@article{21760,
  abstract     = {3I/ATLAS is the third interstellar object discovered to date, following 1I/‘Oumuamua and 2I/Borisov. Its unusually high excess velocity and active cometary nature make it a key probe of the Galactic population of icy planetesimals. Understanding its origin requires its past trajectory through the Galaxy to be traced and the possible role of stellar encounters to be assessed, both as a potential origin and a perturber to its orbit. We integrated the orbit of 3I/ATLAS backward in time for 10 Myr, together with a sample of Gaia DR3 stars with high-quality astrometry and radial velocities, to identify close passages within 2 pc. We identify 93 nominal encounters, 62 of which are significant at the 2σ level. However, none of these encounters produced any meaningful perturbation. The strongest perturber Gaia DR3 6863591389529611264 at 0.30 pc and with a relative velocity of 35 km s−1, imparted only a velocity change of ∣Δv∣  ≃  5  ×  10−4 km s−1 to the orbit of 3I/ATLAS. Our results indicate that no stellar flybys within the past 10 Myr and 500 pc contained in Gaia DR3 can account for the present trajectory of 3I/ATLAS or be associated with its origin. We further show that 3I/ATLAS is kinematically consistent with a thin-disk population, despite its large peculiar velocity.},
  author       = {Pérez-Couto, X. and Torres Rodriguez, Santiago and Villaver, E. and Mustill, A. J. and Manteiga, M.},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{3I/ATLAS: In search of the witnesses to its voyage}},
  doi          = {10.3847/1538-4357/ae56ff},
  volume       = {1001},
  year         = {2026},
}

@article{20930,
  abstract     = {Context. Beta Pictoris is an A-type star that hosts a complex planetary system with two massive gas giants and a prominent debris disc. Variable absorption lines in its stellar spectrum have been interpreted as signatures of exocomets – comet-like bodies transiting the star. Stellar flybys can gravitationally perturb objects in the outer comet reservoir, altering their orbits and potentially injecting them into the inner system, thereby triggering exocomet showers.
Aims. We assessed the contribution of stellar flybys to the observed exocomet activity by reconstructing the stellar encounter history of β Pictoris in the past and future.
Methods. We used Gaia DR3 data, supplemented with radial velocities from complementary spectroscopic surveys, to compile a catalogue of stars currently within 80 pc of β Pictoris. Their orbits were integrated backwards and forwards in time in an axisymmetric Galactic potential (via the GALA package) to identify encounters within 2 pc of the system.
Results. We identified 99 416 stars currently within 80 pc of β Pictoris with resolved kinematics. Among these, 49 stars (including the eight components of five binaries) encounter β Pictoris within 2 pc between –1.5 Myr and +2 Myr. For four of the binaries, the centre-of-mass trajectories also pass within 2 pc. We estimated the sample to be more than 60% complete within 0.5 Myr of today.
Conclusions. Despite β Pictoris being the eponym of its famous moving group, none of the identified encounters involved its moving group members; all are unrelated field stars. We found no encounter capable of shaping the observed disc structures, although stellar flybys may contribute to the long-term evolution of an Oort Cloud-like structure. Our catalogue constitutes the most complete reconstruction of the β Pictoris encounter history to date and provides a robust foundation for future dynamical simulations.},
  author       = {Gragera-Más, J. L. and Torres Rodriguez, Santiago and Mustill, A. J. and Villaver, E.},
  issn         = {1432-0746},
  journal      = {Astronomy & Astrophysics},
  publisher    = {EDP Sciences},
  title        = {{A kinematic history of stellar encounters with Beta Pictoris}},
  doi          = {10.1051/0004-6361/202555940},
  volume       = {704},
  year         = {2025},
}

