ESA | Science & Technology | XMM-Newton | 26 Feb 2018
In 2014, ESA's XMM-Newton spotted X-rays emanating from the massive star Rho Ophiuchi A and, last year, found these to ebb and flow periodically in the form of intense flares – both unexpected results. The team has now used ESO's Very Large Telescope to find that the star boasts a strong magnetic field, confirming its status as a cosmic lighthouse.
Stars like the Sun are known to produce strong X-ray flares, but massive stars appear to be very different. In stars upwards of eight solar masses X-ray emission is steady, and no such star had been confidently observed to repeatedly flare in this part of the spectrum – until recently.
In 2014, a team of scientists used ESA's XMM-Newton space observatory to observe a massive star named Rho Ophiuchi A. This star sits at the heart of the Rho Ophiuchi Dark Cloud, a nearby region known to be actively forming new stars. Surprisingly, the data showed an abundance of X-rays streaming out from the star, prompting the team to look closer.
"We observed the star with XMM-Newton for almost 40 hours and found something even more unexpected," says Ignazio Pillitteri of the INAF–Osservatorio Astronomico di Palermo, Italy, and leader of the research team.
"Rather than a smooth, steady emission, the X-rays pulsed periodically outwards from Rho Ophiuchi A, varying over a period of roughly 1.2 days as the star rotated – like an X-ray lighthouse! This is quite a new phenomenon in stars bigger than the Sun." ...
Smooth X-ray variability from ρ Ophiuchi A+B. A strongly magnetized primary B2 star? - Ignazio Pillitteri et al
- Astronomy & Astrophysics 567:L4 (July 2014) DOI: 10.1051/0004-6361/201424243
arXiv.org > astro-ph > arXiv:1406.5049 > 19 Jul 2014
- Astronomy & Astrophysics 602:A92 (June 2017) DOI: 10.1051/0004-6361/201630070
arXiv.org > astro-ph > arXiv:1703.04686 > 14 Mar 2017 (v1), 27 Mar 2017 (v2)