Chandra observation of Polaris: census of low-mass companions

Evans, Nancy Remage, Guinan, Edward, Engle, Scott, Wolk, Scott J., Schlegel, Eric, Mason, Brian D., Karovska, Margarita, and Spitzbart, Bradley (2010) Chandra observation of Polaris: census of low-mass companions. Astronomical Journal, 139 (5). pp. 1968-1974.

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We have observed Cepheid Polaris (α UMi A: F7 Ib [Aa] + F6 V [Ab]) with Chandra ACIS-I for 10 ks. An X-ray source was found at the location of Polaris with log LX = 28.89 erg s–1 (0.3-8 keV) and kT = 0.6 keV. A spectrum this soft could come from either the supergiant or the dwarf, as shown by comparable coronal stars. Two resolved low-mass visual companions, "C" and "D," are not physical members of the system based on the lack of X-rays (indicating an age older than the Cepheid) and inconsistent proper motions. Polaris B is not an X-ray source, consistent with its early F spectral type, and probably does not have a lower mass companion itself. A possible more distant member is identified, and an additional less plausible one. This provides a complete census of companions out to 0.1 pc covering a mass ratio range of an order of magnitude and a ΔV of nearly 15 mag.

Item ID: 17283
Item Type: Article (Research - C1)
ISSN: 1538-3881
Keywords: binaries: general; stars: variables: Cepheids; X-rays: stars
Date Deposited: 29 May 2011 22:19
FoR Codes: 02 PHYSICAL SCIENCES > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970102 Expanding Knowledge in the Physical Sciences @ 100%
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