A TiO study of the black hole binary GRO J0422+32 in a very low state

N. A. Webb, T. Naylor, Z. Ioannou, P. A. Charles, T. Shahbaz

Research output: Contribution to journalArticle

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Abstract

We present 53 simultaneous photometric (I band) and spectroscopic (6900-9500 Å) observations of GRO J0422+32, taken during 1997 December. From these we determine that J0422+32 was in its lowest state yet observed, at I = 20.44 ± 0.08. Using relative spectrophotometry, we show that it is possible to correct very accurately for telluric absorption. Following this, we use the TiO bands at 7055 and 7589 Å for a radial velocity study and thereby obtain a semi-amplitude of 378 ± 16km s-1, which yields f(M) = 1.191 ± 0.021 M and q = 9.0+2.2 -2.7, consistent with previous observations. We further demonstrate that this little-explored method is very powerful for such systems. We also determine a new orbital ephemeris of HJD = 245 0274.4156 ± 0.0009 + 0.212 1600 ± 0.000 0002E. We see some evidence for an ellipsoidal modulation, from which we determine the orbital inclination of J0422 + 32 to be less than 45°. We therefore calculate a minimum mass for the primary of 2.22 M, consistent with a black hole, but not necessarily the supermassive one proposed recently (1997) by Beekman et al. We obtain an M4-5 spectral type for the secondary star, and determine that the secondary contributes 38 ± 2 per cent of the flux that we observe from J0422+32 over the range 6950-8400 Å. From this we calculate the distance to the system to be 1.39 ± 0.15 kpc.

Original languageEnglish
Pages (from-to)528-534
Number of pages7
JournalMonthly Notices of the Royal Astronomical Society
Volume317
Issue number3
Publication statusPublished - Sep 21 2000

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spectrophotometry
orbitals
radial velocity
inclination
modulation
stars
method

Keywords

  • Accretion, accretion discs
  • Binaries: close
  • Black hole physics
  • Stars: fundamental parameters
  • Stars: individual: GRO J0422 + 32
  • Stars: late-type

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

A TiO study of the black hole binary GRO J0422+32 in a very low state. / Webb, N. A.; Naylor, T.; Ioannou, Z.; Charles, P. A.; Shahbaz, T.

In: Monthly Notices of the Royal Astronomical Society, Vol. 317, No. 3, 21.09.2000, p. 528-534.

Research output: Contribution to journalArticle

Webb, NA, Naylor, T, Ioannou, Z, Charles, PA & Shahbaz, T 2000, 'A TiO study of the black hole binary GRO J0422+32 in a very low state', Monthly Notices of the Royal Astronomical Society, vol. 317, no. 3, pp. 528-534.
Webb, N. A. ; Naylor, T. ; Ioannou, Z. ; Charles, P. A. ; Shahbaz, T. / A TiO study of the black hole binary GRO J0422+32 in a very low state. In: Monthly Notices of the Royal Astronomical Society. 2000 ; Vol. 317, No. 3. pp. 528-534.
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abstract = "We present 53 simultaneous photometric (I band) and spectroscopic (6900-9500 {\AA}) observations of GRO J0422+32, taken during 1997 December. From these we determine that J0422+32 was in its lowest state yet observed, at I = 20.44 ± 0.08. Using relative spectrophotometry, we show that it is possible to correct very accurately for telluric absorption. Following this, we use the TiO bands at 7055 and 7589 {\AA} for a radial velocity study and thereby obtain a semi-amplitude of 378 ± 16km s-1, which yields f(M) = 1.191 ± 0.021 M⊙ and q = 9.0+2.2 -2.7, consistent with previous observations. We further demonstrate that this little-explored method is very powerful for such systems. We also determine a new orbital ephemeris of HJD = 245 0274.4156 ± 0.0009 + 0.212 1600 ± 0.000 0002E. We see some evidence for an ellipsoidal modulation, from which we determine the orbital inclination of J0422 + 32 to be less than 45°. We therefore calculate a minimum mass for the primary of 2.22 M⊙, consistent with a black hole, but not necessarily the supermassive one proposed recently (1997) by Beekman et al. We obtain an M4-5 spectral type for the secondary star, and determine that the secondary contributes 38 ± 2 per cent of the flux that we observe from J0422+32 over the range 6950-8400 {\AA}. From this we calculate the distance to the system to be 1.39 ± 0.15 kpc.",
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