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Observing stars


The first academic semester in Chile had just finished in June. It was a very long semester, with so much work, and we really needed a break. The first week of July, however, promised to be everything but a break: The stellar and galactic astronomy group led by Prof Paula Jofre obtained observing time for two projects at two different observatories during the same nights.  Dr. Claudia Aguilera, the PI of the project about observing white dwarfs with Goodman at SOAR,  was attending the Cool Stars conference in Toulouse, France, and needed an observer. The PhD student Sara Vitali, the other PI of the project about observing stars in the Sagitarius galaxy with MIKE at Magellan, had finally arrived in Chile and was very much looking forward to go to Las Campanas.

COVID however is not over and the observations had to be done remotely. This offered a unique opportunity to do it together from the Astronomy Nucleus, which also served to just catch up with in-person activities for the group, something so needed after the pandemic!

So, no break for us, but time to think of monitors and cables, good internet access, proper observing plans for collecting targets,  get food for everybody, and of course, stay awake all night long! It was super fun! We finished an exhausting week energised and happy. Happy because we enjoy being together, because we love observing the stars, and because we feel we are at the right place doing the right thing.

In the next months much data will be analysed, and interesting science will be done.

We have discovered new polluted white dwarfs. These tiny compact objects should not have metals in their atmospheres, but some still do. We believe these metals come from a disrupted rocky planet. How did that planet form and evolve? How was the system before both the star and the planet died? To answer these questions, we need to know properties such as the chemical composition of the mother star, which we can’t know from the white dwarf. But those we observed have a companion, much larger and brighter, formed out of the very same material as the white dwarf. In the future, we will take a spectrum of the companion and learn a lot about that destroyed rocky planet. Claudia has been working on this project with us as a postdoc funded by the joint committee ESO-Chile, and is now taking a new faculty position at PUC and we are thrilled that this exciting project has given us a great collaborator for many years to come.

We also observed metal-poor stars from the Sagitarius galaxy, collecting photon after photon of these very distant and faint stars during hours. There is only a handful of metal-poor stars characterised in Sagitarius, but they carry important information about the early epochs of the formation of this dwarf galaxy that is now in the process of accretion with the Milky Way. Sara is part of the Pristine collaboration, who has developed a photometric filter to capture metal-poor stars. Sara is pioneering the spectroscopic follow up campaign of the metal-poor stars in Sagitarius as part of her PhD, and we will try to analyse these tricky spectra now what we have understood how much observing time they cost and how special they are!

During the poor weather conditions we took the opportunity to follow up bright stars from the newest Gaia data released in June 2022 selected by the PhD student Danielle de Brito Silva to have a very particular kinematic behaviour. We are so curious about the nature of these stars!

Last but not least, we realised we all love ginger and cheesecake!