Related papers: The Ups and Downs of Alpha Centauri
The Sun has a steady 11-year cycle in magnetic activity most well-known by the rising and falling in the occurrence of dark sunspots on the solar disk in visible bandpasses. The 11-year cycle is also manifest in the variations of emission…
We present time series photometry of Bienor in four observation campaigns from 2013 to 2016 and compare them with previous observations in the literature dating back to 2000. The results show a remarkable decline in the amplitude of the…
This paper investigates the long-term orbital stability of small bodies near the central binary of the Alpha Centauri system. Test particles on circular orbits are integrated in the field of this binary for 32000 binary periods or…
Significant advances in science always take place when the state of the art in instrumentation improves dramatically. NASA's Chandra X-Ray Observatory represents such an advance. Launched in July of 1999, Chandra is an observatory designed…
The R CrA region was observed in the 3.5 and 6.2 cm continuum with high angular resolutions (0.6--1.7 arcseconds) using the Very Large Array. Archival data sets were also analyzed for comparison, which provided angular resolutions up to 0.3…
The variabile star Delta Scorpii is in conjunction with the Sun at the end of November each year. We studied its magnitude by averaging the observations of 28 Nov - 1 Dec from 1996 to 2013 using the coronograph LASCO C3 on-board the SOHO…
We analyze a 162 ks HETG Chandra observation of the O7.5 III(n)((f)) star xi Per, together with contemporaneous H alpha observations. The X-ray spectrum of this star is similar to other single O stars, and not pathological in any way. Its…
Solar flares, with energies ranging over several orders of magnitude, result from impulsive release of energy due to magnetic reconnection in the corona. Barring a handful, almost all microflares observed in X-rays are associated with the…
We carried out a statistical study of the `quiet' solar corona during the descending phase of the sunspot cycle 24 (i.e. 2015 January - 2019 May) using data obtained with the Gauribidanur RAdioheliograPH (GRAPH) at 53 MHz and 80 MHz…
In a study of Chandra High Energy Transmission Grating spectra of Algol, we clearly detect Doppler shifts caused by the orbital motion of Algol B. These data provide the first definitive proof that the X-ray emission of Algol is dominated…
Recent intensive monitoring campaigns of active galactic nuclei (AGN) have provided simultaneous X-ray, UV, and optical data of unprecedented quality. The observations reveal a strong correlation between the UV and optical variability, but…
The current cycle minimum appears to be deeper and broader than recent cycle minima, and this minimum appears similar to the minima in the early 1900s. With the best-ever solar irradiance measurements from several different satellite…
We have analysed the light curve of the two brightest X-ray flares from the Galactic Center black hole, one flare observed by XMM-Newton on October 3, 2002 (Porquet et al. 2003), and the other flare observed by Chandra on October 26, 2000…
We present a final summary of all ROSAT X-ray observations of nearby stars. All available ROSAT observations with the ROSAT PSPC, HRI and WFC have been matched with the CNS4 catalog of nearby stars and the results gathered in the Nearby…
An unusual object, G2, had its pericenter passage around Sgr A*, the $4\times10^6$ M$_\odot$ supermassive black hole in the Galactic Centre, in Summer 2014. Several research teams have reported evidence that following G2's pericenter…
Starting in 2012, we began an unprecedented observational program focused on the supermassive black hole in the center of our Galaxy, Sgr A*, utilizing the High Energy Transmission Gratings Spectrometer (HETGS) instrument on the Chandra…
The Galactic black hole X-ray binary XTE J1650-500 entered a quiescent regime following the decline from the 2001-2002 outburst that led to its discovery. Here we report on the first detection of its quiescent counterpart in a 36 ks…
Cen A hosts the closest active galactic nucleus to the Milky Way, which makes it an ideal target for investigating the dynamical processes in the vicinity of accreting supermassive black holes. In this paper, we present 14 Chandra HETGS…
We present the results of a 2.5-year multiwavelength monitoring programme of Cygnus X-1, making use of hard and soft X-ray data, optical spectroscopy, UBVJHK photometry and radio data. In particular we confirm that the 5.6-day orbital…
In this article, we report an evidence of very high and statistically significant relationship between hemispheric asymmetry in solar coronal rotation rate and solar activity. Our approach is based on cross correlation of hemispheric…