J/ApJ/950/141 The ELM Survey South. II. 28 new WD binaries (Kosakowski+, 2023)
The ELM Survey South.
II. Two dozen new low-mass white dwarf binaries.
Kosakowski A., Brown W.R., Kilic M., Kupfer T., Bedard A., Gianninas A.,
Agueros M.A., Barrientos M.
<Astrophys. J., 950, 141 (2023)>
=2023ApJ...950..141K 2023ApJ...950..141K
ADC_Keywords: Binaries, eclipsing; Stars, white dwarf; Spectra, optical;
Radial velocities; Stars, masses; Parallaxes, trigonometric;
Surveys
Keywords: Compact binary stars ; Eclipsing binary stars ; White dwarf stars ;
Spectroscopy
Abstract:
We present the results from our ongoing spectroscopic survey targeting
low-mass white dwarf binaries, focusing on the southern sky. We used a
Gaia DR2- and eDR3-based selection and identified 28 new binaries,
including 19 new extremely low-mass (ELM) white dwarfs, one short
period, likely eclipsing, DABZ, and two potential LISA binaries. We
present the orbital and atmospheric parameters for each new binary
based on our spectroscopic follow up. Four of our new binaries show
periodic photometric variability in TESS 2 minutes cadence data,
including one new eclipsing double-lined spectroscopic binary. Three
others show periodic photometric variability in ZTF, including one new
eclipsing binary. We provide estimates for the inclinations and scaled
component radii for these ZTF variables, based on light-curve modeling
of our high-speed photometric follow-up observations. Our observations
have increased the sample of ELM Survey binaries identified in the
southern sky to 41, an increase of 64%. Future time domain surveys,
such as BlackGEM and the Vera C. Rubin Observatory Legacy Survey of
Space and Time, will efficiently identify photometric variables in the
southern sky and significantly increase the population of southern sky
low-mass white dwarf binaries, leading to a more complete all-sky
population of these systems.
Description:
We used a similar observing strategy as in previous extremely low-mass
(ELM) Survey publications: we obtained one optical spectrum for each
of our candidates to confirm their nature and perform spectroscopic
fitting with model atmospheres. For objects consistent with ELM white
dwarfs (5.0≲logg≲7.2), we obtained multiple additional spectra to
check for radial velocity variability and constrain their orbital
periods.
For follow-up observations, we used:
(1) the Southern Astrophysical Research Telescope (SOAR) 4.1m
telescope with the Goodman spectrograph, with a spectral resolution
∼2.6Å over the wavelength range 3550-5300Å. These data were
taken as part of the NOAO programs 2019B-0004, 2020B-0013, and
2021A-0007, and NOIRLab 2022A-161017.
(2) the Gemini South 8.1m telescope, located on Cerro Pachon in Chile
with the GMOS-S spectrograph and the Gemini North 8.1m telescope,
located on Mauna Kea in Hawai'i with the GMOS spectrograph, with
resolutions ∼2.8Å and ∼5.5Å over the spectral range
3600-6750Å. These data were obtained as part of the programs
GN-2021A-Q-203, GN-2021A-Q-300, GS-2020B-Q-304, GS-2021A-Q-300, and
GS-2021B-Q-304.
(3) the 6.5m Walter Baade Magellan 1 Telescope at the Las Campanas
Observatory in Chile with the Magellan Echellette (MagE) spectrograph,
with a resolving power R∼4800 covering the wavelength range 3600-7000Å.
(4) the 1.5m Tillinghast telescope at Fred Lawrence Whipple
Observatory (FLWO) located on Mt. Hopkins in Arizona. Our primary
setup used the FAST spectrograph with a spectral resolution ∼3.6Å
covering the spectral range 3500-7400Å. A handful of observations
used a slightly different setup resulting in a spectral resolution
∼1.8Å covering the spectral range 3650-5300Å.
(5) the 6.5m Multiple Mirror Telescope (MMT) with the blue channel
spectrograph, mainly with a ∼1.2Å resolution over the wavelength
range 3600-4500Å.
(6) the 2.4m Hiltner telescope at the MDM observatory, located in Kitt
Peak, Arizona, with the OSMOS spectrograph, with a spectral resolution
of 3.6Å over the wavelength range 3600-5930Å.
