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The Effect of Stream Interaction Regions on ICME Structures Observed in Longitudinal Conjunction
Lugaz, Noé; Scolini, Camilla; Galvin, Antoinette B. +1 more
We study two interplanetary coronal mass ejections (ICMEs) observed at Mercury and at 1 au by spacecraft in longitudinal conjunction, investigating the question: what causes the drastic alterations observed in some ICMEs during propagation, while other ICMEs remain relatively unchanged? Of the two ICMEs, the first one propagated relatively self-si…
Taking snapshots of the jet-ISM interplay: The case of PKS 0023-26
Morganti, Raffaella; Oosterloo, Tom; Tadhunter, Clive +2 more
We present high angular resolution (0.13-0.4 arcsec) ALMA CO(2-1) and 1.7 mm continuum observations of the far-infrared-bright galaxy PKS 0023−26 (z = 0.32), which hosts a young radio source as well as a luminous optical active galactic nucleus (AGN). Although young, the powerful radio source has already grown to a size of a few kiloparsec, making…
The IGRINS YSO Survey. I. Stellar Parameters of Pre-main-sequence Stars in Taurus-Auriga
Johns-Krull, Christopher M.; Hwang, Narae; Lee, Jae-Joon +19 more
We present fundamental parameters for 110 canonical K- and M-type (1.3-0.13 M⊙) Taurus-Auriga young stellar objects (YSOs). The analysis produces a simultaneous determination of effective temperature (Teff), surface gravity (log g), magnetic-field strength (B), and projected rotational velocity ( $v\sin i$ ). Our method emplo…
Towards constraining warm dark matter with stellar streams through neural simulation-based inference
Bertone, Gianfranco; Banik, Nilanjan; Weniger, Christoph +2 more
A statistical analysis of the observed perturbations in the density of stellar streams can in principle set stringent constraints on the mass function of dark matter subhaloes, which in turn can be used to constrain the mass of the dark matter particle. However, the likelihood of a stellar density with respect to the stream and subhaloes parameter…
Age-dating Red Giant Stars Associated with Galactic Disk and Halo Substructures
Angus, Ruth; Huber, Daniel; Saunders, Nicholas +12 more
The vast majority of Milky Way stellar halo stars were likely accreted from a small number (≲3) of relatively large dwarf galaxy accretion events. However, the timing of these events is poorly constrained and predominantly relies on indirect dynamical mixing arguments or imprecise age measurements of stars associated with debris structures. Here, …
Selection Functions in Astronomical Data Modeling, with the Space Density of White Dwarfs as a Worked Example
Everall, Andrew; Boubert, Douglas; Hogg, David W. +6 more
Statistical studies of cataloged object properties are central to astrophysics. But one cannot model those objects' population properties without the sample's selection function, the quantitative understanding of which objects could have ended up in such a catalog. As didactic introductions to this topic are scarce in the astrophysical literature,…
The Red Supergiant Content of M31 and M33
Drout, Maria R.; Massey, Philip; Levesque, Emily M. +2 more
We identify red supergiants (RSGs) in our spiral neighbors M31 and M33 using near-IR (NIR) photometry complete to a luminosity limit of $\mathrm{log}L/{L}_{\odot }=4.0$ . Our archival survey data cover 5 deg2 of M31, and 3 deg2 for M33, and are likely spatially complete for these massive stars. Gaia is used to remove foregrou…
Revealing a High Water Abundance in the Upper Mesosphere of Mars With ACS Onboard TGO
Montmessin, Franck; Belyaev, Denis A.; Fedorova, Anna A. +7 more
We present the first water vapor profiles encompassing the upper mesosphere of Mars, 100-120 km, far exceeding the maximum altitudes where remote sensing has been able to observe water to date. Our results are based on solar occultation measurements by Atmospheric Chemistry Suite (ACS) onboard the ExoMars Trace Gas Orbiter (TGO). The observed wave…
The large-scale magnetic field of Proxima Centauri near activity maximum
Donati, Jean-François; Bonfils, Xavier; Delfosse, Xavier +5 more
We report the detection of a large-scale magnetic field at the surface of the slowly rotating fully convective (FC) M dwarf Proxima Centauri. 10 circular polarization spectra, collected from 2017 April to July with the HARPS-Pol spectropolarimeter, exhibit rotationally modulated Zeeman signatures suggesting a stellar rotation period of 89.8 ± 4.0 …
511 keV excess and primordial black holes
Hooper, Dan; Keith, Celeste
An excess of 511 keV photons has been detected from the central region of the Milky Way. It has been suggested that the positrons responsible for this signal might be produced through the Hawking evaporation of primordial black holes. After evaluating the constraints from INTEGRAL, COMPTEL, and Voyager 1, we find that black holes in mass range of …