J/ApJ/899/123 Spitzer follow up of 95 brown dwarfs (Meisner+, 2020)
Spitzer Follow-up of Extremely Cold Brown Dwarfs Discovered by the Backyard
Worlds: Planet 9 Citizen Science Project.
Meisner A.M., Faherty J.K., Kirkpatrick J.D., Schneider A.C., Caselden D.,
Gagne J., Kuchner M.J., Burgasser A.J., Casewell S.L., Debes J.H.,
Artigau E., Bardalez Gagliuffi D.C., Logsdon S.E., Kiman R., Allers K.,
Hsu C.-C., Wisniewski J.P., Allen M.B., Beaulieu P., Colin G., Durantini
Luca H.A., Goodman S., Gramaize L., Hamlet L.K., Hinckley K., Kiwy F.,
Martin D.W., Pendrill W., Rothermich A., Sainio A., Schumann J.,
Andersen N.S., Tanner C., Thakur V., Thevenot M., Walla J., Wedracki Z.,
Aganze C., Gerasimov R., Theissen C.
<Astrophys. J., 899, 123 (2020)>
=2020ApJ...899..123M 2020ApJ...899..123M
ADC_Keywords: Stars, brown dwarf; Stars, Y-type; Stars, T-type;
Photometry, infrared; Spectra, infrared; Positional data;
Proper motions; Effective temperatures
Keywords: Y dwarfs ; Brown dwarfs ; T dwarfs ; Visual binary stars ;
Proper motions ; Solar neighborhood ; Infrared astronomy
Abstract:
We present Spitzer follow-up imaging of 95 candidate extremely cold
brown dwarfs discovered by the Backyard Worlds: Planet 9 citizen
science project, which uses visually perceived motion in multiepoch
Wide-field Infrared Survey Explorer (WISE) images to identify
previously unrecognized substellar neighbors to the Sun. We measure
Spitzer [3.6]-[4.5] color to phototype our brown dwarf candidates,
with an emphasis on pinpointing the coldest and closest Y dwarfs
within our sample. The combination of WISE and Spitzer astrometry
provides quantitative confirmation of the transverse motion of 75 of
our discoveries. Nine of our motion-confirmed objects have best-fit
linear motions larger than 1"/yr; our fastest-moving discovery is
WISEAJ155349.96+693355.2 (µ∼2.15/yr), a possible T-type subdwarf.
We also report a newly discovered wide-separation (∼400au) T8 comoving
companion to the white dwarf LSPMJ0055+5948 (the fourth such system to
be found), plus a candidate late T companion to the white dwarf
LSRJ0002+6357 at 5.5 projected separation (∼8700au if associated).
Among our motion-confirmed targets, five have Spitzer colors most
consistent with spectral type Y. Four of these five have exceptionally
red Spitzer colors suggesting types of Y1 or later, adding
considerably to the small sample of known objects in this especially
valuable low-temperature regime. Our Y dwarf candidates begin bridging
the gap between the bulk of the Y dwarf population and the coldest
known brown dwarf.
Description:
We have presented critical Spitzer photometric follow-up of 95 brown
dwarf candidates discovered by the Backyard Worlds citizen science
project.
WISE is a 0.4m aperture space telescope mapping the entire sky n all
four of its broad mid-infrared channels (W1=3.4um, W2=4.6um, W3=12um,
and W4=22um) during the first half of 2010. gathering WISE photometry,
we gave preference to CatWISE photometry when available. In the
absence of CatWISE photometry, we next checked AllWISE for photometry.
In the event that neither CatWISE nor AllWISE photometry was
available, we use photometry from the unWISE Catalog .
We used the 6.5m Baade Magellan telescope and the Folded-port InfraRed
Echellette (FIRE) spectrograph to obtain NIR spectra of eight objects
on our Spitzer programs. Observations were made for four sources on
2018 December 1 under clear conditions and an additional four sources
under poor conditions: one object on 2019 December 10 and three
objects on 2019 December 12. For all observations, we used the prism
mode and the 0.6" slit (R∼100) covering the full 0.8-2.5um band.
We used the Keck II telescope and the Near-Infrared Echellette
Spectrometer (NIRES) on 2019 October 28 and 2018 September 1 to obtain
0.94-2.45um NIR spectra of two objects.