(7) the 2.1m Otto Struve telescope at the McDonald Observatory near
Fort Davis, Texas to obtain high-speed photometric follow up of our
binaries to confirm the variability seen in various sky survey data
archives. We used the ProEM frame-transfer CCD detector with either
the BG40, g-, r-, or i-band filters.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
wdbin.dat 169 29 White dwarf parameters determined through optical
spectroscopy for the 28 new binaries identified in
this work (Table 1) and orbital solutions (Table 2)
tablea1.dat 45 813 Radial velocity measurements for the 28 new
binaries identified in this work
tablea2.dat 101 287 Atmospheric parameters (assuming pure-hydrogen
atmospheres) for objects observed as part of our
follow-up campaign
--------------------------------------------------------------------------------
See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
II/385 : VLT Survey Telescope ATLAS DR4 (Shanks+, 2025)
J/ApJS/156/47 : DA WDs from the Palomar Green Survey (Liebert+, 2005)
J/ApJ/723/1072 : The ELM survey. I. Low-mass white dwarfs (Brown+, 2010)
J/ApJ/743/138 : Sp. survey of bright white dwarfs (Gianninas+, 2011)
J/A+A/557/A19 : Mass & age of extreme low-mass white dwarfs (Althaus+, 2013)
J/ApJ/769/66 : The ELM survey. V. White dwarf binaries (Brown+, 2013)
J/A+A/557/A119 : Eclipsing binary system LL Aquarii (Southworth, 2013)
J/ApJ/794/35 : Binary WDs atmospheric parameters (Gianninas+, 2014)
J/ApJ/812/167 : The ELM survey. VI. 11 new ELM WD bin. (Gianninas+, 2015)
J/ApJ/818/155 : The ELM survey. VII. 15 new ELM WD candidates (Brown+, 2016)
J/A+A/595/A35 : Low-mass helium WDs evolutionary models (Istrate+, 2016)
J/ApJ/848/11 : Spectroscopic & photometric analysis of WDs (Bedard+, 2017)
J/AJ/156/102 : The TESS Input Cat. & Candidate Target List (Stassun+, 2018)
J/MNRAS/488/2892 : Gaia DR2 extremely low-mass WD candidates (Pelisoli+, 2019)
J/ApJ/901/93 : Model atm. analysis of hot WDs from SDSSDR12 (Bedard+, 2020)
J/ApJ/889/49 : The ELM Survey. VIII. Final double WD bin. (Brown+, 2020)
J/A+A/634/A93 : Limb-darkening coeff. for compact stars (Claret+, 2020)
J/ApJ/894/53 : ELM Survey South. I. 6 new ELM WDs RVs (Kosakowski+, 2020)
J/A+A/650/A102 : SDSS J160429.12+100002.2 spectra (Irrgang+, 2021)
J/ApJ/933/94 : The ELM survey. IX. SDSS+Gaia WD binaries (Brown+, 2022)
J/ApJ/936/5 : LAMOST parameters for 188 white dwarfs (Wang+, 2022)
Byte-by-byte Description of file: wdbin.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Name Object identifier
13- 15 A3 --- Flag Flag (s) (G1)
17- 18 I2 h RAh Hour of Right Ascension (ICRS) at Epoch=2016.0
20- 21 I2 min RAm Minute of Right Ascension (ICRS) at Epoch=2016.0
23- 28 F6.3 s RAs Second of Right Ascension (ICRS) at Epoch=2016.0
30 A1 --- DE- Sign of the Declination (ICRS) at Epoch=2016.0
31- 32 I2 deg DEd Degree of Declination (ICRS) at Epoch=2016.0
34- 35 I2 arcmin DEm Arcminute of Declination (ICRS) at Epoch=2016.0
37- 42 F6.3 arcsec DEs Arcsecond of Declination (ICRS) at Epoch=2016.0
44- 48 I5 K Teff [8740/22850] Stellar effective temperature
50- 52 I3 K e_Teff [130/500] Uncertainty in Teff
54- 57 F4.2 [cm/s2] logg [5.24/7.5] Log, surface gravity
