From February 12 to March 16, 2026, I was hosted by Dr. Andreas Sander at the Astronomisches Rechen-Institut (ARI) of Heidelberg University, in the frame of the OCEANS project. The main goal was to get a solid working knowledge of the PoWR (Potsdam Wolf-Rayet) stellar atmosphere code and find ways to integrate it into the self-consistent wind modelling pipeline I have been developing. During the stay, I ran PoWR atmosphere models for O-type stars and managed to get the code installed on the servers back at my home institution for future use — something that should pay off considerably down the line. A particularly interesting advance was learning to implement a physically motivated initial velocity profile using HydWind, replacing the standard beta-law assumption. This brings us a step closer to linking the CMF radiative transfer framework with m-CAK theory in a more unified and consistent way. The pending objective going forward is to formally connect PoWR with LOCUS and HydWind, so that it can serve as a reliable source of self-consistent synthetic flux profiles for wind parameter determination.

The visit coincided with a trip by the KU Leuven group of Prof. Jon Sundqvist, which made for a particularly lively week — it was great to meet Nicolas Moens and Cassandra Van der Sijpt and discuss radiation-driven winds from different angles. As with the other secondments, I had the opportunity to present my work at a group meeting, which is always a useful exercise. Throughout the stay, Roel Lefever and Elissa Schösser were incredibly helpful, patiently walking me through PoWR's intricacies while also engaging in substantive discussions about the broader context of the work. Even if the collaboration was mostly oriented towards learning rather than a specific joint publication, the exchange was genuinely enriching and has opened up clear avenues for future work together.

Heidelberg was a wonderful place to be based for a month. The weather cooperated nicely and allowed for some great day trips — Speyer and Strasbourg were both memorable, with cathedrals that carry centuries of history in a way that is hard not to find impressive. German culture is quite different from Chilean, but the warmth and goodwill we encountered throughout the stay made for a very pleasant surprise. All in all, another reminder of how much these secondments offer beyond the science alone.

During my secondment at the Astronomical Institute of the Czech Academy of Sciences (ASU) in Ondřejov, I focused on scientific training and knowledge exchange through collaborations on stellar winds, stellar variability, and numerical modelling. The stay was full-time throughout the week, which allowed for continuous discussions and a productive rhythm of work in a quiet and focused research environment.

The main part of my visit was devoted to collaboration with Dieter Nickeler and Michaela Kraus. Together, we discussed the time-dependent evolution of perturbations in line-driven stellar winds within the framework of mCAK theory. In my hydrodynamic implementation, the radiative acceleration includes both continuum and line driving, with the line force computed from the Sobolev optical-depth parameter, an ionization correction, and the finite-disk correction factor, and then applied directly to the radial momentum equation. We also explored the evolution of wave-like perturbations injected near the wind base, implemented as localized sinusoidal velocity perturbations with a Gaussian radial profile, in order to study how these disturbances propagate through the outflow and affect the wind structure. These discussions were further connected to the broader question of how a structured stellar wind may interact with the circumstellar and interstellar environment.

During my stay, I also gave a seminar at ASU on 17 February entitled Planetary Tidal Disruption Events as a Driver of Extreme Stellar Variability. In this talk, I presented hydrodynamic simulations of planetary tidal disruption events and discussed how they may help explain extreme stellar variability in young stellar objects. The seminar provided a valuable opportunity to exchange ideas on transient phenomena, accretion, and the interpretation of unusual variability.

I also discussed with Julieta Sanchez her work on the theoretical modelling of non-adiabatic pulsations in B supergiants. In particular, we talked about the numerical challenges involved in computing non-adiabatic pulsation modes without relying on adiabatic solutions as the starting point. This exchange opened an interesting basis for a future collaboration, connecting her expertise in stellar pulsations with my background in numerical hydrodynamics.

Overall, the secondment was a very valuable experience, both scientifically and personally. It allowed me to strengthen collaborations, exchange ideas across different areas of stellar astrophysics, and work in an environment especially well suited for focused and sustained research.

