J/ApJ/831/89 Eclipsing LMXB at the center of 3FGL J0427.9-6704 (Strader+, 2016)
A new γ-ray loud, eclipsing low-mass X-ray binary.
Strader J., Li K.-L., Chomiuk L., Heinke C.O., Udalski A., Peacock M.,
Shishkovsky L., Tremou E.
<Astrophys. J., 831, 89-89 (2016)>
=2016ApJ...831...89S 2016ApJ...831...89S (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, X-ray ; Photometry, UBVRI ; Photometry, infrared ;
Gamma rays
Keywords: binaries: spectroscopic; pulsars: general; stars: neutron;
X-rays: binaries
Abstract:
We report the discovery of an eclipsing low-mass X-ray binary at the
center of the 3FGL error ellipse of the unassociated Fermi/Large Area
Telescope γ-ray source 3FGL J0427.9-6704. Photometry from OGLE
and the SMARTS 1.3m telescope and spectroscopy from the SOAR telescope
have allowed us to classify the system as an eclipsing low-mass X-ray
binary (P=8.8hr) with a main-sequence donor and a neutron-star
accretor. Broad double-peaked H and He emission lines suggest the
ongoing presence of an accretion disk. Remarkably, the system shows
separate sets of absorption lines associated with the accretion disk
and the secondary, and we use their radial velocities to find evidence
for a massive (∼1.8-1.9M☉) neutron-star primary. In addition to
a total X-ray eclipse with a duration of ∼2200s observed with NuSTAR,
the X-ray light curve also shows properties similar to those observed
among known transitional millisecond pulsars: short-term variability,
a hard power-law spectrum (Γ∼1.7), and a comparable 0.5-10keV
luminosity (∼2.4x1033erg/s). We find tentative evidence for a
partial (∼60%) γ-ray eclipse at the same phase as the X-ray
eclipse, suggesting the γ-ray emission may not be confined to
the immediate region of the compact object. The favorable inclination
of this binary is promising for future efforts to determine the origin
of γ-rays among accreting neutron stars.
Description:
We converted the OGLE instrumental magnitudes i and v into standard I
and V filters using the equations I=i-0.338-0.0047(v-i) and
V=v-0.066-0.072(v-i), with (v-i) assumed from a smoothed version of
the light curve for epochs with only one filter available. We also
converted the OGLE UTC HJD values into Barycentric Julian Date (BJD)
on the Barycentric Dynamical Time (TDB) system. The OGLE-IV photometry
comprise 368 epochs in I and 28 epochs in V, spanning 2010 March 07 to
2015 November 29 (Udalski+ 2015AcA....65....1U 2015AcA....65....1U).
From 2016 January 16 to May 1 (UT), we obtained optical BVI and
near-IR H photometry of the source on most clear nights using ANDICAM
on the SMARTS 1.3m telescope at CTIO. On a few nights multiple sets of
observations were taken; the total number of epochs was 62-64 per
band, depending on the band. The exposure time in each BVI was 300s;
the on-source exposure time in H varied but was typically 500-600s.
Objects:
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RA (ICRS) DE Designation(s) (Period)
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04 27 56 -67 04.7 3FGL J0427.9-6704 = 2FGL J0427.2-6705 (P=0.366720)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 30 642 OGLE and SMARTS photometry of 3FGL J0427.9-6704
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See also:
J/ApJ/820/8 : 3FGL sources statistical classifications (Saz Parkinson+, 2016)
J/ApJS/218/23 : Fermi LAT third source catalog (3FGL) (Acero+, 2015)
J/ApJS/209/9 : Unidentified gamma-ray sources. IV. X-ray (Paggi+, 2013)
J/ApJS/208/17 : 2nd Fermi LAT cat. of gamma-ray pulsars (2PC) (Abdo+, 2013)
J/ApJS/207/19 : Hard X-ray survey from Swift-BAT 2004-2010 (Baumgartner+, 2013)
J/AcA/63/1 : OGLE-IV Magellanic Bridge Data supernovae (Kozlowski+, 2013)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 15 F15.7 d BJD Barycentric Julian Date (TDB) of observation
17- 22 F6.3 mag mag [15.5/20.3] Photometric Vega magnitude in Band
24- 28 F5.3 mag e_mag [0.004/0.4] Uncertainty in mag
30 A1 --- Band [BVIH] Photometric band used in the observation
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 27-Jan-2017