represent an important increase in the number of young, massive Cepheids known in Galactic open clusters. We also consider new Gaia (data release 2) parallaxes and proper motions for members of Be 51 and Be 55; the uncertainties on the parallaxes do not allow us to refine our distance estimates to these clusters, but the well-constrained proper motion measurements furnish further confirmation of cluster membership. However, future final Gaia parallaxes for such objects should provide valuable independent distance measurements, improving the calibration of the period-luminosity relationship, with implications for the distance ladder out to cosmological scales.
Astronomy & Astrophysics, 2018
Context. NGC 3105 is a young open cluster hosting blue, yellow, and red supergiants. This rare co... more Context. NGC 3105 is a young open cluster hosting blue, yellow, and red supergiants. This rare combination makes it an excellent laboratory for constraining evolutionary models of high-mass stars. It has been poorly studied, and the fundamental parameters such as its age or distance are not well defined.Aims. We intend to characterise in an accurate way the cluster and its evolved stars, for which we derive for the first time atmospheric parameters and chemical abundances.Methods. We performed a complete analysis combiningUBVRphotometry with spectroscopy. We obtained spectra with classification purposes for 14 blue stars and high-resolution spectroscopy for an in-depth analysis of the six other evolved stars.Results. We identify 126 B-type likely members within a radius of 2.7 ± 0.6 arcmin, which implies an initial mass,Mcl≈ 4100M⊙. We find a distance of 7.2 ± 0.7 kpc for NGC 3105, placing it atRGC= 10.0 ± 1.2 kpc. Isochrone fitting supports an age of 28 ± 6 Ma, implying masses arou...
Monthly Notices of the Royal Astronomical Society, 2018
We present a self-consistent study of cool supergiants (CSGs) belonging to the Magellanic clouds.... more We present a self-consistent study of cool supergiants (CSGs) belonging to the Magellanic clouds. We calculated stellar atmospheric parameters using LTE KURUCZ and MARCS atmospheric models for more than 400 individual targets by fitting a careful selection of weak metallic lines. We explore the existence of a T eff scale and its implications in two different metallicity environments (each Magellanic cloud). Critical and in-depth tests have been performed to assess the reliability of our stellar parameters (i.e. internal error budget, NLTE systematics). In addition, several Monte Carlo tests have been carried out to infer the significance of the T eff scale found. Our findings point towards a unique T eff scale that seems to be independent of the environment.
Proceedings of the International Astronomical Union, 2015
Very recently, a number of obscured massive open clusters have been identified in the Milky Way. ... more Very recently, a number of obscured massive open clusters have been identified in the Milky Way. A very significant fraction of them lie either close to the base of the Scutum Arm or towards Galactic longitude of 350°. We are studying these clusters and their neighbourhoods, finding very good evidence for a major starburst region close to the near tip of the Galactic Long Bar.
EAS Publications Series, 2013
We are using a sample of more than 50 standard very late-type stars, taken from Isaac Newton Tele... more We are using a sample of more than 50 standard very late-type stars, taken from Isaac Newton Telescope at R ~ 9000 in the 8100–9100 A range, in order to develop criteria for spectral and luminosity classification of very late-type stars in the Gaia region. In this article, we brief in a few pages the main challenges on this issue, as well as the literature about it, and we present some preliminary results.
The authors present X-ray observations of the Be/X-ray transient 4U 0115+63 taken with the OSSE i... more The authors present X-ray observations of the Be/X-ray transient 4U 0115+63 taken with the OSSE instrument on board of the Compton Gamma Ray Observatory which show the occurrence of a flare around May 1994. They have studied the evolution of the continuum spectrum and searched for possible changes in the pulse period during the flaring event. They also present long-term
The Astrophysical Journal, 2006
XTE J1739-302 is a transient X-ray source with unusually short outbursts, lasting on the order of... more XTE J1739-302 is a transient X-ray source with unusually short outbursts, lasting on the order of hours. Here we give a summary of X-ray observations we have made of this object in outburst with the Rossi X-ray Timing Explorer (RXTE) and at a low level of activity with the Chandra X-ray Observatory, as well as observations made by other groups. Visible and infrared spectroscopy of the mass donor of XTE J1739-302 are presented in a companion paper. The Xray spectrum is hard both at low levels and in outburst, but somewhat variable, and there is strong variability in the absorption column from one outburst to another. Although no pulsation has been observed, the outburst data from multiple observatories show a characteristic timescale for variability on the order of 1500-2000 s. The Chandra localization (right ascension 17 h 39 m 11.58 s , declination −30 • 20 ′ 37.6 ′′ , J2000) shows that despite being located less than 2 • from the Galactic Center and highly absorbed, XTE J1739-302 is actually a foreground object with a bright optical counterpart. The combination of a very short outburst timescale and a supergiant companion is shared with several other recently-discovered systems, forming a class we designate as Supergiant Fast X-ray Transients (SFXTs). Three persistently bright X-ray binaries with similar supergiant companions have also produced extremely short, bright outbursts: Cyg X-1, Vela X-1, and 1E 1145.1-6141.
