J/AJ/169/337 MOBStIRS: Bow shocks parameters from Zooniverse (Whisnant+, 2025)
The Milky Way Project MOBStIRS: Parameterizing infrared stellar-wind bow shock
morphologies with Citizen Science.
Whisnant A.S., Povich M.S., Patten N., Kobulnicky H.A.
<Astron. J., 169, 337 (2025)>
=2025AJ....169..337W 2025AJ....169..337W
ADC_Keywords: Galactic plane; Photometry, infrared; Milky Way; Stars, OB
Keywords: Stellar bow shocks ; Educational software ; Infrared astronomy ;
Massive stars ; Stellar mass loss ; Circumstellar dust
Abstract:
Mass-loss influences stellar evolution, especially for massive stars
with strong winds. Stellar wind bow shock nebulae driven by Galactic
OB stars can be used to measure mass-loss rates (Mdot). The
standoff distance (R0) between the star and the bow shock is set by
momentum flux balance between the stellar wind and the surrounding
interstellar medium (ISM). We created the Milky Way Project: mass-loss
rates for OB Stars driving infrared bow shocks (MOBStIRS) using the
online Zooniverse citizen science platform. We enlisted several
hundred students to measure R0 and two other projected shape
parameters for 764 cataloged infrared bow shocks. MOBStIRS
incorporated 1528 JPEG cutout images produced from Spitzer GLIMPSE and
MIPSGAL survey data. Measurements were aggregated to compute shape
parameters for each bow shock image deemed high quality by
participants. The average statistical uncertainty on R0 is 12.5% but
varies from <5% to ∼40% among individual bow shocks, contributing
significantly to the total error budget of Mdot. The derived nebular
morphologies agree well with (magneto) hydrodynamic simulations of bow
shocks driven by the winds of OB stars moving at Va=10-40km/s with
respect to the ambient ISM. A systematic correction to R0 to account
for viewing angle appears unnecessary for computing Mdot. Slightly
more than half of MOBStIRS bow shocks are asymmetric, which could
indicate anisotropic stellar winds, ISM clumping on sub-pc scales,
time-dependent instabilities, and/or misalignments between the local
ISM magnetic field and the star-bow- shock axis.
Description:
We use data from the Spitzer Space Telescope to create images of
individual IR bow shocks to be measured by citizen scientists through
the online Zooniverse platform. The Galactic Legacy Infrared Mid-Plane
Survey Extraordinaire (GLIMPSE; Benjamin+, 2003PASP..115..953B 2003PASP..115..953B;
Churchwell+, 2009PASP..121..213C 2009PASP..121..213C) and MIPSGAL (Carey+, 2009PASP..121...76C 2009PASP..121...76C)
surveyed the inner Galactic midplane with continuous coverage of
Galactic longitudes 0°≤|l|≤65° and latitudes |b|≤1.2°.
GLIMPSE (II/293) is a survey of Galactic Plane central parts made with
the Infrared Array Camera (IRAC) aboard the Spitzer Space Telescope
(SST). The four IRAC bands are centered at approximately 3.6, 4.5, 5.8
and 8.0um.
MIPSGAL is a 278deg2 survey of the inner Galactic plane using the
Multiband Infrared Photometer for Spitzer (MIPS) aboard the Spitzer
Space Telescope. The survey field was imaged in two passbands, 24 and
70um with resolutions of 6" and 18", respectively. The data for the
survey were collected in three epochs, 2005 September-October, 2006
April, and 2006 October.
The Milky Way Project (MWP) was first introduced in 2010 as the 10th
Zooniverse project, and subsequently the ∼3 million classifications
made by citizen scientists were used identify 2600 candidate IR
bubbles and 599 IR bow shock-driving stars (Simpson+2012, J/MNRAS/424/2442;
Jayasinghe+2019, J/MNRAS/488/1141). About 300 of the IR bow shocks were new
discoveries, not previously cataloged by Kobulnicky+2016 (J/ApJS/227/18).
