HP Lyrae

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HP Lyrae
HPLyrLightCurve.png
A blue band light curve for HP Lyrae, adapted from Wenzel (2013) [1]
Observation data
Epoch J2000       Equinox J2000
Constellation Lyra
Right ascension 19h 21m 39.066s [2]
Declination +39° 56′ 08.05″ [2]
Apparent magnitude  (V)10.43 [3] (10.2 - 10.8 [4] )
Characteristics
Spectral type A2-F2 Iab [4]
U−B color index +0.1 - +0.5 [4]
B−V color index +0.3 - +0.7 [4]
Variable type RV Tau [5]
Astrometry
Radial velocity (Rv)−107 [5]  km/s
Proper motion (μ)RA: −2.485±0.038 [6]   mas/yr
Dec.: −5.500±0.047 [6]   mas/yr
Parallax (π)0.0822 ± 0.0242  mas [6]
Distance 6,700±380 [7]   pc
Absolute magnitude  (MV)−4.5 [4]
Orbit [7]
Period (P)1,631 days
Eccentricity (e)0.17
Argument of periastron (ω)
(secondary)		5.5°
Semi-amplitude (K1)
(primary)		7.7 km/s
Details [5]
Mass 0.6 [7]   M☉
Radius 60 [7]   R☉
Luminosity 3,900±400 [7]   L☉
Surface gravity (log g)1.0  cgs
Temperature 5,900 [7]   K
Metallicity [Fe/H]−1.0  dex
B
Mass 0.5 - 0.6 [7]   M☉
Other designations
HP  Lyrae, TYC  3138-54-1, ASAS  J192139+3956.1, IRAS  19199+3950, 2MASS  J19213906+3956080, AAVSO  1918+39
Database references
SIMBAD data

HP Lyrae (HP Lyr) 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.

Contents

Discovery

HP Lyr was first reported to be variable in 1935 by Otto Morgenroth of the Sonneberg Observatory. The range was given as 9.5 - 10.5 and the variability type only as long-period. [8] In 1961, it was formally designated as a β Lyr eclipsing variable with two A type supergiants in a close orbit producing smooth continuous variations with alternating minima of different depths. The period was given as 140.75 days, covering two maxima, and both a deep primary minimum and a slightly less deep secondary minimum. [9]

In 2001 a request was made for observations of HP Lyr. [10] Shortly after it was reported that HP Lyr was likely to be an RV Tauri variable rather than an eclipsing binary. [11] This was confirmed with a more detailed study published in 2002. [4] Some authors still maintain that the spectral type and nature of variation mean HP Lyr is more likely to be an eclipsing variable. [12]

Variability

HP Lyr varies by about 0.5 magnitude over a "halfperiod" of 68.4 days. [7] The formal period, defined for an RV Tauri variable as being from deep minimum to deep minimum is twice that length. Its spectrum changes from A2-3 at maximum to F2 at the deepest minima. The radial velocity changes are typical for the pulsations of an RV Tauri variable, but are not compatible with a binary orbit. The spectral type and colour indicated that it was likely to be the hottest known RV Tauri star. [4]

Until 1960, the period of HP Lyr was very consistent at 140.75 days. Since then it has been observed to reduce to below 140 days, probably quite suddenly. A survey of historic photography including the star showed that the period changed in 1962 or 1963, taking no more than four cycles to reach a new value of 138.66 days. [1]

Properties

A 2005 study of the elemental abundances of RV Tauri stars calculated that HP Lyr had a temperature around 6,300  K and typical abundances for an RV Tauri variable. It also revealed that the abundances were altered by dust-gas separation in circumstellar material. [5] HP Lyr has been included in a catalog of confirmed post-AGB stars, highly evolved and on its way to becoming a white dwarf. [13] In 2017, the temperature was calculated to be 5,900 K, still one of the hottest known RV Tau variables. [7]

The distance is uncertain, although large. Gaia Data Release 2 contains a parallax indicating a distance of around 12,000  pc . [6] Using luminosities derived from a period-luminosity-colour relationship, together with interstellar extinctions, gives a distance of around 6,700 K. From the radius and effective temperature, the radius is calculated to be 60 R☉. [7]

HP Lyrae is a post-AGB star, one that has completed its evolution along the asymptotic giant branch (AGB) and is now rapidly shedding its outer layers prior to becoming a white dwarf. During this process it becomes hotter and crosses the instability strip which causes it to become unstable and pulsate. [7]

Binary

Many RV Tauri stars are found to be in binary systems, and HP Lyrae has an invisible companion in a 1,631  d orbit. Its properties are not known, but the mass is estimated to be a little under 0.6 M☉, leaving open the possibility that it is a white dwarf. [7]