We observed 42 of our brown dwarf candidates in the MKO J band with
the Camera PAnoramique Proche Infra-Rouge (CPAPIR) wide-field
(30'x30') NIR camera located at the Observatoire du Mont-Megantic
(OMM) 1.6m observatory between 2018 May and 2020 January. We have also
compiled archival NIR photometry for members of our sample using the
WFCAM Science Archive (UKIRT/WFCAM) and VISTA Science Archive
(VISTA/VIRCAM).
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 45 4 Targets without any spitzer counterpart
table2.dat 120 93 Mid-infrared photometry from WISE and spitzer
table3.dat 82 10 Details on spectroscopic follow-Up
table4.dat 77 314 Recalibrated WISE W2 positions
table5.dat 83 93 Spitzer ch2 coordinates used in linear motion fits
table6.dat 111 93 Linear motion fit results combining WISE and
spitzer astrometry
table7.dat 96 69 Ground-based NIR photometry from the VISTA/UKIRT
archives and OMM follow-up for motion-confirmed
members of our sample
table8.dat 41 33 Additional OMM J band photometry
table9.dat 105 75 Derived parameters of motion-confirmed objects with
Spitzer 3.6um and 4.5um photometry
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See also:
B/simbad : Simbad objects catalogue (M.Wenger 2000)
II/307 : WISE Preliminary Data Release (Cutri+ 2011)
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
II/314 : UKIDSS-DR8 LAS, GCS and DXS Surveys (Lawrence+ 2012)
II/328 : AllWISE Data Release (Cutri+ 2013)
II/329 : VIKING catalogue data release 1 (Edge+, 2013)
II/359 : The VISTA Hemisphere Survey (VHS) catalog DR4.1 (McMahon+, 2013)
II/343 : VIKING catalogue data release 2 (Edge+, 2016)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
II/357 : The Dark Energy Survey (DES): Data Release 1 (Abbott+, 2018)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
II/363 : The band-merged unWISE Catalog (Schlafly+, 2019)
II/365 : The CatWISE2020 catalog (version 28-Jan-2021) (Marocco+, 2020)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/AJ/123/3409 : SDSS M, L, and T dwarfs (Hawley+, 2002)
J/AJ/127/2856 : Brown dwarfs in the 2MASS Survey (Burgasser+, 2004)
J/ApJ/651/502 : Spitzer IRAC photometry of M, L, and T dwarfs (Patten+, 2006)
J/AJ/137/1 : Proper motions & astrometry late-type dwarfs (Faherty+, 2009)
J/ApJS/197/19 : First brown dwarfs discovered by WISE (Kirkpatrick+, 2011)
J/ApJS/201/19 : Hawaii Infrared Parallax Program. I. (Dupuy+, 2012)
J/ApJ/753/156 : T/Y brown dwarfs with WISE photometry (Kirkpatrick+, 2012)
J/AJ/145/136 : Astrometry & photometry of nearby white dwarfs (Limoges+, 2013)
J/ApJ/783/122 : AllWISE motion survey (Kirkpatrick+, 2014)
J/ApJ/781/4 : Photometry high proper motion objects from WISE (Luhman, 2014)
J/ApJ/792/30 : NEOWISE magnitudes for near-Earth objects (Mainzer+, 2014)
J/ApJS/219/19 : Census of nearby white dwarfs from SUPERBLINK (Limoges+, 2015)
J/ApJS/224/36 : The AllWISE motion survey (AllWISE2) (Kirkpatrick+, 2016)
J/ApJ/817/112 : NEOWISE/AllWISE high proper motion objects (Schneider+, 2016)
J/ApJ/867/109 : Spitzer observations of Y and T dwarfs (Martin+, 2018)
J/MNRAS/482/4570 : Gaia DR2 white dwarf candidates (Gentile Fusillo+, 2019)
J/ApJS/240/19 : Parallaxes of late-T and Y dwarfs (Kirkpatrick+, 2019)
J/ApJ/889/176 : Very low-mass binaries with Gaia DR2 data (Faherty+, 2020)
J/ApJ/891/171 : COCONUTS. I. Spectra of a WD & T4 comoving syst. (Zhang+, 2020)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 I8 --- AOR Spitzer Astronomical Observation Request
10- 34 A25 --- Source Source designation (1)
36- 40 F5.2 mag W2mag [16.14/16.49] WISE W2 4.6µm magnitude
42- 45 F4.2 mag e_W2mag [0.12/0.2] Uncertainty in W2mag
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Note (1): Each objects designation prefix corresponds to the WISE catalog
from which the quoted W2 magnitude has been drawn.
