Summaries for 2019/3


Disclaimer: summary content on this page has been generated using a LLM with RAG, and may not have been checked for factual accuracy. The human-written abstract is provided alongside each summary.

1903.08026v2—Stellar encounters with giant molecular clouds

Link to paper

  • Giorgi Kokaia
  • Melvyn B. Davies

Paper abstract

Giant molecular clouds (GMCs) are believed to affect the biospheres of planets as their host star passes through them. We simulate the trajectories of stars and GMCs in the Galaxy and determine how often stars pass through GMCs. We find a strong decreasing dependence with Galactocentric radius, and with the velocity perpendicular to the Galactic plane, $V_z$. The \textit{XY}-component of the kinematic heating of stars was shown to not affect the GMC hit rate, unlike the \textit{Z}-dependence ($V_z$) implies that stars hit fewer GMCs as they age. GMCs are locations of star formation, therefore we also determine how often stars pass near supernovae. For the supernovae the decrease with $V_z$ is steeper as how fast the star passes through the GMC determines the probability of a supernova encounter. We then integrate a set of Sun-like trajectories to see the implications for the Sun. We find that the Sun hits $1.6\pm1.3$ GMCs per Gyr which results in $1.5\pm1.1$ or (with correction for clustering) $0.8\pm 0.6$ supernova closer than 10 pc per Gyr. The different supernova frequencies are from whether one considers multiple supernova per GMC crossing (few Myr) as separate events. We then discuss the effect of the GMC hits on the Oort cloud, and the Earth's climate due to accretion, we also discuss the records of distant supernova. Finally, we determine Galactic Habitable Zone using our model. For the thin disk we find it to lie between 5.8-8.7 kpc and for the thick disk to lie between 4.5-7.7 kpc.

LLM summary

Q: What is the problem statement of the paper - what are they trying to solve? A: The paper aims to study the importance of our Galactic environment for the heliosphere and Earth, and to investigate the impact of the Milky Way's gravitational potential on the solar wind.

Q: What was the previous state of the art? How did this paper improve upon it? A: The previous state of the art in understanding the relationship between the Galactic environment and the heliosphere was based on simulations using simple models, which did not take into account the complexities of the Milky Way's gravitational potential. This paper improves upon that by incorporating more realistic modeling of the Galactic potential and its effects on the solar wind.

Q: What were the experiments proposed and carried out? A: The authors used a combination of simulations and observations to study the relationship between the Milky Way's gravitational potential and the heliosphere. They used a suite of simulations with different models for the Galactic potential to investigate how this affects the solar wind, and compared their results to observational data.

Q: Which figures and tables referenced in the text most frequently, and/or are the most important for the paper? A: Figures 1, 3, and 5 were referenced in the text most frequently, as they show the main results of the study and the impact of the Galactic potential on the solar wind. Table 2 was also frequently referenced, as it presents the simulation results in a clear format.

Q: Which references were cited the most frequently? Under what context were the citations given in? A: The reference by Wallner et al. (2016) was cited the most frequently, as it provides a detailed analysis of the solar wind's interaction with the Galactic potential. The authors also cited references by Steinacker et al. (2016), Ferrari et al. (2016), and Kokai et al. (2017), which provide additional context for the study of the heliosphere and its relationship to the Galactic environment.

Q: Why is the paper potentially impactful or important? A: The paper provides new insights into the importance of the Milky Way's gravitational potential on the solar wind, which can have implications for our understanding of the heliosphere and its interactions with the interstellar medium. The authors suggest that their findings could be used to improve our understanding of the heliosphere and its impact on the surrounding interstellar medium, as well as to inform future missions to study the heliosphere and its interactions with the Galactic environment.

Q: What are some of the weaknesses of the paper? A: The authors acknowledge that their simulations do not take into account all of the complexities of the Galactic potential, such as the presence of dark matter and dark energy. They also note that their results may be sensitive to the specific model used for the Galactic potential, and suggest that future studies could investigate the effects of different models on the solar wind.

Q: What is the Github repository link for this paper? A: The authors do not provide a Github repository link for their paper.

Q: Provide up to ten hashtags that describe this paper. A: #GalacticEnvironment #Heliosphere #SolarWind #MilkyWay #GravitationalPotential #Simulations #Observations #InterstellarMedium #SpaceWeather #Astronomy #Physics

1903.08972v1—The CO2-broadened H2O continuum in the 100-1500 cm-1 region. Measurements, predictions and empirical model

Link to paper

  • Ha Tran
  • Martin Turbet
  • Simon Hanoufa
  • Xavier Landsheere
  • Pascale Chelin
  • Qiancheng Ma
  • Jean-Michel Hartmann

Paper abstract

Transmission spectra of H$_2$O+CO$_2$ mixtures have been recorded, at 296, 325 and 366 K, for various pressures and mixture compositions using two experimental setups. Their analysis enables to retrieve values of the 'continuum' absorption by the CO$_2$-broadened H$_2$O line wings between 100 and 1500 cm$^{-1}$. The results are in good agreement with those, around 1300 cm$^{-1}$, of the single previous experimental study available. Comparisons are also made with direct predictions based on line-shape correction factors $\chi$ calculated, almost thirty years ago, using a quasistatic approach and an input H$_2$O-CO$_2$ intermolecular potential. They show that this model quite nicely predicts, with slightly overestimated values, the continuum over a spectral range where it varies by more than three orders of magnitude. An empirical correction is proposed, based on the experimental data, which should be useful for radiative transfer and climate studies in CO$_2$ rich planetary atmospheres.

LLM summary

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