HP Lyrae

HP Lyrae
Observation data
Epoch J2000      Equinox J2000
Constellation Lyra
Right ascension 19h 21m 39.066s[1]
Declination +39° 56′ 08.05″[1]
Apparent magnitude (V) 10.43[2] (10.2 - 10.8[3])
Characteristics
Spectral type A2-F2 Iab[3]
U−B color index +0.1 - +0.5[3]
B−V color index +0.3 - +0.7[3]
Variable type RV Tau[4]
Astrometry
Radial velocity (Rv)−107[4] km/s
Proper motion (μ) RA: –3.1 ± 1.5[2] mas/yr
Dec.: –3.3 ± 1.5[2] mas/yr
Parallax (π)−0.29 ± 0.23[5] mas
Distance~5,000[3]) pc
Absolute magnitude (MV)−4.5[3]
Details[4]
Surface gravity (log g)1.0 cgs
Temperature6,300 K
Metallicity [Fe/H]−1.0 dex
Other designations
HP Lyrae, TYC 3138-54-1, ASAS J192139+3956.1, IRAS 19199+3950, 2MASS J19213906+3956080, AAVSO 1918+39
Database references
SIMBADdata

HP Lyrae is a variable star in the constellation Lyra, with a visual magnitude between 10.2 and 10.8.

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.[6] 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.[7]

In 2001 a request was made for observations of HP Lyr[8] and shortly after it was reported that HP Lyr was likely to be an RV Tauri variable rather than an eclipsing binary.[9] This was confirmed with a more detailed study published in 2002. [3] Some authors still maintain that the spectral type and nature of variation mean HP Lyr is more likely to be an eclipsing variable.[10]

HP Lyr varies by about 0.5 magnitude over a "halfperiod" of 69.35 days. The formal period, defined for an RV Tauri variable from deep minimum to deep minimum is 138.7 days. 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 not compatible with a binary orbit. The spectral type and colour indicated that it was likely to be the hottest known RV Tauri star.[3]

Until 1960, the period of HP Lyr was very consistent at 140.75 days. Since then it was 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.[11]

A 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.[4] HP Lyr has been included in a catalog of confirmed post-AGB stars, highly evolved and on its way to becoming a white dwarf.[12]

References

  1. 1 2 Cutri, R. M.; Skrutskie, M. F.; Van Dyk, S.; Beichman, C. A.; Carpenter, J. M.; Chester, T.; Cambresy, L.; Evans, T.; Fowler, J.; Gizis, J.; Howard, E.; Huchra, J.; Jarrett, T.; Kopan, E. L.; Kirkpatrick, J. D.; Light, R. M.; Marsh, K. A.; McCallon, H.; Schneider, S.; Stiening, R.; Sykes, M.; Weinberg, M.; Wheaton, W. A.; Wheelock, S.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". VizieR On-line Data Catalog: II/246. Originally published in: 2003yCat.2246....0C. 2246. Bibcode:2003yCat.2246....0C.
  2. 1 2 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. doi:10.1888/0333750888/2862.
  3. 1 2 3 4 5 6 7 8 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. Bibcode:2002AcA....52..293G. arXiv:astro-ph/0210448 Freely accessible.
  4. 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: 432–445. Bibcode:2005ApJ...627..432G. arXiv:astro-ph/0503344 Freely accessible. doi:10.1086/430265.
  5. ↑ Gaia Collaboration (2016). "VizieR Online Data Catalog: Gaia DR1 (Gaia Collaboration, 2016)". VizieR On-line Data Catalog: I/337. Originally published in: Astron. Astrophys. 1337. Bibcode:2016yCat.1337....0G.
  6. ↑ Morgenroth, O. (1935). "23 neue Veränderliche". Astronomische Nachrichten. 255 (23): 425–428. Bibcode:1935AN....255..425M. doi:10.1002/asna.19352552303.
  7. ↑ Wenzel, W. (1961). "Two Variables of Beta Lyrae Type with Long Periods". Information Bulletin on Variable Stars. 1: 1. Bibcode:1961IBVS....1....1W.
  8. ↑ Meyer, R. (2001). "Beobachtungsaufruf: HP Lyr". BAV Rundbrief. 50: 5. Bibcode:2001BAVSR..50....5M.
  9. ↑ Hassforther, B. (2002). "HP Lyrae ist wahrscheinlich ein RV-Tauri-Stern". BAV Rundbrief. 51: 182. Bibcode:2002BAVSR..51..182H.
  10. ↑ Alfonso-Garzón, J.; Domingo, A.; Mas-Hesse, J. M.; Giménez, A. (2012). "The first INTEGRAL-OMC catalogue of optically variable sources". Astronomy & Astrophysics. 1210. Bibcode:2012A&A...548A..79A. arXiv:1210.0821 Freely accessible [astro-ph.IM]. doi:10.1051/0004-6361/201220095.
  11. ↑ Wenzel, W. (2013). "HP Lyrae -- the sudden period decrease". Minutes on Variable Stars. Sonneberg Observatory (MVS13–01).
  12. ↑ 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. Bibcode:2007A&A...469..799S. doi:10.1051/0004-6361:20067035.
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