Related Research Articles

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Lyra is a small constellation. It is one of the 48 listed by the 2nd century astronomer Ptolemy, and is one of the modern 88 constellations recognized by the International Astronomical Union. Lyra was often represented on star maps as a vulture or an eagle carrying a lyre, and hence is sometimes referred to as Vultur Cadens or Aquila Cadens, respectively. Beginning at the north, Lyra is bordered by Draco, Hercules, Vulpecula, and Cygnus. Lyra is nearly overhead in temperate northern latitudes shortly after midnight at the start of summer. From the equator to about the 40th parallel south it is visible low in the northern sky during the same months.

<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.

<span class="mw-page-title-main">RV Tauri</span> Star in the constellation Taurus

RV Tauri is a star in the constellation Taurus. It is a yellow supergiant and is the prototype of a class of pulsating variables known as RV Tauri variables. It is a post-AGB star and a spectroscopic binary about 4,700 light years away.

<span class="mw-page-title-main">RV Tauri variable</span> Class of luminous variable star

RV Tauri variables are luminous variable stars that have distinctive light variations with alternating deep and shallow minima.

<span class="mw-page-title-main">17 Lyrae</span> Star in the constellation Lyra

17 Lyrae is a multiple star system in the constellation Lyra, 143 light years away from Earth.

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

R Lyrae, also known as its Flamsteed designation 13 Lyrae, is a 4th magnitude semiregular variable star in the constellation Lyra, approximately 350 light years away from Earth. It is a red giant star of the spectral type M5III, currently at the last stages of evolution. It is much larger and brighter, yet cooler, than the Sun. In the near-infrared J band, it is brighter than the nearby Vega.

<span class="mw-page-title-main">HR 4049</span> Protoplanetary nebula in the constellation Antlia

HR 4049, also known as HD 89353 and AG Antliae, is a binary post-asymptotic-giant-branch (post-AGB) star in the constellation Antlia. A very metal-poor star, it is surrounded by a thick unique circumbinary disk enriched in several molecules. With an apparent magnitude of about 5.5, the star can readily be seen under ideal conditions. It is located approximately 1,700 parsecs (5,500 ly) distant.

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

RR Lyrae is a variable star in the Lyra constellation, figuring in its west near to Cygnus. As the brightest star in its class, it became the eponym for the RR Lyrae variable class of stars and it has been extensively studied by astronomers. 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.

<span class="mw-page-title-main">R Scuti</span> Variable star in the constellation Scutum

R Scuti is a star in the constellation of Scutum. It is a yellow supergiant and is a pulsating variable known as an RV Tauri variable. It was discovered in 1795 by Edward Pigott at a time when only a few variable stars were known to exist.

<span class="mw-page-title-main">R Sagittae</span> Star in the constellation Sagitta

R Sagittae is an RV Tauri variable star in the constellation Sagitta that varies from magnitude 8.0 to 10.5 in 70.77 days. It is a post-AGB low mass yellow supergiant that varies between spectral types G0Ib and G8Ib as it pulsates. Its variable star designation of "R" indicates that it was the first star discovered to be variable in the constellation. It was discovered in 1859 by Joseph Baxendell, though classified as a semi regular variable until RV Tauri variables were identified as a distinct class in 1905.

<span class="mw-page-title-main">AC Herculis</span> Spectroscopic binary star in the constellation Hercules

AC Herculis, is an RV Tauri variable and spectroscopic binary star in the constellation of Hercules. It varies in brightness between apparent magnitudes 6.85 and 9.0.

<span class="mw-page-title-main">U Monocerotis</span> Variable star system in the constellation Monoceros

U Monocerotis is a pulsating variable star and spectroscopic binary in the constellation Monoceros. The primary star is an RV Tauri variable, a cool luminous post-AGB star evolving into a white dwarf.

<span class="mw-page-title-main">S Cassiopeiae</span> Star in the constellation Cassiopeia

S Cassiopeiae is a Mira variable and S-type star in the constellation Cassiopeia. It is an unusually cool star, rapidly losing mass and surrounded by dense gas and dust producing masers.

<span class="mw-page-title-main">IK Tauri</span> Mira variable star in the constellation Taurus

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<span class="mw-page-title-main">IRAS 08544−4431</span> Variable star in the constellation Vela

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<span class="mw-page-title-main">SX Centauri</span> Supergiant variable star in the constellation Centaurus

SX Centauri is a variable star in the constellation Centaurus. An RV Tauri variable, its light curve alternates between deep and shallow minima, varying its apparent magnitude from 9.1 to 12.4. From the period-luminosity relationship, it is estimated to be around 1.6 kpc from Earth. Gaia Data Release 2 gives a parallax of 0.2175 mas, corresponding to distance of about 4,600 pc.