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 26 A26 --- Source Source designation
28- 28 A1 --- f_Source Discovery flag (1)
30- 32 A3 --- Motion Motion confirmed? (77 yes, 16 no)
34- 34 A1 --- l_W1mag [>] Limit flag on W1mag
36- 40 F5.2 mag W1mag [15.26/19.67]? WISE W1 3.4µm magnitude
42- 45 F4.2 mag e_W1mag [0.03/0.6]? Uncertainty in W1mag
47- 51 F5.2 mag W2mag [13.76/16.78] WISE W2 4.6µm magnitude
53- 56 F4.2 mag e_W2mag [0.02/0.2] Uncertainty in W2mag
58- 58 A1 --- f_W2mag Flag on W2mag (2)
60- 60 A1 --- l_W1-W2 [>] Limit flag on W1-W2
62- 65 F4.2 mag W1-W2 [0.17/3.75]? WISE W1-W2 color
67- 70 F4.2 mag e_W1-W2 [0.04/0.6]? Uncertainty for W1-W2
72- 79 I8 --- AOR Spitzer Astronomical Observation Request
81- 86 F6.3 mag 3.6mag [15.08/19.1]? Spitzer/IRAC 3.6µm band magnitude
88- 92 F5.3 mag e_3.6mag [0.01/0.3]? Uncertainty in 3.6mag
94- 99 F6.3 mag 4.5mag [13.95/16.79] Spitzer/IRAC 4.5µm band magnitude
101-105 F5.3 mag e_4.5mag [0.01/0.06] Uncertainty in 4.5mag
107-111 F5.3 mag 3.6-4.5 [0.002/3.26]? Spitzer [3.6-4.5] color
113-117 F5.3 mag e_3.6-4.5 [0.02/0.3]? Uncertainty in 3.6-4.5
120-120 I1 --- Ref [1/6] WISE photometry reference (3)
--------------------------------------------------------------------------------
Note (1): The discovery of CWISEPJ135937.65-435226.9 was presented in
Meisner+, 2020ApJ...889...74M 2020ApJ...889...74M, but its more recent p14299 Spitzer
photometry provided here is deeper than that of
Meisner+, 2020ApJ...889...74M 2020ApJ...889...74M.
Note (2): Flag as follows:
b = WISE photometry is or may be contaminated by blending (21 occurrences)
Note (3): References as follows:
1 = CatWISE Preliminary catalog; Cutri+, 2011, II/307
2 = unWISE Catalog; Schlafly+, 2019, II/363
3 = AllWISE catalog; Cutri+, 2013, II/328
4 = CatWISE Preliminary catalog reject table;
5 = Faherty+, 2020, J/ApJ/889/176
6 = CatWISE 2020 catalog; Marocco+, 2020, II/365
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 25 A25 --- Source Source designation
27- 27 A1 --- f_Source Source flag (1)
29- 35 A7 --- Tel Telescope; Baade or Keck II
37- 41 A5 --- Instr Instrument
43- 44 I2 d Obs.D Day of observation
46- 48 A3 "month" Obs.M Month of observation
50- 53 I4 yr Obs.Y [2018/2019] Year of observation
56- 58 I3 s Texp [120/300] Exposure time
60- 61 I2 --- Nf [3/12] Number of nod frames
63- 70 A8 --- Std Telluric standard star
72- 76 A5 --- Cond Conditions; Clear or Poor
78- 82 A5 --- SpT Spectral Type
--------------------------------------------------------------------------------
Note (1): See Faherty+, 2020, J/ApJ/889/176 for details on this system.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 26 A26 --- Source Source designation
28- 37 F10.6 deg RAdeg [0.62/359] Right Ascension (ICRS)
39- 48 F10.6 deg DEdeg [-84/80] Declination (ICRS)
50- 53 I4 mas dRA [95/1237] Positional uncertainty, Right Ascension
55- 58 I4 mas dDE [91/1247] Positional uncertainty, Declination
60- 68 A9 --- Slice Time slice (1)
70- 77 F8.2 d MJD [55312/58453] Mean Modified Julian Date of
observation; JD-2400000.5
--------------------------------------------------------------------------------
Note (1): See Table 5 of Meisner+, 2020ApJ...889...74M 2020ApJ...889...74M for definitions
