HD 118285
SPB star in the constellation Chamaeleon
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HD 118285, also known as HR 5115, is a variable star located in the southern circumpolar constellation Chamaeleon. DY Chamaeleontis (DY Cha) is its variable star designation. It has an average apparent magnitude of 6.32,[3] placing it near the limit for naked eye visibility. The object is located relatively far at a distance of 864 light years based on Gaia DR3 parallax measurements but is receding with a heliocentric radial velocity of 18 km/s.[8] At its current distance, HD 118285's brightness is diminished by 0.58 magnitudes due to interstellar dust.[16]
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Chamaeleon |
| Right ascension | 13h 39m 11.99015s[2] |
| Declination | −75° 41′ 01.6128″[2] |
| Apparent magnitude (V) | 6.32[3] (6.34 - 6.38)[4] |
| Characteristics | |
| Evolutionary stage | main sequence star[5] |
| Spectral type | B8 IV[6] |
| U−B color index | −0.26[7] |
| B−V color index | +0.01[7] |
| Variable type | SPB[4] |
| Astrometry | |
| Radial velocity (Rv) | 18.2±2.3[8] km/s |
| Proper motion (μ) | RA: −20.690 mas/yr[2] Dec.: −14.712 mas/yr[2] |
| Parallax (π) | 3.7743±0.0289 mas[2] |
| Distance | 864 ± 7 ly (265 ± 2 pc) |
| Absolute magnitude (MV) | −0.54[9] |
| Details | |
| Mass | 3.63±0.12[5] M☉ |
| Radius | 5.52±0.28[10] R☉ |
| Luminosity | 293+50 −42[5] L☉ |
| Temperature | 11,350+79 −78[5] K |
| Metallicity [Fe/H] | 0.00[11] dex |
| Rotational velocity (v sin i) | 67[12] km/s |
| Age | 309[13] Myr |
| Other designations | |
| 49 G. Chamaeleontis[14], DY Cha, CD−75°632, CPD−75°882, FK5 503, GC 18406, HD 118285, HIP 66607, HR 5115, SAO 257069[15] | |
| Database references | |
| SIMBAD | data |
HD 118285's variability was first observed in a 1998 Hipparcos survey focusing on the discovery of slowly pulsating B-type stars (SPB).[17] It was later confirmed to be an SPB star and given the variable designation DY Chamaeleontis.[18] It fluctuates between magnitudes 6.34 and 6.38 in the visual passband with a period of 23 hours.[4]
This is a slightly evolved B-type star with a stellar classification of B8 IV.[6] Contrary to the classification, stellar evolution models from Zorec and Royer (2012) model it as a dwarf star that has completed 89.1% of its main sequence life.[5] It has 3.6 times the mass of the Sun[5] and 5.5 times its girth.[10] It radiates 293 times the luminosity of the Sun from its photosphere at an effective temperature of 11,350 K,[5] giving it a bluish-white hue. It is estimated to be 309 million years old[13] and spins modestly with a projected rotational velocity of 67 km/s.[12]