@article{18984,
  abstract     = {Although planets have been found orbiting binary systems, whether they can survive binary interactions is debated. While the tightest-orbit binaries should host the most dynamically stable and long-lived circumbinary planetary systems, they are also the systems that are expected to experience mass transfer, common envelope evolution, or stellar mergers. In this study, we explore the effect of stable non-conservative mass transfer on the dynamical evolution of circumbinary planets. We present a new script that seamlessly integrates binary evolution data from the 1D binary stellar evolution code MESA into the N-body simulation code REBOUND. This integration framework enables a comprehensive examination of the dynamical evolution of circumbinary planets orbiting mass-transferring binaries, while simultaneously accounting for the detailed stellar structure evolution. In addition, we introduce a recalibration method to mitigate numerical errors from updates of binary properties during the system's dynamical evolution. We construct a reference binary model in which a 2.21M⊙ star loses its hydrogen-rich envelope through non-conservative mass transfer to the 1.76M⊙ companion star, creating a 0.38M⊙ subdwarf. We find the tightest stable orbital separation for circumbinary planets to be ≃2.5 times the binary separation after mass transfer. Accounting for tides by using the interior stellar structure, we find that tidal effects become apparent after the rapid mass transfer phase and start to fade away during the latter stage of the slow mass transfer phase. Our research provides a new framework for exploring circumbinary planet dynamics in interacting binary systems.},
  author       = {Xing, Zepei and Torres Rodriguez, Santiago and Götberg, Ylva Louise Linsdotter and Trani, Alessandro A. and Korol, Valeriya and Cuadra, Jorge},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  number       = {1},
  pages        = {285--292},
  publisher    = {Oxford University Press},
  title        = {{Combining REBOUND and MESA: Dynamical evolution of planets orbiting interacting binaries}},
  doi          = {10.1093/mnras/stae2820},
  volume       = {537},
  year         = {2025},
}

@article{18306,
  abstract     = {Neutral sodium (Na i) is an alkali metal with a favorable absorption cross section such that tenuous gases are easily illuminated at select transiting exoplanet systems. We examine both the time-averaged and time-series alkali spectral flux individually, over 4 nights at a hot Saturn system on a ∼2.8 day orbit about a Sun-like star WASP-49 A. Very Large Telescope/ESPRESSO observations are analyzed, providing new constraints. We recover the previously confirmed residual sodium flux uniquely when averaged, whereas night-to-night Na i varies by more than an order of magnitude. On HARPS/3.6 m Epoch II, we report a Doppler redshift at vΓ,NaD = + 9.7 ± 1.6 km s−1 with respect to the planet's rest frame. Upon examining the lightcurves, we confirm night-to-night variability, on the order of ∼1%–4% in NaD, rarely coinciding with exoplanet transit, not readily explained by stellar activity, starspots, tellurics, or the interstellar medium. Coincident with the ∼+10 km s−1 Doppler redshift, we detect a transient sodium absorption event dFNaD/F⋆ = 3.6% ± 1% at a relative difference of ΔFNaD(t) ∼ 4.4% ± 1%, lasting ΔtNaD ≳ 40 minutes. Since exoplanetary alkali signatures are blueshifted due to the natural vector of radiation pressure, estimated here at roughly ∼−5.7 km s−1, the radial velocity is rather at +15.4 km s−1, far larger than any known exoplanet system. Given that the redshift magnitude vΓ is in between the Roche limit and dynamically stable satellite orbits, the transient sodium may be a putative indication of a natural satellite orbiting WASP-49 A b.},
  author       = {Oza, Apurva V. and Seidel, Julia V. and Hoeijmakers, H. Jens and Unni, Athira and Kesseli, Aurora Y. and Schmidt, Carl A. and Sivarani, Thirupathi and Bello-Arufe, Aaron and Gebek, Andrea and Meyer Zu Westram, Moritz and Sousa, Sérgio G. and Lopes, Rosaly M.C. and Hu, Renyu and De Kleer, Katherine and Fisher, Chloe and Charnoz, Sébastien and Baker, Ashley D. and Halverson, Samuel P. and Schneider, Nick M. and Psaridi, Angelica and Wyttenbach, Aurélien and Torres Rodriguez, Santiago and Bhatnagar, Ishita and Johnson, Robert E.},
  issn         = {2041-8213},
  journal      = {Astrophysical Journal Letters},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{Redshifted sodium transient near exoplanet transit}},
  doi          = {10.3847/2041-8213/ad6b29},
  volume       = {973},
  year         = {2024},
}