BW Sculptoris

{{Short description|Dwarf nova in the constellation Sculptor}}

{{Starbox begin

| name = BW Sculptoris

}}

{{Starbox image

| image = 250px

| caption = BW Sculptoris is the blue star in the center

| credit = Legacy Surveys/D. Lang (Perimeter Institute)

}}

{{Starbox observe

| epoch = J2000

| equinox = J2000

| constell = Sculptor

| ra = {{RA|23|53|00.8742}}

| dec = {{Dec|-38|51|46.6625}}

| appmag_v = 16.5

}}

{{Starbox character

| type = white dwarf + brown dwarf

| class = D + T

| variable = cataclysmic variable

}}

{{Starbox astrometry

| prop_mo_ra = {{val|81.036|0.043}}

| prop_mo_dec = {{val|-63.109|0.050}}

| pm_footnote = {{Cite Gaia DR3|2307289214897332480}}

| parallax = 10.6786

| p_error = 0.0524

| parallax_footnote =

}}

{{Starbox orbit

| reference =

| primary = BW Scl A

| name = BW Scl B

| period_unitless = 78.23 minutes

| axis_unitless = {{val|0.58|0.02|u=solar radius}}

| inclination = {{val|64.3|3.6}}

| k1 = {{val|27.7|3.0}}

| k2 = {{Val|461|13}}

}}

{{Starbox detail

| component1 = A

| mass = {{val|0.85|0.04}} or {{val|1.007|0.010|0.012}}

| radius = {{val|0.00800|0.00014|0.00011|fmt=none}}{{Cite journal |last1=Pala |first1=A F |last2=Gänsicke |first2=B T |last3=Belloni |first3=D |last4=Parsons |first4=S G |last5=Marsh |first5=T R |last6=Schreiber |first6=M R |last7=Breedt |first7=E |last8=Knigge |first8=C |last9=Sion |first9=E M |last10=Szkody |first10=P |last11=Townsley |first11=D |last12=Bildsten |first12=L |last13=Boyd |first13=D |last14=Cook |first14=M J |last15=De Martino |first15=D |date=2022-03-11 |title=Constraining the evolution of cataclysmic variables via the masses and accretion rates of their underlying white dwarfs |journal=Monthly Notices of the Royal Astronomical Society |volume=510 |issue=4 |pages=6110–6132 |doi=10.1093/mnras/stab3449 |doi-access=free |arxiv=2111.13706 |issn=0035-8711}}

| temperature = {{val|15145|51|57|fmt=commas}}

| gravity = {{val|8.635|0.017|0.020}}

| component2 = B

| mass_mj2 = {{val|53.4|6.3}}

| radius_rj2 = {{val|1.03|0.05}}

}}

{{Starbox catalog

| names = RX J2353.0-3852, HE 2350-3908, 2MASS J23530086-3851465, MCT 2350-3908, TIC 183676876, AAVSO 2347-39

}}

{{Starbox reference

| Simbad = BW+Sculptoris

}}

{{Starbox end}}

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).{{Cite journal |last1=Neustroev |first1=Vitaly V. |last2=Mäntynen |first2=Iikka |date=2023-08-01 |title=A brown dwarf donor and an optically thin accretion disc with a complex stream impact region in the period-bouncer candidate BW Sculptoris |journal=Monthly Notices of the Royal Astronomical Society |volume=523 |issue=4 |pages=6114–6137 |doi=10.1093/mnras/stad1730 |doi-access=free |issn=0035-8711|arxiv=2212.03264 |bibcode=2023MNRAS.523.6114N }}

File:BWSclLightCurve.png 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.{{Cite journal |last1=Abbott |first1=T. M. C. |last2=Fleming |first2=T. A. |last3=Pasquini |first3=L. |date=1997-02-01 |title=The ROSAT cataclysmic variable RX J2353.0-3852. |journal=Astronomy and Astrophysics |volume=318 |pages=134–139 |bibcode=1997A&A...318..134A |issn=0004-6361}} 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).{{Cite journal |last1=Augusteijn |first1=T. |last2=Wisotzki |first2=L. |date=1997-08-01 |title=HE 2350-3908: a dwarf nova with a 78^m^ orbital period. |journal=Astronomy and Astrophysics |volume=324 |pages=L57–L60 |bibcode=1997A&A...324L..57A |issn=0004-6361}}{{cite journal |last1=Kazarovets |first1=E. V. |last2=Samus |first2=N. N. |last3=Durlevich |first3=O. V. |title=The 75th Name-List of Variable Stars |journal=Information Bulletin on Variable Stars |date=March 2000 |volume=4870 |pages=1–47 |url=https://ibvs.konkoly.hu/pub/ibvs/4801/4870.pdf |bibcode=2000IBVS.4870....1K |access-date=8 December 2024}} Both authors noted the low mass transfer. Earlier mass ratios hinted at a low mass donor and Neustroev & Mäntynen were able to narrow down the mass of the white dwarf to {{Val|0.85|0.04|ul=Solar mass}} and the mass of the donor to {{val|0.051|0.006|u=Solar mass}} ({{val|53.4|6.3|ul=Jupiter mass}}), 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.