A Moving Cluster Distance to the Exoplanet 2M1207b in the TW Hydrae Association

“Using the constraints on luminosity and age (Chauvin et al. 2005), I interpolate masses from the non-gray evolutionary tracks of Burrows et al. (1997), the DUSTY tracks of Chabrier et al. (2000), and the COND tracks of Baraffe et al. (2003).”

“For all three models, the inferred upper mass limit of 2M1207 B (∼5-7MJup) is less than half of the deuterium-burning mass limit (∼13MJup; Burrows et al. 1997), and less than half of the maximum mass of Doppler velocity planets (∼15MJup; Marcy et al. 2005).”

“Using the constraints on luminosity and age (Chauvin et al. 2005), I interpolate masses from the non-gray evolutionary tracks of Burrows et al. (1997), the DUSTY tracks of Chabrier et al. (2000), and the COND tracks of Baraffe et al. (2003).”

“With the previous distance estimates (∼70 pc), Chauvin et al. (2004) estimates mass of 25MJup and 5MJup for A and B, respectively.”

“None have been directly imaged, however two have had their light detected through transit studies with the Spitzer Space Telescope (HD 209458b and TRes-1b; Charbonneau et al. 2005; Deming et al. 2005).”

“None have been directly imaged, however two have had their light detected through transit studies with the Spitzer Space Telescope (HD 209458b and TRes-1b; Charbonneau et al. 2005; Deming et al. 2005).”

“I add to TWA numbers 1 through 25 (Zuckerman & Song 2004) the three, new, low-mass candidate members 2M1207 and 2MASSW J1139511-315921 from Gizis (2002), and SSSPM J1102-3431 from Scholz et al. (2005).”

“I calculate luminosities using these absolute magnitudes, and the bolometric correction estimates of Golimowski et al. (2004).”

“Gizis (2002) discovered 2M1207 in a spectroscopic survey of red 2MASS sources, and claimed that the object was a ∼10 Myr-old, ∼25MJup member of the nearby (∼55 pc) TW Hya association (TWA; Webb et al. 1999b).”

“While astrophysically interesting in its own right as a representative of the new class of young, accreting brown dwarfs (e.g. Muzerolle et al. 2005; Mohanty et al. 2005), it appears that 2M1207 may become most famous for being the host “Sun” for the first imaged extrasolar planet – if indeed…”

“Considering the variations between published evolutionary tracks, especially for stars which are young and low-mass (Hillenbrand & White 2004), the cluster parallax distance should be considered an improved estimate.”

“There have been suggestions that some TWA stars may actually be background members of the ∼16-Myr-old Lower Centaurus-Crux (LCC) OB subgroup at d ≃ 110 pc (e.g. Mamajek & Feigelson 2001; Mamajek et al. 2002).”

“Such cloudlets could have been accelerated away from the LCC O-star population through the rocket effect (Oort & Spitzer 1955), and compressed to form stars due to radiation-driven implosion (Bertoldi & McKee 1990).”

“I add to TWA numbers 1 through 25 (Zuckerman & Song 2004) the three, new, low-mass candidate members 2M1207 and 2MASSW J1139511-315921 from Gizis (2002), and SSSPM J1102-3431 from Scholz et al. (2005).”

“The only published distance estimates to 2M1207 are ∼70 pc (Chauvin et al. 2004) and 70± 20 pc (Chauvin et al. 2005).”

“While astrophysically interesting in its own right as a representative of the new class of young, accreting brown dwarfs (e.g. Muzerolle et al. 2005; Mohanty et al. 2005), it appears that 2M1207 may become most famous for being the host “Sun” for the first imaged extrasolar planet – if indeed…”

“Such cloudlets could have been accelerated away from the LCC O-star population through the rocket effect (Oort & Spitzer 1955), and compressed to form stars due to radiation-driven implosion (Bertoldi & McKee 1990).”

