Constraining the X-ray luminosities of asymptotic giant branch stars: TX camelopardalis and T cassiopeia

Joel H. Kastner*, Noam Soker

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

To probe the magnetic activity levels of asymptotic giant branch (AGB) stars, we used XMM-Newton to search for X-ray emission from two well-studied objects, TX Cam and T Cas. The former star displays polarized maser emission, indicating magnetic field strengths of B ∼ 5 G, and the latter is one of the nearest known AGB stars. Neither star was detected by XMM-Newton. We use the upper limits on EPIC (CCD detector) count rates to constrain the X-ray luminosities of these stars and derive LX < 1031 ergs s-1 (<1030 ergs s-1) for an assumed X-ray emission temperature TX = 3 × 106 K (107 K). These limits represent ≲10% (≲1%) of the X-ray luminosity expected under models in which AGB magnetic fields are global and potentially play an important role in collimating and/or launching AGB winds. We suggest, instead, that the B field strengths inferred from maser observations are representative of localized magnetic clouds.

Original languageEnglish
Pages (from-to)978-982
Number of pages5
JournalAstrophysical Journal
Volume608
Issue number2 I
DOIs
StatePublished - 20 Jun 2004
Externally publishedYes

Keywords

  • Stars: AGB and post-AGB
  • Stars: magnetic fields
  • Stars: mass loss
  • Stars: winds, outflows
  • X-rays: ISM

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