| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Centaurus |
| Right ascension | 14h 07m 47.92976s[1] |
| Declination | −39° 45′ 42.7671″[1] |
| Apparent magnitude (V) | 12.2–15.6[2] |
| Characteristics | |
| Evolutionary stage | Pre-main sequence[3] |
| Spectral type | K5 IVe Li[3][4] |
| Variable type | rotational T Tau andeclipsing[2] |
| Astrometry | |
| Radial velocity (Rv) | 5.904±0.151[4] km/s |
| Proper motion (μ) | RA: −23.108±0.015mas/yr[1] Dec.: −21.048±0.017mas/yr[1] |
| Parallax (π) | 7.2351±0.0140 mas[1] |
| Distance | 450.8 ± 0.9 ly (138.2 ± 0.3 pc) |
| Details | |
| Mass | 0.977+0.023 −0.045[5] M☉ |
| Radius | 1.0661+0.0062 −0.0139[6] R☉ |
| Luminosity | 0.3431+0.0067 −0.0064[6] L☉ |
| Surface gravity (log g) | 4.302+0.0243 −0.0243[6] cgs |
| Temperature | 4343+24 −29[6] K |
| Metallicity[Fe/H] | −0.1903+0.0448 −0.0422[6] dex |
| Rotation | 3.206±0.002 d[7]: 6 [a] |
| Rotational velocity (v sin i) | 14.6±0.4[8] km/s |
| Age | ~16[3] or21.38+4.30 −7.60[9]: 2 Myr |
| Other designations | |
| V1400 Cen,GSC 07807-00004,2MASS J14074792–3945427,WISE J140747.91–394542.9,1SWASP J140747.93–394542.6,ASAS J140748–3945.7[4] | |
| Database references | |
| SIMBAD | data |
V1400 Centauri, also known as1SWASP J140747.93−394542.6 or simplyJ1407, is a young,pre-main-sequence star that waseclipsed by the likely free-floatingsubstellar objectJ1407b in April–June 2007. With an age around 20 million years, the star is about as massive as the Sun and is located in the constellationCentaurus at a distance of 451light-years away from the Sun. V1400 Centauri is a member of Upper Centaurus–Lupus subgroup of theScorpius–Centaurus association, a group of young, comoving stars close to the Sun.
The star has beencatalogued in as early as the 1990s by theHubbleGuide Star Catalog, which identified the star and measured its position in a pair ofphotographic plates taken in 1974 and 1979.[10] The star has been catalogued by othersky surveys, including theAll Sky Automated Survey (ASAS),Two Micron All-Sky Survey (2MASS),Super Wide Angle Search for Planets (1SWASP), and theWide-field Infrared Survey Explorer (WISE).[4] Typically in these catalogues, the star is givendesignations such as 1SWASP J140747.93–394542.6, which comprises the survey name followed by the star's location inequatorial coordinates.[4] As such designations can be unwieldy, researchers simply call the star "J1407".[3]: 5 [11]
The star was given the officialvariable star designation V1400 Centauri in 2015, when it was added to theInternational Astronomical Union'sGeneral Catalogue of Variable Stars.[12] A 2018 research paper onstars with unusual dimming periods nicknamed V1400 Centauri "Mamajek's Object", after the astronomer Eric Mamajek who identified the star's unusual dimming in 2007.[13]
V1400 Centauri is located in the constellationCentaurus, about 40 degrees south of thecelestial equator.[4] The most recentparallax measurements by theGaia spacecraft indicate V1400 Centauri is located 450.8 ± 0.9light-years (138.2 ± 0.3parsecs) from the Sun.[1] Observations of V1400 Centauri's position over time have shown that it has a southwestward[b]proper motion consistent with that of theScorpius–Centaurus association, anOB association of young stars with ages between 11–17 million years and distances between 380–470 ly (118–145 pc) from the Sun.[3]: 4 The Scorpius–Centaurus association is the nearest OB association to the Sun, and is believed to have formed out of amolecular cloud that has since been blown away by thestellar winds of the association's most massive stars.[14]: 236, 250
V1400 Centauri is closest to the Upper Centaurus–Lupus subgroup of the Scorpius–Centaurus association, which has an age range of 14–18 million years and distance range of 380–460 ly (115–141 pc).[3]: 5-6 Given V1400 Centauri's similar distance and proper motion, it very likely belongs to the Scorpius–Centaurus association, which would mean it must be a young star within the age range of the Upper Centaurus–Lupus subgroup.[3]: 5-6 A 2012 estimate of V1400 Centauri's age assumes it is equal to 16 million years,[3]: 6 the mean age of the Upper Centaurus–Lupus subgroup, while a 2018 estimate fromGaia measurements puts the star's age at21.38+4.30
−7.60 million years.[9]: 2
V1400 Centauri is apre-main sequence star ofspectral class K5 IVe Li.[4][3]: 5 "K" means V1400 Centauri is an orangeK-type star, and the adjoining number "5" ranks V1400 Centauri's relative temperature on a scale of 9 (coolest) to 0 (hottest) for K-type stars. V1400 Centauri is given thesubgiantluminosity class "IV", because it has a brighterluminosity thanK-type main-sequence stars (luminosity class V).[3]: 5 [c] The letter "e" indicates V1400 Centauri exhibits weakhydrogen-alphaemission lines in itsvisible light spectrum.[3]: 5 Lastly, "Li" indicates V1400 Centauri is abundant inlithium.[3]: 5
