FR Scuti

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FR Scuti
Scutum constellation map.svg
Location of FR Scuti
Observation data
Epoch J2000.0       Equinox J2000.0
Constellation Scutum [1]
Right ascension 18h 23m 22.79s [2]
Declination −12° 40′ 51.8″ [2]
Apparent magnitude  (V)10.0 –10.8 [3]
Characteristics
Evolutionary stage Red supergiant + OB stars [ citation needed ]
Spectral type M2.5Iabep + B [4]
Variable type Algol + LC [3]
Astrometry
Radial velocity (Rv)+22.16 [2] km/s
Proper motion (μ)RA: +0.187 [2] mas/yr
Dec.: −1.64 [2] mas/yr
Parallax (π)0.4154±0.0667  mas [5]
Distance approx. 8,000  ly
(approx. 2,400  pc)
Other designations
FR Sct, HIP 90115, TIC 119217144, TYC 5698-2284-1, IRAS 18205-1242, 2MASS J18232280-1240518, SDSS J143900.24+641730.1 [2]
Database references
SIMBAD data

FR Scuti (also known as FR Sct or HIP 90115) is a hierarchical triple star system located in the constellation of Scutum. It is classified as a VV Cephei-type system, which typically consists of a cool red supergiant and a hot companion, but in this case the hot component is itself a close binary, making the overall system a triple. It was once thought to be a symbiotic binary, exhibiting unique spectral emission lines and photometric variability, but is now though to be a detached eclisping binary with additional irregular pulsations of the cool supergiant. [6] [7] [8] [9] [10] Another star system similar to FR Scuti is TIC 290061484. [11]

Contents

Charecterstics

Visual band light curves for FR Scuti, adapted from Pigulski and Michalska (2007), are shown. The upper panel shows the long-term variability, with the effects of eclipses removed, and the lower panel shows the variability due to eclipses, with the effects of long-term variability removed. FRSctLightCurve.png
Visual band light curves for FR Scuti, adapted from Pigulski and Michalska (2007), are shown. The upper panel shows the long-term variability, with the effects of eclipses removed, and the lower panel shows the variability due to eclipses, with the effects of long-term variability removed.

The system consists of a cool red supergiant primary and a smaller hotter companion. The hot companion is itself a close binary, likely consisting of two massive B-type stars (inferred from the VV Cephei classification and emission lines). The two hot stars occupy an inner orbit, while the M supergiant has an wider orbit. This hierarchical structure makes it unique among VV Cephei systems, which are rare massive binaries related to, but distinct from, symbiotic stars. The system is also a radio source, likely due to thermal emission from plasma ionized by the hot components' ultraviolet radiation interacting with the M supergiant's wind. [6]

Spectral features

The spectrum is composite, showing emission lines typical of VV Cephei systems (hydrogen, [Fe II]), but uniquely includes stronger [Fe III] and [O III] lines, which may indicate hotter components or effects from the hot binary's duplicity. These features were first noted in 1956. [6]

References

  1. ↑ Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters . 38 (5): 331. arXiv: 1108.4971 . Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. XHIP record for this object at VizieR.
  2. 1 2 3 4 5 6 "FR Scuti". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2025-09-04.
  3. 1 2 "FR Scuti". International Variable Star Index. AAVSO . Retrieved 2025-10-07.
  4. ↑ Pantaleoni González, M.; Maíz Apellániz, J.; Barbá, R. H.; Negueruela, I. (2020-01-01). "A Catalog of Galactic Multiple Systems with a Red Supergiant and a B Star". Research Notes of the AAS. 4 (1): 12. arXiv: 2001.11680 . Bibcode:2020RNAAS...4...12P. doi: 10.3847/2515-5172/ab712b . ISSN   2515-5172.
  5. ↑ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv: 2208.00211 . Bibcode:2023A&A...674A...1G. doi: 10.1051/0004-6361/202243940 . S2CID   244398875. Gaia DR3 record for this source at VizieR.
  6. 1 2 3 4 Pigulski, A.; Michalska, G. (February 2007). "FR Scuti: a Triple VV Cephei-type System of Particular Interest". Information Bulletin on Variable Stars. 5757: 1. Bibcode:2007IBVS.5757....1P. ISSN   0374-0676.
  7. ↑ Lebzelter, T.; Mowlavi, N.; Lecoeur-Taibi, I.; Trabucchi, M.; Audard, M.; García-Lario, P.; Gavras, P.; Holl, B.; Fombelle, G. Jevardat de; Nienartowicz, K.; Rimoldini, L.; Eyer, L. (2023-06-01). "Gaia Data Release 3 - The second Gaia catalogue of long-period variable candidates". Astronomy & Astrophysics. 674: A15. arXiv: 2206.05745 . Bibcode:2023A&A...674A..15L. doi:10.1051/0004-6361/202244241. ISSN   0004-6361.
  8. ↑ Munari, U.; Traven, G.; Masetti, N.; Valisa, P.; Righetti, G. -L.; Hambsch, F. -J.; Frigo, A.; Čotar, K.; De Silva, G. M.; Freeman, K. C.; Lewis, G. F.; Martell, S. L.; Sharma, S.; Simpson, J. D.; Ting, Y. -S.; Wittenmyer, R. A.; Zucker, D. B. (2021). "The GALAH survey and symbiotic stars - I. Discovery and follow-up of 33 candidate accreting-only systems". Monthly Notices of the Royal Astronomical Society. 505 (4): 6121. arXiv: 2104.02686 . Bibcode:2021MNRAS.505.6121M. doi: 10.1093/mnras/stab1620 .
  9. ↑ Brandt, Timothy D. (2021-06-01). "The Hipparcos–Gaia Catalog of Accelerations: Gaia EDR3 Edition". The Astrophysical Journal Supplement Series. 254 (2): 42. arXiv: 2105.11662 . Bibcode:2021ApJS..254...42B. doi: 10.3847/1538-4365/abf93c . ISSN   0067-0049.
  10. ↑ Kervella, Pierre; Arenou, Frédéric; Mignard, François; Thévenin, Frédéric (2019-03-01). "Stellar and substellar companions of nearby stars from Gaia DR2 - Binarity from proper motion anomaly". Astronomy & Astrophysics. 623: A72. arXiv: 1811.08902 . Bibcode:2019A&A...623A..72K. doi:10.1051/0004-6361/201834371. ISSN   0004-6361.
  11. ↑ Balzer, Ashley (2024-10-02). "NASA Scientific Visualization Studio | NASA's TESS Spots Record-breaking Stellar Triplets". NASA Scientific Visualization Studio. Retrieved 2025-10-03.
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