of the WISE/NEOWISE time slices used for W2 astrometry.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 26 A26 --- Source Source designation
28- 35 I8 --- AOR Spitzer Astronomical Observation Request
37- 48 F12.8 deg RAdeg [0.62/359] Right Ascension (ICRS)
50- 61 F12.8 deg DEdeg [-84/80] Declination (ICRS)
63- 64 I2 mas dRA [11/78] Positional uncertainty, Right Ascension
66- 67 I2 mas dDE [10/73] Positional uncertainty, Declination
69- 76 F8.2 d MJD [55241/58847] Modified Julian Date of observation;
JD-2400000.5
78- 78 I1 --- Method [1/9] Method number (1)
81- 83 I3 --- Ncalib [4/139] Number of Gaia DR2 calibrators (2)
--------------------------------------------------------------------------------
Note (1): The astrometric calibrator selection "method number" here refers
to the method number listed in Table 6 of Meisner+, 2020ApJ...889...74M 2020ApJ...889...74M.
Note (2): Ncalib is the number of Gaia DR2 sources used for Spitzer ch2
astrometric recalibration. See Section 8.4.1 of
Meisner+, 2020ApJ...889...74M 2020ApJ...889...74M for additional details.
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Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 26 A26 --- Source Source designation
28- 38 F11.7 deg RAdeg [0.62/359] Right Ascension (ICRS) at Ep=MJD
40- 49 F10.7 deg DEdeg [0.36/84] Declination (ICRS) at Ep=MJD
51- 52 I2 mas dRA [11/77] Positional uncertainty, Right Ascension
54- 55 I2 mas dDE [11/71] Positional uncertainty, Declination
57- 64 F8.2 d MJD [55379/58806] Reference Modified Julian Date
(MJD)
66- 70 I5 mas/yr pmRA [-1684/1150] Proper motion, in right ascension
72- 73 I2 mas/yr e_pmRA [11/99] Uncertainty in pmRA
75- 79 I5 mas/yr pmDE [-2053/1348] Proper motion, in declination
81- 82 I2 mas/yr e_pmDE [10/98] Uncertainty in pmDE
84- 87 I4 mas/yr pmTot [12/2157] Total proper motion
89- 90 I2 mas/yr e_pmTot [10/98] Uncertainty in pmTot
92- 97 F6.1 --- chi2-m [0.1/3447] significance of motion χ2
statistic
99-103 F5.2 --- chi2 [0.01/25.16] χ2 statistic
105-106 I2 --- dof [2/12] Degrees of Freedom
108-111 F4.2 --- chi2-n [0/5.26] Reduced χ2 statistic (1)
--------------------------------------------------------------------------------
Note (1): chi2-n=chi2/dof
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Byte-by-byte Description of file: table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 26 A26 --- Source Source designation
28- 28 A1 --- l_Ymag [>] Limit flag for Ymag (1)
30- 34 F5.2 mag Ymag [18.48/20.5]? Y band magnitude
36- 39 F4.2 mag e_Ymag [0.02/0.3]? Uncertainty in Ymag
41- 41 A1 --- l_Jmag [>] Limit flag for Jmag (1)
43- 47 F5.2 mag Jmag [16.07/20.36] MKO J band magnitude
49- 52 F4.2 mag e_Jmag [0/0.7]? Uncertainty in Jmag
54- 54 A1 --- l_Hmag [>] Limit flag for Hmag (1)
56- 60 F5.2 mag Hmag [17.86/19.51]? MKO H band magnitude
62- 65 F4.2 mag e_Hmag [0.03/0.2]? Uncertainty in Hmag
67- 71 F5.2 mag Kmag [18.2/18.2]? MKO K band magnitude
73- 76 F4.2 mag e_Kmag [0.1/0.2]? Uncertainty in Kmag
78- 78 A1 --- l_Ksmag [>] Limit flag for Ksmag (1)
80- 84 F5.2 mag Ksmag [17.38/18.89]? Ks band magnitude
86- 89 F4.2 mag e_Ksmag [0.05/0.3]? Uncertainty in Ksmag
