RY Scuti

RY Scuti is an eclipsing binary in the constellation of Scutum. It consists of a massive central star with an accretion disc and a blue supergiant donor. It is

RY Scuti
RY Scuti

Image of RY Scuti's surrounding dusty (orange) and ionised (blue) tori.
Credit: Nathan Smith et al. (2011)
Observation data
Epoch J2000      Equinox ICRS
Constellation Scutum
Right ascension 18h 25m 31.48s[1]
Declination −12° 41′ 24.2″[1]
Apparent magnitude (V) 9.12 – 9.72[2]
Characteristics
Apparent magnitude (U) 10.25[3]
Apparent magnitude (B) 10.38±0.99[4]
Apparent magnitude (G) 8.63±0.01[1]
Apparent magnitude (R) 9.46±0.04[4]
Apparent magnitude (J) 6.25±0.02[5]
Apparent magnitude (H) 5.85±0.02[5]
Apparent magnitude (K) 5.46±0.02[5]
Variable type β Lyr[2]
Massive Component
Spectral type O7[6]
Supergiant
Evolutionary stage Blue supergiant
Spectral type O9.7 Ibpe[7]
Astrometry
Proper motion (μ) RA: −0.333±0.023 mas/yr[1]
Dec.: −2.026±0.018 mas/yr[1]
Parallax (π)0.4748±0.0220[1] mas
Distance1800±100[8] pc
Massive Component
Absolute bolometric
magnitude (Mbol)		−8.3±0.1[6]
Supergiant
Absolute bolometric
magnitude (Mbol)		−8.7±0.1[6]
Orbit
Period (P)11.125 d[6]
Semi-major axis (a)69.9±2.3[7][6]″
Eccentricity (e)~0[7]
Inclination (i)82.4±0.3[6]°
Semi-amplitude (K1)
(primary)		59±9[7] km/s
Semi-amplitude (K2)
(secondary)		249±3[7] km/s
Details
Metallicity [Fe/H]−2.23±0.03[9] dex
Massive Component
Mass30.0±2.1[7][6] M☉
Radius9.7±0.2[6] R☉
Luminosity160000+20000
−10000[6] L☉
Surface gravity (log g)3.94±0.03[6] cgs
Temperature37000+2000
−1000[6] K
Rotational velocity (v sin i)194±18[7] km/s
Supergiant
Mass7.1±1.2[7][6] M☉
Radius18.4±0.3[6] R☉
Luminosity240000+20000
−20000[6] L☉
Surface gravity (log g)2.76±0.02[6] cgs
Temperature30000+1000
−1000[6] K
Rotational velocity (v sin i)80±3[7] km/s
Other designations
RY Sct, HD 169515, ALS 5024, ALS 9603, AN 34.1908, BD-12 5045, CMC 207024, CMC 161458, GCRV 10896, GEN# +1.00169515, GSC 05698-02356, Hen 3-1694, HIP 90303, HIC 90303, IRAS 18227-1243, JP11 2974, LS IV -12 54, LS 5024, MCW 684, PPM 234519, RAFGL 5235S, SAO 161458, SBC7 679, SBC9 1049, HV 3076, TYC 5698-2356-1, UBV M 22925, UCAC2 27342864, UCAC4 387-094010, uvby98 100169515, WEB 15453, YZC 11 6294
Database references
SIMBADdata

RY Scuti is an eclipsing binary in the constellation of Scutum. It consists of a massive central star with an accretion disc and a blue supergiant donor. It is surrounded by a dusty and an ionised torus.[6]

Observational history

RY Scuti was first observed between 1886 at Bonn Observatory in the Southern Durchmusterung with the designation BD-12 5045.[10] It was initially classified as a B[e] star in 1925.[11] It was later added to the General Catalogue of Variable Stars between 1948 and 1952, where it was designated RY Scuti.[11][12]

Star system

Massive component

The central star is surrounded by a hot, optically thick accretion disc created due to roche lobe overflow (RLOF) from the orbiting supergiant.[6] Once it has stopped accreting, the surrounding disc might become optically thin, making it more visible.[13]

Spectral classification

Due to its shallow SiIII, OII and NII lines, it was initially estimated to have a spectral type of B2 and later as B0.5 I due to its absorption spectrum's similarity with that of HD 185859.[14][7] However, the luminosity-sensitive lines present are much stronger than what is typically observed, indicating that they originate from low-density plasma and therefore most likely apply to the surrounding accretion disc rather than the star itself.[7] Instead, the star is more likely to be of spectral type O7 due to its high effective temperature.[6]

Supergiant

The supergiant component is less massive but more luminous and larger than the central star. Its high abundance in neon, sulphur and iron indicates that large portions of its outer envelope have been stripped away due to RLOF, leaving hydrogen-poor material exposed.[9]

Supernova

Once the massive component has accreted all the material gained from RLOF, it is expected to become a B[e] supergiant. If it has accreted the entire outer envelope of its companion, the supergiant is expected to explode in a type Ib/c supernova or otherwise as a type IIb supernova.[13]

