W Hydrae

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W Hydrae
WHyaLightCurve.png
The visual band light curve of W Hydrae, from AAVSO data [1]
Observation data
Epoch J2000.0        Equinox J2000.0
Constellation Hydra
Right ascension 13h 49m 01.998s
Declination −28° 22′ 03.49″
Apparent magnitude  (V)7.7 - 11.6 [2]
Characteristics
Spectral type M7.5e-M9ep [3]
Apparent magnitude  (J)-1.7 [4]
Variable type Mira
Astrometry
Parallax (π)10.18±2.36  mas [5]
Distance 320+98
−59  ly
(98+30
−18  pc) [5]
Details
Mass 2.14+1.07
−0.71 [6]   M☉
Radius 436+134
−80 [7] [a]   R☉
Luminosity 9,290+2,460
−1,940 [6]   L☉
Temperature 3,000 [6]   K
Other designations
W Hya, CCDM J13491-2822A, HD 120285, RAFGL 1650, CPD-27° 4792, HIP 67419, SAO 181981, AAVSO 1343-27, IRAS 13462-2807, GC 18659, TYC 6728-19-1.
Database references
SIMBAD data

W Hydrae is a Mira-type variable star in the constellation Hydra. The star is nearly located within the Solar neighborhood, at 320 light years from the Solar System. It has a visual apparent magnitude range of 5.6 to 10. In the near-infrared J band it has a magnitude of -1.7, [4] is the 7th brightest star in the night sky, and is even brighter than Sirius.

Contents

Water masers and dust

Spectrum of water vapour towards W Hydrae obtained with APEX Observations of the star W Hydrae using SEPIA (eso1543e).jpg
Spectrum of water vapour towards W Hydrae obtained with APEX

The star also shows signs of intense water emissions, indicative of the presence of a wide disk of dust and water vapour. [8] Such emissions cover a zone spanning between 10.7 Astronomical Units (within Saturn's orbital zone) and 1.2 parsecs (or nearly 247,500 Astronomical Units, as far away as the Oort Cloud in Solar System).

Notes

  1. ↑ Radius calculated using a distance of 98+30
    −18      parsecs     and an angular diameter of 41.4  milliarcseconds (0.041 arcsec). 98 •0.041 = diameter of 4.06  AU , which is multiplied by 107.5 to convert from AU to R☉.

References

  1. ↑ "Download Data". aavso.org. AAVSO. Retrieved 1 October 2021.
  2. ↑ "GCVS Query=W Hya". General Catalogue of Variable Stars @ Sternberg Astronomical Institute, Moscow, Russia . Retrieved 2012-08-22.
  3. ↑ 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.
  4. 1 2 "V* W Hya". SIMBAD Astronomical Database. Retrieved 2012-08-21.
  5. 1 2 Vlemmings, W. H. T.; Van Langevelde, H. J.; Diamond, P. J.; Habing, H. J.; Schilizzi, R. T. (2003). "VLBI astrometry of circumstellar OH masers: Proper motions and parallaxes of four AGB stars". Astronomy & Astrophysics. 407: 213–224. arXiv: astro-ph/0305405 . Bibcode:2003A&A...407..213V. doi:10.1051/0004-6361:20030766. S2CID   11505142.
  6. 1 2 3 Takeuti, Mine; Nakagawa, Akiharu; Kurayama, Tomoharu; Honma, Mareki (2013). "A Method to Estimate the Masses of Asymptotic Giant Branch Variable Stars". Publications of the Astronomical Society of Japan. 65 (3): 60. Bibcode:2013PASJ...65...60T. doi: 10.1093/pasj/65.3.60 .
  7. ↑ Ohnaka, K.; Wong, K. T.; Weigelt, G.; Hofmann, K.-H. (November 2024). "Contemporaneous high-angular-resolution imaging of the AGB star W Hya in vibrationally excited H 2 O lines and visible polarized light with ALMA and VLT/SPHERE-ZIMPOL". Astronomy & Astrophysics. 691: L14. arXiv: 2411.09759 . doi:10.1051/0004-6361/202451977. ISSN   0004-6361.
  8. ↑ Zubko & Elitzur, Moshe (2000). "Water and Dust Emission from W Hydrae". The Astrophysical Journal . 544 (2): 137–140. arXiv: astro-ph/0009440 . Bibcode:2000ApJ...544L.137Z. doi:10.1086/317317. S2CID   17702515.


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