“The radial velocity of HIP 54477 is not well constrained (vrad=+16.2± 10 km s −1; Barbier-Brossat & Figon 2000), but consistent with that for a TWA member at its position (+12.2± 1.6 km s−1).”

“These errors are very consistent with the SuperCOSMOS positional errors quoted by Hambly et al. (2001).”

“The small, young stellar groups associated with η Cha, ǫ Cha, and β Pic show many of these same symptoms (Mamajek et al. 1999, 2000; Ortega et al. 2002; Jilinski et al. 2005), although the η and ǫ Cha clusters appear to be more strongly bound than the TWA and β Pic groups.”

“Further observations of its radial velocity (Mohanty et al. 2003) and proper motion (Scholz et al. 2005) are roughly consistent with TWA membership.”

“If one calculates cluster parallax distances to “TWA” objects using the space motion vector of LCC (Madsen et al. 2002), the mean distances in column 7 of Table 1 change by less than ±5% (rms).”

“2 catalog (Urban et al. 1998) at http://ad.usno.navy.mil/ac/ squares fit to the 4 SuperCOSMOS points, and found their scatter consistent with positional errors of σα∗ = 143 mas and σδ = 196 mas.”

“The small, young stellar groups associated with η Cha, ǫ Cha, and β Pic show many of these same symptoms (Mamajek et al. 1999, 2000; Ortega et al. 2002; Jilinski et al. 2005), although the η and ǫ Cha clusters appear to be more strongly bound than the TWA and β Pic groups.”

“…globule formation scenario for TWA might explain a few observational quirks of the group, namely its location (∼70 pc away from the nearby LCC OB subgroup), age (∼7 Myr younger than LCC), space motion vector (directed ∼5 km s−1 away from the LCC; Mamajek et al. 2000), and low stellar density.”

“Part of the offset may be due to gravitational redshift, which for the typical ∼10Myr-old TWA member with mass ∼0.5M⊙ should be of order ∼0.4 km s−1(Greenstein & Trimble 1967, using radii from the D’Antona & Mazzitelli 1997 tracks), compared to ∼0.6 km s−1 for the Sun.”

“The analysis of MF01 included tens of X-ray-selected stars in their analysis which have been since shown to not be pre-MS stars (SZB03, Torres et al. 2003).”

“ANALYSIS Although a trigonometric parallax is not yet available for 2M1207, one can exploit the star’s putative membership in the TW Hya association to derive a distance using the cluster parallax (or “moving-cluster”) method (e.g. Atanasijevic 1971; de Bruijne 1999a).”

“If one calculates cluster parallax distances to “TWA” objects using the space motion vector of LCC (Madsen et al. 2002), the mean distances in column 7 of Table 1 change by less than ±5% (rms).”

“Cloudlets analogous to those on the periphery of Vel OB2 (Kim et al. 2005) and Ori OB1 (Lee et al. 2005) may be the evolutionary predecessors of small, unbound, ∼10 Myr-old associations like TWA.”

“Further observations of its radial velocity (Mohanty et al. 2003) and proper motion (Scholz et al. 2005) are roughly consistent with TWA membership.”

“Blaauw (1956, 1964) suggested that linear expansion or contraction may be detectable if deviations are present between the observed spectroscopic radial velocities, and those predicted from the moving group method for parallel motion.”

“For discussions on trying to detect the linear expansions of unbound associations, see Blaauw (1956, 1964), Bertiau (1958), Jones (1971), Brown et al. (1997), Dravins et al. (1999), and Madsen et al. (2002).”

“For discussions on trying to detect the linear expansions of unbound associations, see Blaauw (1956, 1964), Bertiau (1958), Jones (1971), Brown et al. (1997), Dravins et al. (1999), and Madsen et al. (2002).”

“An unexplained radial velocity offset of 0.4 km s−1 appears to be present among low-mass Hyades members (Gunn et al. 1988), even after accounting for gravitational redshift.”

