Astronomers investigate the Southern Beehive cluster

A world workforce of astronomers has carried out the primary asteroseismic examine of the younger open cluster NGC 2516, higher generally known as the Southern Beehive. Outcomes of the examine, published Nov. 28 on the pre-print server arXiv, unveil essential info concerning the properties and stellar content material of this cluster.

Open clusters (OCs), shaped from the identical large molecular cloud, are teams of stars loosely gravitationally sure to one another. Thus far, greater than 1,000 of them have been found within the Milky Way, and scientists are nonetheless in search of extra, hoping to seek out a wide range of these stellar groupings. Increasing the record of identified galactic open clusters and learning them intimately might be essential for enhancing our understanding of the formation and evolution of our galaxy.

Found nearly three centuries in the past, the Southern Beehive is a vibrant and younger OC within the southern sky within the constellation Carina. The cluster is positioned some 1,300 light years away and has a near-solar metallicity, whereas its mass is estimated to be a minimum of 100,000 solar plenty.

Though many observations of the Southern Beehive have been performed, no asteroseismic examine of this cluster has been performed but. That’s the reason a gaggle of astronomers led by Gang Li of the Catholic College Leuven (KU Leuven) in Belgium has employed NASA’s Transiting Exoplanet Survey Satellite tv for pc (TESS), ESA’s Gaia satellite, and the Fiber-fed Prolonged Vary Optical Spectrograph (FEROS) at ESO’s La Silla Observatory in Chile, to carry out photometric and spectroscopic observations of this OC.

The primary goal of this observational marketing campaign was to detect gravity-mode oscillations within the cluster’s early-type main-sequence members.

“We chosen the 301 member stars with not more than gentle contamination as our pattern. We analyzed the full-frame picture (FFI) gentle curves, which offer almost steady observations within the first and third years of TESS monitoring. We additionally collected high-resolution spectra utilizing FEROS for the g-mode pulsators, with the goal to evaluate the Gaia efficient temperatures and gravities, and to arrange for future seismic modeling,” the researchers defined.

The observations performed by Li’s workforce revealed a wide range of several types of variable stars within the Southern Beehive. They recognized 24 g-mode pulsators (Gamma Doradus or Slowly Pulsating B [SPB] stars), 35 Delta Scuti pulsators, 147 stars with floor modulations, 5 eclipsing binaries, and three post-main-sequence stars.

For the Delta Scuti stars, the astronomers discovered that their amplitude spectra are well-ordered when sorted by temperature. It turned out that in cooler stars, a collection of frequencies at roughly 21.07/day had been noticed, whereas the warmer p-mode pulsators show one other collection of frequency peaks of round 33/day.

Moreover, the examine discovered that Gamma Doradus stars within the cluster have inner rotation charges as excessive as 50% of their important worth, whereas the SPB stars exhibit rotation charges near their important price. The researchers famous that that is considerably sooner than the typical worth for these noticed for single pulsators.

The collected knowledge additionally allowed the workforce to derive the age and extinction worth at 550 nm—they had been calculated to be 102 million years and 0.53 magazine, respectively.

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