91- 96 A6 --- Instr Instrument used (2)
--------------------------------------------------------------------------------
Note (1): Magnitude limits are 5σ
Note (2): Instruments as follows:
CPAPIR = Camera PAnoramique Proche Infra-Rouge at the Observatoire du
Mont-Megantic 1.6m observatory
VIRCAM = Visible and Infrared Survey Telescope for Astronomy InfraRed
CAMera at Cerro Paranal Observatory in Chile
WFCAM = WFCAM for the UK Infrared Telescope on Mauna Kea
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Byte-by-byte Description of file: table8.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 26 A26 --- Source Source designation
28- 28 A1 --- l_Jmag [>] Limit flag for Jmag
30- 34 F5.2 mag Jmag [15.73/19.82] MKO J band magnitude (1)
36- 39 F4.2 mag e_Jmag [0.05/0.9]? Uncertainty in Jmag
41 A1 --- f_Jmag [a] Flag(s) on Jmag (2)
--------------------------------------------------------------------------------
Note (1): This table reports follow-up J band photometry for targets not
motion confirmed and/or with higher significance J band measurements
from archival data sets. Magnitude limits are 5σ.
Note (2): The OMM photometry for WISEU 0055+5947 is contaminated by blending
with a brighter nearby source, resulting in a reported magnitude that is
artificially bright.
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Byte-by-byte Description of file: table9.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 26 A26 --- Source Source designation
28- 28 A1 --- f_Source Source flag (1)
30- 31 A2 --- l_SphT [≥] Limit flag on SphT
33- 36 F4.1 --- SphT [5/11] Spectral "phototype" (2)
38- 42 F5.2 mag 4.5MAG [12.53/16.19] Spitzer/IRAC 4.5um absolute
magnitude
44- 47 F4.2 mag E_4.5MAG [0.2/0.6] upper error on Mch2
49- 52 F4.2 mag e_4.5MAG [0.2/0.6] lower error on Mch2
54- 57 F4.1 pc Dist [7.1/42.9] Photometric distance estimate
59- 61 F3.1 pc E_Dist [1.4/6.4] upper error on Dist
63- 65 F3.1 pc e_Dist [1.2/5.6] lower error on Dist
67- 70 I4 K Teff [303/1006]? Effective temperature
72- 74 I3 K E_Teff [82/132]? upper error on Teff
76- 78 I3 K e_Teff [82/124]? lower error on Teff
80- 84 F5.2 mag Hch2 [16.23/22.42] Spitzer/IRAC 4.5um reduced proper
motion; Hch2=mch2+5log10(µ)+5
86- 89 F4.2 mag E_Hch2 [0.04/0.47] upper error on Hch2
91- 94 F4.2 mag e_Hch2 [0.04/0.39] lower error on Hch2
96- 98 I3 km/s Vtan [13/395] Tangential velocity
100-101 I2 km/s E_Vtan [3/48] upper error on Vtan
103-105 I3 km/s e_Vtan [3/44] lower error on Vtan
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Note (1): Bardalez Gagliuffi+, 2020arXiv200412829B 2020arXiv200412829B presents a
trigonometric parallax for WISEA J083011.95+283716.0 yielding more
reliable estimates for its phototype, Mch2, distance, Teff, and Vtan.
Note (2): Photometric spectral type values are defined such that SpT=6
for T6, SpT=7 for T7,... SpT=11 for Y1. WISEA J053535.43-644518.5 is
omitted from this table despite being motion-confirmed, since its
relatively blue ch1-ch2∼0 color does not provide a well-constrained
Spitzer-based phototype. WISEU J224547.11-433341.5 has been omitted
because it lacks a ch1 magnitude and hence a Spitzer phototype.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 19-Oct-2021