“I approximately follow the convergent point grid technique of Jones (1971).”

“Mamajek & Feigelson (2001) and Lawson & Crause (2005) have suggested that TWA 14-19 are probably members of the more distant (∼120 pc; de Zeeuw et al. 1999) and older (∼16 Myr; Mamajek et al. 2002) Lower Centaurus Crux OB association (LCC).”

“This fact, combined with the finding that most of the stars in the MF01 convergent point analysis are not pre-MS (Song et al. 2002), suggests that their convergent point and dynamical age for the TWA (8.3 Myr) are not valid.”

“Small-scale star-formation in cometary globules on the edge of OB associations has strong observational support (Reipurth 1983; Ogura & Sugitani 1998), and there is strong evidence for triggering by the massive stellar population (e.g. Kim et al. 2005; Lee et al. 2005).”

“After excluding TWA 12, 17, 18, 19, 22, and 24 as TWA members, I characterize the final TWA membership with probability plots (so as to be immune to the effects of outliers; Lutz & Upgren 1980): dTWA = 49± 3 (s.e.m.)± 12 (1σ) pc, αTWA = 174 ◦.8± 12◦.3 (1σ), and δTWA = –37 ◦.1± 7◦.5 (1σ).”

“Mamajek & Feigelson (2001) and Lawson & Crause (2005) have suggested that TWA 14-19 are probably members of the more distant (∼120 pc; de Zeeuw et al. 1999) and older (∼16 Myr; Mamajek et al. 2002) Lower Centaurus Crux OB association (LCC).”

“This fact, combined with the finding that most of the stars in the MF01 convergent point analysis are not pre-MS (Song et al. 2002), suggests that their convergent point and dynamical age for the TWA (8.3 Myr) are not valid.”

“The small, young stellar groups associated with η Cha, ǫ Cha, and β Pic show many of these same symptoms (Mamajek et al. 1999, 2000; Ortega et al. 2002; Jilinski et al. 2005), although the η and ǫ Cha clusters appear to be more strongly bound than the TWA and β Pic groups.”

“ANALYSIS Although a trigonometric parallax is not yet available for 2M1207, one can exploit the star’s putative membership in the TW Hya association to derive a distance using the cluster parallax (or “moving-cluster”) method (e.g. Atanasijevic 1971; de Bruijne 1999a).”

“Cloudlets analogous to those on the periphery of Vel OB2 (Kim et al. 2005) and Ori OB1 (Lee et al. 2005) may be the evolutionary predecessors of small, unbound, ∼10 Myr-old associations like TWA.”

“I corrected the DENIS position for the 2MASS-DENIS offset found by Cabrera-Lavers & Garzón (2003), since the 2MASS positional errors are much smaller than DENIS’s (2MASS is tied to the ICRS via the Tycho-2 catalog to an accuracy of ∼80 mas; Cutri et al. 2003).”

“In addition, based on the study of Mamajek (2005) and parallax data from Weinberger et al. (2013), stars TWA 14, TWA 15A, TWA 15B, TWA 17, TWA 18, TWA 19A, TWA 19B, and TWA 24 are likely members of the Lower Centaurus-Crux subgroup of the Scorpius-Centaurus OB association and thus may be subject to…”

“The moving cluster distances and probabilities were calculated following Mamajek (2005) using the de Bruijne et al. (2001) convergent point solution with Hipparcos, Tycho-2, or UCAC2 proper motions (in order of preference).”

“Another limitation is that some young groups appear to have little net expansion (Mamajek (2005); Makarov (2007)), so that a time when the members were closest together is illdefined.”

“TWA 19 AB is a young star that was defined as a candidate member of TWA by Mamajek (2005), but later listed as a likely contaminant from LCC by Gagné et al. (2017a) based on a preliminary version of BANYAN Σ.”