Measurements from theGaia spacecraft's third and most recent data release (Gaia DR3) indicate V1400 Centauri is about 7% larger than the Sun in radius (1.07 R☉; 740,000 km; 460,000 mi),[6] but is slightly less massive than the Sun.[5][9]: 2 Depending on whethermagnetic effects are taken into account in V1400 Centauri'sstellar evolution or not, the star's mass could be either0.98 M☉ or0.89 M☉, respectively.[5]: 4 Young stars tend to be magnetically active,[15] and neglecting their magnetic effects results in an underestimation of their mass.[5]: 4, 9 An older estimate of V1400 Centauri's mass fromGaia's second data release (Gaia DR2) in 2018 gives0.95 M☉, but does not take magnetic effects into account.[9]: 2
V1400 Centauri is cooler and less luminous than the Sun, with an effective temperature of about 4,300 K (4,030 °C; 7,280 °F) and a luminosity about 34% that of the Sun.[6] V1400 Centauri has an estimatedsurface gravity of about200 m/s2 (over 20 times thegravity of Earth), based onGaia measurements of the star's brightness, distance, and color.[1][d]Gaia measurements also indicate V1400 Centauri has a lowermetallicity than the Sun.[1][e] Viewed from Earth, V1400 Centauri appears marginally redder than a typical K5-type star due tolight extinction byinterstellar dust between Earth and the star.[f] The star does not exhibit excessthermal emission in near- and mid-infrared wavelengths and lacks strong emission lines in its spectrum, which indicates it lacks a substantialaccretion disk orprotoplanetary disk.[3]: 10
Like most young stars, V1400 Centaurirotates rapidly with a rotation period of approximately 3.2 days.[3]: 8 The rapid rotation of V1400 Centauri strengthens its magnetic field via thedynamo process, which leads to the formation ofstarspots on its surface.[7]: 6 As V1400 Centauri rotates, its starspots come into and out of view, causing the star's brightness to periodically fluctuate by 5%, or about 0.1magnitudes inamplitude.[7]: 2 The star's rotation period varies by 0.02 days over a 5.4-year-longmagnetic activity cycle, due to the long-term movement of starspots across the star'sdifferentially rotating surface.[7]: 6 [16]: 2847 V1400 Centauri is known to emitsoft X-rays[3]: 8 due to itscorona being heated by its rotationally-strengthened magnetic field.[17] Because of its young age, starspot variability, and lack of dust accretion, V1400 Centauri is classified as a weak-linedT Tauri variable.[8]: 412 [2]
Spectroscopic measurements ofDoppler broadening in V1400 Centauri's spectral absorption lines indicate the star has a projected rotational velocity of14.6±0.4 km/s.[8]: 415–416 Given V1400 Centauri's rotation period, radius, and temperature, the star's true equatorial rotation velocity is15.7±1.7 km/s,[8]: 418 which indicates that the star's rotation axis is inclined68°±10° with respect to Earth's line of sight.[8]: 419
During 7 April to 4 June 2007,[g] telescopes of the SuperWide Angle Search for Planets (SuperWASP) andAll Sky Automated Survey (ASAS) projects recorded V1400 Centauri undergoing a series of significant dimming events for 56 days.[7] The pattern of these dimming events was complex yet nearly symmetrical, indicating they were caused by an opaque, disk-like structure eclipsing the star.[3]: 5 The object that eclipsed V1400 Centauri is now known asJ1407b, asubstellar object surrounded by a dustycircumplanetary disk about 90 million kilometers (56 million miles) in radius.
V1400 Centauri's eclipse by J1407b was discovered on 3 December 2010 by Mark Pecaut,[3]: 5 who was agraduate student of Eric E. Mamajek at theUniversity of Rochester.[20] Mamajek, Pecaut, and collaborators announced the discovery in 2012.[20] Mamajek's team initially hypothesized that J1407b is aringedexoplanet orbrown dwarf orbiting the star,[3]: 8 but that has since been disfavored by later studies. V1400 Centauri does not show repeating eclipses, telescope observations showed no orbiting companions, and the disk of J1407b would be unstable if it orbited the star, which suggests that J1407b likely does not orbit V1400 Centauri and is instead a free-floating object that coincidentally passed in front of the star.[11]: 2 In this case, J1407b's coincidental eclipse of V1400 Centauri would be considered an extremely rare event that will never happen again.[21]: 9 [20]
High-resolution imaging by theAtacama Large Millimeter Array (ALMA) in 2017 revealed a single object near V1400 Centauri, which might be J1407b. The object's distance from V1400 Centauri appears to match the expected distance travelled by J1407b if it was a free-floating object. The object's brightness is suggestive of a dusty circumplanetary disk surrounding aplanetary-mass object below 6Jupiter masses. However, the object has only been observed by ALMA once, so it is not yet known whether it is a moving foreground object or a stationary backgroundgalaxy.[11] Recent observations by ALMA in June and July 2024 will likely determine whether this object is J1407b or not.[22]
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