J/ApJ/856/38 Optical LCs of the counterpart to IC 10 X-2 (Kwan+, 2018)
An optical and infrared time-domain study of the supergiant fast X-ray
transient candidate IC 10 X-2.
Kwan S., Lau R.M., Jencson J., Kasliwal M.M., Boyer M.L., Ofek E.,
Masci F., Laher R.
<Astrophys. J., 856, 38-38 (2018)>
=2018ApJ...856...38K 2018ApJ...856...38K (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, X-ray; Photometry, RI
Keywords: accretion, accretion disks; stars: mass-loss; supergiants
X-rays: binaries
Abstract:
We present an optical and infrared (IR) study of IC 10 X-2, a
high-mass X-ray binary in the galaxy IC 10. Previous optical and X-ray
studies suggest that X-2 is a Supergiant Fast X-ray Transient: a
large-amplitude (factor of ∼100), short-duration (hours to weeks)
X-ray outburst on 2010 May 21. We analyze R- and g-band light curves
of X-2 from the intermediate Palomar Transient Factory taken between
2013 July 15 and 2017 February 14 that show high-amplitude (≳1mag),
short-duration (≲8days) flares and dips (≳0.5mag). Near-IR
spectroscopy of X-2 from Palomar/TripleSpec show He I,
Paschen-γ, and Paschen-β emission lines with similar shapes
and amplitudes as those of luminous blue variables (LBVs) and LBV
candidates (LBVc). Mid-IR colors and magnitudes from Spitzer/Infrared
Array Camera photometry of X-2 resemble those of known LBV/LBVcs. We
suggest that the stellar companion in X-2 is an LBV/LBVc and discuss
possible origins of the optical flares. Dips in the optical light
curve are indicative of eclipses from optically thick clumps formed in
the winds of the stellar counterpart. Given the constraints on the
flare duration (0.02-0.8 days) and the time between flares
(15.1±7.8days), we estimate the clump volume filling factor in the
stellar winds, fV, to be 0.01<fV<0.71, which overlaps with values
measured from massive star winds. In X-2, we interpret the origin of
the optical flares as the accretion of clumps formed in the winds of
an LBV/LBVc onto the compact object.
Description:
The primary source of our near-IR data was the IRAC on board the
Spitzer Space Telescope. In addition, we performed near-IR imaging in
the JHKs channels and near-IR spectroscopy at the Palomar Observatory
on 2016 July 18 (Figure 1). To complement the Spitzer images, we
obtained near-infrared images of IC 10 X-2 in the J, H, and Ks bands
on 2016 July 18 using the Wide Field Infrared Camera (WIRC) on the
200inch Hale Telescope at the Palomar Observatory (P200).
Near-infrared spectroscopy was performed using the Triple Spectrograph
(TripleSpec) instrument during the same observation run to complement
visible-spectrum spectroscopy by Laycock+ (2014ApJ...789...64L 2014ApJ...789...64L).
We used optical photometry of IC 10 X-2 from the IPAC/iPTF Discovery
Engine. The iPTF uses the Palomar Observatory 1.2m Oschin Telescope.
Optical light curves in the R and g bands, spanning 2010 November
14-2017 February 14 and 2009 August 25-2017 January 10, respectively,
were generated for IC 10 X-2. All R and g band photometries are shown
in Tables 2 and 3.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
00 20 20.91 +59 17 59.0 IC 10 X-2 = NAME IC 10 X-2
----------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 22 318 IPAC/iPTF R-band photometry
table3.dat 22 65 IPAC/iPTF g-band photometry
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See also:
V/106 : Catalogue of X-ray binaries (Liu+ 2001)
J/ApJ/836/64 : Luminous variable stars in M31 + M33. IV. (Humphreys+, 2017)
J/ApJS/216/10 : DUSTiNGS. I. The Good Source Catalog (Boyer+, 2015)
J/ApJ/789/104 : SNe IIn observations and properties (Ofek+, 2014)
J/A+A/562/A2 : 100-month Swift catalogue of SFXTs (Romano+, 2014)
J/A+A/465/993 : Spectral atlas of massive stars around He I (Groh+, 2007)
J/MNRAS/362/1065 : XMM/Chandra study of IC 10 (Wang+, 2005)
J/A+A/377/925 : Radial velocity curves of Vela X-1 (Barziv+, 2001)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 11 F11.5 d MJD Modified Julian Date
13- 17 F5.2 mag Rmag [17.3/19.3] Apparent R band Vega magnitude
19- 22 F4.2 mag e_Rmag [0.01/0.3] Uncertainty in Rmag
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Byte-by-byte Description of file:table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 F11.5 d MJD Modified Julian Date
13- 17 F5.2 mag gmag [18.1/20.6] Apparent g band Vega magnitude
19- 22 F4.2 mag e_gmag [0.02/0.4] Uncertainty in gmag
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 13-Feb-2019