WASP-178
WASP-178, also known as KELT-26 and HD 134004, is a star located in the southern constellation of Lupus. In late 2019, the star was discovered to be orbited by an ultra-hot Jupiter planet, WASP-178b.
Physical properties
| Star | Mass (M☉) | Radius (R☉) | Spectral type | Temperature (K) | Luminosity (L☉) | Age (Myr) |
|---|---|---|---|---|---|---|
| WASP-178 | 2.07/1.93 | 1.67[1]/1.801[2] | A1IV-V | 9350[1]/8640[2] | 16.2/21.4 | 430 |
| Sirius A | 2.063 | 1.711 | A0mA1 Va | 9940 | 25.4 | 242 |
WASP-178 is an A-type main-sequence star or subgiant with a spectral type of A1IV-V.[1] The star is comparable to Sirius A in mass and radius, but slightly cooler, older, and less luminous. It is about twice as massive as the Sun and has a radius of 1.67 or 1.80 R☉, with an effective temperature of roughly 9,000 K. A 2019 estimate of 9350±150 K[1] makes WASP-178 the second-hottest host to a hot Jupiter ever discovered, behind KELT-9 (10,170 K) and ahead of MASCARA-2 (8,980 K),[1], though a lower estimate (8,640 K) provided by another paper[2] may put it below MASCARA-2. The star is around 20 times[2][3] brighter than the Sun and is 430+310
−250 million years old.[2] Much like Sirius A, the star is a likely Am star and a slow rotator, with a rotational velocity of 8.2–12.2 km/s.[1][2] For comparison, Sirius A has a rotational velocity of 16 km/s,[4] while typical A-type stars rotate much faster at around 160 km/s.[5] It has a near-[2] or above-solar[1] metallicity. The star is rich in chromium, nickel, yttrium, and barium, while being slightly poor in calcium and scandium.[1]
Variability
Aside from periodic dimming caused by the transiting planet, the star experiences regular oscillations in brightness by a few thousandths of a magnitude. The period at which the oscillations occur is measured to be 0.185 days, almost exactly one-eighteenth of WASP-178b's orbital period. The planet's mass is likely too small to cause periodic swaying of the host star, therefore it remains to be known whether this is merely coincidental. The nature of the luminosity fluctuations (namely the period and amplitude), along with the star's position within the instability strip in the Hertzsprung–Russell diagram implies that WASP-178 may be a Delta Scuti variable.[2]
Possible companion
Planetary system
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Hellier, Coel; et al. (2019-11-21). "WASP-South hot Jupiters: WASP-178b, WASP-184b, WASP-185b, and WASP-192b". Monthly Notices of the Royal Astronomical Society. 490 (1): 1479–1487. doi:10.1093/mnras/stz2713. ISSN 0035-8711.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Martínez, Romy Rodríguez; et al. (2020-09-01). "KELT-25 b and KELT-26 b: A Hot Jupiter and a Substellar Companion Transiting Young A Stars Observed by TESS*". The Astronomical Journal. 160 (3): 111. doi:10.3847/1538-3881/ab9f2d. ISSN 0004-6256.
- ↑ Stassun, Keivan G.; et al. (2019-10-01). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. doi:10.3847/1538-3881/ab3467. ISSN 0004-6256.
- ↑ Royer, F.; et al. (2002). "Rotational velocities of A-type stars: I. Measurement of v sin i in the southern hemisphere". Astronomy & Astrophysics. 381 (1): 105–121. doi:10.1051/0004-6361:20011422. ISSN 0004-6361.
- ↑ Yang, Wuming; et al. (2013-02-22). "EVOLUTION OF ROTATIONAL VELOCITIES OF A-TYPE STARS". The Astrophysical Journal. 765 (2): L36. doi:10.1088/2041-8205/765/2/L36. ISSN 2041-8205.
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