“For our kinematic parallax calculations we followed Mamajek (2005) and used updated space motions for US, UCL and LCC tabulated in Chen et al. (2011)8.”

“…for assigning distances to each star, however in cases where these are not available or the associated uncertainties are prohibitively large, we adopt either a kinematic distance from the literature or derive one using the so-called ‘convergent point’ method (de Bruijne 1999; Mamajek 2005).”

“However, even if the estimated age of a single star were younger, the dynamical age and cluster age are both consistent with 7–10 Myr (e.g. Mamajek 2005; Ducourant et al. 2014).”

“…Lawson et al. 2002; Gizis 2002; Feigelson et al. 2003; Luhman & Steeghs 2004; Luhman 2004a; Lyo et al. 2004; Song et al. 2004; Zuckerman & Song 2004; Mamajek 2005; Scholz et al. 2005; Looper et al. 2007; Luhman et al. 2008a; Kastner et al. 2008) and young late-type dwarfs in the solar…”

“2M1207-3932 2M1207-3932 is a M8-L dwarf binary (Gizis 2002; Chauvin et al. 2004) in the 10 Myr old TW Hya Association (Webb et al. 1999; Mamajek 2005).”

“We adopt the formalism and methods of Mamajek (2005) and adopt the updated Sco-Cen subgroup space motions listed in Chen et al. (2011).”

“…(18) Vrba et al. (2004), (19) Leggett et al. (2012), (20) Burgasser et al. (2008c), (21) Tinney et al. (2003), (22) Faherty et al. (2014), (23)Mamajek (2005), (24) Manjavacas et al. (2014), (25) Burningham et al. (2011), (26) Geballe et al. (2001), (27) van Altena et al. (1995), (28) van…”

“TWA TWA 19: This star (G5V) was rejected as a member of TWA and suggested instead to be member of the ScorpiusCentaurus complex by Mamajek (2005) and Torres et al. (2008).”

“For these reasons, we are currently targeting all of our low-gravity objects for proper motion, radial velocity, and parallax measurements in order to derive their UVW space motions and to confirm or refute cluster membership (Mamajek 2005).”

“Faherty et al. (2012) measure a distance of 28.5± 3.5 pc for this object, and Weinberger et al. (2013a) measure 42.0± 4.5 pc. Mamajek (2005) measure a radial velocity of 11.6±2 km s−1 and propose it as a TWA member.”

“…TW Hya, SR 21 and HD 135344B, are part of the class of so-called “transitional” or “cold” disks, which show dust gaps or holes out to 4, 18 and 45AU, respectively (Calvet et al. 2002; Brown et al. 2007), at distances of 51, 120 and 84 pc (Mamajek 2005; Loinard et al. 2008; Sylvester et al. 1996).”

“Weinberger et al. (2013) and Ducourant et al. (2014) also report parallaxes for this object of 23.8± 2.6mas and 26.2± 1.1mas, respectively, which agree with ours at 0.1σ and 1.3σ (as does the Mamajek 2005 kinematic parallax of 25.0 ± 2.5 mas).”

“Following the techniques discussed in Mamajek (2005), we find that Alcor’s revised Hipparcos proper motion toward the UMa convergent point is µυ = 120.9 ± 0.1 mas yr −1, and the perpendicular motion is µτ = 9.2 ± 0.1 mas yr−1.”

“— (1) Webb et al. (1999), (2) Navascués (2006) (3) Mamajek (2005), (4) Torres et al. (2006), (5) Weinberger et al. (2013), (6) Yee & Jensen (2010), (7) Binks & Jeffries (2014), (8) Malo et al. (2014b), (9) Mamajek & Bell (2014), (10) Torres et al. (2008), (11) Torres et al. (2000) (12) Zuckerman…”

“…et al. 1999; Jayawardhana et al. 1999; Zuckerman et al. 2001c, 2004; Gizis 2002; Song et al. 2002, 2003; Kastner et al. 2008; Scholz et al. 2005; Mamajek 2005; Looper et al. 2007; Torres et al. 2008; Fernández et al. 2008; da Silva et al. 2009; Looper et al. 2010a, 2010b; Rodriguez et al.…”

“• Radial velocities: By definition, young moving groups are comoving with a very small velocity dispersion (σ ∼1 km/s for TWA; Mamajek 2005), and hence the radial velocities of Tuc-Hor members should correlate very well with the projection of the group UVW velocity into the line of sight.”

