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Details for Revision 3
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Name
  alf UMi  
AAVSO UID
000-BBF-045 (929 observations)  
Constellation
Ursa Minor Sequence
J2000.0
02 31 49.08 +89 15 50.8  (37.95450 +89.26411) Search nearby
B1950.0 01 48 56.46 +89 01 43.1
Galactic coord. 123.281 +26.461
Other names

(Internal only)
1 UMi 3XMM J023145.5+891548 AAVSO 0122+88
ADS 1477 A BD+88 8 CCDM J02319+8915A
CXO J023149.5+891550 CXOGSG J023150.1+891550 HD 8890
HIP 11767 HR 424 IRAS 01490+8901
Polaris RAFGL 273 SAO 308
TYC 4628-237-1 WDS J02318+8916Aa  
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Variability type
DCEPS
Spectral type F7Ib-F8Ib
Mag. range
1.97 - 2.00 V
Discoverer --
Epoch
09 Feb 1945 (HJD 2431495.813) Ephemeris
Outburst --
Period 3.9696 d
Rise/eclipse dur. 50%  (48 h)
Remarks
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1 Otero, Sebastian Alberto Triple system. From RV variations, probably spotted with P ~120 d? (2024ApJ...971..190E).
2 Riesen, Peter Polaris is the current northern pole star. This will remain the case until about 3000 AD.
3 Otero, Sebastian Alberto Period increased (3.9696 d. in 1989-1993 Hipparcos data, 3.97204 d. in 2008-2023 AAVSO V data, but the trend reversed and it is decreasing again while the amplitude stopped increasing. Changes in pulsation behaviour over the last century may be related to the binary nature of the system, as they seem to occur near each periastron passage, when the secondary (F6V) comes within 29 stellar radii of the Cepheid in its eccentric orbit with P= 29.433 yr. (2023arXiv230903257T)
4 Otero, Sebastian Alberto Amplitude decrease during the 20th century. Currently, amplitude varies but always below 0.05 mag. Period is increasing.
5 GCVS Team VB A (B 8.20m, F3V, 18.3", 218deg); SB1 (Porb = 10969d, E = 0.655 [K.W.Kamper, N.R.Evans, R.W. Lyons, JRAS Can 78, N5, 173, 1984.]). P var. There is a non-linear term in the elements: +1.9877d*10**(-7)*E**2. The amplitude of light and radial velocity variation decreased in 1982. A(V) = 0.04m (1984).
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References
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1 Evans, N. R.; Schaefer, G. H.; Gallenne, A.; et al., 2024, The Orbit and
Dynamical Mass of Polaris: Observations with the CHARA Array		 2024ApJ...971..190E
2 Torres, G., 2023, The Spectroscopic Orbit of Polaris, and its Pulsation
Properties		 2023arXiv230903257T
3 A.Arellano Ferro, ApJ 274, 755, 1983. 1983ApJ...274..755A
4 Hertzsprung, E., 1911, Nachweis der Veränderlichkeit von alpha Ursae
minoris		 1911AN....189...89H
External Links
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Supporting Documents
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2 Phase plot Otero, Sebastian Alberto 2023-09-15 14:33 UTC Phase plot with AAVSO V data.
1 Alpha Ursae Minoris light curve Otero, Sebastian Alberto 2007-12-04 19:56 UTC Light curve using Hipparcos data transformed to V. showing the current small amplitude of the star.
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Revision History
Currently approved revision is checked. Click revision number to view details of that revision.
5 Otero, Sebastian Alberto 2023-09-15 14:33 UTC Period, epoch and amplitude from AAVSO (2008-2023) V data.
4 Schmeer, Patrick 2018-07-05 10:46 UTC Discoverer added from 1911AN....189...89H.
3 Otero, Sebastian Alberto 2007-12-04 19:56 UTC HIP position. HIP photometry transformed to V used for the range.
2 Koppelman, Michael 2007-12-04 07:36 UTC The SIMBAD links fills in Polaris for this star but you can't search for it by that name. I'm hoping this fixes that.
1 Admin, VSX 2005-12-18 01:33 UTC Initial database population.

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