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 language | English (US) |
|---|---|
| Pages (from-to) | 102-104 |
| Number of pages | 3 |
| Journal | Proceedings of the International Astronomical Union |
| Volume | 2 |
| Issue number | S240 |
| DOIs | |
| State | Published - Aug 1 2006 |
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All Science Journal Classification (ASJC) codes
- Physics and Astronomy (miscellaneous)
- Aerospace Engineering
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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 journal › Article
TY - JOUR
T1 - Polaris
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
PY - 2006/8/1
Y1 - 2006/8/1
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.
AB - 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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U2 - 10.1017/S1743921306005370
DO - 10.1017/S1743921306005370
M3 - Article
VL - 2
SP - 102
EP - 104
JO - Proceedings of the International Astronomical Union
JF - Proceedings of the International Astronomical Union
SN - 1743-9213
IS - S240
ER -