“Our TWA catalog comprises all stars considered to be associati n members by Mamajek (2005) and3 further members discovered since by Looper et al. (2007, 2010a,b); Shkolnik et al. (2011).”

“The absolute K-magnitude of 9.1 is then about 2 magnitudes brighter than for corresponding field objects, providing clear evidence of a larger radius and young age; this height above the main sequence is similar to that observed for other late-type members of Upper Sco (Lodieu et al. 2007) and TW Hya (Mamajek 2005; Te…”

“…Procedure We assume that the disks have a Keplerian velocity field, using stellar masses and distances from the literature to model the rotation pattern (0.6M⊙ at 51 pc for TW Hya and 2.3M⊙ at 122pc for HD 163296; see Calvet et al. 2002; Webb et al. 1999; Mamajek 2005; van den Ancker et al. 1998).”

“This is not surprising, since the 3Y5 MJup estimates by Chauvin et al. (2004) and Mamajek (2005) were based on age-Mbol analyses.”

“Results using the 1 Myr isochrone are reported with filled circles, those using the 3 Myr isochrne with filled triangles, and those using the 10 Myr isochrone with filled squares.”

“Indeed, since the separation implies a period of at leas (depending on the eccentricity) 1700 yr, detectable orbital evolution orchange of the velocity amplitude are not expected in the near future (Mamajek 2005), precluding both astrometry and radial-velocity measurements.”

“At a distance of 51±4 pc (Mamajek 2005), it is the closest known classical T Tauri star, and a suite of observational studies have shown that TW Hya harbors a massive disk of gas and dust.”

“10◦), isolated classical T Tauri star (see, e.g., Kastner et al. 1997; Webb et al. 1999; Krist et al. 2000; Mamajek 2005).”

“TW Hya is the closest (51 pc, Mamajek 2005) known young T Tauri star (age ∼ 4− 10 Myrs, Webb et al. 1999), and has a massive, face-on optically thick disk.”

“…self-consistent with the interpretation that this star is a nearby (distance ∼ 130 9 The distance and peculiar velocity were calculated following Mamajek (2005), using the UCAC3 proper motion for J1407, and the updated estimate of the mean space motion for UCL from Chen et al. (2011): (U, V,…”

“We also compared the projected and radial motions of the stars to that for an “ideal” member following the convergent point techniques discussed in Mamajek (2005).”

“…Lupus (190 pc ± 27 pc, Wichmann et al. 1998), Ophiuchus (160 pc, Whittet 1974), Taurus-Auriga (142 pc ± 14 pc, Wichmann et al. 1998), TW Hya (50 pc ± 12 pc, Mamajek 2005), MBM12 (275 pc, Luhman 2001), L1642, aka MBM20 (112–160 pc, Hearty et al. 2000, 140 pc adopted), NGC 5367, Circinus, L162 and…”

“With mK = 16.93 ±0.11 (Chauvin et al. 2004), a K-band bolometric correction of 3.25 ±0.14 (Mamajek 2005), and a distance of 52.4 ±1.1 pc (Ducourant et al. 2008), 2M1207b has a luminosity of logL/L⊙ = −4.73 ± 0.12.”

“In particular, there appears to be a dearth of M3–M7 stars (Figures 1 and 2; Mamajek 2005 and references therein).”

“At a distance of only ∼ 51 ± 4 pc (Mamajek 2005), TW Hya is one of the best studied protoplanetary disks, with extensive photometric data available from UV to cm wavelengths.”