During my secondment at the Instituto de Astrofísica de Canarias (IAC), I worked in collaboration with Sergio Simón-Díaz and members of his group. Throughout the visit, I actively participated in the group meetings, where ongoing research projects and recent results were discussed. I also delivered a short presentation about my current research on rapidly rotating massive stars and the spectral modelling with the ZPEKTR code.

During my stay, I collaborated with the group using their database to model some targets with the ZPEKTR models from my grid. These interactions led to several scientific discussions that provided valuable feedback to improve my work. In addition, I had the opportunity to test and learn how to run the SPAMMS code developed by Michel Abdul-Masih. The SPAMMS models are similar to the ones I am using with ZPEKTR, so it was particularly interesting to compare the two approaches and see how different modelling strategies handle the same type of stars.

During the visit, together with Felipe Ortiz and Felipe Figueroa, we also had the opportunity to explore several beautiful places on the island, including the Drago Milenario. We also visited the Teide Observatory, thanks to the organization of the PhD student Alba Casabuenas from the group, which provided an excellent opportunity to learn more about the observational facilities operated by the institute.

During my one-month stay at the Instituto de Astrofísica de Canarias (IAC) in Tenerife, I worked with Sergio Simón-Díaz. My project focuses on stellar and wind parameter estimation of massive stars using quantitative spectroscopy and neural networks with Monte Carlo Dropout. While the method performs well on synthetic data, extending it to observed spectra requires a substantial amount of real observational data. Sergio provided me with spectra from the IACOB database along with stellar parameter estimates produced by his group, and gave guidance on the most relevant spectral lines and parameters for this type of analysis. I spent most of my time at the IAC incorporating this data into the training pipeline and testing the resulting improvements. I also presented my work at one of the group's weekly meetings, which produced useful feedback on the project.

Outside of work, Alba Casasbuenas organized a visit to the Teide Observatory for me, Felipe Figueroa and Daniela Turis, two colleagues also completing their secondments at the IAC, which gave us the chance to see the facilities up close and appreciate the imposing presence of the volcano.

Together with these two colleagues, we also explored several parts of the island, including the streets of La Laguna, the natural trails of Anaga, a performance at the Tenerife Auditorium, the butterfly house in Icod de los Vinos, and the beaches of El Médano.

During my visit, I was hosted by Prof. Sergio Simón Díaz at the Instituto de Astrofísica de Canarias (IAC) in Tenerife, in the frame of the OCEANS project. The focus of the stay was advancing the self-consistent determination of stellar wind parameters in massive OB stars, using the LOCUS and HydWind codes within the theoretical framework of m-CAK line-driven wind theory. A good part of the time was devoted to improving and refactoring the existing codebase — translating it into a more efficient programming language to substantially speed up the computation of wind models. Using a sample of the IACOB survey database of O-type stars, theoretical wind parameters were derived following the methodology of Figueroa et al. (2026). What remains ahead is checking whether the obtained parameters reproduce the observed line profiles, which will be assessed through FASTWIND to evaluate the physical consistency of the wind solutions — a natural next step that this secondment has helped set up.

The atmosphere at the IAC was genuinely stimulating. I had the chance to attend the regular massive stars group meetings and connect with faculty members and postgraduate students working in the field — conversations that more often than not spilt beyond the meeting room and into broader discussions about hot star physics. A highlight was the visit to the Observatorio del Teide, where getting to see the various telescope facilities up close was a real treat. I also had the opportunity to present my own work at one of the group meetings, which was a valuable experience both for communicating recent progress and for getting direct feedback from the community.

On a more personal note, Tenerife turned out to be an absolutely beautiful place to spend a month. Beyond La Laguna and Santa Cruz, I got to visit Icod de los Vinos, El Médano, and Candelaria, covering quite a bit of the island. The mild climate and the genuine warmth of the people made the stay not just productive but truly enjoyable. It's the kind of place that makes it hard to leave.

