ALMA image of CK Vulpeculae. Credit: ALMA (ESO/NAOJ/NRAO)/S. P. S. Eyres.
When Is a Nova Not a 'Nova'? When a White Dwarf and a Brown Dwarf Collide
Using the ALMA telescope, an international team of astronomers, including members of the UK ARC Node, have found evidence for the collision of a white dwarf and a brown dwarf. The collision was originally observed by astronomers in the year 1670 and at that time recorded as a nova.
The modern ALMA observations toward the object, known as CK Vulpeculae, have found the object is not a true nova but instead the result of a stellar collision between two types of dwarf stars. Unusual isotope ratios and the detection of lithium provide the strong evidence for a brown dwarf being one part of the colliding pair. The collision has also lead to the creation of a spectacular hourglass structure observed in the ALMA data.
More information is available in the press release.
CASA Imaging Issues Affecting Some ALMA Products
Recently, an issue in CASA mosaic imaging has been recognised. The JAO elected to understand and characterise the issue before informing the user community. The investigation has uncovered two issues affecting both 7- and 12-m data taken over the past few ALMA cycles and CASA releases. In brief, the two issues are:
- Mosaic data taken in the 7-m array from Cycles 1-4 and imaged by the various CASA versions during this time suffer from a ~10% overestimation in the fluxes throughout the map. This issue was resolved in Cycle 5 (CASA version 5.1.1) and beyond. ALMA is working to regenerate all these mosaics within the archive.
- A more complex issue affecting Cycle 5 (CASA version 5.1.1 to 5.3, all versions) and affects all Cycle 5 mosaics. The effect is some variation in the recovered flux, but how large an effect depends on the aspect ratio of the mosaic in question. The observatory will contact PIs of projects which are effected.
For more detail please read the full announcement from ALMA.