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Probing multicomponent FIMP scenarios with gamma-ray telescopes
Ibarra, Alejandro; Herms, Johannes
We consider a scenario where the dark sector includes two Feebly Interacting Massive Particles (FIMPs), with couplings to the Standard Model particles that allow their production in the Early Universe via thermal freeze-in. These couplings generically lead to the decay of the heavier dark matter component into the lighter, possibly leading to obse…
Interplanetary consequences and geoeffectiveness of CME associated with major solar flare from NOAA AR 12673
Soni, Shirsh Lata; Gupta, Radhe Shyam; Verma, Pyare Lala
In this reported work, we study a major X-class flare (X9.3) that arose from NOAA Active Region (AR) 12673 on 2017 September 6, from 11:53 UT to 12:10 UT in multi-wavelength views. This event also produced a fast coronal mass ejection (CME). NOAA AR 12673 emerged at S09W30 on 2017 September 6 and grew rapidly to a large AR. On 2017 September 9, th…
The Ophiuchus stream progenitor: a new type of globular cluster and its possible Sagittarius connection
Bovy, Jo; Fattahi, Azadeh; Navarro, Julio F. +2 more
The Ophiuchus stream is a short arc-like stellar feature of uncertain origin located ∼5 kpc North of the Galactic centre. New proper motions from the second Gaia data release reconcile the direction of motion of stream members with the stream arc, resolving a puzzling mismatch reported in earlier work. We use N-body simulations to show that the st…
Unexpected late-time temperature increase observed in the two neutron star crust-cooling sources XTE J1701-462 and EXO 0748-676
Degenaar, N.; Wijnands, R.; Homan, J. +4 more
Transient low-mass X-ray binaries (LMXBs) that host neutron stars (NSs) provide excellent laboratories for probing the dense matter physics present in NS crusts. During accretion outbursts in LMXBs, exothermic reactions may heat the NS crust, disrupting the crust-core equilibrium. When the outburst ceases, the crust cools to restore thermal equili…
Mid-infrared reflectance spectroscopy of aubrite components
Helbert, Joern; Hiesinger, Harald; Weber, Iris +5 more
Aubrites Peña Blanca Spring and Norton County were studied in the mid-infrared reflectance as part of a database for the MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer) instrument on the ESA/JAXA BepiColombo mission to Mercury. Spectra of bulk powder size fractions from Peña Blanca Spring show enstatite Reststrahlen bands (RB) at 9 µ…
Binary star sequence in the outskirts of the disrupting Galactic open cluster UBC 274
Piatti, Andrés E.
We report the identification of a numerous binary star population in the recently discovered ∼3 Gyr old open cluster UBC 274. It becomes visible when the cluster color-magnitude diagram is corrected by differential reddening and spans mass ratio (q) values from 0.5 up to 1.0. Its stellar density radial profile and cumulative distribution as a func…
LAMOST J040643.69+542347.8: The Fastest Rotator in the Galaxy
Li, Guang-Wei
Rotation and binary interaction play important roles in understanding the nature of massive stars (≳8M⊙). Some interesting transients, such as the long-duration gamma-ray bursts, are thought to be originated from fast-rotating massive stars. Because the strong stellar wind can effectively spin down a metal-rich massive star with fast ro…
Automatic Coronagraph Image Classification with Machine Learning Methods
Zhang, Yan; Feng, Li; Li, Hui +5 more
The detection of Coronal Mass Ejections (CMEs) is an important prerequisite for establishing a CME event database and realizing the prediction of CME interplanetary propagation. The Lyman-alpha Solar Telescope (LST) aboard the ASO-S (Advanced Space-based Solar Observatory) satellite will be equipped with a white-light coronagraph. The images with …
Interstellar Extinction in the Direction of the Young Open Cluster NGC 6530
Topasna, G. A.; Kaltcheva, N. T.; Jones, R. H.
We present UBVRI polarization observations of 12 B-type stars in the direction of the young open cluster NGC 6530, nine of them confirmed as probable members. The maximum degree of polarization for our target stars ranges from 0.16% to 2.84%, with an average value of 1.1%. We note variations of the polarization vector orientations across the clust…
Leveraging HST with MUSE: II. Na-abundance variations in intermediate age star clusters
Martocchia, S.; Salaris, M.; Larsen, S. +13 more
Ancient (>10 Gyr) globular clusters (GCs) show chemical abundance variations in the form of patterns among certain elements, e.g. N correlates with Na and anticorrelates with O. Recently, N abundance spreads have also been observed in massive star clusters that are significantly younger than old GCs, down to an age of ~2 Gyr. However, so far N …