HD 137509

HD 137509

The visual band light curve of HD 137509, adapted from Lanz & Mathys (1991)[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Apus
Right ascension 15h 31m 27.11494s[2]
Declination −71° 03′ 43.6643″[2]
Apparent magnitude (V) 6.89[3]
Characteristics
Spectral type B9p (SiCrFe)[4]
B8 He wk SiCrFe[5]
B−V color index −0.125±0.004[3]
Variable type α2 CVn[6]
Astrometry
Radial velocity (Rv)+0.50[7] km/s
Proper motion (μ) RA: −16.276[2] mas/yr
Dec.: −15.503[2] mas/yr
Parallax (π)5.0410 ± 0.0503 mas[2]
Distance647 ± 6 ly
(198 ± 2 pc)
Absolute magnitude (MV)0.45[3]
Details
Mass3.43±0.17[8] M☉
Radius2.81[9] R☉
Luminosity123[3] L☉
Surface gravity (log g)4.3[5] cgs
Temperature13,100±500[5] K
Rotation4.492 d[8]
Rotational velocity (v sin i)20±2[5] km/s
Age124[10] Myr
Other designations
NN Aps, CD−70°1302, GC 20810, HD 137509, HIP 76011, SAO 257290[11]
Database references
SIMBADdata

HD 137509 is a star in the southern constellation of Apus, positioned less than a degree from the northern constellation boundary with Triangulum Australe.[12] It has the variable star designation of NN Apodis, or NN Aps for short, and ranges in brightness from an apparent visual magnitude of 6.86 down to 6.93 with a period of 4.4916 days.[6] The star is located at a distance of approximately 647 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +0.50 km/s.[7]

In 1973, W. P. Bidelman and D. J. MacConnell found this to be a peculiar A star of the silicon type.[13] During a reclassification of the spectra of southern stars in 1975, A. P. Cowley and N. Houk noted the strength of hydrogen lines and weakness of helium are more typical of a class near B9. It shows a luminosity above the main sequence, which is common for a peculiar A star. The stellar atmosphere appears deficient in helium, but shows a rich variety of metallic lines. However, there are no lines of manganese or mercury, so it's not a Hg–Mn Ap star.[14] HD 137509 is now classified as B9p (SiCrFe)[4] or B8 He wk SiCrFe,[5] matching a late-type, helium-weak Bp star with overabundances of silicon, chromium, and iron.

This star was found to be photometrically variable by L. O. Lodén and A. Sundman in 1989, and a variable spectrum was noted by H. Pedersen in 1979.[13] It has one of the strongest magnetic fields recorded for a chemically peculiar star, measured at around 29 kG,[4] and shows a strong quadrupolar component.[15] Both variances of the star allow its rotation period to be precisely measured.[13] It is classified as a Alpha2 Canum Venaticorum variable.[6] The star is about 124[10] million years old with 3.4[8] times the mass of the Sun and 2.8[9] times the Sun's radius. On average it is radiating ~123[3] times the luminosity of the Sun from its photosphere at an effective temperature of 13,100 K.[5]

  1. ^ Cite error: The named reference Lanz was invoked but never defined (see the help page).
  2. ^ a b c d e Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  3. ^ a b c d e Cite error: The named reference Anderson_Francis_2012 was invoked but never defined (see the help page).
  4. ^ a b c Cite error: The named reference Shulyak_et_al_2008 was invoked but never defined (see the help page).
  5. ^ a b c d e f Cite error: The named reference Bailey_Landstreet_2013 was invoked but never defined (see the help page).
  6. ^ a b c Cite error: The named reference Samus_et_al_2017 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference BarbierBrossat_et_al1994 was invoked but never defined (see the help page).
  8. ^ a b c Cite error: The named reference Netopil_et_al_2017 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference Shulyak_et_al_2014 was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference Gontcharov2012 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Sinnott_Perryman_1997 was invoked but never defined (see the help page).
  13. ^ a b c Cite error: The named reference Mathys_Lanz_1997 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Cowley_Houk_1975 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Kochukhov2006 was invoked but never defined (see the help page).