LIKELY
MILKY WAY
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| M 2-9 | IRAS 17028-1004 | GSC2.4.2 S8MB000028 | AAVSO - |
| SIMBAD PN M 2-9 | Pan-STARRS 95822564081809528 | SAO - | VSX - |
| GAIA DR3 4335188603873318656 | SkyMapper 170537.95-100832.6 | WRAY - | GCVS - |
| 2MASS J17053796-1008325 | HIP - | Hen - | BD - |
| WISE J170537.95-100832.3 | TYC - | ESO - | HD - |
| Bidelman (1954) | - | Allen (1984) | - | Belzcyński et al. (2001) | - |
| Gaposchkin (1957) | - | Kenyon (1986) | - | Akras et al. (2019) | M 2-9 (Susp.) |
| Boyarchuk (1969) | - | Vaidis (1988, 1991) | - |
| Right ascension (°) | 256.4082Ref | Parallax (mas) | 0.457±0.244Ref | Reddening E(B-V) (mag) | 0.49±0.01Ref, Note |
| Declination (°) | -10.1424Ref | Distance (kpc) | 3.24Ref, Note, 2.93Ref, Note | ||
| Galactic longitude (°) | 10.8993Ref | Proper motion in α (mas/yr) | 8.86±0.30Ref | ||
| Galactic latitude (°) | 18.0557Ref | Proper motion in δ (mas/yr) | -8.90±0.22Ref |
| X-Ray | - | IR type | D?Ref | Radio | YesRef |
| X-Ray type | - | J (mag) | 11.20Ref | Flickering | - |
| GALEX FUV (mag) | - | H (mag) | 9.18Ref | Outbursts | - |
| GALEX NUV (mag) | - | K (mag) | 7.00Ref | Outburst type | - |
| IUE | YesRef | WISE W1 (mag) | 4.10Ref | Jets | YesRef |
| FUSE | NoRef | WISE W2 (mag) | 1.25Ref | Resolved nebula | YesRef |
| U (mag) | - | WISE W3 (mag) | -0.22Ref | IPmax (eV) | 35.1Ref |
| B (mag) | 15.11Ref | WISE W4 (mag) | -2.84Ref | [O III] lines | YesRef |
| V (mag) | 14.30Ref | IRAS 12μm (Jy) | 50.50Ref | He II lines | NoRef |
| R (mag) | - | IRAS 25μm (Jy) | 110.00Ref | [Fe VII] lines | NoRef |
| I (mag) | - | IRAS 60μm (Jy) | 124.00Ref | O VI lines | NoRef |
| BP (mag) | 13.84Ref | IRAS 100μm (Jy) | 75.80Ref | ||
| G (mag) | 13.86Ref | AKARI S09 (Jy) | 38.07Ref | ||
| RP (mag) | 12.49Ref | AKARI S18 (Jy) | 73.25Ref |
| Orbital period (days) | 31411.5?±1826.25Ref | γ velocity (km/h) | - | Size of giant’s orbit (AU) | - |
| Eccentricity | 0.1±0.05Ref | RV of giant (km/h) | - | Separation (AU) | - |
| Inclination (°) | - | Inferior conj. of giant (JD) | - | Mass function | - |
| Eclipses | - | Mass ratio | - | ||
| Orbital ephemeris | - |
| Spectral type | - | Mass (M⊙) | - | Pulsation | - |
| Eff. temperature (K) | - | Radius (R⊙) | - | Type | - |
| IR type | D?Ref | Luminosity (L⊙) | - | Pulsation period (days) | - |
| Metallicity [Fe/H] | - | Pulsation ephemeris | - |
| Type/Spectral type | - | Mass (M⊙) | - | Spin period (min) | - |
| Shell-burning/Accreting-only | shell-burning?Ref | Radius (R⊙) | - | Accretion disk | - |
| Eff. temperature (K) | - | Luminosity (L⊙) | - | ||
| Lower limit (K) | - | ||||
| Upper limit (K) | - |
Allen & Swings (1972) proposed a young PN or symbiotic star nature for M 2-9 based on the high density of the core. No clear stellar source in the infrared was detected during their observations. Swings & Andrillat (1979) claimed that the spectra of the object resembled those of B[e] stars and protoplanetary nebulae. Subsequent IUE observations of Feibelman (1984) indicated the presence of a hot component within a binary nucleus. The results from Solf (2000), particularly the observation of fast bipolar jets, further supported the hypothesis of a symbiotic nature for M 2-9. Clyne et al. (2015) reported that the star's position in the diagnostic diagram aligns with a symbiotic classification, and the shape of the Hα emission line resembles that of known symbiotic stars. The bipolar nebula exhibited short-term changes, as noted in Kohoutek & Surdej (1980) and Corradi et al. (2011). De La Fuente et al. (2022) claimed that the collimated fast wind displays morphological spatial variability, providing further support for the symbiotic classification.