Polaris

Mass and multiplicity

Nancy Remage Evans, Gail Schaefer, Howard E. Bond, Edmund Nelan, Giuseppe Bono, Margarita Karovska, Scott Wolk, Dimitar Sasselov, Edward Guinan, Scott Engle, Eric Schlegel, Brian Mason

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Polaris, the nearest and brightest classical Cepheid, is a member of at least a triple system. It has a wide (18) physical companion, the F-type dwarf Polaris B. Polaris itself is a single-lined spectroscopic binary with an orbital period of 30 years (Kamper 1996). By combining Hipparcos measurements of the instantaneous proper motion with long-term measurements and the Kamper radial-velocity orbit, Wielen et al (2000) have predicted the astrometric orbit of the close companion. Using the Hubble Space Telescope and the Advanced Camera for Surveys' High-Resolution Channel with an ultraviolet (F220W) filter, we have now directly detected the close companion. Based on the Wielen et al orbit, the Hipparcos parallax, and our measurement of the separation (0.176 0.002), we find a preliminary mass of 5.0 1.5 M for the Cepheid and 1.38 0.61 M for the close companion. These values will be refined by additional HST observations scheduled for the next 3 years. We have also obtained a Chandra ACIS-I image of the Polaris field. Two distant companions C and D are not X-rays sources and hence are not young enough to be physical companions of the Cepheid. There is one additional stellar X-ray source in the field, located 253 from Polaris A, which is a possible companion. Further investigation of such a distant companion is valuable to confirm the full extent of the system.

Original languageEnglish (US)
Pages (from-to)102-104
Number of pages3
JournalProceedings of the International Astronomical Union
Volume2
Issue numberS240
DOIs
StatePublished - Aug 1 2006

Fingerprint

Orbits
orbits
ultraviolet filters
X rays
Space telescopes
parallax
proper motion
filter
Hubble Space Telescope
radial velocity
x rays
Cameras
cameras
orbitals
high resolution
young

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy (miscellaneous)
  • Aerospace Engineering

Cite this

Evans, N. R., Schaefer, G., Bond, H. E., Nelan, E., Bono, G., Karovska, M., ... Mason, B. (2006). Polaris: Mass and multiplicity. Proceedings of the International Astronomical Union, 2(S240), 102-104. https://doi.org/10.1017/S1743921306005370
Evans, Nancy Remage ; Schaefer, Gail ; Bond, Howard E. ; Nelan, Edmund ; Bono, Giuseppe ; Karovska, Margarita ; Wolk, Scott ; Sasselov, Dimitar ; Guinan, Edward ; Engle, Scott ; Schlegel, Eric ; Mason, Brian. / Polaris : Mass and multiplicity. In: Proceedings of the International Astronomical Union. 2006 ; Vol. 2, No. S240. pp. 102-104.
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Evans, NR, Schaefer, G, Bond, HE, Nelan, E, Bono, G, Karovska, M, Wolk, S, Sasselov, D, Guinan, E, Engle, S, Schlegel, E & Mason, B 2006, 'Polaris: Mass and multiplicity', Proceedings of the International Astronomical Union, vol. 2, no. S240, pp. 102-104. https://doi.org/10.1017/S1743921306005370

Polaris : Mass and multiplicity. / Evans, Nancy Remage; Schaefer, Gail; Bond, Howard E.; Nelan, Edmund; Bono, Giuseppe; Karovska, Margarita; Wolk, Scott; Sasselov, Dimitar; Guinan, Edward; Engle, Scott; Schlegel, Eric; Mason, Brian.

In: Proceedings of the International Astronomical Union, Vol. 2, No. S240, 01.08.2006, p. 102-104.

Research output: Contribution to journalArticle

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T2 - Mass and multiplicity

AU - Evans, Nancy Remage

AU - Schaefer, Gail

AU - Bond, Howard E.

AU - Nelan, Edmund

AU - Bono, Giuseppe

AU - Karovska, Margarita

AU - Wolk, Scott

AU - Sasselov, Dimitar

AU - Guinan, Edward

AU - Engle, Scott

AU - Schlegel, Eric

AU - Mason, Brian

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N2 - Polaris, the nearest and brightest classical Cepheid, is a member of at least a triple system. It has a wide (18) physical companion, the F-type dwarf Polaris B. Polaris itself is a single-lined spectroscopic binary with an orbital period of 30 years (Kamper 1996). By combining Hipparcos measurements of the instantaneous proper motion with long-term measurements and the Kamper radial-velocity orbit, Wielen et al (2000) have predicted the astrometric orbit of the close companion. Using the Hubble Space Telescope and the Advanced Camera for Surveys' High-Resolution Channel with an ultraviolet (F220W) filter, we have now directly detected the close companion. Based on the Wielen et al orbit, the Hipparcos parallax, and our measurement of the separation (0.176 0.002), we find a preliminary mass of 5.0 1.5 M for the Cepheid and 1.38 0.61 M for the close companion. These values will be refined by additional HST observations scheduled for the next 3 years. We have also obtained a Chandra ACIS-I image of the Polaris field. Two distant companions C and D are not X-rays sources and hence are not young enough to be physical companions of the Cepheid. There is one additional stellar X-ray source in the field, located 253 from Polaris A, which is a possible companion. Further investigation of such a distant companion is valuable to confirm the full extent of the system.

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Evans NR, Schaefer G, Bond HE, Nelan E, Bono G, Karovska M et al. Polaris: Mass and multiplicity. Proceedings of the International Astronomical Union. 2006 Aug 1;2(S240):102-104. https://doi.org/10.1017/S1743921306005370