Monthly Notices of the Royal Astronomical Society, 2008
The spectral distributions of Be/X-ray binaries in the Large Magellanic Cloud and Galaxy have bee... more The spectral distributions of Be/X-ray binaries in the Large Magellanic Cloud and Galaxy have been shown to differ significantly from the distribution of isolated Be stars in the Galaxy. Population synthesis models can explain this difference in spectral distributions through substantial angular momentum loss from the binary system. In this work, we explore the spectral distribution of Be/X-ray binaries in the Small Magellanic Cloud (SMC) using high signalto-noise ratio spectroscopy of a sample of 37 optical counterparts to known X-ray pulsars. Our results show that the spectral distribution of Be/X-ray binaries in the SMC is consistent with that of the Galaxy, despite the lower metallicity environment of the SMC. This may indicate that, although the metallicity of the SMC is conducive to the formation of a large number of high-mass X-ray binaries, the spectral distribution of these systems is likely to be most strongly influenced by angular momentum losses during binary evolution, which are not particularly dependent on the local metallicity.
Monthly Notices of the Royal Astronomical Society, 2003
The observed characteristics of the nebulosity surrounding the Small Magellanic Cloud (SMC) high-... more The observed characteristics of the nebulosity surrounding the Small Magellanic Cloud (SMC) high-mass X-ray binary XTE J0111.2−7317 are examined in the context of three possible nebular types: supernova remnant, bowshock and H II region. Observational evidence is presented which appears to support the interpretation that the nebulosity surrounding XTE J0111.2-7317 is an H II region. The source therefore appears to be a normal SMC Be X-ray binary (BeXRB) embedded in a locally enhanced interstellar medium which it has photoionized to create an H II region. This is supported by observations of the X-ray outburst seen with the Burst and Transient Source Experiment (BATSE) and Rossi X-ray Timing Explorer (RXTE) in 1998-1999. It exhibited characteristics typical of a giant or type II outburst in a BeXRB including large spin-up rates, L X 10 38 erg cm −2 s −1 , and a correlation between spin-up rate and pulsed flux. However, the temporal profile of the outburst was unusual, consisting of two similar intensity peaks, with the first peak of shorter duration than the second.
Astronomy and Astrophysics, 2002
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Astronomy & Astrophysics, 2002
We carried out optical observations of the field of the X-ray pulsator RX J0806.3+1527. A blue V ... more We carried out optical observations of the field of the X-ray pulsator RX J0806.3+1527. A blue V = 21.1 star was found to be the only object consistent with the X-ray position. VLT FORS spectra revealed a blue continuum with no intrinsic absorption lines. Broad (v ∼ 1500 km s −1), low equivalent width (∼-1 ÷-6Å) emission lines from the HeII Pickering series were clearly detected. B, V and R time-resolved photometry revealed the presence of ∼15% pulsations at the ∼321 s X-ray period, confirming the identification. These findings, together with the period stability and absence of any additional modulation in the 1 min−5 hr period range, argue in favour of the orbital interpretation of the 321 s pulsations. The most likely scenario is thus that RX J0806.3+1527 is a double degenerate system of the AM CVn class. This would make RX J0806.3+1527 the shortest orbital period binary currently known and one of the best candidates for gravitational wave detection.
Astronomy and Astrophysics, 2002
Aims. Pointed observations with XMM-Newton provide the basis for creating catalogues of X-ray sou... more Aims. Pointed observations with XMM-Newton provide the basis for creating catalogues of X-ray sources detected serendipitously in each field. This paper describes the creation and characteristics of the 2XMM catalogue. Methods. The 2XMM catalogue has been compiled from a new processing of the XMM-Newton EPIC camera data. The main features of the processing pipeline are described in detail. Results. The catalogue, the largest ever made at X-ray wavelengths, contains 246 897 detections drawn from 3491 public XMM-Newton observations over a 7-year interval, which relate to 191 870 unique sources. The catalogue fields cover a sky area of more than 500 deg 2. The non-overlapping sky area is ∼360 deg 2 (∼1% of the sky) as many regions of the sky are observed more than once by XMM-Newton. The catalogue probes a large sky area at the flux limit where the bulk of the objects that contribute to the X-ray background lie and provides a major resource for generating large, well-defined X-ray selected source samples, studying the X-ray source population and identifying rare object types. The main characteristics of the catalogue are presented, including its photometric and astrometric properties
Astronomy & Astrophysics, 2012
Context. Recent studies have shown that the area around the massive, obscured cluster RSGC3 may h... more Context. Recent studies have shown that the area around the massive, obscured cluster RSGC3 may harbour several clusters of red supergiants. Aims. We analyse a clump of photometrically selected red supergiant candidates 20 south of RSGC3 in order to confirm the existence of another of these clusters. Methods. Using medium-resolution infrared spectroscopy around 2.27 μm, we derived spectral types and velocities along the line of sight for the selected candidates, confirming their nature and possible association. Results. We find a compact clump of eight red supergiants and four other candidates at some distance, all of them spectroscopically confirmed red supergiants. The majority of these objects must form an open cluster, which we name Alicante 10. Because of the high reddening and strong field contamination, the cluster sequence is not clearly seen in 2MASS or GPS-UKIDSS. From the observed sources, we derive E(J − K S) = 2.6 and d ≈ 6 kpc. Conclusions. Although the cluster is smaller than RSGC3, it has an initial mass in excess of 10 000 M , and it seems to be part of the RSGC3 complex. With the new members this association already has 35 spectroscopically confirmed red supergiants, confirming its place as one of the most active sites of recent stellar formation in the Galaxy.
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Papers by Ignacio Negueruela