26Aluminum from Massive Binary Stars. II. Rotating Single Stars Up to Core Collapse and Their Impact on the Early Solar System

Radioactive nuclei were present in the early solar system (ESS), as inferred from analysis of meteorites. Many are produced in massive stars, either during their lives or their final explosions. In the first paper of this series (Brinkman et al. 2019), we focused on the production of 26Al in massive binaries. Here, we focus on the production of another two short-lived radioactive nuclei, 36Cl and 41Ca, and the comparison to the ESS data. We used the MESA stellar evolution code with an extended nuclear network and computed massive (10–80 M ⊙), rotating (with initial velocities of 150 and 300 km s−1) and nonrotating single stars at solar metallicity (Z = 0.014) up to the onset of core collapse. We present the wind yields for the radioactive isotopes 26Al, 36Cl, and 41Ca, and the stable isotopes 19F and 22Ne. In relation to the stable isotopes, we find that only the most massive models, ≥60 and ≥40 M ⊙ give positive 19F and 22Ne yields, respectively, depending on the initial rotation rate. In relation to the radioactive isotopes, we find that the ESS abundances of 26Al and 41Ca can be matched with by models with initial masses ≥40 M ⊙, while 36Cl is matched only by our most massive models, ≥60 M ⊙. 60Fe is not significantly produced by any wind model, as required by the observations. Therefore, massive star winds are a favored candidate for the origin of the very short-lived 26Al, 36Cl, and 41Ca in the ESS.

In Search of Infall Motion in Molecular Clumps. III. HCO+ (1-0) and H13CO+ (1-0) Mapping Observations toward Confirmed Infall Sources

The study of infall motion helps us to understand the initial stages of star formation. In this paper, we use the IRAM 30 m telescope to make mapping observations of 24 infall sources confirmed in previous work. The lines we use to track gas infall motions are HCO+ (1-0) and H13CO+ (1-0). All 24 sources show HCO+ emissions, while 18 sources show H13CO+ emissions. The HCO+ integrated intensity maps of 17 sources show clear clumpy structures; for the H13CO+ line, 15 sources show clumpy structures. We estimated the column density of HCO+ and H13CO+ using the RADEX radiation transfer code, and the obtained [HCO+]/[H2] and [H13CO+]/[HCO+] of these sources are about 10−11–10−7 and 10−3–1, respectively. Based on the asymmetry of the line profile of the HCO+, we distinguish these sources: 19 sources show blue asymmetric profiles, and the other sources show red profiles or symmetric peak profiles. For eight sources that have double-peaked blue line profiles and signal-to-noise ratios greater than 10, the RATRAN model is used to fit their HCO+ (1-0) lines, and to estimate their infall parameters. The mean V in of these sources is 0.3–1.3 km s−1, and the M ̇ in is about 10−3–10−4 M ⊙ yr−1, which is consistent with the results of intermediate or massive star formation in previous studies. The V in estimated from the Myers model is 0.1–1.6 km s−1, and the M ̇ in is within 10−3–10−5 M ⊙ yr−1. In addition, some identified infall sources show other star-forming activities, such as outflows and maser emissions. Especially for those sources with a double-peaked blue asymmetric profile, most of them have both infall and outflow evidence.

Wind of a young massive star colliding with a supernova remnant shell

The fast stellar winds of massive stars, along with supernovae, determine the dynamics within the star-forming regions. Within a compact star cluster, counterpropagating supersonic MHD shock flows associated with winds and supernova remnants can provide favorable conditions for efficient Fermi I particle acceleration up to energies > 10 PeV over a short timescale of several hundred years. To model the nonthermal spectra of such systems it is necessary to know the complex structure of colliding supersonic flows. In this paper using the PLUTO code we study on a subparsec scale a 2D MHD model of the collision of a core-collapse supernova remnant with a magnetized wind of a hot rotating O-star. As a result the detailed high resolution (~ 10−4 pc) maps of density, magnetic field, and temperature during the the wind - supernova shell interaction are presented.

Modeling of cosmic ray 22Ne-enrichment in compact star clusters

22Ne/20Ne isotopic ratio is found to be about 5 times higher in Galactic cosmic rays (GCRs) than in the solar wind. In this paper we develop the hypothesis that the 22Ne overabundance in CRs is generated in compact massive star clusters which contain populations of Wolf-Rayet stars. Winds of Wolf-Rayet stars are considered to have high content of 22Ne. We assume that particle acceleration occurs on the ensemble of strong shocks from the massive stars’ winds. We present a model of cosmic ray enrichment with 22Ne, adding isotopic yields from supernovae and taking into account the acceleration efficiency during the lifetime of the stars. The impact of the parameters (the initial mass function in the cluster, rotation velocity, black hole cut-off mass) is discussed. The energy balance for our model is calculated.

M17 MIR: A Massive Protostar with Multiple Accretion Outbursts *

We report the discovery of a massive protostar M17 MIR embedded in a hot molecular core in M17. The multiwavelength data obtained during 1993–2019 show significant mid-IR (MIR) variations, which can be split into three stages: the decreasing phase during 1993.03–mid-2004, the quiescent phase from mid-2004 to mid-2010, and the rebrightening phase from mid-2010 until now. The variation of the 22 GHz H2O maser emission, together with the MIR variation, indicates an enhanced disk accretion rate onto M17 MIR during the decreasing and rebrightening phases. Radiative transfer modeling of the spectral energy distributions of M17 MIR in the 2005 epoch (quiescent) and 2017 epoch (accretion outburst) constrains the basic stellar parameters of M17 MIR, which is an intermediate-mass protostar (M * ∼ 5.4 M ⊙) with M ̇ acc ∼ 1.1 × 10 − 5 M ⊙ yr − 1 in the 2005 epoch and M ̇ acc ∼ 1.7 × 10 − 3 M ⊙ yr − 1 in the 2017 epoch. The enhanced M ̇ acc during outburst induces the luminosity outburst ΔL ≈ 7600 L ⊙. In the accretion outburst, a larger stellar radius is required to produce M ̇ acc consistent with the value estimated from the kinematics of H2O masers. M17 MIR shows two accretion outbursts (Δt ∼ 9–20 yr) with outburst magnitudes of about 2 mag, separated by a 6 yr quiescent phase. The accretion outburst occupies 83% of the time over 26 yr. The accretion rate in outburst is variable with amplitude much lower than the contrast between quiescent and outburst phases. The extreme youth of M17 MIR suggests that minor accretion bursts are frequent in the earliest stages of massive star formation.