“TW Hya is the closest known (at 51 pc, Mamajek 2005) classical T Tauri star with a nearly face-on (e.g., Qi et al. 2006) transition disk that exhibits an inner hole in its (IR-emitting) dust distribution (Calvet et al. 2002, Ratzka et al. 2007, Hughes et al. 2009).”

“The remaining TW Hya association (TWA) members have kinematic distances calculated by Mamajek (2005).”

“However, for anexpanding subgroup, the convergent point analysis will give the velocity of a group member participating in the linear expansion at the position of the Sun (e.g. Brown et al. 1997; Mamajek 2005), which is not the quantity that interests us here.”

“The system 2MASS1207334-393254 (sep∼41 AU, 2M1207A∼21MJup, 2M1207b∼5MJup) demonstrated that very low-mass objects could remain bound for at least 8 Myr (Chauvin et al. 2004; 2005c; Mamajek 2005; Song et al. 2006).”

“As a comparison, Mamajek (2005) derived an age for TWA based on the moving cluster distance method, an expansion age.”

“With its distance of 51 ± 4 pc (Mamajek 2005) and its estimated age of ∼ 10 Myr (Ho ff et al. 1998; Webb et al. 1999) TW Hya is a Rosetta stone for investigating the transition phase from disks to planets.”

“Being at only 51 pc (Mamajek 2005) and clearly presenting evidence for photoevaporation, TW Hya is the ideal target to provide additional observational constraints to models of disk photoevaporation and to help determine wind mass-loss rates.”

“The nearby TWHya association is one of the most important of such groups, but the coevality or even membership is somewhat uncertain for some objects (Mamajek 2005).”

“However, the convergent point location is not very sensitive to these estimates (see Mamajek 2005).”

“Its membership in the TW Hydra moving association (Gizis 2002) implies a young age (10 Myr; Webb et al. 1999; Mamajek 2005), and correspondingly low substellar masses for its late-type M and L dwarf components.”

“HIP 53484 (HD 94893): Excess appears real, dust temperature is 151K. Mamajek (2005) noted this star in looking for new members of the TW Hydrae association, but rejected it due to a large distance (97pc) and∼15◦ distance from the association centroid.”

“New Data in TWA Members of the TW Hya association (TWA) are especially appealing as spectral standards since they are nearby and are just old enough to no longer be obscured by their natal molecular cloud (30–80 pc, ∼ 10 Myr, Webb et al. 1999; Mamajek 2005).”

“A rich discussion of the constitution of TWA and a useful source of data utilized by many authors is presented in Mamajek (2005).”

“A similar problem exists at the northern boundary of LCC and TW Hya, where young stars at 70–150 pc have ambiguous memberships (Lawson & Crause 2005; Mamajek 2005).”

“(Mamajek 2005; Mamajek & Meyer 2007) and with trigonometric parallax measurements (Biller & Close 2007; Gizis et al. 2007; Ducourant et al. 2008).”

“Subsequent surveys and analyses have since brought the number of proposed members to about 30 (Zuckerman et al. 2001b; Gizis 2002; Reid 2003; Torres et al. 2003; Zuckerman & Song 2004; Mamajek 2005; Barrado y Navascués 2006; Torres et al. 2008).”

“Kinematics can be used to estimate ages via traceback analysis, which has proved challenging in the past (Blaauw 1964; Brown et al. 1997; Mamajek 2005; Pecaut et al. 2012), but may now be feasible with Gaia astrometry (Crundall et al. 2019; Wright 2020).”

“At a distance of 51 pc (Mamajek 2005), TW Hya is the nearest T Tauri star and a well-known transition object.”

“A kinematic distance of 34 pc is used for Hen 3-600 (Mamajek 2005).”

