Past Pizza Lunches

Number of entries: 155

03
May 2019

Outflows from young stars


Start: 12:15h
Speaker: Manuel Fernández-López (Instituto Argentino de Radioastronomía)
Place: Sala Alberto Lobo (ICE building, Campus UAB)

Outflows are ubiquitous in star-forming regions. They are associated with accretion events and trace the rich chemistry produced by shocks and heating surrounding protostars. Protostellar outflows yield a turbulent feedback that can be of relevance in the Galactic energy budget. We carried out morphological…
Start: 12:15h
Speaker: Manuel Fernández-López (Instituto Argentino de Radioastronomía)
Place: Sala Alberto Lobo (ICE building, Campus UAB)

Outflows are ubiquitous in star-forming regions. They are associated with accretion events and trace the rich chemistry produced by shocks and heating surrounding protostars. Protostellar outflows yield a turbulent feedback that can be of relevance in the Galactic energy budget. We carried out morphological studies toward outflows in low and high-mass star-forming regions. All of these works are part of an effort to derive information on the accretion, feedback, ejection mechanisms, and the dynamics of the launching protostars in nearby environments using detailed interferometric observations. We will make a brief review on the subject and show some of our most interesting and recent results. 
26
April 2019

The discovery of a comet fragment inside a meteorite provides clues about water delivery


Start: 12:15h
Speaker: Josep M. Trigo-Rodríguez
Place: Sala Alberto Lobo

In our Meteorite Microscopy Clean Room we have discovered the first cometary fragment found inside a meteorite, precisely in the CR2 carbonaceous chondrite LaPaz 02342. This finding demonstrates that the class of meteorites known as carbonaceous chondrites contains clues to the composition of more fragile…
Start: 12:15h
Speaker: Josep M. Trigo-Rodríguez
Place: Sala Alberto Lobo

In our Meteorite Microscopy Clean Room we have discovered the first cometary fragment found inside a meteorite, precisely in the CR2 carbonaceous chondrite LaPaz 02342. This finding demonstrates that the class of meteorites known as carbonaceous chondrites contains clues to the composition of more fragile objects that formed in regions distant from the Sun, about 4,560 million years ago. The chemical and isotopic evidence suggests that the clast was probably subjected to cosmic ray irradiation, and accreted into the asteroid preserving an ice mantle, so it demonstrates wet accretion. The results are published in the journal Nature Astronomy: http://dx.doi.org/10.1038/S41550-019-0737-8
12
April 2019

EoS in neutron stars - recent results on cooling and tidal deformabilities


Start: 12:15h
Speaker: Laura Tolos
Place: Sala Alberto Lobo

We present our recent results on cooling and tidal deformabilities of neutron stars using a recently developed hadronic equation-of-state (EoS) for the neutron star interior. The hadronic EoS is obtained from a phenomenological approach that reproduces the properties of nuclear matter and finite nuclei,…
Start: 12:15h
Speaker: Laura Tolos
Place: Sala Alberto Lobo


We present our recent results on cooling and tidal deformabilities of neutron stars using a recently developed hadronic equation-of-state (EoS) for the neutron star interior. The hadronic EoS is obtained from a phenomenological approach that reproduces the properties of nuclear matter and finite nuclei, while fulfilling the restrictions on high-density matter deduced from heavy-ion collisions, measurements of massive 2Msun neutron stars, and neutron star radii below 13 km. On the one hand, we perform cooling simulations and find that the cooling observations are compatible with a soft EoS close to saturation density, hence it generates small neutron star radii. However, our model favors large stellar masses, above 1.8Msun, to explain the colder isolated neutron stars that have been observed, even if nucleon pairing is present. On the other hand, we analyze the possibility of a phase transition leading to twin stars fulfilling the information following the gravitational-wave event GW170817. We find that the data from GW170817 could be interpreted as produced by the merger of a binary system of hybrid stars, or of a hybrid star with a neutron star. Indeed, our results seem to favor the presence of a hybrid star in the inspiral phase if future gravitational-wave detections measure chirp masses smaller than 1.2Msun and tidal deformabilities of 1.4 Msun less than 400.
 
