RR Lyrae

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RR Lyrae
Rr lyrae ltcrv en.svg
Illustration of the typical light curve for RR Lyrae.
Observation data
Epoch J2000       Equinox J2000
Constellation Lyra
Right ascension 19h 25m 27.91285s [1]
Declination +42° 47′ 03.6942″ [1]
Apparent magnitude  (V)7.195 [2]  (7.06–8.12) [3]
Characteristics
Spectral type A7III - F8III
U−B color index +0.172 [2]
B−V color index +0.181 [2]
Variable type RR Lyr [4]
Astrometry
Radial velocity (Rv)-72.4 [5]  km/s
Proper motion (μ)RA: -109.68 [1]   mas/yr
Dec.: -195.75 [1]   mas/yr
Parallax (π)3.64 ± 0.23  mas [6]
Distance 900 ± 60  ly
(270 ± 20  pc)
Absolute magnitude  (MV)0.600 ± 0.126 [7]
Details
Mass 0.65 [8]   M☉
Radius 5.1 to 5.6 [8]   R☉
Luminosity 49 ± 5 [8]   L☉
Surface gravity (log g)2.4 ± 0.2 [8]   cgs
Temperature 6,125 ± 50 [8]   K
Metallicity [Fe/H]–1.16 [7]   dex
Other designations
RR  Lyr, 2MASS  J19252793+4247040, NLTT  47799, HD  182989, BD+42°3338, HIP  95497, SAO  48421, LTT  15677 [9]
Database references
SIMBAD data

RR Lyrae is a variable star in the Lyra constellation, figuring in its west near to Cygnus. [10] As the brightest star in its class, [11] it became the eponym for the RR Lyrae variable class of stars [3] and it has been extensively studied by astronomers. [7] RR Lyrae variables serve as important standard candles that are used to measure astronomical distances. The period of pulsation of an RR Lyrae variable depends on its mass, luminosity and temperature, while the difference between the measured luminosity and the actual luminosity allows its distance to be determined via the inverse-square law. Hence, understanding the period-luminosity relation for a local set of such stars allows the distance of more distant stars of this type to be determined. [12]

Contents

History

The variable nature of RR Lyrae was discovered by the Scottish astronomer Williamina Fleming at Harvard Observatory in 1901. [10]

The distance of RR Lyrae remained uncertain until 2002 when the Hubble Space Telescope's fine guidance sensor was used to determine the distance of RR Lyrae within a 5% margin of error, yielding a value of 262 parsecs (855 light-years ). [13] When combined with measurements from the Hipparcos satellite and other sources, the result is a distance estimate of 258  pc (841  ly ).

Variable star class

RR Lyrae-type variable stars (not RR Lyr itself) close to the galactic center from the VVV ESO public survey Variable stars close to the Galactic Centre.jpg
RR Lyrae-type variable stars (not RR Lyr itself) close to the galactic center from the VVV ESO public survey

This type of low-mass star has consumed the hydrogen at its core, evolved away from the main sequence, and passed through the red giant stage. Energy is now being produced by the thermonuclear fusion of helium at its core, and the star has entered an evolutionary stage called the horizontal branch (HB). The effective temperature of an HB star's outer envelope will gradually increase over time. When its resulting stellar classification enters a range known as the instability strip—typically at stellar class A—the outer envelope can begin to pulsate. [12] RR Lyrae shows just such a regular pattern of pulsation, which is causing its apparent magnitude to vary between 7.06 and 8.12 over a short cycle lasting 0.567 days (13 hours, 36 minutes). [3] Each radial pulsation causes the radius of the star to vary between 5.1 and 5.6 times the Sun's radius. [8]

This star belongs to a subset of RR Lyrae-type variables that show a characteristic behavior called the Blazhko effect, [14] named after Russian astronomer Sergey Blazhko. This effect is observed as a periodic modulation of a variable star's pulsation strength or phase; sometimes both. It causes the light curve of RR Lyrae to change from cycle to cycle. In 2014, Time-series photometric observations demonstrated the physical origin of this effect. [15]

Other stellar classifications

As with other RR Lyrae-type variables, RR Lyrae itself has a low abundance of elements other than hydrogen and helium – what astronomers term its metallicity: It belongs to the Population II category of stars that formed during the early period of the Universe when there was a lower abundance of metals in star-forming regions. [16]

