The X-shooter Spectral Library (XSL): Data release 2

Gonneau, A.; Lyubenova, M.; Lançon, A.; Trager, S. C.; Peletier, Reynier F.; Arentsen, Anke; Chen, Yan Ping; Coelho, P.; Dries, M.; Falcón-Barroso, J.; Prugniel, Philippe; Sánchez‐Blázquez, P.; Vazdekis, Alexandre; Verro, Kristiina

doi:10.1051/0004-6361/201936825

Cited by 87 publications

(80 citation statements)

References 71 publications

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“…We have compared the spectra of XSL-DR2 (Gonneau et al 2020) with the theoretical spectra of the Göttingen Spectral Library (Husser et al 2013), at low and intermediate resolution (R = 500 and 3000), for wavelengths extending from the near ultraviolet to the near-infrared (∼350 nm to 2.45 µm), with the main aim of determining whether a good match to both the energy distributions and the spectral features can be obtained simultaneously.…”

Section: Discussionmentioning

confidence: 99%

A comparison between X-shooter spectra and PHOENIX models across the HR-diagram

Lançon

Gonneau

Verro

et al. 2021

A&A

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Aims. The path towards robust near-infrared extensions of stellar population models involves the confrontation between empirical and synthetic stellar spectral libraries across the wavelength ranges of photospheric emission. Indeed, the theory of stellar emission enters all population synthesis models, even when this is only implicit in the association of fundamental stellar parameters with empirical spectral library stars. With its near-ultraviolet to near-infrared coverage, the X-shooter Spectral Library (XSL) allows us to examine to what extent models succeed in reproducing stellar energy distributions (SEDs) and stellar absorption line spectra simultaneously. Methods. As a first example, this study compares the stellar spectra of XSL with those of the Göttingen Spectral Library, which are based on the PHOENIX synthesis code. The comparison was carried out both separately in the three arms of the X-shooter spectrograph known as UVB, VIS and NIR, and jointly across the whole spectrum. We did not discard the continuum in these comparisons; only reddening was allowed to modify the SEDs of the models. Results. When adopting the stellar parameters published with data release DR2 of XSL, we find that the SEDs of the models are consistent with those of the data at temperatures above 5000 K. Below 5000 K, there are significant discrepancies in the SEDs. When leaving the stellar parameters free to adjust, satisfactory representations of the SEDs are obtained down to about 4000 K. However, in particular below 5000 K and in the UVB spectral range, strong local residuals associated with intermediate resolution spectral features are then seen; the necessity of a compromise between reproducing the line spectra and reproducing the SEDs leads to dispersion between the parameters favored by various spectral ranges. We describe the main trends observed and we point out localized offsets between the parameters preferred in this global fit to the SEDs and the parameters in DR2. These depend in a complex way on the position in the Hertzsprung–Russell diagram (HRD). We estimate the effect of the offsets on bolometric corrections as a function of position in the HRD and use this for a brief discussion of their impact on the studies of stellar populations. A review of the literature shows that comparable discrepancies are mentioned in studies using other theoretical and empirical libraries.

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Section: Discussionmentioning

confidence: 99%

A comparison between X-shooter spectra and PHOENIX models across the HR-diagram

Lançon

Gonneau

Verro

et al. 2021

A&A

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“…The model was obtained from the Phoenix stellar spectral atlas (Allard & Hauschildt 1995), and corresponds to a star with solar metallicity, log g = 0, and a temperature of 2000 K, which is the lowest available temperature in their grid. The observed spectrum (HV 12149) was obtained from the DR2 of the X-shooter Spectral Library (XSL; Gonneau et al 2020), and corresponds to a very luminous asymptotic-giant-branch (AGB) star, classified as M8.5 II (González-Fernández et al 2015).…”

Section: Near-infraredmentioning

confidence: 99%

The luminous red nova AT 2018bwo in NGC 45 and its binary yellow supergiant progenitor

