We present Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm continuum and molecular-line observations of the star-forming region G40.282−0.219. The continuum resolves the source, previously considered a single massive young stellar object (MYSO), into three compact cores within a common natal clump. Using 13 bright molecular transitions, we investigate gas kinematics, chemistry, and evolutionary differences among the cores. MM1 is the dominant continuum source. MM2, the second-brightest core, drives a powerful outflow; its SiO jet shows velocity offsets of ±25 km s ^−1 from the systemic velocity. SiO jet and wider-angle H _2 CO and CH _3 OH emission trace the outflow, whose alignment with the H _2 knot MHO 2463 suggests a preceding ejection from MM2. MM3 is weakest in continuum but appears to be the principal hot core, harboring Class II 6.7 GHz CH _3 OH masers and the richest molecular inventory, including complex organic molecules (CH _3 OH and CH _3 CN) and shock/dense-gas tracers (OCS, HC _3 N, H _2 CO, and SO). We find clear spatial decoupling between continuum brightness and chemical, outflow, and maser activity. MM1 appears chemically poor, whereas weaker MM2 harbors outflow activity, and the least-bright MM3 contains an MYSO, the highest dust temperature, and the greatest chemical complexity. These hot cores may represent an evolutionary sequence from youngest MM1 to most evolved MM3 within one fragmenting clump. We conclude that accretion luminosity, localized heating, and evolutionary stage, rather than 1.3 mm continuum flux, likely govern observable chemical richness in clustered high-mass star-forming regions.
We present the X-ray surface brightness maps of the jet from the quasar PKS 0637−752, using two epochs of archival Chandra observations (1999 and 2017). We present, for the first time, a model of the faint inner jet extending from 3 $\mathop{.}\limits^{{\unicode{x02033}}}$ 4 to 7″ from the core, interpreting its X-ray emission as inverse Compton (CMB) scattering of cosmic microwave background photons by the synchrotron-emitting relativistic electrons. The inner jet contrasts with the bright outer part of the jet, dominated by several discrete knots for which upper limits to the Fermi gamma-ray flux rule out the CMB mechanism. It is the first detailed CMB model published for this inner jet. We examine three physically motivated scenarios, distinguished by the high-energy cutoff of the electron distribution, that can account for the observed radio, millimeter/submillimeter, and X-ray emission while remaining consistent with optical and gamma-ray upper limits. We also report for the first time X-rays from the radio lobe at the end of the receding jet.
The energy spectra of Galactic cosmic rays (GCRs) serve as critical probes of their astrophysical origins and propagation mechanisms through the interstellar medium. Among the key physical processes shaping the observed spectra, solar modulation, driven by turbulent heliospheric magnetic fields and the variability of the solar wind, plays a dominant role in modifying GCR fluxes within the inner heliosphere. The recent release of time-dependent flux measurements for He, Li, Be, B, C, N, and O by AMS-02 provides unprecedented precision to investigate solar modulation phenomena. In this study, we demonstrate that Li, Be, B, C, N, and O nuclei exhibit solar modulation parameters consistent with those of protons (p) and He within a modified force-field approximation (FFA) framework incorporating rigidity-dependent modulation potentials. By positing that GCRs with the same charge sign share solar modulation parameters, we further forecast daily fluxes of Ne, Mg, and Si from 2011 to 2020.
Coronal dimmings mark the footpoint regions of coronal mass ejections (CMEs). Measuring the photospheric magnetic field within dimmings offers a direct view of how the eruption’s footpoints evolve. We track the footpoint magnetic flux imbalance across the lifetime of 48 coronal dimmings observed on disk. In contrast to studies based on difference imaging—which measure a blend of the evacuated footpoint cavity and the projected CME plasma cloud—we detect dimmings directly in Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) 193 Å images as transient coronal holes (CHs) with the COronal DImming Tracker (CoDiT), isolating the footpoint cavity and its Helioseismic and Magnetic Imager (HMI) magnetic properties within an evolving boundary. In simple cases, we observe the footpoint flux imbalance growing as the dimming expands, reaching a peak at maximum area, and gradually relaxing as the dimming fades. However, the observation of this coherent rise-and-relax process depends on eruption number: when separating the sample by the number of associated ≥C-class flares, we observe it in single-eruption dimmings, but find it washed out in multieruption dimmings, where several eruptions overprint the same region. A displaced-region null test confirms that the effect is specific to the erupting footpoints and not a property of one-sided field in general: the single-eruption dimming correlation between area and flux imbalance significantly exceeds the quiet-Sun baseline, whereas active regions (ARs)—despite their far larger static imbalance—do not track area at all. We interpret the coherent growth and decay of the dimming footpoint magnetic flux imbalance as consistent with interchange reconnection contributing to the dimming’s evolution.
For more than a decade, observers have been tracking a population of enigmatic dusty objects orbiting the central supermassive black hole of the Milky Way, Sagittarius A ^⋆ (SgrA*). In one interpretation, these objects are products of stellar mergers enshrouded in gaseous-dusty envelopes, which account for their infrared excess, emission lines, and stability against the tidal forces of SgrA*. Recent near-infrared observations of D9, one of the dusty objects, revealed that it embeds a spectroscopic stellar binary. In this work, we present full-fledged N -body simulations of an eccentric disk of binary stars similar to the young stellar disk observed around SgrA*. We find that some of the binaries in the disk are naturally drawn toward SgrA* and merge there due to Kozai–Lidov (KL) oscillations in their orbits. Together with the observed nature of D9, these findings represent a self-consistent picture of how the population of the observed dusty objects could have been brought into existence. The binary fraction in our N -body model evolves to increase with distance from SgrA*, which is also in agreement with the observational constraints. Our simulations also suggest that besides the dusty objects, stellar mergers are present within the young stellar disk, which could be identified as chemically peculiar or fast-rotating stars. Our results show that the dynamical evolution of binary stars in the young stellar disk plays a crucial role in shaping the stellar content in the Galactic Center.