The trajectory of this star is carrying it along an orbit that is close to the plane of the Milky Way, taking it no more than 680 ly (210 pc) above or below this plane. The Blazhko period for RR Lyrae is 39.1 ± 0.3 days. [3] The orbit has a high eccentricity, bringing RR Lyrae as close as 6.80  kly (2.08  kpc ) to the Galactic Center at periapsis, and taking it as far as 59.9 kly (18.4 kpc) at apapsis. [17]

Related Research Articles

<span class="mw-page-title-main">RR Lyrae variable</span> Type of variable star

RR Lyrae variables are periodic variable stars, commonly found in globular clusters. They are used as standard candles to measure (extra) galactic distances, assisting with the cosmic distance ladder. This class is named after the prototype and brightest example, RR Lyrae.

<span class="mw-page-title-main">Beta Lyrae</span> Multiple star system in the constellation of Lyra

Beta Lyrae officially named Sheliak, the traditional name of the system, is a multiple star system in the constellation of Lyra. Based on parallax measurements obtained during the Hipparcos mission, it is approximately 960 light-years distant from the Sun.

Eta Lyrae, a name Latinized from η Lyrae, is a likely binary star system in the northern constellation of Lyra. It has the traditional name Aladfar and is faintly visible to the naked eye with an apparent visual magnitude of 4.43. The system is located at a distance of approximately 1,390 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −8 km/s.

<span class="mw-page-title-main">Kappa Lyrae</span> Star in the constellation Lyra

κ Lyrae, Latinized as Kappa Lyrae, is a solitary star in the northern constellation of Lyra, near the constellation border with Hercules. It is visible to the naked eye as a faint, orange-hued point of light with an apparent visual magnitude of 4.33. This object is located approximately 252 light years from the Sun based on parallax, but is moving closer with a radial velocity of −24 km/s.

<span class="mw-page-title-main">Iota Lyrae</span> Binary star in the constellation Lyra

ι Lyrae, Latinised as Iota Lyrae, is a binary star in the northern constellation of Lyra. It is visible to the naked eye as a dim, blue-white hued star with an apparent visual magnitude that fluctuates around 5.22. This object is located approximately 910 light years distant from the Sun based on parallax, but is drifting nearer with a radial velocity of −26 km/s.

The Blazhko effect, also known as the Tseraskaya–Blazhko effect, and which is sometimes called long-period modulation, is a variation in period and amplitude in RR Lyrae type variable stars. Sergey Blazhko first reported its observation by Lidiya Tseraskaya in 1907, in the star RW Draconis.

<span class="mw-page-title-main">Rho Puppis</span> Star in the southern constellation of Puppis

Rho Puppis, formally named Tureis, is a star in the southern constellation of Puppis. With an average apparent visual magnitude of 2.78, it is the third-brightest member of this generally faint constellation. Based upon parallax measurements made during the Hipparcos mission, Rho Puppis is located at a distance of 63.5 light-years from the Sun. It is the prototype of the ρ Puppis class of evolved Am stars.

<span class="mw-page-title-main">SX Phoenicis</span>

SX Phoenicis is a variable star in the southern constellation Phoenix. With an apparent visual magnitude ranging around 7.33, it is too faint to be readily seen with the naked eye and requires binoculars. It is located 272 light years from the Sun, as determined from an annual parallax shift of 12 mas.

<span class="mw-page-title-main">64 Eridani</span> Single, yellow-white hued star in the constellation Eridanus

64 Eridani is a single, yellow-white hued star in the constellation Eridanus having variable star designation S Eridani. It is faintly visible to the naked eye with an apparent visual magnitude of 4.77. The annual parallax shift is measured at 12.01 mas, which equates to a distance of about 272 light years. In addition to its proper motion, it is moving closer to the Sun with a radial velocity of around −9 km/s.

Zeta<sup>1</sup> Lyrae Star in the constellation Lyra

Zeta1 Lyrae, Latinized from ζ1 Lyrae, is a binary star in the northern constellation of Lyra. Based upon an annual parallax shift of 20.89 mas as seen from Earth, the pair are located about 156 light years from the Sun. It is visible to the naked eye with an apparent visual magnitude of 4.37.

