Astronomy:M51-ULS-1

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M51-ULS-1, also known as RX J132943+47115, is a high-mass X-ray binary (HMXB) system in the constellation of Canes Venatici.[1][2][3] The binary system is located in the Whirlpool Galaxy, a nearby spiral galaxy some 28 million light years (or 8.6 million parsecs) away.[1][2] The binary system has an apparent visual magnitude of 24.01.[1] The binary system was discovered in 1995 in a ROSAT survey of X-ray sources in the Whirlpool Galaxy and NGC 5195.[4]

Characteristics

M51-ULS-1 is a high-mass X-ray binary system in the Whirlpool Galaxy consisting of two components, a blue supergiant, and a compact object.[2][3][5] The binary system has a predicted age between 4 and 16 million years old; it was also found that the system is probably no older than 100 million years old.[3] The compact object orbits the more massive blue supergiant star in a orbit with a semi-major axis of 50 R☉, and it was found that the semi-major axis of the binary is no larger than 3 astronomical units.[3]

The primary star, M51-ULS-1 A, is a massive, luminous early to late blue supergiant star.[2][3][6] The primary star has a spectral type of B2-8la discovered using Hubble Space Telescope photometry.[3] The primary star has a mass of about 20 M☉.[2] Because of the star's mass it is predicted that the primary star might undergo a hydrogen-poor supernovae in the future.[3] The primary star has an estimated size of <25 R☉,[3][6] based on a luminosity of ~260,000 L☉[lower-alpha 1] and a derived effective temperature of approximately 26,000 K.[3][lower-alpha 2]

The secondary object, M51-ULS-1 B, is a stellar remnant and is either a black hole or neutron star.[2][3][5] If the secondary object is a black hole, it would have a mass of 10 M☉; classifying the secondary object as a stellar-mass black hole.[3] If it is a black hole, using its mass it would have a Schwarzschild radius of roughly 30 kilometers.[3] If the secondary object is a neutron star, it would have mass of 1.4 M☉.[3] It is known that the secondary object is accreting 10−6 M☉ worth of material every year from the primary star.[3]

Planetary system

Representation of Orbit of M51-ULS-1 b

In September 2020, a candidate exoplanet named M51-ULS-1 b was discovered in the system using the Chandra X-ray Observatory.[2][3][5] The putative exoplanet is mainly notable for being the first extragalactic planet candidate with strong evidence.[2][3][5] The potential exoplanet was detected by the eclipses of the X-ray source (XRS);[3] i. e. M51-ULS-1 B, the compact object orbiting the primary star. The candidate exoplanet is likely slightly smaller than the planet Saturn.[3][7] The unconfirmed exoplanet orbits both of the objects in the system in about 70 years, and has a semi-major axis of 45 AU.[2][3][5] It was suggested that the planet could be a white dwarf, however this was ruled out because of the fact it would cause a lensing event and not a dip in flux.[3] It was also proposed that it may be a cloud of gas, however the discoverers found this as an unlikely explanation.[3] Due to M51-ULS-1 b orbiting a potential black hole it may be classified as a blanet.

The M51-ULS-1 planetary system[3][7]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(years) 		Eccentricity Inclination Radius
b (unconfirmed) — 45 70 — — 0.7 RJ

See also

Notes

  1. ↑ 1039 erg/s = 260,010.4004 L☉
  2. ↑ Applying the Stefan–Boltzmann law with a nominal solar effective temperature of 5,772 K:
    (5,77226,068)4⋅260,010=25 R⊙.

References

  1. ↑ 1.0 1.1 1.2 "RX J132943+47115". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=RX+J132943%2B47115. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 "First Evidence of a Planet Identified Beyond Our Galaxy". 25 October 2021. https://science.nasa.gov/universe/exoplanets/exoplanet-discoveries/first-evidence-of-a-planet-identified-beyond-our-galaxy/. 
  3. ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 3.20 3.21 Di Stefano, R. (2020). "M51-ULS-1b: The First Candidate for a Planet in an External Galaxy". arXiv:2009.08987 [astro-ph.HE]. {{cite arXiv}}: Cite has empty unknown parameter: |journal= (help); Unknown parameter |access-date= ignored (help); Unknown parameter |url= ignored (help)
  4. ↑ Ehle, M.; Pietsch, W.; Beck, R. (1995). "ROSAT high-resolution X-ray observations of the galaxies M51 and NGC5195". Astronomy and Astrophysics 295: 289. Bibcode: 1995A&A...295..289E. 
  5. ↑ 5.0 5.1 5.2 5.3 5.4 "Chandra Sees Evidence for Possible Planet in Another Galaxy". https://chandra.harvard.edu/photo/2021/m51/. 
  6. ↑ 6.0 6.1 Terashima, Yuichi; Inoue, Hirohiko; Wilson, Andrew S. (2006). "Hubble Space Telescope Identification of the Optical Counterparts of Ultraluminous X-Ray Sources in M51". The Astrophysical Journal 645 (1): 264. doi:10.1086/504251. Bibcode: 2006ApJ...645..264T. 
  7. ↑ 7.0 7.1 "EPE Results for M51-ULS-1 b". https://exoplanet.eu/catalog/m51_uls_1_b--7496/. 



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