The objects we used are a subset of the Kobulnicky+2016 and Jayasinghe+2019
catalogs, we don't present any new sources.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 21 240 List of citizen scientist participants by username
and number of images classified
table2.dat 105 586 Apparent shape parameter measurements for IR bow
shocks in the MOBStIRS final sample
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See also:
II/293 : GLIMPSE Source Catalog (I + II + 3D) (IPAC 2008)
J/MNRAS/424/2442 : Catalog of bubbles from Milky Way Project (Simpson+, 2012)
J/AJ/149/64 : MIPSGAL 24um point source catalog (Gutermuth+, 2015)
J/ApJS/227/18 : Candidate stellar bowshock nebulae from MIR (Kobulnicky+, 2016)
J/MNRAS/488/1141 : Milky Way Proj. DR2 bubbles & bow shocks (Jayasinghe+, 2019)
J/AJ/158/73 : Param. of OB stars & their bow shock nebulae (Kobulnicky+, 2019)
J/ApJS/251/29 : Stellar bow shock nebulae spectroscopic obs. (Chick+, 2020)
J/A+A/663/A36 : Most massive stars and their clumped winds (Brands+, 2022)
J/AJ/164/86 : Kinematic and astrometric data for SBN stars (Kobulnicky+, 2022)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 A17 --- Username Citizen scientist username
19- 21 I3 --- nCl [1/432] Number of classifications
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/896] Bowshock number (1)
5- 26 A22 --- Name Subject name, GLLL.llll+BB.bbbb or
MWP2GLLL.llll+BB.bbbbb (7)
28- 29 I2 --- nCS [5/56] Number of citizen science
classifications
31- 34 F4.2 --- Frac [0.5/1] Fraction of measurements that were
confident
36- 40 F5.1 arcsec R0pre [-99/267] Previous R0 standoff distance
measurement (2)
42- 47 F6.2 arcsec R0CS [3.1/247.5] Citizen science R0 standoff
distance measurement (2)
49- 53 F5.2 arcsec R0err [0.17/33.5] Statistical uncertainty on R0
standoff distance (2)
55- 60 F6.2 arcsec R90 [4.1/396.5] R90 (3)
62- 66 F5.2 arcsec e_R90 [0.3/58.6] Uncertainty in R90 (3)
68- 73 F6.2 arcsec Rc [5.6/484.8] Rc (4)
75- 79 F5.2 arcsec e_Rc [0.3/56.6] Uncertainty in Rc
81 I1 --- O+F [1/2] Flag indicating successful
classifications of original (O) and/or
flipped (F) images (5)
83- 85 I3 --- Asym [-99/1] Flag indicating symmetry (6)
87- 90 F4.2 --- Planitude [0.9/3.9] Projected planitude (Rc/R0)
92- 95 F4.2 --- e_Planitude [0.06/1.3] Uncertainty in projected
planitude
97- 100 F4.2 --- Alatude [0.6/2.41] Projected alatude (R90/R0)
102- 105 F4.2 --- e_Alatude [0.03/0.9] Uncertainty in projected alatude
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Note (1): These numbers were assigned according to
Kobulnicky+2016 (J/ApJS/227/18) and Jayasinghe+2019 (J/MNRAS/488/1141).
Note (2): R0 is measured from the driving star to the apex of the arc.
Note (3): R90 is the distance from the driving star to the arc, perpendicular
to the symmetry axis of the bow shock.
Note (4): Rc is the best-fitting circle along the arc of the bow shock, which
is not necessarily centered on the driving star.
Note (5): Classification flag as follows:
2 = The bow shock had successful classifications on both the original and
flipped image versions (224 occurrences)
1 = The bow shock had successful classifications on either the original or
flipped image (362 occurrences)
Note (6): Symmetry flag as follows:
1 = The bow shock was determined to be asymmetric (270 occurrences)
0 = The bow shock was determined to be symmetric (92 occurrences)
-99 = The O+F parameter is equal to 1 (224 occurrences)
Note (7): The objects are a subset of the Kobulnicky+2016 (J/ApJS/227/18) and
Jayasinghe+2019 (J/MNRAS/488/1141) catalogs, no new sources are presented.
However, different ID formatting and, in some cases, different coordinates
for the objects' central stars are used, preventing a direct match by name
with the Kobulnicky+2016 and Jayasinghe+2019 catalogs.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Robin Leichtnam [CDS] 19-Mar-2026