<span class="mw-page-title-main">Kappa Pavonis</span> Variable star in the constellation Pavo

Kappa Pavonis is a variable star in the constellation Pavo. It is the brightest W Virginis variable in the sky.

<span class="mw-page-title-main">UY Scuti</span> Star in the constellation Scutum

UY Scuti (BD-12°5055) is a red supergiant star, located 5,900 light-years away in the constellation Scutum. It is also a pulsating variable star, with a maximum brightness of magnitude 8.29 and a minimum of magnitude 10.56, which is too dim for naked-eye visibility. It is considered to be one of the largest known stars, with a radius estimated at 909 solar radii, thus a volume of 750 million times that of the Sun. This estimate implies if it were placed at the center of the Solar System, its photosphere would extend past the orbit of Mars or even the asteroid belt.

<span class="mw-page-title-main">BL Boötis</span> Star in the constellation Boötes

BL Boötis is a pulsating star in the constellation Boötes. It is the prototype of a class of anomalous Cepheids which is intermediate in the H-R diagram between the type I classical Cepheids and the type II Cepheids.

Nu1 Lyrae (ν1 Lyrae) is a star in the northern constellation of Lyra. Based upon an annual parallax shift of 2.49 mas as seen from Earth, it is located approximately 1,300 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.35 due to interstellar dust. With an apparent visual magnitude of 5.91, the star is barely bright enough to be visible with the naked eye on a dark night.

<span class="mw-page-title-main">HP Lyrae</span> Variable star in the constellation Lyra

HP Lyrae is a variable star in the constellation Lyra, with a visual magnitude varying between 10.2 and 10.8. It will likely be an RV Tauri variable, an unstable post-AGB star losing mass before becoming a white dwarf.

<span class="mw-page-title-main">V473 Lyrae</span> Star in the constellation Lyra

V473 Lyrae is a variable star in the constellation Lyra. It is an unusual Classical Cepheid variable with a visual range of 5.99 to 6.35.

<span class="mw-page-title-main">19 Lyrae</span> Star in the constellation Lyra

19 Lyrae is a single variable star located approximately 950 light years away from the Sun in the northern constellation of Lyra. It has the variable star designation V471 Lyr, while 19 Lyrae is the Flamsteed designation. This object is just bright enough to be visible to the naked eye, appearing as a dim, blue-white star with a baseline apparent visual magnitude of 5.93. It is moving closer to the Earth with a heliocentric radial velocity of −30 km/s, and may come as close as 167 light-years around 8.5 million years from now.

<span class="mw-page-title-main">DY Pegasi</span> Star in the constellation Pegasus

DY Pegasi, abbreviated DY Peg, is a binary star system in the northern constellation of Pegasus. It is a well-studied SX Phoenicis variable star with a brightness that ranges from an apparent visual magnitude of 9.95 down to 10.62 with a period of 1.75 hours. This system is much too faint to be seen with the naked eye, but can be viewed with large binoculars or a telescope. Based on its high space motion and low abundances of heavier elements, it is a population II star system.

<span class="mw-page-title-main">TU Ursae Majoris</span>

TU Ursae Majoris is a variable star in the northern circumpolar constellation of Ursa Major. It is classified as a Bailey-type 'ab' RR Lyrae variable with a period of 0.557648 days that ranges in brightness from apparent visual magnitude of 9.26 down to 10.24. The distance to this star is approximately 2,090 light years based on parallax measurements. It is located near the north galactic pole at a distance that indicates this is a member of the galactic halo.

<span class="mw-page-title-main">X Cygni</span> Variable star in the constellation Cygnus

X Cygni is a variable star in the northern constellation of Cygnus, abbreviated X Cyg. This is a Delta Cephei variable that ranges in brightness from an apparent visual magnitude of 5.85 down to 6.91 with a period of 16.386332 days. At it brightest, this star is dimly visible to the naked eye. The distance to this star is approximately 628 light years based on parallax measurements. It is drifting further away with a radial velocity of 8.1 km/s. This star is a likely member of the open cluster Ruprecht 173.