Nebula

RY Scuti is surrounded by a nebula which consists of a dusty and an ionised torus.[13] The ionised torus is likely driven by episodic ejections and is expanding nonuniformly at a mean rate of 10 mas yr-1, indicating that the ejection that caused it took place between 1877 and 1885. Evidence of photometric variability during the time period indicates that one or both of the components in the system underwent an outburst similar to S Doradus.[15][13] The rate of expansion of the dusty torus indicates that it formed between 1718 and 1790. They are likely to have been shaped by the massive component's accretion disc as they are clearly separated, which likely means that they are not hydrodynamically interacting, which would mean that a former large disc couldn't have shaped them.[13]

References

  1. ^ a b c d e "Gaia DR3 4152599133132654720". vizier.cds.unistra.fr. Retrieved 2026-07-06.
  2. ^ a b "VSX: Detail for RY Sct". vsx.aavso.org. Retrieved 2026-07-06.
  3. ^ Reed, B. Cameron (21 January 2003). "Catalog of Galactic OB Stars". The Astronomical Journal. 125 (5): 2531–2533. Bibcode:2003AJ....125.2531R. doi:10.1086/374771.
  4. ^ a b "UCAC4 387-094010". vizier.cds.unistra.fr. Retrieved 2026-07-06.
  5. ^ a b c "2MASS J18253147-1241241". vizier.cds.unistra.fr. Retrieved 2026-07-06.
  6. ^ a b c d e f g h i j k l m n o p q r s Djurašević, G.; Vince, I.; Atanacković, O. (8 April 2008). "Accretion Disk in the Massive Binary RY Scuti". The Astronomical Journal. 136 (2): 767–772. Bibcode:2008AJ....136..767D. doi:10.1088/0004-6256/136/2/767.
  7. ^ a b c d e f g h i j k Grundstorm, Erika D.; Gies, Douglas R.; Hillwig, Todd C.; McSwain, M. Virginia; Smith, Nathan; Gehrz, Robert D.; Stahl, Otmar; Kaufer, Andreas (27 March 2007). "A Spectroscopic Study of Mass Outflows in the Interacting Binary RY Scuti". The Astrophysical Journal. 667 (1): 505–519. arXiv:0706.3206. Bibcode:2007ApJ...667..505G. doi:10.1086/521043.
  8. ^ Smith, Nathan; Gehrz, Robert D.; Stahl, Otmar; Balick, Bruce; Kaufer, Andreas (17 June 2002). "The WR+OB Progenitor RY Scuti: Intensive Spectroscopy of Its Compact Double-Ring Nebula". The Astrophysical Journal. 578 (1): 464–485. Bibcode:2002ApJ...578..464S. doi:10.1086/342365.
  9. ^ a b Taft, Sarah H.; Gehrz, Robert D.; Woodward, Charles E.; Smith, Nathan; Perron, Isabelle; Citro, Annalisa (7 October 2024). "Simulating Chemical Abundances in the Circumstellar Nebula of the Late Stage Binary RY Scuti". The Astronomical Journal. 169 (5): 8. arXiv:2503.15602. Bibcode:2025AJ....169..271T. doi:10.3847/1538-3881/adc251.
  10. ^ "BD-12 5045". vizier.cds.unistra.fr. Retrieved 2026-07-06.
  11. ^ a b "V* RY Sct". simbad.u-strasbg.fr. Retrieved 2026-07-06.
  12. ^ Samus, N. N.; Durlevich, O. V.; Kazarovets, R. V. (17 July 1997). "The General Catalog of Variable Stars (gcvs)". Baltic Astronomy. 6 (2): 296–299. Bibcode:1997BaltA...6..296S. doi:10.1515/astro-1997-0229.
  13. ^ a b c d e Smith, Nathan; Gehrz, Robert D.; Campbell, Randy; Kassis, Marc; Le Mignant, David; Kuluhiwa, Kawailehua; Filippenko, Alexei V. (21 July 2011). "Episodic mass loss in binary evolution to the Wolf-Rayet phase: Keck and HST proper motions of RY Scuti's nebula". Monthly Notices of the Royal Astronomical Society. 418 (3): 1959–1972. arXiv:1105.2329. Bibcode:2011MNRAS.418.1959S. doi:10.1111/j.1365-2966.2011.19614.x.
  14. ^ Skul'skij, M. Yu. (August 1992). "Investigation of the absorption spectrum of RY SCT : identification of the secondary component's lines, the orbital elements and principles of the component mass determination using spectra of developed circumstellar structures". Astronomicheskii Zhurnal. 69: 803–820. Bibcode:1992AZh....69..803S.
  15. ^ Smith, Nathan; Gehrz, Robert D.; Goss, W. M. (18 April 2001). "Proper Motion and Excitation Structure of the Expanding Ionized Rings around RY Scuti". The Astronomical Journal. 122 (5): 2700–2706. Bibcode:2001AJ....122.2700S. doi:10.1086/323710.

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