Search Publications
Quasars as standard candles. IV. Analysis of the X-ray and UV indicators of the disc-corona relation
Signorini, Matilde; Risaliti, Guido; Lusso, Elisabeta +4 more
Context. A non-linear relation between quasar monochromatic luminosities at 2500 Å and 2 keV holds at all observed redshifts and luminosities, and it has been used to derive quasar distances and to build a Hubble diagram of quasars. The choice of the X-ray and UV indicators has so far been somewhat arbitrary and has typically relied on photometric…
Deep drilling in the time domain with DECam: survey characterization
Clarkson, William I.; Lee, Chien-Hsiu; Rest, Armin +41 more
This paper presents a new optical imaging survey of four deep drilling fields (DDFs), two Galactic and two extragalactic, with the Dark Energy Camera (DECam) on the 4-m Blanco telescope at the Cerro Tololo Inter-American Observatory (CTIO). During the first year of observations in 2021, >4000 images covering 21 deg2 (seven DECam poin…
An elusive dark central mass in the globular cluster M4
Anderson, Jay; Bedin, Luigi R.; Bellini, Andrea +4 more
Recent studies of nearby globular clusters have discovered excess dark mass in their cores, apparently in an extended distribution, and simulations indicate that this mass is composed mostly of white dwarfs (respectively stellar-mass black holes) in clusters that are core collapsed (respectively with a flatter core). We perform mass-anisotropy mod…
Mass Accretion, Spectral, and Photometric Properties of T Tauri Stars in Taurus Based on TESS and LAMOST
Lin, Chia-Lung; Ip, Wing-Huen; Luo, A. -Li +3 more
We present the analysis of 16 classical T Tauri stars (CTTSs) using LAMOST and TESS data, investigating spectral properties, photometric variations, and mass accretion rates. All 16 stars exhibit emissions in Hα lines, from which the average mass accretion rate of 1.76 × 10‑9 M ⊙ yr‑1 is derived. Two of the stars, …
Coronal Densities, Temperatures, and Abundances during the 2019 Total Solar Eclipse: The Role of Multiwavelength Observations in Coronal Plasma Characterization
Del Zanna, Giulio; DeLuca, Edward; Mason, Helen +7 more
The Airborne Infrared Spectrometer (AIR-Spec) offers an unprecedented opportunity to explore the near-infrared (NIR) wavelength range. It has been flown at two total solar eclipses, in 2017 and 2019. The wavelength range of the much-improved instrument on the second flight (2019 July 2) was shifted to cover two density-sensitive lines from S XI. I…
Stable accretion in young stars: the cases of EX Lupi and TW Hya
Ábrahám, P.; Kóspál, Á.; Scholz, A. +8 more
We examine the long-term spectroscopic and photometric variability of EX Lupi and TW Hya, studying the presence of stable accretion and the role it plays in the observed variability. Analysing the velocity modulations of the emission lines with STAR-MELT, we obtain information on the structure of the accretion columns and the disc-star connection.…
The pristine nature of SMSS 1605−1443 revealed by ESPRESSO
Rebolo, R.; Zapatero Osorio, M. R.; Allende Prieto, C. +20 more
Context. SMSS J160540.18−144323.1 is the carbon-enhanced metal-poor (CEMP) star with the lowest iron abundance ever measured, [Fe/H] = −6.2, which was first reported with the SkyMapper telescope. The carbon abundance is A(C)≈6.1 in the low-C band, as the majority of the stars in this metallicity range. Yet, constraining the isotopic ratio of key s…
Synchronous Rotation in the (136199) Eris-Dysnomia System
Bacon, D.; Smith, M.; Abbott, T. M. C. +48 more
We combine photometry of Eris from a 6 month campaign on the Palomar 60 inch telescope in 2015, a 1 month Hubble Space Telescope WFC3 campaign in 2018, and Dark Energy Survey data spanning 2013-2018 to determine a light curve of definitive period 15.771 ± 0.008 days (1σ formal uncertainties), with nearly sinusoidal shape and peak-to-peak flux vari…
Probing the nature of the low state in the extreme ultraluminous X-ray pulsar NGC 5907 ULX1
Salvaterra, R.; Pinto, C.; Israel, G. L. +13 more
NGC 5907 ULX1 is the most luminous ultra-luminous X-ray pulsar (ULXP) known to date, reaching luminosities in excess of 1041 erg s−1. The pulsar is known for its fast spin-up during the on-state. Here, we present a long-term monitoring of the X-ray flux and the pulse period between 2003 and 2022. We find that the source was i…
A type II solar radio burst without a coronal mass ejection
Vainio, R.; Kilpua, E. K. J.; Kumari, A. +2 more
Context. The Sun produces the most powerful explosions in the Solar System, solar flares, which can also be accompanied by large eruptions of magnetised plasma, coronal mass ejections (CMEs). These processes can accelerate electron beams up to relativistic energies through magnetic reconnection processes during solar flares and CME-driven shocks. …