05
April 2019

White dwarfs in the Gaia era


Start: 12:15h
Speaker: Alberto Rebassa Mansergas (Universitat Politècnica de Catalunya)
Place: Sala Alberto Lobo

The vast majority of stars will end, or have ended, their lives in the form of a white dwarf. These objects have the average size of the Earth, however they can be more massive than the Sun. This makes white dwarfs to be extremely dense and to have exceptional properties. In this talk we will study the…
Start: 12:15h
Speaker: Alberto Rebassa Mansergas (Universitat Politècnica de Catalunya)
Place: Sala Alberto Lobo

The vast majority of stars will end, or have ended, their lives in the form of a white dwarf. These objects have the average size of the Earth, however they can be more massive than the Sun. This makes white dwarfs to be extremely dense and to have exceptional properties. In this talk we will study the physical characteristics of these exotic objects and we will see how the data provided by the Gaia satellite is helping us to significantly increase our understanding of white dwarfs.
 
22
March 2019

Does the size matter?: The case of HH80-81 disk


Start: 12:15h
Speaker: Nacho Añez López (Institut de Ciències de l'Espai (CSIC-IEEC))
Place: Sala Alberto Lobo (ICE building, Campus UAB)

Understanding how high-mass stars form and evolve is one of the hot topics in astrophysics, due to the high impact that these objects have in the life of a galaxy. It is well known that low-mass stars are formed through an accretion disk which transport gas and dust from the envelope of the system…
Start: 12:15h
Speaker: Nacho Añez López (Institut de Ciències de l'Espai (CSIC-IEEC))
Place: Sala Alberto Lobo (ICE building, Campus UAB)

Understanding how high-mass stars form and evolve is one of the hot topics in astrophysics, due to the high impact that these objects have in the life of a galaxy. It is well known that low-mass stars are formed through an accretion disk which transport gas and dust from the envelope of the system to the protostar. HH80-81 seems to be very similar to the disk-jet systems found in low- and intermediate-mass protostars presenting a highly collimated and well-defined jet, a compact dust disk clearly perpendicular to the jet and possible rotating motions of the molecular gas around the massive protostar. The linear polarization of the dust emission is detected almost all along the disk, and its properties suggest that dust polarization is produced mainly by selfscattering. Polarization characteristic suggest that dust settling has not occurred yet with a maximum dust grain size between 50 and 500 microns. We applied disk models that have been successfully explained disks around low-mass prototstars as those developed by D'Alessio et al. (2001, 2006). These models satisfactorily explain the ALMA image at 1.14 mm with a massive central object (~20 Msun) and a massive disk (~7 Msun). The models shows that in first approximation the high-mass star formation process seems to be a scale up version of the low-mass star-formation scenario.
15
March 2019

Chemical Complexity in Space and Earth Induced by Solid State Surfaces. Investigations by means of Quantum Chemistry


Start: 12:15h
Speaker: Albert Rimola (Chemistry Department, UAB)
Place: Sala Alberto Lobo

Our universe is molecularly rich [1-3], comprising from the most essential molecules (such as H2, H2O and NH3), passing through complex organic molecules (namely, COMs, molecules between 6 – 13 atoms where at least one is C rendering its organic character), reaching more evolved complex organic compounds,…
Start: 12:15h
Speaker: Albert Rimola (Chemistry Department, UAB)
Place: Sala Alberto Lobo