Blagorodnova

Klencki

Pejcha

et al. 2021

A&A

127

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Luminous Red Novae (LRNe) are astrophysical transients associated with the partial ejection of a binary system's common envelope (CE) shortly before its merger. Here we present the results of our photometric and spectroscopic follow-up campaign of AT 2018bwo (DLT 18x), a LRN discovered in NGC 45, and investigate its progenitor system using binary stellar-evolution models. The transient reached a peak magnitude of M r = −10.97 ± 0.11 and maintained this brightness during its optical plateau of t p = 41 ± 5 days. During this phase, it showed a rather stable photospheric temperature of ∼3300 K and a luminosity of ∼ 10 40 erg s −1 . Although the luminosity and duration of AT 2018bwo is comparable to the LRNe V838 Mon and M31-2015LRN, its photosphere at early times appears larger and cooler, likely due to an extended mass-loss episode before the merger. Towards the end of the plateau, optical spectra showed a reddened continuum with strong molecular absorption bands. The IR spectrum at +103 days after discovery was that of a M8.5 II type star, analogous to an extended AGB star. The reprocessed emission by the cooling dust was also detected in the mid-infrared bands ∼1.5 years after the outburst. Archival Spitzer and Hubble Space Telescope data taken 10 − 14 years before the transient event suggest a progenitor star with T prog ∼ 6500 K, R prog ∼ 100 R and L prog = 2 × 10 4 L , and an upper limit for optically thin warm (1000 K) dust mass of M d < 10 −6 M . Using stellar binary-evolution models, we determined the properties of binary systems consistent with the progenitor parameter space. For AT 2018bwo, we infer a primary mass of 12−16 M , which is 9−45% larger than the ∼11 M obtained using single-star evolution models. The system, consistent with a yellow-supergiant primary, was likely in a stable masstransfer regime with −2.4 ≤ log(Ṁ/M yr −1 ) ≤ −1.2 a decade before the main instability occurred. During the dynamical merger, the system would have ejected 0.15−0.5 M with a velocity of ∼500 km s −1 .

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“…In the last few decades, this issue has been mitigated with the advent of a large number of intermediate-resolution stellar libraries and stellar population models (see e.g. Bruzual & Charlot 2003;Valdes et al 2004;Coelho et al 2005;Sánchez-Blázquez et al 2006;Prugniel et al 2007;Vazdekis et al 2010;Gonneau et al 2020;Maraston et al 2020) that have helped to greatly reduce the so-called effect of template mismatch (e.g. Falcón- Barroso et al 2003).…”

Section: Introductionmentioning

confidence: 99%

BAYES-LOSVD: A Bayesian framework for non-parametric extraction of the line-of-sight velocity distribution of galaxies

Falcón-Barroso

Martig

2021

A&A

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We introduce BAYES-LOSVD, a novel implementation of the non-parametric extraction of line-of-sight velocity distributions (LOSVDs) in galaxies. We employed Bayesian inference to obtain robust LOSVDs and associated uncertainties. Our method relies on a principal component analysis to reduce the dimensionality on the set of templates required for the extraction and thus increase the performance of the code. In addition, we implemented several options to regularise the output solutions. Our tests, conducted on mock spectra, confirm the ability of our approach to model a wide range of LOSVD shapes, overcoming limitations of the most widely used parametric methods (e.g., Gauss-Hermite expansion). We present examples of LOSVD extractions for real galaxies with known peculiar LOSVD shapes, including NGC 4371, IC 0719, and NGC 4550, using MUSE and SAURON integral-field unit (IFU) data. Our implementation can also handle data from other popular IFU surveys (e.g., ATLAS3D, CALIFA, MaNGA, SAMI).

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The X-shooter Spectral Library (XSL): Data release 2

Cited by 87 publications

References 71 publications

A comparison between X-shooter spectra and PHOENIX models across the HR-diagram

A comparison between X-shooter spectra and PHOENIX models across the HR-diagram

The luminous red nova AT 2018bwo in NGC 45 and its binary yellow supergiant progenitor

BAYES-LOSVD: A Bayesian framework for non-parametric extraction of the line-of-sight velocity distribution of galaxies

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