Search Publications
Machine learning initialization to accelerate Stokes profile inversions
Ruiz Cobo, B.; Quintero Noda, C.; Orozco Suárez, D. +3 more
Context. At present, an exponential growth in scientific data from current and upcoming solar observatories is expected. Most of the data consist of high spatial and temporal resolution cubes of Stokes profiles taken in both local thermodynamic equilibrium (LTE) and non-LTE spectral lines. The analysis of such solar observations requires complex i…
Sunspot tilt angles revisited: Dependence on the solar cycle strength
Jiang, Jie; Jiao, Qirong; Wang, Zi-Fan
Context. The tilt angle of sunspot groups is crucial in the Babcock-Leighton (BL) type dynamo for the generation of the poloidal magnetic field. Some studies have shown that the tilt coefficient, which excludes the latitudinal dependence of the tilt angles, is anti-correlated with the cycle strength. If the anti-correlation exists, it will be show…
Which Milky Way masses are consistent with the slightly declining 5-25 kpc rotation curve?
Hammer, F.; Jiao, Y.; Wang, J. L. +1 more
Context. Discoveries of extended rotation curves have suggested that spiral galaxy halos contain dark matter. This has led to many studies that estimated the total mass of the Galaxy, mostly using the Navarro, Frenk, and White (NFW) density profile.
Aims: We determine the effect that the choice of the dark matter profile has on the predicted …
A proto-helium white dwarf stripped by a substellar companion via common-envelope ejection. Uncovering the true nature of a candidate hypervelocity B-type star
Geier, S.; Heber, U.; Irrgang, A. +3 more
In the past, SDSS J160429.12+100002.2 wass spectroscopically classified as a blue horizontal branch (BHB) star. Assuming a luminosity that is characteristic of BHB stars, the object's radial velocity and proper motions from Gaia Early Data Release 3 would imply that its Galactic rest-frame velocity exceeds its local escape velocity. Consequently, …
GRAVITY K-band spectroscopy of HD 206893 B. Brown dwarf or exoplanet
Lutz, D.; Genzel, R.; Sturm, E. +93 more
Context. Near-infrared interferometry has become a powerful tool for studying the orbital and atmospheric parameters of substellar companions.
Aims: We aim to reveal the nature of the reddest known substellar companion HD 206893 B by studying its near-infrared colors and spectral morphology and by investigating its orbital motion.
Method…
Uncovering erosion effects on magnetic flux rope twist
Pal, Sanchita; Pomoell, Jens; Price, Daniel J. +2 more
Context. Magnetic clouds (MCs) are transient structures containing large-scale magnetic flux ropes from solar eruptions. The twist of magnetic field lines around the rope axis reveals information about flux rope formation processes and geoeffectivity. During propagation MC flux ropes may erode via reconnection with the ambient solar wind. Any eros…
Stellar Population Astrophysics (SPA) with TNG. Atmospheric parameters of members of 16 unstudied open clusters
Vallenari, A.; Bragaglia, A.; Spina, L. +12 more
Context. Thanks to the modern understanding of stellar evolution, we can accurately measure the ages of open clusters (OCs). Given their position, they are ideal tracers of the Galactic disc. Gaia data release 2, besides providing precise parallaxes, led to the detection of many new clusters, opening a new era for the study of the Galactic disc. H…
Solar origins of a strong stealth CME detected by Solar Orbiter
Long, David M.; Möstl, Christian; Davies, Emma E. +6 more
Aims: We aim to locate the origin of a stealth coronal mass ejection (CME) detected in situ by the MAG instrument on board Solar Orbiter and make connections between the CME observed at the Sun and the interplanetary CME (ICME) measured in situ.
Methods: Remote sensing data were analysed using advanced image processing techniques to iden…
A stringent upper limit of 20 pptv for methane on Mars and constraints on its dispersion outside Gale crater
Daerden, F.; Forget, F.; Montmessin, F. +17 more
Context. Reports on the detection of methane in the Martian atmosphere have motivated numerous studies aiming to confirm or explain its presence on a planet where it might imply a biogenic or more likely a geophysical origin.
Aims: Our intent is to complement and improve on the previously reported detection attempts by the Atmospheric Chemist…
APOGEE spectroscopic evidence for chemical anomalies in dwarf galaxies: The case of M 54 and Sagittarius
Bizyaev, Dmitry; Beers, Timothy C.; Minniti, Dante +7 more
We present evidence for globular cluster stellar debris in a dwarf galaxy system (Sagittarius; Sgr) based on an analysis of high-resolution H-band spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. We add [N/Fe], [Ti/Fe], and [Ni/Fe] abundance ratios to the existing sample of potential members of M 54; this is…