59- 62 F4.2 [cm/s2] e_logg [0.04/0.3] Uncertainty in logg
64- 67 F4.2 Msun Mstar [0.18/0.43]? Stellar mass
69- 72 F4.2 Msun e_Mstar [0.01/0.04]? Uncertainty in Mstar
74- 77 F4.1 mag Gmag [13.8/19]? Gaia DR3 G-band magnitude
79- 82 F4.2 mas plx [0.5/6.1] Gaia DR3 parallax
84- 87 F4.2 mas e_plx [0.02/0.3] Uncertainty in plx
89- 96 F8.6 d Per [0.027/1.2] Orbital Period
98-105 F8.6 d e_Per [1e-06/0.01] Uncertainty in Per
107-111 F5.1 km/s K [79/514] Velocity semi-amplitude
113 I1 km/s E_K [8]? Upper uncertainty on K
115-117 F3.1 km/s e_K [1/9.5] Lower (or symmetric) uncertainty on K
119-124 F6.1 km/s gamma [-140/147]? Systemic velocity
126-128 F3.1 km/s E_gamma [6/7.1]? Upper uncertainty on K
130-133 F4.1 km/s e_gamma [1/29.5]? Lower (or symmetric) uncertainty on K
135 A1 --- l_M2 Limit flag on M2
137-140 F4.2 Msun M2 [0.1/1.1]? Companion mass
142-145 F4.2 Msun E_M2 [0.05/0.05]? Upper uncertainty on M2
147-150 F4.2 Msun e_M2 [0.01/0.1]? Lower (or symmetric) uncertainty
on M2
152 A1 --- l_taum Limit flag on taum
154-160 F7.3 Gyr taum [0.021/371.4]? Merger timescale
162-167 F6.3 Gyr e_taum [0.001/71.7]? Uncertainty in taum
169 I1 --- Disk [0/1] Galactic disk (flag=1) or halo
membership
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Name Object identifier
13- 25 F13.8 d HJD [3852.76/9935.72] Heliocentric Julian date;
HJD-2450000.0
27- 35 F9.4 km/s RVel [-498/493] Radial Velocity
37- 45 F9.5 km/s e_RVel [1.3/113] Uncertainty in RVel
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- Gaia Gaia DR3 identifier (source_id)
21- 23 A3 --- Flag Flag(s) (G1)
25- 26 I2 h RAh Hour of Right Ascension (ICRS) at Epoch=2016.0
28- 29 I2 min RAm Minute of Right Ascension (ICRS) at
Epoch=2016.0
31- 36 F6.3 s RAs Second of Right Ascension (ICRS) at
Epoch=2016.0
38 A1 --- DE- Sign of the Declination (ICRS) at Epoch=2016.0
39- 40 I2 deg DEd Degree of Declination (ICRS) at Epoch=2016.0
42- 43 I2 arcmin DEm Arcminute of Declination (ICRS) at Epoch=2016.0
45- 50 F6.3 arcsec DEs Arcsecond of Declination (ICRS) at Epoch=2016.0
52- 56 I5 K Teff [9290/45500] Stellar effective temperature
58- 61 I4 K e_Teff [140/5070] Uncertainty in Teff
63- 66 F4.2 [cm/s2] logg [4.9/8.4] Log, surface gravity
68- 71 F4.2 [cm/s2] e_logg [0.04/0.9] Uncertainty in logg
73- 77 F5.2 mag Gmag [13.2/20]? Gaia DR3 G-band magnitude
79- 84 F6.3 mag BP-RP [-0.51/0.55] Gaia DR3 BP-RP color
86- 90 F5.3 mag e_BP-RP [0.004/0.05] Uncertainty in BP-RP
92- 96 F5.2 mas plx [0.5/25.6] Gaia DR3 parallax
98-101 F4.2 mas e_plx [0.03/0.5] Uncertainty in plx
--------------------------------------------------------------------------------
Global notes:
Note (G1): Flags as follows:
a = Photometric variability: TESS high-cadence;
b = Photometric variability: ZTF;
c = Pelisoli & Vos (2019, J/MNRAS/488/2892) ELM white dwarf candidate;
s = The atmospheric parameter values for J1506-1125 displayed in
this table are based on single-star models. We describe our
multi-component modeling to J1506-1125 in Section 6, which does not
identify a unique solution.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
Kosakowski et al. Paper I. 2020ApJ...894...53K 2020ApJ...894...53K Cat. J/ApJ/894/53
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 04-Aug-2025