At the beginning of 2026, from January 4 to February 3, I was hosted by prof. Lydia Cidale at the University of La Plata (UNLP), in the frame of the OCEANS project. The subject of our ongoing collaboration is the study of variability in B-type supergiant stars (BSGs) using public available data from large-scale photometric surveys and optical spectroscopy conducted and processed by the host group. With recently obtained observing time with the Jorge Sahade (JS) 2.15m telescope at the CASLEO observatory, we were co-planning our observations of BSGs that will be simultaneously monitored by the TESS telescope, during the period February-May 2026. The synergistic approach using ground and space-based data will help us to untangle the origin of the fine photometric variability, investigate possible connection between the stellar wind and pulsations, and to draw correlations with the parameters of these objects. Moreover, along with the PhD student M. Ruiz Diaz, time was also devoted on the analysis of multi-periodic signal and red noise of five BSGs as part of an ongoing study of their wind (Ruiz Diaz in prep.), whereas the contamination in the light curves of BSGs and the ways to addressing it using modern tools was explored along with the PhD student A. Alberici. With the latter student, we co-planned observations of binaries containing BSGs during the upcoming observing program for the purposes of modeling their orbital parameters, an objective of my next secondment trip to UNLP with OCEANS.

The period of Jan 17-22 was exceptionally intriguing, as I had the chance to attend the observing procedure led by M. Ruiz Diaz and L. Cidale, at the JS 2.15m telescope. Our trip to the province of San Juan and then, to the facilities of the CASLEO observatory at the altitude of ~2300 m, was a stimulating experience. The trip served the purposes of a BSG study of Ruiz DIaz, yet I had the chance to also obtain data of a transition-phase massive star and synchronously with the TESS satellite, as a foretaste of the upcoming program. Beyond this experience, the desolate landscape of the Argentinian mountains offered some memorable moments.

Thanks to OCEANS, distances are shortened and different cultures are met. The hot climate in the city of La Plata was challenging during January, yet it was nicely balanced by the smooth collaborative workflow.

During my stay in Valparaiso, I worked with Rodrigo Meneses at the Faculty of Engineering of the University of Valparaiso. Our main objective is obtaining precise values for the non-adiabatic pulsation modes of massive stars with highly non-adiabatic envelopes (log(L/M)>4). In order to accomplish this, we are studying the Riccati method using a shooting method independent of the adiabatic roots, which are known to be very different from the non-adiabatic ones in this case. We began deducing the perturbed equations for the radial and non-radial case assuming linear perturbations. We focused on radial pulsations. We wrote the pulsation equations as a function of the radius. We applied the Riccati method and obtained the Riccati equation as a function of this variable. This method requires the proper selection of an intermediate grid point to obtain the set of equations for the interior and external regions of the star. In order to select this value, we developed a MESA model of a massive star at the post-RSG stage with high log(L/M) and studied the asymptotic behaviour of the stellar structure coefficients involved in our set of equations, in function of the radius for this MESA model. Our next step is to discretize the problem.

Besides my work with Rodrigo, I had the chance to discuss my paper on the use of Intrinsic Mode Functions (IMF) to analyze the red noise in massive stars with Alejandra Christen at the Statistical Institute of the University of Valparaiso and I gave a seminar on this topic entitled “Filtering red noise in massive stars with IMF”. I also joined Alejandra and other professors at the “PhD Student Seminar 2025 “ devoted to the training of phD students in the presentation of their research projects.

Beyond work, I enjoyed Valparaiso’s traditional cuisine, the beach, and the breathtaking landscapes. I am deeply grateful to Rodrigo, Alejandra, Michel Cure and Catalina Arcos for their kindness, time, and the nice moments we shared. They made my stay meaningful, valuable for my work, and really enjoyable. I'm looking forward to visiting Valparaiso again!

During this stay at the Facultad de Ciencias Astronómicas y Geofísicas of the Universidad Nacional de La Plata, I worked with Jorge Combi, Federico García, and the GARX group on several projects related to high-mass X-ray binaries. It was a very productive period, with many useful discussions and significant progress on different ongoing lines of research. The visit was particularly important because it allowed us to finalise and submit the articles we had been working on throughout the past year, which have recently been accepted for publication. On a personal level, returning to La Plata always means a lot to me, since it was at this university that I studied Astronomy before moving to the Instituto de Astrofísica de Canarias to pursue my PhD. For that reason, coming back is always special, both professionally and personally. Stays like this are important not only because of the science, but also because they help maintain a close and active collaboration with a group that I value deeply, not only as colleagues but also as friends.