Search Publications
Investigation of the coronal heating through phase relation of solar activity indexes
Li, K. J.; Xu, J. C.; Yin, Z. Q. +2 more
The coronal heating problem is a long-standing perplexing issue. In this study, 13 solar activity indexes are used to investigate their phase relation with the sunspot number (SSN). Only three of them are found to statistically significantly lag the SSN (large-scale magnetic activity) by about one solar rotation period; the three indexes are total…
Bridging the ultraviolet and optical regions: Transformation equations between GALEX and UBV photometric systems
Bilir, S.; Ak, T.; Yontan, T. +6 more
We derive transformation equations between GALEX and UBV colours by using the reliable data of 556 stars. We present two sets of equations: as a function of (only) luminosity class and as a function of both luminosity class and metallicity. The metallicities are provided from the literature, while the luminosity classes are determined by using the…
A survey of extended matter around chromospherically active binary systems
Karakuş, Osman; Ekmekçi, Fehmi
We present an analysis of colour excess (CE) observations for 13 chromospherically active binary systems, together with 27 inactive reference stars of similar spectral types and luminosity classes of the components of these 13 binaries. We used the observations which were made by Johnson-Cousins BVRcIc , 2MASS, and WISE photo…
SkyMapper Southern Survey: Second data release (DR2)
Wolf, Christian; Schmidt, Brian P.; Onken, Christopher A. +6 more
We present the second data release (DR2) of the SkyMapper Southern Survey, a hemispheric survey carried out with the SkyMapper Telescope at Siding Spring Observatory in Australia, using six optical filters: u, v, g, r, i, z. DR2 is the first release to go beyond the ∼18 mag (10σ) limit of the Shallow Survey released in the first data release (DR1)…
Stellar accelerations and the galactic gravitational field
Easther, Richard; Silverwood, Hamish
Typical stars in the Milky Way galaxy have velocities of hundreds of kilometres per second and experience gravitational accelerations of ∼10-10 m s-2, resulting in velocity changes of a few centimetres per second over a decade. Measurements of these accelerations would permit direct tests of the applicability of Newtonian dyn…
Galactic calibration of the tip of the red giant branch
Clementini, Gisella; Da Costa, Gary; Mould, Jeremy
Indications from Gaia data release 2 are that the tip of the red giant branch (a population II standard candle related to the helium flash in low mass stars) is close to -4 in absolute I magnitude in the Cousins photometric system. Our sample is high-latitude southern stars from the thick disk and inner halo, and our result is consistent with long…
Two's company, three's a crowd: SALT reveals the likely triple nature of the nucleus of the extreme abundance discrepancy factor planetary nebula Sp 3
Miszalski, Brent; Manick, Rajeev; Rauch, Thomas +3 more
The substantial number of binary central stars of planetary nebulae (CSPNe) now known (∼50) has revealed a strong connection between binarity and some morphological features including jets and low-ionisation structures. However, some morphological features and asymmetries might be too complex or subtle to ascribe to binary interactions alone. In t…
Analysis of the disc components of our galaxy via kinematic and spectroscopic procedures
Bilir, S.; Karaali, S.; Plevne, O. +1 more
We used the spectroscopic and astrometric data provided from the GALactic Archaeology with HERMES (GALAH) Data Release (DR2) and Gaia DR2, respectively, for a large sample of stars to investigate the behaviour of the [α/Fe] abundances via two procedures, that is, kinematically and spectroscopically. With the kinematical procedure, we investigated …
Difference of source regions between fast and slow coronal mass ejections
Filippov, B.
Coronal mass ejections (CMEs) are tightly related to filament eruptions and usually are their continuation in the upper solar corona. It is common practice to divide all observed CMEs into fast and slow ones. Fast CMEs usually follow eruptive events in active regions near big sunspot groups and associated with major solar flares. Slow CMEs are mor…
SkyMapper Southern Survey: First Data Release (DR1)
Wolf, Christian; Murphy, Simon J.; Schmidt, Brian P. +14 more
We present the first data release of the SkyMapper Southern Survey, a hemispheric survey carried out with the SkyMapper Telescope at Siding Spring Observatory in Australia. Here, we present the survey strategy, data processing, catalogue construction, and database schema. The first data release dataset includes over 66 000 images from the Shallow …