References

  1. 1 2 3 4 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv: 0708.1752 , Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID   18759600
  2. 1 2 3 Schoeneich, W.; Lange, D. (1979), "UBV observations of RR Lyr", Information Bulletin on Variable Stars, 1557: 1–2, Bibcode:1979IBVS.1557....1S
  3. 1 2 3 4 Kolenberg, K.; et al. (February 2011), "Kepler photometry of the prototypical Blazhko star RR Lyr: an old friend seen in a new light", Monthly Notices of the Royal Astronomical Society , 411 (2): 878–890, arXiv: 1011.5908 , Bibcode:2011MNRAS.411..878K, doi: 10.1111/j.1365-2966.2010.17728.x , S2CID   73597094
  4. ↑ Samus, N. N.; Durlevich, O. V.; et al. (2009), "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)", VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S, 1, Bibcode:2009yCat....102025S
  5. ↑ Wilson, Ralph Elmer (1953), "General Catalogue of Stellar Radial Velocities", Carnegie Institute Washington D.C. Publication, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W
  6. ↑ Brown, A.G.A.; et al. (Gaia Collaboration) (November 2016), "Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties", Astronomy and Astrophysics, 595 (A): 2, arXiv: 1609.04172v1 , Bibcode:2016A&A...595A...2G, doi:10.1051/0004-6361/201629512, S2CID   1828208
  7. 1 2 3 Catelan, M.; Cortés, C. (April 2008), "Evidence for an Overluminosity of the Variable Star RR Lyrae, and a Revised Distance to the LMC", The Astrophysical Journal, 676 (2): L135–L138, arXiv: 0802.2063 , Bibcode:2008ApJ...676L.135C, doi:10.1086/587515, S2CID   17268929
  8. 1 2 3 4 5 6 Kolenberg, K.; et al. (September 2010), "An in-depth spectroscopic analysis of the Blazhko star RR Lyrae. I. Characterisation of the star: abundance analysis and fundamental parameters" (PDF), Astronomy and Astrophysics, 519: A64, arXiv: 1004.5156 , Bibcode:2010A&A...519A..64K, doi:10.1051/0004-6361/201014471, S2CID   6401091 [ permanent dead link ]
  9. ↑ "V* RR Lyr -- Variable Star of RR Lyr type", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-01-08
  10. 1 2 Burnham, Robert Jr. (1978), Burnham's Celestial Handbook, vol. 2, New York: Dover Publications, ISBN   0-486-23568-8
  11. ↑ Templeton, Matthew (September 24, 2010), RR Lyrae, American Association of Variable Star Observers , retrieved 2012-01-08
  12. 1 2 Salaris, Maurizio; Cassisi, Santi (2005), Evolution of stars and stellar populations, John Wiley and Sons, pp. 181–182, ISBN   0-470-09220-3
  13. ↑ Benedict, G. Fritz; et al. (January 2002), "Astrometry with the Hubble Space Telescope: A Parallax of the Fundamental Distance Calibrator RR Lyrae", The Astronomical Journal, 123 (1): 473–484, arXiv: astro-ph/0110271 , Bibcode:2002AJ....123..473B, doi:10.1086/338087, S2CID   59150013
  14. ↑ Smith, Horace A.; et al. (January 2003), "The Blazhko Effect of RR Lyrae in 1996", The Publications of the Astronomical Society of the Pacific, 115 (803): 43–48, Bibcode:2003PASP..115...43S, doi: 10.1086/345458
  15. ↑ Chadid, M. (2014), "First Detection of Multi-shocks in RR Lyrae Stars from Antarctica: A Possible Explanation of the Blazhko Effect", The Astronomical Journal, 148 (5): 88–94, Bibcode:2014AJ....148...88C, doi:10.1088/0004-6256/148/5/88, S2CID   121252232
  16. ↑ Inglis, Mike (2003), Observer's guide to stellar evolution: the birth, life, and death of stars, Patrick Moore's practical astronomy series, Springer, p. 162, ISBN   1-85233-465-7
  17. ↑ Maintz, G.; de Boer, K. S. (October 2005), "RR Lyrae stars: kinematics, orbits and z-distribution", Astronomy and Astrophysics, 442 (1): 229–237, arXiv: astro-ph/0507604 , Bibcode:2005A&A...442..229M, doi:10.1051/0004-6361:20053231, S2CID   54194736
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