J/MNRAS/511/4500 Collision of two stellar associations (Yep+, 2022)
Collision of two stellar associations in the nearby Gum nebula.
Yep A.C., White R.J.
<Mon. Not. R. Astron. Soc. 511, 4500-4510 (2022)>
=2022MNRAS.511.4500Y 2022MNRAS.511.4500Y (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Associations, stellar ; Photometry ; Optical ;
Stars, distances ; Stars, masses
Keywords: comets: general - stars: fundamental parameters -
stars: kinematics and dynamics -
open clusters and associations: general -
Abstract:
Based on Gaia DR2 data and new CHIRON radial velocities, we have
discovered that two nearby stellar associations UPK 535
(318.08±0.29pc, 25+15-10Myr, 174 stars) and Yep 3
(339.54±0.25pc, 45+55-20Myr, 297 stars) in the Gum Nebula have
recently collided. We project stars' current positions, motions, and
measurement uncertainties backward and forward through time in a
10000-trial Monte Carlo simulation. On average, the associations'
centres of mass come within 18.89±0.73pc of each other
0.84±0.03Myr ago. A mode of 54±7 close (<1pc) stellar encounters
occur during the collision. We cannot predict specific star-star close
encounters with our current ∼7.6pc distance precision and
21.5-per-cent-complete radial velocity sample. Never the less, we find
that two stars in UPK 535 and two stars in Yep 3 undergo a nonspecific
close encounter in >70 per cent of trials and multiple close
encounters in ∼30 per cent. On average, the closest approach of any
two stars is 0.13±0.06pc, or 27000±12000au. With impulse-tracing
values up to 2.7+3.1-1.1(M☉/pc2)/(km/s) , such close
encounters could perturb stars' Oort cloud comets (if present), cause
heavy bombardment events for exoplanets (if present), and reshape
solar system architectures. Finally, an expansion of our simulation
suggests other associations in the region are also interacting.
Association collisions may be commonplace, at least in the Gum Nebula
straddling the Galactic plane, and may spur solar system evolution
more than previously recognized.
Description:
Coordinates, proper motions, and photometry for UPK 535 (table3a.dat)
and Yep 3 (table3b.dat) are drawn from Gaia DR2. Distances are from
Bailer Jones et al. (2018AJ....156...58B 2018AJ....156...58B, Cat. I/347). Spectral types,
radial velocities, and masses are from our own spectroscopic analysis.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3a.dat 426 174 UPK 535
table3b.dat 426 297 Yep 3
--------------------------------------------------------------------------------
See also:
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
Table 1: Position and motion cuts for isolating the associations UPK 535 and
Yep 3 from Gaia DR2 data.
-------------------------------------------------------------------------------
Name RA DE Dist pmRA pmDE
(deg) (deg) (pc) (mas/yr) (mas/yr)
-------------------------------------------------------------------------------
UPK 535 123.0 - 131.0 -55.0 - -47.5 290 - 350 -14.5 - -11.5 1.1 - 4.1
Yep 3 126.3 - 134.0 -55.0 - -49.5 320 - 370 -14.5 - -11.5 9.0 - 12.0
-------------------------------------------------------------------------------
Byte-by-byte Description of file: table3?.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- GaiaDR2 Gaia DR2 source ID
(Caution, some wrong identifiers)
21- 42 A22 --- Name Name of spectroscopically observed star
44- 61 F18.14 deg RAdeg Right ascension (J2000)
63- 81 F19.15 deg DEdeg Declination (J2000)
83- 88 F6.4 mas plx Parallax
90- 95 F6.4 mas e_plx Standard error in parallax
97-103 F7.3 mas/yr pmRA Proper motion in right ascension (1)
105-110 F6.4 mas/yr e_pmRA Standard error in proper motion in
right ascension, pmRA*cosDE
112-118 F7.4 mas/yr pmDE Proper motion in declination (2)
120-125 F6.4 mas/yr e_pmDE Standard error in proper motion in
declination
127-146 F20.16 km/s RV ? Spectroscopic heliocentric radial velocity
148-166 F19.17 km/s e_RV ? Error in radial velocity
168-176 F9.6 mag Gmag ? Gaia DR2 G-band mean magnitude
178-198 F21.19 mag e_Gmag ? Error in G magnitude from error in flux
200-208 F9.6 mag BPmag ? Gaia DR2 integrated BP mean magnitude
210-230 F21.19 mag e_BPmag ? Error in BP magnitude from error in flux
232-240 F9.6 mag RPmag ? Gaia DR2 integrated RP mean magnitude
242-262 F21.19 mag e_RPmag ? Error in RP magnitude from error in flux
264-282 F19.16 mag Vmag ? Johnson V magnitude from BP and RP
284-304 F21.19 mag e_Vmag ? Error in V magnitude
306-311 A6 --- SpType ? Spectral type
313-320 F8.6 --- e_SpType ? Class error in spectral type
322-328 A7 --- BinFlag ? Spectroscopic binary star flag
330-345 F16.12 pc Dist Distance (3)
347-365 F19.16 pc E_Dist Uncertainty (upper) on distance
from parallax error
367-385 F19.16 pc e_Dist Uncertainty (lower) on distance
from parallax error
387-405 F19.17 Msun Mass ? Stellar mass from spectral type or BP-RP
color or corrected absolute G magnitude
407-426 F20.18 Msun e_Mass Error in stellar mass
--------------------------------------------------------------------------------
Note (1): This is the tangent plane projection of the proper motion
vector in the direction of increasing right ascension.
Note (2): This is the tangent plane projection of the proper motion
vector in the direction of increasing declination.
Note (3): Distances are from Bailer Jones et al. (2018AJ....156...58B 2018AJ....156...58B,
Cat. I/347).
--------------------------------------------------------------------------------
History:
From Alexandra C. Yep, ayep(at)astro.gsu.edu
Acknowledgements:
For Gaia DR2 data: Gaia team
For distances: Bailer-Jones et al. (2018AJ....156...58B 2018AJ....156...58B, Cat. I/347)
For CHIRON spectra: T. Henry, W.-C. Jao, L. Paredes, A. Nisak, H. James,
et al. of the CHIRON team
(End) Alexandra C. Yep [Ga. St. Univ.], Patricia Vannier [CDS] 07-Jan-2022