Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2603.13463

Exploring the surface of HD 189733 via Doppler shadow analysis of planetary transits

E. C. Gonçalves·E. Cristo·W. Dethier·N. C. Santos·S. G. Sousa·P. T. P. Viana·T. Azevedo Silva·R. Allart·V. Bourrier
View original source ↗Read source document ↗Export metadata ↓

Abstract

Transmission spectroscopy has greatly advanced the study of exoplanet atmospheres, but stellar surface heterogeneities can contaminate transit spectra. Characterising how stellar spectra vary across the stellar disc is therefore essential to disentangle stellar and planetary contributions. Transit observations can probe the local stellar spectra along the planet's transit chord. We study centre-to-limb variations of line profiles across the surface of HD 189733 using the ESPRESSO spectrograph. Building on previous work, we assess the feasibility of applying the Doppler shadow technique with ESPRESSO and compare the results with solar observations and numerical simulations. We analyse spectra obtained during two transits of HD 189733 b. Each spectrum was cross-correlated with two masks of selected Fe I lines, producing four sets of cross-correlation functions (CCFs). Using a Doppler shadow methodology, we retrieved local stellar profiles along the transit chord. These were compared with previous studies, with disc-resolved solar spectra from IAG ATLAS and with transit simulations generated using SOAPv4 and synthetic spectra from Turbospectrum based on MARCS stellar atmosphere models under LTE and NLTE conditions. For three Fe I CCF sets we detect a statistically significant increase in line depth from stellar limb to centre, consistent with Turbospectrum predictions, although solar data show a weaker gradient. For one CCF set we also find that line widths decrease from limb to centre, consistent with solar observations but not reproduced by the simulations. These results demonstrate the capability of ESPRESSO to measure centre-to-limb variations of spectral line profiles on other stars. While the local CCF profiles of HD 189733 agree with solar data, discrepancies in line widths suggest that additional physical processes are required to reproduce the observed profiles.

Explore related subjects

astro-ph.SRastro-ph.EP

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

E. C. Gonçalves, E. Cristo, W. Dethier, N. C. Santos, S. G. Sousa, P. T. P. Viana, T. Azevedo Silva, R. Allart, V. Bourrier. 2026-03-13. Exploring the surface of HD 189733 via Doppler shadow analysis of planetary transits. https://doi.org/10.1051/0004-6361%2F202557655

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Stellar characterization with photometric colors from J-PLUS and 2MASS surveys

Aims. We aim at deriving stellar atmospheric parameters based on the photometric data from the Javalambre Photometric Local Universe Survey (J-PLUS) in addition to near-infrared photometry from the Two Micron All-Sky Survey (2MASS). Methods. Our method consists of a semi-supervised machine learning approach based on the k-means method combined with a modified k-nearest neighbors algorithm. This method compares the observed photometry to a set of reference data to estimate the stellar effective temperature ($T_{\rm eff}$), surface gravity ($\log{g}$), and metallicity ([Fe/H]) of stars from J-PLUS Data Release 3 (DR3). Results. We estimated $T_{\rm eff}$, $\log{g}$, and [Fe/H], for approximately 5.6 million stars from J-PLUS DR3, along with their errors.Our results were in agreement with spectroscopic estimates from LAMOST and APOGEE.We also applied a dimension reduction method, seeking greater efficiency by reducing the computation time and minimizing the needed information for calculating the stellar parameters, resulting in a subset of 11 colors. From this approach, stellar parameters were obtained for approximately six million stars. Conclusions. Our results demonstrated the potential of using a method built from machine learning algorithms that do not require prior training. Additionally, it was shown that the proposed method allowed estimating reliable atmospheric parameters even when the available photometry did not fulfill all photometric quality criteria. We defined a neighborhood parameter, which assesses the reliability of our estimations and indicates that objects with smaller neighborhoods values have lower uncertainties.

astro-ph.SR↗
arXiv2026

Population demographics of post-interaction WDMS binaries: From common envelope evolution to stable mass transfer

Close white dwarf (WD) + main-sequence (MS) binaries are end products of mass transfer (MT) that occurred prior to WD formation, making their population demographics a powerful probe of binary evolution. Several recent works have constructed samples of WD+MS binaries with well-understood selection functions using data from wide-field surveys. These include (a) AU-scale astrometric binaries from Gaia that can be shown to contain a WD on dynamical grounds, (b) AU-scale astrometric binaries in which a hot WD is detected through a GALEX UV excess, and (c) close binaries discovered through eclipses. Together, these samples probe outcomes of both stable MT and common-envelope evolution, and interactions on both the red giant branch (RGB) and asymptotic giant branch (AGB). We forward model the three observed samples simultaneously. This approach produces robust constraints on uncertain binary evolution parameters because binaries removed from one population are predicted to appear in another. Our modeling includes a realistic initial binary population and treatments of the selection effects affecting all samples. We confirm that MT from AGB donors requires a critical accretor-to-donor mass ratio of $\sim0.4$ as found in previous work, and find that this is more stable than MT from RGB donors, for which we constrain a critical ratio $\gtrsim0.65$. A common envelope efficiency of $αλ\sim0.3$ matches the relative numbers of close and wide systems and the period distribution of close systems. Most stable MT products in the sample, including those with RGB donors, retain nonzero eccentricities ($\simeq0.1$). The model does not fully reproduce the mass distribution of main-sequence stars in post-common envelope binaries, which shows a cliff below the fully convective limit, possibly pointing to missing physics that may warrant future work.

astro-ph.SR↗
arXiv2026

A large shell around the hypergiant VY Canis Majoris

We report the detection of a remarkable shell around the red hypergiant VY CMa using data from the Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx). The shell, which in projection on the plane of the sky appears as a ring, is almost circular in appearance. It has an external diameter of $\sim14'$ to $15'$, and is seen most clearly in the SPHEREx 7827A spectro-photometric image. Filaments, radially aligned with VY CMa, are seen to cut across the shell in several places. We discuss the possibility that the shell is matter swept out from the neighboring star forming region Sh 2-310, by the wind from VY CMa. Resonant atomic scattering, a light echo, or Extended Red Emission are explored as the source of the observed SPHEREx emission. However, no interpretation is without difficulty and further observations are most desirable.

astro-ph.SR↗