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What causes the absence of pulsations in Central Compact Objects in supernova remnants?
Xiao, Guang-Cheng; Schwope, Axel; Ji, Li +3 more
Most young neutron stars belonging to the class of Central Compact Objects (CCOs) in supernova remnants do not have known periodicities. We investigated seven such CCOs to understand the common reasons for the absence of detected pulsations. Making use of XMM-Newton, Chandra, and NICER observations, we perform a systematic timing and spectral anal…
An extreme case of galaxy and cluster co-evolution at z = 0.7
Smail, I.; Koekemoer, A. M.; Richard, J. +3 more
We report the discovery of eMACS J0252.4-2100 (eMACS J0252), a massive and highly evolved galaxy cluster at z = 0.703. Our analysis of Hubble Space Telescope imaging and VLT/MUSE and Keck/DEIMOS spectroscopy of the system finds a high-velocity dispersion of 1020$^{+180}_{-190}$ km s-1 and a high (if tentative) X-ray luminosity of (1.2 ±…
Searching for the brightest stars in galaxies outside the Local Group
Tikhonov, Nikolay; Galazutdinova, Olga; Sholukhova, Olga +3 more
This paper introduces a technique for searching for bright massive stars in galaxies beyond the Local Group. To search for massive stars, we processed the results of stellar photometry from the Hubble Space Telescope (HST) images using the DAOPHOT and DOLPHOT packages. The results of such searches are demonstrated with examples of the galaxies DDO…
Does a Magnetosphere Protect the Ionosphere?
Gunell, Herbert; Maggiolo, Romain
Multifilter Observations of the Complex Periodic Variations in the M-dwarf Star RIK 90
Koen, Chris
The star RIK 90 is a member of a group of recently discovered young T Tauri stars showing complex periodic modulations of their light output, which have been difficult to explain. As one of the brightest, and having a relatively short period, RIK 90 is of particular interest. Thirty-three hours of contemporaneous BVRCIC photo…
The Hα line emission of the Be star β Psc: the last 40 yr
Diaz, Marcos P.; Amôres, Eduardo B.; Levenhagen, Ronaldo S. +1 more
A study on the photosphere and disc of the Be star β Psc is presented. We recover almost 40 yr of high-resolution spectroscopic observations and additional data gathered from the BeSS data base. We evaluate the photospheric parameters from the spectral energy distribution (SED) and fittings of state-of-the-art non-LTE model atmospheres to observed…
Searching for chemical abundance variations in young star clusters in the Magellanic Clouds: NGC 411, NGC 1718, and NGC 2213
Zucker, Daniel B.; de Grijs, Richard; Kapse, Shalmalee
The conventional picture of coeval, chemically homogeneous, populous star clusters - known as 'simple' stellar populations (SSPs) - is a view of the past. Photometric and spectroscopic studies reveal that almost all ancient globular clusters in the Milky Way and our neighbouring galaxies exhibit star-to-star light-element abundance variations, typ…
Effects of anisotropy on absorption cross-section spectra of medium-sized spheroidal corundum particles
Mutschke, H.; Höfer, S.; Mayerhöfer, Th. G.
Context. It has been widely accepted that corundum particles condense in the atmospheres of oxygen-rich asymptotic giant branch stars and effectively produce an infrared emission feature at 13 µm. Laboratory experiments have predicted that these particles have the shape of oblate spheroids.
Aims: We investigate the influence of the mate…
A search for pulsar companions around low-mass white dwarfs
Kramer, Michael; Athanasiadis, Tilemachos M.; Berezina, Marina +4 more
We report on a search for pulsars at the positions of eight low-mass white dwarfs and one higher mass white dwarf with the 100-m Effelsberg Radio Telescope. These systems have orbital parameters suggesting that their unseen companions are either massive white dwarfs or neutron stars (NSs). Our observations were performed at 1.36 GHz, reaching sens…
Blending and obscuration in weak-lensing magnification
Gaztanaga, E.; Schmidt, S. J.; Tyson, J. A. +1 more
We test the impact of some systematic errors in weak-lensing (WL) magnification measurements with the COSMOS 30-band photo-z Survey flux limited to Iauto < 25.0 using correlations of both source galaxy counts and magnitudes. Systematic obscuration effects are measured by comparing counts and magnification correlations. We use the Adv…