In fast wind or when the local Coulomb collision frequency is low, observations show that solar wind minor ions and ion sub-populations flow with different bulk velocities. Measurements indicate that the drift speed of both alpha particles and proton beams with respect to the bulk or core protons rarely exceeds the local Alfvén speed, suggesting that a magnetic instability or other wave-particle process limits their maximum drift. We compare simultaneous alpha particle, proton beam, and proton core observations from instruments on the Wind spacecraft spanning over 20 years. In nearly collisionless solar wind, we find that the normalized alpha particle drift speed is slower than the normalized proton beam speed; no correlation between fluctuations in both species' drifts about their means; and a strong anti-correlation between collisional age and alpha-proton differential flow, but no such correlation with proton beam-core differential flow. Controlling for the collisional dependence, both species' normalized drifts exhibit similar statistical distributions. In the asymptotic, zero Coulomb collision limit, the youngest measured differential flows most strongly correlate with an approximation of the Alfvén speed that includes proton pressure anisotropy. In this limit and with this most precise representation, alpha particles drift at 67% and proton beam drift is approximately 105% of the local Alfvén speed. We posit that one of two physical explanations is possible. Either (1) an Alfvénic process preferentially accelerates or sustains proton beams and not alphas or (2) alpha particles are more susceptible to either an instability or Coulomb drag than proton beams.
The velocity of alpha particles relative to protons can vary depending on the solar wind type and distance from the Sun (Marsch 2012). Measurements from the previous spacecraft provided the alpha-proton's differential velocities down to 0.3 au. Parker Solar Probe (PSP) now enables insights into differential flows of newly accelerated solar wind closer to the Sun for the first time. Here, we study the difference between proton and alpha bulk velocities near PSP perihelia of Encounters 3-7 when the core solar wind is in the field of view of the Solar Probe Analyzer for Ions (SPAN-I) instrument. …
Reaching the boundary between stellar kinematic groups and very wide binaries. II. alpha Lib + KU Lib: a common proper motion system in Castor separated by 1.0 pc
Young transiting exoplanets (< 100 Myr) provide crucial insight into atmospheric evolution via photoevaporation. However, transmission spectroscopy measurements to determine atmospheric composition and mass loss are challenging due to the activity and prominent stellar disk inhomogeneities present on young stars. We observed a full transit of V1298 Tau c, a 23 Myr, 5.59$R_\oplus$ planet orbiting a young K0-K1.5 solar analogue with GRACES on Gemini-North. We were able to measure the Doppler tomographic signal of V1298 Tau c using the Ca II infrared triplet (IRT) and find a projected obliquity o…
Determining ages of stars for reconstructing the history of the Milky Way remains one of the most difficult tasks in astrophysics. This involves knowing when it is possible to relate the stellar mass with its age and when it is not. The young $α-$rich (YAR) stars present such a case in which we are still not sure about their ages because they are relatively massive, implying young ages, but their abundances are $α-$enhanced, which implies old ages. We report the results from new observations from a long-term radial-velocity-monitoring campaign complemented with high-resolution spectroscopy, as…
As part of the ongoing effort to characterize the low-mass (sub)stellar population in a sample of massive young clusters, we have targeted the ~2 Myr old cluster NGC 2244. The distance to NGC 2244 from Gaia DR2 parallaxes is 1.59 kpc, with errors of 1% (statistical) and 11% (systematic). We used the Flamingos-2 near-infrared camera at the Gemini-South telescope for deep multi-band imaging of the central portion of the cluster (~2.4pc^2). We determined membership in a statistical manner, through a comparison of the cluster's color-magnitude diagram to that of a control field. Masses and extinct…
At young ages, when radiation from the host star is high, and the planet is hot and inflated after formation, planetary atmospheric mass loss can be extremely strong compared to older planets. In turn, stellar winds are faster and denser for young stars compared to evolved main-sequence stars. Their interaction with escaping planetary atmospheres can substantially affect atmospheric mass loss rates, as well as the observable signatures of escaping atmospheres, with both effects expected to occur differently for young and evolved planets. We perform a comparative study of two systems around sta…
To reveal the origins of diffuse H-alpha emissions observed around the Herbig star MWC 1080, we have performed a high-resolution near-infrared (NIR) spectroscopic observation using the Immersion GRating INfrared Spectrograph (IGRINS). In the NIR H and K bands, we detected various emission lines (six hydrogen Brackett lines, seven H2 lines, and an [Fe II] line) and compared their spatial locations with the optical (H-alpha and [S II]) and radio (13CO and CS) line maps. The shock-induced H2 and [Fe II] lines indicate the presence of multiple outflows, consisting of at least three, associated you…
Exploring the Galactic chemical evolution and enrichment scenarios with open clusters allows us to understand the history of the Milky Way disk. High-resolution spectra of OCs are a crucial tool, as they provide precise chemical information, to combine with precise distances and ages. The aim of the Stellar Population Astrophysics project is to derive homogeneous and accurate comprehensive chemical characterization of a number of poorly studied OCs.Using the HARPS-N echelle spectrograph at the Telescopio Nazionale Galileo, we obtained high-resolution spectra of giant stars in 18 OCs, 16 of whi…
