BW Sculptoris

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BW Sculptoris
BW Sculptoris.jpg
BW Sculptoris is the blue star in the center
Credit: Legacy Surveys/D. Lang (Perimeter Institute)
Observation data
Epoch J2000       Equinox J2000
Constellation Sculptor
Right ascension 23h 53m 00.8742s
Declination −38° 51′ 46.6625″
Apparent magnitude  (V)16.5
Characteristics
Evolutionary stage white dwarf + brown dwarf
Spectral type D + T [1]
Variable type cataclysmic variable
Astrometry
Proper motion (μ)RA: 81.036±0.043  mas/yr [2]
Dec.: −63.109±0.050  mas/yr [2]
Parallax (π)10.6786 ± 0.0524  mas [2]
Distance 305 ± 1  ly
(93.6 ± 0.5  pc)
Orbit [1]
PrimaryBW Scl A
CompanionBW Scl B
Period (P)78.23 minutes
Semi-major axis (a)0.58±0.02 R☉
Inclination (i)64.3±3.6°
Semi-amplitude (K1)
(primary)		27.7±3.0 km/s
Semi-amplitude (K2)
(secondary)		461±13 km/s
Details
A
Mass 0.85±0.04 [1] or 1.007+0.010
−0.012 [3]   M☉
Radius 0.00800+0.00014
−0.00011 [3]   R☉
Surface gravity (log g)8.635+0.017
−0.020 [3]   cgs
Temperature 15,145+51
−57 [3]   K
B
Mass 53.4±6.3 [1]   MJup
Radius 1.03±0.05 [1]   RJup
Other designations
RX J2353.0-3852, HE 2350-3908, 2MASS J23530086-3851465, MCT 2350-3908, TIC 183676876, AAVSO 2347-39
Database references
SIMBAD data

BW Sculptoris is WZ Sge-type dwarf nova and a candidate period bouncer. The binary consists of a white dwarf and a brown dwarf donor that orbits the white dwarf every 78.23 minutes. BW Sculptoris is one of the closest and brightest cataclysmic variable stars with a brightness of magnitude16.5 and a distance of 93.3 parsecs. It also has the shortest period for any CVs known to date (as of August 2023). [1]

A visual band light curve for BW Sculptoris, adapted from Augusteijn and Wisotzki (1997) BWSclLightCurve.png
A visual band light curve for BW Sculptoris, adapted from Augusteijn and Wisotzki (1997)

BW Sculptoris was discovered in 1997 by two teams. Abbott et al. discovered it with ROSAT as RX J2353.0-3852. [5] Augusteijn & Wisotzki discovered it independently in the Hamburg/ESO survey with the ESO 1.52 meter telescope and it was originally designated HE 2350–3908 (it received its variable star designation, BW Sculptoris, in the year 2000). [4] [6] Both authors noted the low mass transfer. [5] [4] Earlier mass ratios hinted at a low mass donor and Neustroev & Mäntynen were able to narrow down the mass of the white dwarf to 0.85±0.04  M☉ and the mass of the donor to 0.051±0.006 M☉ (53.4±6.3  MJ ), making the donor a brown dwarf. BW Sculptoris is a candidate period bouncer. This is an evolutionary stage of a cataclysmic variable in which a donor star looses enough mass to evolve into a substellar object or brown dwarf. This occurs together with a decrease of the orbital period until the period reaches 70–80 minutes, at which point the period increases again. It is suspected that BW Sculptoris already passed this minimum and that the orbital period will increase in the future. [1]

Superoutburst of 2011

BW Sculptoris experienced a superoutburst with an amplitude of 7.5 mag in October 2011. The superoutburst was first detected by M. Linnolt (AAVSO) on October 21 with a visual magnitude of 9.6. On October 31 an ordinary superhump developed and on November 12 BW Sculptoris entered the rapid fading phase. [7] Even 10 years after the superoutburst the star has not returned to its pre-outburst level. [1]

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References

  1. 1 2 3 4 5 6 7 8 Neustroev, Vitaly V.; Mäntynen, Iikka (2023-08-01). "A brown dwarf donor and an optically thin accretion disc with a complex stream impact region in the period-bouncer candidate BW Sculptoris". Monthly Notices of the Royal Astronomical Society. 523 (4): 6114–6137. arXiv: 2212.03264 . Bibcode:2023MNRAS.523.6114N. doi: 10.1093/mnras/stad1730 . ISSN   0035-8711.
  2. 1 2 3 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.
  3. 1 2 3 4 Pala, A F; Gänsicke, B T; Belloni, D; Parsons, S G; Marsh, T R; Schreiber, M R; Breedt, E; Knigge, C; Sion, E M; Szkody, P; Townsley, D; Bildsten, L; Boyd, D; Cook, M J; De Martino, D (2022-03-11). "Constraining the evolution of cataclysmic variables via the masses and accretion rates of their underlying white dwarfs". Monthly Notices of the Royal Astronomical Society . 510 (4): 6110–6132. arXiv: 2111.13706 . doi: 10.1093/mnras/stab3449 . ISSN   0035-8711.
  4. 1 2 3 Augusteijn, T.; Wisotzki, L. (1997-08-01). "HE 2350-3908: a dwarf nova with a 78^m^ orbital period". Astronomy and Astrophysics. 324: L57 –L60. Bibcode:1997A&A...324L..57A. ISSN   0004-6361.
  5. 1 2 Abbott, T. M. C.; Fleming, T. A.; Pasquini, L. (1997-02-01). "The ROSAT cataclysmic variable RX J2353.0-3852". Astronomy and Astrophysics. 318: 134–139. Bibcode:1997A&A...318..134A. ISSN   0004-6361.
  6. ↑ Kazarovets, E. V.; Samus, N. N.; Durlevich, O. V. (March 2000). "The 75th Name-List of Variable Stars" (PDF). Information Bulletin on Variable Stars. 4870: 1–47. Bibcode:2000IBVS.4870....1K . Retrieved 8 December 2024.
  7. ↑ Kato, Taichi; Hambsch, Franz-Josef; Maehara, Hiroyuki; Masi, Gianluca; Miller, Ian; Noguchi, Ryo; Akasaka, Chihiro; Aoki, Tomoya; Kobayashi, Hiroshi; Matsumoto, Katsura; Nakagawa, Shinichi; Nakazato, Takuma; Nomoto, Takashi; Ogura, Kazuyuki; Ono, Rikako (2013-02-01). "Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae. IV. The Fourth Year (2011-2012)". Publications of the Astronomical Society of Japan. 65: 23. arXiv: 1210.0678 . Bibcode:2013PASJ...65...23K. doi:10.1093/pasj/65.1.23. ISSN   0004-6264.
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