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Metallicity determination of M dwarfs. Expanded parameter range in metallicity and effective temperature
Lindgren, Sara; Heiter, Ulrike
Context. Reliable metallicity values for late K and M dwarfs are important for studies of the chemical evolution of the Galaxy and advancement of planet formation theory in low-mass environments. Historically it has been challenging to determine the stellar parameters of low-mass stars because of their low surface temperature, which causes several…
Transition from eruptive to confined flares in the same active region
Aulanier, G.; Schmieder, B.; Chandra, R. +2 more
Context. Solar flares are sudden and violent releases of magnetic energy in the solar atmosphere that can be divided into two classes: eruptive flares, where plasma is ejected from the solar atmosphere resulting in a coronal mass ejection (CME), and confined flares, where no CME is associated with the flare.
Aims: We present a case study show…
A Hubble Space Telescope Survey for Novae in M87. II. Snuffing out the Maximum Magnitude-Rate of Decline Relation for Novae as a Non-standard Candle, and a Prediction of the Existence of Ultrafast Novae
Welch, D. L.; Lauer, Tod R.; Mikołajewska, Joanna +9 more
The extensive grid of numerical simulations of nova eruptions from the work of Yaron et al. first predicted that some classical novae might significantly deviate from the Maximum Magnitude-Rate of Decline (MMRD) relation, which purports to characterize novae as standard candles. Kasliwal et al. have announced the observational detection of a new c…
Primeval very low-mass stars and brown dwarfs - II. The most metal-poor substellar object
Homeier, D.; Pinfield, D. J.; Jones, H. R. A. +4 more
SDSS J010448.46+153501.8 has previously been classified as an sdM9.5 subdwarf. However, its very blue J - K colour (-0.15 ± 0.17) suggests a much lower metallicity compared to normal sdM9.5 subdwarfs. Here, we re-classify this object as a usdL1.5 subdwarf based on a new optical and near-infrared spectrum obtained with X-shooter on the Very Large T…
Investigating the Origins of Two Extreme Solar Particle Events: Proton Source Profile and Associated Electromagnetic Emissions
Vainio, Rami; Valtonen, Eino; Pohjolainen, Silja +13 more
We analyze the high-energy particle emission from the Sun in two extreme solar particle events in which protons are accelerated to relativistic energies and can cause a significant signal even in the ground-based particle detectors. Analysis of a relativistic proton event is based on modeling of the particle transport and interaction, from a near-…
Cassini microwave observations provide clues to the origin of Saturn's C ring
Nicholson, P. D.; Hedman, M. M.; Janssen, M. A. +6 more
Despite considerable study, Saturn's rings continue to challenge current theories for their provenance. Water ice comprises the bulk of Saturn's rings, yet it is the small fraction of non-icy material that is arguably more valuable in revealing clues about the system's origin and age. Herein, we present new measurements of the non-icy material fra…
Global ULF waves generated by a hot flow anomaly
Zhao, L. L.; Zhang, H.; Zong, Q. G.
Hot flow anomalies (HFAs), which are frequently observed near Earth's bow shock, are phenomena resulting from the interaction between interplanetary discontinuities and Earth's bow shock. Such transient phenomena upstream the bow shock can cause significant deformation of the bow shock and the magnetosphere, generating traveling convection vortice…
The Evolution and Physical Parameters of WN3/O3s: A New Type of Wolf-Rayet Star
Massey, Philip; Hillier, D. John; Morrell, Nidia +1 more
As part of a search for Wolf-Rayet (WR) stars in the Magellanic Clouds, we have discovered a new type of WR star in the Large Magellanic Cloud (LMC). These stars have both strong emission lines, as well as He II and Balmer absorption lines and spectroscopically resemble a WN3 and O3V binary pair. However, they are visually too faint to be WN3+O3V …
The β Pictoris association low-mass members: Membership assessment, rotation period distribution, and dependence on multiplicity
Lanzafame, A. C.; Messina, S.; Zhang, L. +6 more
Context. Low-mass members of young loose stellar associations and open clusters exhibit a wide spread of rotation periods. Such a spread originates from the distributions of masses and initial rotation periods. However, multiplicity can also play a significant role.
Aims: We aim to investigate the role played by physical companions in multipl…
Mpc-scale diffuse radio emission in two massive cool-core clusters of galaxies
Babul, Arif; Bertoldi, Frank; Bonafede, Annalisa +4 more
Radio haloes are diffuse synchrotron sources on scales of ∼1 Mpc that are found in merging clusters of galaxies, and are believed to be powered by electrons re-accelerated by merger-driven turbulence. We present measurements of extended radio emission on similarly large scales in two clusters of galaxies hosting cool cores: Abell 2390 and Abell 22…