Our universe is molecularly rich [1-3], comprising from the most essential molecules (such as H2, H2O and NH3), passing through complex organic molecules (namely, COMs, molecules between 6 – 13 atoms where at least one is C rendering its organic character), reaching more evolved complex organic compounds, in which in some cases are of biological relevance, such as amino acids, nucleobases and sugars. Formation of early Solar-type systems involves successive steps, mainly represented by the prestellar, protostellar, protoplanetary disk, and planetesimal and planet formation phases. This evolution goes hand-in-hand with an increase of the molecular complexity, in which more complex molecules form at each step [4]. The usual interpretation of the complex scenario of molecular reactions occurring in space is through a cascade of gas-phase reactions [5]. Nevertheless, it has since long recognized, with kinetic models, that gas-phase process alone cannot justify the abundance in the universe of even the simplest molecule, H2, but resort to reactions occurring on cosmic grain surfaces is mandatory to reconcile prediction with observation [6]. Accordingly, a key role of the chemical complexity is also played by cosmic solid state materials, as their surfaces provide catalytic sites that favor pivotal chemical reactions. A possible fate of the cosmic biomolecules is to reach Earth through meteorites or comets to become one of the building blocks for the formation of the pristine biopolymers. Biopolymer formation is very difficult, as these reactions are thermodynamically disfavoured in water with high kinetic barriers [7]. However, it has been long proposed that naturally-occurring minerals could have played a key role favouring these reactions, as they present specific surface sites that can adsorb and concentrate prebiotic organic compounds [8,9]. Computational quantum chemical methods may help in clarifying possible reactive channels towards molecule formations using proper atomistic structural models of the systems (including the extended surfaces), as they allow us to characterize chemical paths along the potential energy surfaces.In the talk, we discuss few examples from our own work for simulating essential molecules and COMs on interstellar grains as well as formation of polypeptides via condensation reaction of amino acids on mineral surfaces.
08
March 2019

Pulsations in (few, exotic) hot subdwarf stars


Start: 12:15h
Speaker: Marcelo Miller Bertolami (Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata)
Place: Sala Alberto Lobo

Most hot subdwarf stars (spectral types sdBs, sdOs) are core helium-burning stars at the blue end of the horizontal branch with masses slightly below half a solar mass. They are found in all Galactic stellar populations and are sufficiently common to account for the UV-upturn of early-type galaxies.…
Start: 12:15h
Speaker: Marcelo Miller Bertolami (Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata)
Place: Sala Alberto Lobo


Most hot subdwarf stars (spectral types sdBs, sdOs) are core helium-burning stars at the blue end of the horizontal branch
with masses slightly below half a solar mass. They are found in all Galactic stellar populations and are sufficiently common to
account for the UV-upturn of early-type galaxies. Yet, the evolutionary channel leading to them does not seem to be the same
in all stellar populations. While in the Galactic Field half of the sdBs reside in close binaries, most hot subdwarfs in galactic
clusters seem to be the outcome of single stellar evolution. 
Thanks to the discovery of  multi-periodic brightness variations in a significant fraction of these stars, asteroseismology has become a 
useful tool to constrain the internal structure of these stars and consequently their evolutionary histories.
Two main families of sdB pulsators exist, the hot rapid pulsators (sdBVr, pressure modes, with periods 80–400 s) and the
cold slow pulsators (sdBVs, gravity modes with periods 2500-7000s). Pulsations in both groups of stars of can be
explained by the action of the kappa mechanism acting on the opacity bump due to M-shell ionizations of iron group
elements.  While the vast majority of pulsating sdB stars belong to these two families there exists a small group of He-rich hot
subdwarfs that display anomalous pulsation properties that cannot be explained by this mechanism.
In this talk I will first review properties of hot subdwarf stars as well as the evolutionary channels proposed for their
formation. Then I will describe the main properties of hot subdwarf pulsators as well as the driving mechanism behind their
pulsations.  Finally, I will discuss recent work we have been doing to explain the pulsations in He-rich hot subdwarfs and to
test possible evolutionary channels for the formation of He-rich hot subdwarfs.
 