“…been estimated for the TW Hya moving group, ranging from 4.7 ± 0.6 Myr (Makarov et al. 2005) to ∼8.3 Myr (Makarov & Fabricius 2001; de la Reza et al. 2006) and even a 95% confidence lower limit of 10 Myr (Mamajek 2005), all depending on the choice of members used to calculate the kinematic age.”

“INTRODUCTION TW Hydrae is a nearby (∼51 pc; Mamajek 2005), young (∼10 Myr; Webb et al. 1999) star surrounded by an accretion disk that evinces a large inner hole as judged from the observed spectral energy distribution (SED; Calvet et al. 2002).”

“At a distance of ∼ 51 pc (Mamajek 2005), TW Hya is one of the nearest T Tauri stars.”

“We only observed bona fide members identified in the convergent point analysis of Mamajek (2005); thus we excluded TWA 17, 18, 19AB, and 24.”

“Although membership is highly probable, a parallax for the system and verification using cluster convergence-point methods (e.g., Torres et al. 2006; Mamajek 2005; Galli et al. 2012) is essential for unambiguous association.”

“…60 Garden Street, Cambridge, MA 02138 2 Kapteyn Astronomical Institute, University of Groningen, 9700 AV Groningen, The Netherlands 3 Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA, Leiden, The Netherlands cumstellar disks, farther only than TW Hydrae (51pc; Mamajek 2005).”

“Both models assume a disk with total gas mass 0.05 M as constrained by the HD rotational lines (Bergin et al. 2013), a distance of 51 pc (Mamajek 2005), and an inclination angle of 7 degree (Qi et al. 2004).”

“Formally recognized as a young physical association composed of five stars by Kastner et al. (1997), its membership swelled to 24 systems in little more than a decade (See Mamajek 2005; Looper et al. 2010 and references there-in).”

“It has been demonstrated, for example, that several objects that were thought to be members of TWA (TWA 12, 14, 15, 17, 18, 19 and 24) are probable members of LCC (Mamajek & Feigelson 2001; Lawson & Crause 2005; Mamajek 2005).”

“…moving group members have aged enough (∼10-100 Myr) to be dispersed from their formation region, they retain small velocity dispersions and their common galactic motion translates to proper motions toward a convergent point in the plane of the sky (see Jones 1971; de Bruijne 1999; Mamajek 2005).”

“5cm = 2.4× 10 −29 ( 51 d )2 LX [µJy] (3) here d is the source distance in pc (where 51 pc is the distance of TW Hya, Mamajek 2005), ΦEUV is measured in photons per second, and LX in erg/s.”

“We also estimate a kinematic distance to WISEA 1147−2040 following the “moving cluster” or “convergent point” method outlined in Mamajek (2005).”

“…associations, based on their sky position, proper motion, and photometry, as well as radial velocities and parallaxes when available (e.g., see Mamajek 2005; Rodriguez et al. 2011; Malo et al. 2013, 2014; Gagné et al. 2014; Kraus et al. 2014; Gagné et al. 2015b; Murphy & Lawson 2015; Riedel…”

“With a revised distance of 53.3±6 pc, based on the moving cluster method, Mamajek (2005) re-estimated the mass of 2M1207 b. Converting the Ks absolute magnitude into luminosity using a bolometric correction appropriate for mid and late-L dwarfs (Golimowski et al. 2004), based on his nearer distance…”

“Mamajek 2005, 19.”

“…the cluster parallax method has increased by 2σ compared to Mamajek (2005, 53± 6 pc) due to the effects of a improved proper motion for 2M1207 (Song et al. 2006), and a revised estimate of the TWA group velocity (22.4± 1 km s−1; which follows Mamajek 2005, but omits the deviant parallax for TWA 9).”

“Hence, we start answering these questions by choosing the well known nearby and isolated disk around TW Hya (51 ± 4 pc, Mamajek 2005) that has an age ranging from 3 Myr (Vacca & Sandell 2011) to 10+10−7 Myr (Barrado Y Navascués 2006).”