J/AJ/145/139 Radial velocities of TYC 3010-1494-1 (Mack+, 2013)
A cautionary tale: MARVELS brown dwarf candidate reveals itself to be a very
long period, highly eccentric spectroscopic stellar binary.
Mack C.E III, Ge J., Deshpande R., Wisniewski J.P., Stassun K.G.,
Gaudi B.S., Fleming S.W., Mahadevan S., De Lee N., Eastman J., Ghezzi L.,
Gonzalez Hernandez J.I., Femenia B., Ferreira L., Porto de Mello G.,
Crepp J.R., Mata Sanchez D., Agol E., Beatty T.G., Bizyaev D.,
Brewington H., Cargile P.A., da Costa L.N., Esposito M., Ebelke G.,
Hebb L., Jiang P., Kane S.R., Lee B., Maia M.A.G., Malanushenko E.,
Malanushenko V., Oravetz D., Paegert M., Pan K., Allende Prieto C.,
Pepper J., Rebolo R., Roy A., Santiago B.X., Schneider D.P., Simmons A.,
Siverd R.J., Snedden S., Tofflemire B.M.
<Astron. J., 145, 139 (2013)>
=2013AJ....145..139M 2013AJ....145..139M
ADC_Keywords: Binaries, spectroscopic ; Radial velocities
Keywords: binaries: spectroscopic - brown dwarfs -
stars: individual: TYC 3010-1494-1
Abstract:
We report the discovery of a highly eccentric, double-lined
spectroscopic binary star system (TYC 3010-1494-1), comprising two
solar-type stars that we had initially identified as a single star
with a brown dwarf companion. At the moderate resolving power of the
MARVELS spectrograph and the spectrographs used for subsequent
radial-velocity (RV) measurements (R≲30000), this particular
stellar binary mimics a single-lined binary with an RV signal that
would be induced by a brown dwarf companion (Msini∼50MJup) to a
solar-type primary. At least three properties of this system allow it
to masquerade as a single star with a very-low-mass companion: its
large eccentricity (e∼0.8), its relatively long period (P∼238days),
and the approximately perpendicular orientation of the semi-major axis
with respect to the line of sight (ω∼189°). As a result of
these properties, for ∼95% of the orbit the two sets of stellar
spectral lines are completely blended, and the RV measurements based
on centroiding on the apparently single-lined spectrum is very well
fit by an orbit solution indicative of a brown dwarf companion on a
more circular orbit (e∼0.3). Only during the ∼5% of the orbit near
periastron passage does the true, double-lined nature and large RV
amplitude of ∼15km/s reveal itself. The discovery of this binary
system is an important lesson for RV surveys searching for substellar
companions; at a given resolution and observing cadence, a survey will
be susceptible to these kinds of astrophysical false positives for a
range of orbital parameters. Finally, for surveys like MARVELS that
lack the resolution for a useful line bisector analysis, it is
imperative to monitor the peak of the cross-correlation function for
suspicious changes in width or shape, so that such false positives can
be flagged during the candidate vetting process.
Description:
A total of 28 spectra (see Table 1) of TYC 3010 were obtained with the
Sloan 2.5m telescope at Apache Point Observatory (APO). The MARVELS
(Multi-object APO Radial Velocity Exoplanet Large-area Survey)
spectrograph was used (R∼12000).
19 radial velocity observations were taken with the APO 3.5m telescope
using the ARC Echelle Spectrograph (ARCES). This spectrograph operates
in the optical regime from ∼3600-10000Å with a resolving power of
R∼31500. The first set of observations were taken from 2010 October to
2011 June. The second set of observations were obtained during 2012
January-February. Table1 shows the 15 ARCES points observed outside of
periastron.
A total of 18 observations were obtained with the 9.2m HET using the
High Resolution Spectrograph (HRS) at a resolving power of R∼30000.
Table1 shows the HET radial velocities obtained with the CCF mask
technique (see Section 2.3.1 for more details).
Objects:
----------------------------------------------------------------------
RA (ICRS) DE Designation(s) (Period)
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11 00 11.45 +39 43 24.7 TYC 3010-1494-1 = BD+40 2392 (P=237.96)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 28 50 Observed heliocentric single-lined radial
velocities for TYC 3010
table2.dat 41 15 Observed heliocentric double-lined radial
velocities for TYC 3010
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See also:
I/259 : The Tycho-2 Catalogue (Hog+ 2000)
J/AJ/143/107 : Radial velocities of TYC 4110-01037-1 (Wisniewski+, 2012)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 13 F13.5 d HJD Heliocentric Julian Date
15 A1 --- Inst Instrument (A, H, M) (G1)
17- 22 F6.3 km/s RV [39.192/62.856] Heliocentric radial velocity (1)
24- 28 F5.3 km/s e_RV σ uncertainty in RV
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Note (1): The ARCES and HRS radial velocity values were measured as absolute
heliocentric radial velocities, while the MARVELS discovery data were
measured on a relative instrumental scale; the MARVELS radial velocities
have been offset to the same (heliocentric) scale as the ARCES and HRS
measurements.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 13 F13.5 d HJD Heliocentric Julian Date
15 A1 --- Inst Instrument (A or H) (G1)
17- 22 F6.3 km/s RV1 [34.45/54.16] Primary heliocentric radial velocity
24- 28 F5.3 km/s e_RV1 σ uncertainty in RV1
30- 35 F6.3 km/s RV2 [68.4/90.97] Secondary heliocentric radial velocity
37- 41 F5.3 km/s e_RV2 σ uncertainty in RV2
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Global notes:
Note (G1): Spectrograph as follows:
A = ARCES (ARC Echelle Spectrograph);
H = HRS (High Resolution Spectrograph);
M = MARVELS (Multi-object APO Radial Velocity Exoplanet Large-area Survey).
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History:
From electronic version of the journal
(End) Sylvain Guehenneux [CDS] 26-May-2014