01
March 2019

On the history of the Universe expansion: Edwin Hubble, Georges Lemaitre and Vesto Slipher


Start: 12:15h
Speaker: Emilio Elizalde
Place: Sala Alberto Lobo

In this talk, a follow up of previous ones, I will present my final conclusions about the role of each of the contributors to the discovery of the Universe expansion, concentrating in particular on the seminal role of Vesto Slipher, and on the ideas that led to the even more important finding that…
Start: 12:15h
Speaker: Emilio Elizalde
Place: Sala Alberto Lobo


In this talk, a follow up of previous ones, I will present my final conclusions about the role of each of the contributors to the discovery of the Universe expansion, concentrating in particular on the seminal role of Vesto Slipher, and on the ideas that led to the even more important finding that our Universe had an origin.
 
22
February 2019

Asteroseismology of Red-Giant and Solar-Analogue stars in the golden age of space photometry and ground-based spectroscopy


Start: 12:15h
Speaker: Paul Beck (Instituto de Astrofisica de Canarias)
Place: Sala Alberto Lobo

Asteroseismology is a powerful tool to study structure and dynamics of the stellar interior as well as their evolution. Such analysis can be done for thousands of stars in differing evolutionary stages from data of unprecedented photometric quality, provided by the NASA Kepler space telescope. In particular,…
Start: 12:15h
Speaker: Paul Beck (Instituto de Astrofisica de Canarias)
Place: Sala Alberto Lobo

Asteroseismology is a powerful tool to study structure and dynamics of the stellar interior as well as their evolution. Such analysis can be done for thousands of stars in differing evolutionary stages from data of unprecedented photometric quality, provided by the NASA Kepler space telescope. In particular, the study of stochastic, solar-like oscillators in combination with high-resolution ground-based spectroscopy has led to numerous breakthroughs in our understanding of the stellar structure and evolution of solar-like stars and is an important tool to characterize the host stars of exoplanets.

In this talk, the principles of asteroseismology of solar-like oscillators will be discussed on the basis of case studies. We first view the best studied case, the Sun. On the main sequence, solar-analogue stars provide a treasure trove of high-quality oscillation spectra which provide besides mass and radius also information on age, activity cycles, etc. Combined with complimentary data, such as activity proxies, surface rotation rate or lithium abundances allow to draw a comprehensive picture of stars like our Sun. Solar-like oscillations are also found further away from the main sequence, in the more advanced evolutionary phases of the sub- and red-giant branch. Due to a characteristic in the oscillation properties, we can use seismology to look even deeper into the stars and ultimately study the properties of the core with seismic techniques.

Finally, an outlook to the forthcoming space missions, such as NASA TESS and ESA PLATO will be given and how they will influence the future of asteroseismology and the search for exoplanets.
15
February 2019

Too fast, too furious: rapid planet formation by gravitational instability


Start: 12:15h
Speaker: Dimitris Stamatellos (University of Central Lancashire)
Place: Sala Alberto Lobo (ICE building, Campus UAB)

Stars are born with discs that during their initial stages of formation are relatively massive, asymmetric and they are being fed with material from their parent clouds. ALMA observations have revealed young discs with multiple gaps and discs with spiral structures. Such features may be due to forming…
Start: 12:15h
Speaker: Dimitris Stamatellos (University of Central Lancashire)
Place: Sala Alberto Lobo (ICE building, Campus UAB)

Stars are born with discs that during their initial stages of formation are relatively massive, asymmetric and they are being fed with material from their parent clouds. ALMA observations have revealed young discs with multiple gaps and discs with spiral structures. Such features may be due to forming planets, raising the exciting possibility that planets and planetary systems may form much faster than it has been previously thought. I will discuss whether gravitational instabilities may be responsible for the fast formation of planet-seeds in early-phase protostellar discs. I will also discuss how young planet-seeds evolve when they form within relatively massive discs, and I will argue that their fate is quite diverse, depending on the detailed physics of their interactions with their parent discs.
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An institute of the Consejo Superior de Investigaciones Científicas

An institute of the Consejo Superior de Investigaciones Científicas
Affiliated with the Institut d'Estudis Espacials de Catalunya

Affiliated with the Institut d'Estudis Espacials de Catalunya