<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.

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SZ Tauri is a variable star in the equatorial constellation of Taurus. The brightness of this star varies from an apparent visual magnitude of 6.39 down to 6.69 with a period of 3.149 days, which is near the lower limit of visibility to the naked eye. The distance to this star is approximately 2,070 light years based on parallax measurements. There is some indication this may be a binary system, but the evidence is inconclusive.

References

  1. 1 2 Wenzel, W. (2013). "HP Lyrae – the sudden period decrease". Minutes on Variable Stars (MVS13–01).
  2. 1 2 Cutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E.; Fowler, John W.; Gizis, John E.; Howard, Elizabeth V.; Huchra, John P.; Jarrett, Thomas H.; Kopan, Eugene L.; Kirkpatrick, J. Davy; Light, Robert M.; Marsh, Kenneth A.; McCallon, Howard L.; Schneider, Stephen E.; Stiening, Rae; Sykes, Matthew J.; Weinberg, Martin D.; Wheaton, William A.; Wheelock, Sherry L.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues. 2246: II/246. Bibcode:2003yCat.2246....0C.
  3. ↑ Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27. Bibcode:2000A&A...355L..27H.
  4. 1 2 3 4 5 6 7 Graczyk, D.; Mikolajewski, M.; Leedjarv, L.; Frackowiak, S. M.; Osiwala, J. P.; Puss, A.; Tomov, T. (2002). "HP Lyr - Possibly the Hottest RV Tau Type Object". Acta Astronomica. 52: 293–304. arXiv: astro-ph/0210448 . Bibcode:2002AcA....52..293G.
  5. 1 2 3 4 Giridhar, Sunetra; Lambert, David L.; Reddy, Bacham E.; Gonzalez, Guillermo; Yong, David (2005). "Abundance Analyses of Field RV Tauri Stars. VI. An Extended Sample". The Astrophysical Journal. 627 (1): 432–445. arXiv: astro-ph/0503344 . Bibcode:2005ApJ...627..432G. doi:10.1086/430265. S2CID   18053310.
  6. 1 2 3 4 Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics . 616. A1. arXiv: 1804.09365 . Bibcode: 2018A&A...616A...1G . doi: 10.1051/0004-6361/201833051 . Gaia DR2 record for this source at VizieR.
  7. 1 2 3 4 5 6 7 8 9 10 11 12 Manick, Rajeev; Van Winckel, Hans; Kamath, Devika; Hillen, Michel; Escorza, Ana (2017). "Establishing binarity amongst Galactic RV Tauri stars with a disc⋆". Astronomy and Astrophysics. 597: A129. arXiv: 1610.00506 . Bibcode:2017A&A...597A.129M. doi:10.1051/0004-6361/201629125. S2CID   119242786.
  8. ↑ Morgenroth, O. (1935). "23 neue Veränderliche". Astronomische Nachrichten. 255 (23): 425–428. Bibcode:1935AN....255..425M. doi:10.1002/asna.19352552303.
  9. ↑ Wenzel, W. (1961). "Two Variables of Beta Lyrae Type with Long Periods". Information Bulletin on Variable Stars. 1: 1. Bibcode:1961IBVS....1....1W.
  10. ↑ Meyer, R. (2001). "Beobachtungsaufruf: HP Lyr". BAV Rundbrief. 50: 5. Bibcode:2001BAVSR..50....5M.
  11. ↑ Hassforther, B. (2002). "HP Lyrae ist wahrscheinlich ein RV-Tauri-Stern". BAV Rundbrief. 51: 182. Bibcode:2002BAVSR..51..182H.
  12. ↑ Alfonso-Garzón, J.; Domingo, A.; Mas-Hesse, J. M.; Giménez, A. (2012). "The first INTEGRAL-OMC catalogue of optically variable sources". Astronomy & Astrophysics. 1210: A79. arXiv: 1210.0821 . Bibcode:2012A&A...548A..79A. doi:10.1051/0004-6361/201220095. S2CID   118428054.
  13. ↑ Szczerba, R.; Siódmiak, N.; Stasińska, G.; Borkowski, J. (2007). "An evolutionary catalogue of galactic post-AGB and related objects". Astronomy and Astrophysics. 469 (2): 799–806. arXiv: astro-ph/0703717 . Bibcode:2007A&A...469..799S. doi:10.1051/0004-6361:20067035. S2CID   16505186.
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