Search Publications
First Laboratory Measurement of Magnetic-field-induced Transition Effect in Fe X at Different Magnetic Fields
Tian, Hui; Bai, Xianyong; Si, Ran +14 more
The magnetic field is extremely important for understanding the properties of the solar corona. However, there are still difficulties in the direct measurement of the coronal magnetic field. The magnetic-field-induced transition (MIT) in Fe X, appearing in coronal spectra, was discovered to have prospective applications in coronal magnetic field m…
Inflow of low-metallicity cool gas in the halo of the Andromeda galaxy
Afruni, Andrea; Fraternali, Filippo; Pezzulli, Gabriele
As the closest L* galaxy to our own Milky Way, the Andromeda galaxy (M31) is an ideal laboratory for studies of galaxy evolution. The AMIGA project has recently provided observations of the cool (T ~ 104 K) phase of the circumgalactic medium (CGM) of M31, using HST/COS absorption spectra along ~40 background QSO sightlines, located up t…
Extending the FIP bias sample to magnetically active stars. Challenging the FIP bias paradigm
van Driel-Gesztelyi, L.; Kriskovics, L.; Baker, D. +6 more
Context. The different elemental abundances of the photosphere and the corona are striking features of not only the Sun, but of other stars as well. This phenomenon is known as the first ionisation potential (FIP) effect, and its strength can be characterized by the FIP bias, the logarithmic abundance difference between low- and high-FIP elements …
Transient obscuration event captured in NGC 3227. III. Photoionization modeling of the X-ray obscuration event in 2019
Kaastra, J. S.; Kriss, G. A.; Bianchi, S. +16 more
Context. A growing number of transient X-ray obscuration events in type I active galactic nuclei suggest that our line of sight to the central engine is not always free. Multiple X-ray obscuration events were reported in the nearby Seyfert 1.5 galaxy NGC 3227 from 2000 to 2016. In late 2019, another X-ray obscuration event was identified with Swif…
Searching for the Signal of a Primordial Black Hole from CMB Lensing and γ-Ray Emissions
Qiu, Taotao; Tan, Xiu-Hui; Xia, Jun-Qing +1 more
In this letter, we search for the signal of primordial black holes (PBHs) by correlating the γ-ray emissions in the MeV energy band produced by the Hawking evaporation and the lensing effect of the cosmic microwave background (CMB). We use the conservative case of the astrophysical model as much as possible in the calculations, since the potential…
Unprecedented change in the position of four radio sources
Frey, Sándor; Melnikov, Alexey; Titov, Oleg +8 more
Astrometric positions of radio-emitting active galactic nuclei (AGNs) can be determined with sub-milliarcsec accuracy using very long baseline interferometry (VLBI). The usually small apparent proper motion of distant extragalactic targets allow us to realize the fundamental celestial reference frame with VLBI observations. However, long-term astr…
The Photometric Study of Six W UMa Systems and Investigation of the Mass-Radius Relations for Contact Binary Stars
Davoudi, Fatemeh; Poro, Atila; Paki, Ehsan +13 more
We present the photometric analysis of six short-period systems (EI Oct, V336 TrA, NX Boo, V356 Boo, PS Boo, and V2282 Cyg). This is the first photometric analysis of these systems except for V336 TrA. Observations were conducted for 27 nights at three observatories in the northern and southern hemispheres. We calculated a new ephemeris for each o…
A Census of Thermally Pulsing AGB Stars in the Andromeda Galaxy and a First Estimate of Their Contribution to the Global Dust Budget
Williams, Benjamin F.; Goldman, Steven R.; Boyer, Martha L. +5 more
We present a near-complete catalog of the metal-rich population of thermally pulsing asymptotic giant branch (AGB) stars in the northwest quadrant of M31. This metal-rich sample complements the equally complete metal-poor Magellanic Cloud AGB catalogs produced by the SAGE program. Our catalog includes Hubble Space Telescope (HST) wide-band photome…
Beyond the Local Volume. II. Population Scaleheights and Ages of Ultracool Dwarfs in Deep HST/WFC3 Parallel Fields
Holwerda, Benne; Burgasser, Adam J.; Ryan, Russell E. +6 more
Ultracool dwarfs (UCDs) represent a significant proportion of stars in the Milky Way, and deep samples of these sources have the potential to constrain the formation history and evolution of low-mass objects in the Galaxy. Until recently, spectral samples have been limited to the local volume (d < 100 pc). Here, we analyze a sample of 164 spect…
Evidence for anisotropic quenching in massive galaxy clusters at z ≈ 0.5
Stott, John P.
A recent observational result finds that the quenching of satellites in groups at z = 0.08 has an angular dependence relative to the semimajor axis of the central galaxy. This observation is described as 'anisotropic quenching' or 'angular conformity'. In this paper, I study the variation in the colour of a mass-limited sample of satellite galaxie…