Uncovering Red and Dusty Ultraluminous X-Ray Sources with Spitzer

Lau, Ryan M.; Heida, Marianne; Walton, D. J.; Kasliwal, M. M.; Adams, S. M.; Cody, Ann Marie; De, Kishalay; Gehrz, R. D.; Fürst, Felix; Jencson, J.; Kennea, J. A.; Masci, Frank J.

doi:10.3847/1538-4357/ab1b1c

Cited by 31 publications

(28 citation statements)

References 160 publications

(196 reference statements)

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“…The broadband spectrum can only be fit by adding two extra components, a blue component that domi-nates the emission bluewards of ∼ 700 nm and a red component that dominates the K-band emission. The excess red emission is also observed in Spitzer observations (Lau et al 2016(Lau et al , 2019 and is consistent with being due to warm dust with a temperature of ∼ 1100 K. The presence of excess blue emission is consistent with predictions from theory (e.g., Copperwheat et al 2005;Ambrosi & Zampieri 2018), and is likely due to an irradiated accretion disc and/or irradiation of the donor star by the bright X-ray source. The strong variability of NGC 300 ULX-1 in X-rays indicates that this component, if it is indeed due to reprocessed Xray emission, may be variable as well.…”

Section: Additional Broadband Componentssupporting

confidence: 87%

Discovery of a Red Supergiant Donor Star in SN2010da/NGC 300 ULX-1

Heida

Lau

Davies

et al. 2019

ApJL

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SN2010da/NGC 300 ULX-1 was first detected as a supernova impostor in May 2010 and was recently discovered to be a pulsating ultraluminous X-ray source. In this letter, we present VLT/X-shooter spectra of this source obtained in October 2018, covering the wavelength range 350-2300 nm. The J-and H-bands clearly show the presence of a red supergiant donor star that is best matched by a MARCS stellar atmosphere with T eff = 3650 − 3900 K and log(L bol /L ) = 4.25 ± 0.10, which yields a stellar radius R = 310 ± 70R . To fit the full spectrum, two additional components are required: a blue excess that can be fitted either by a hot blackbody (T 20, 000 K) or a power law (spectral index α ≈ 4) and is likely due to X-ray emission reprocessed in the outer accretion disk or the donor star; and a red excess that is well fitted by a blackbody with a temperature of ∼ 1100 K, and is likely due to warm dust in the vicinity of SN2010da. The presence of a red supergiant in this system implies an orbital period of at least 0.8-2.1 years, assuming Roche lobe overflow. Given the large donor-tocompact object mass ratio, orbital modulations of the radial velocity of the red supergiant are likely undetectable. However, the radial velocity amplitude of the neutron star is large enough (up to 40-60 km s −1 ) to potentially be measured in the future, unless the system is viewed at a very unfavorable inclination.

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Section: Additional Broadband Componentssupporting

confidence: 87%

Discovery of a Red Supergiant Donor Star in SN2010da/NGC 300 ULX-1

Heida

Lau

Davies

et al. 2019

ApJL

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“…This means that, at the time of writing this manuscript, the photometric and spectroscopic observations provided 3 confirmed RSGs, 12 candidate RSGs, 4 confirmed nebulae, and 14 candidate stellar clusters/active galactic nuclei (AGNs). Recently, Lau et al (2019) observed 96 ULXs within 10 Mpc in the mid-IR with the Spitzer Space Telescope. They detected and identified 12 ULXs with candidate counterparts whose absolute mid-IR magnitude is consistent with being RSGs.…”

mentioning

confidence: 99%

NIR counterparts to ULXs (III): completing the photometric survey and selected spectroscopic results★

López

Heida

Jonker

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Abstract We present results from the remaining sources in our search for near-infrared (NIR) candidate counterparts to ultraluminous X-ray sources (ULXs) within ≃ 10 Mpc. We observed 23 ULXs in 15 galaxies and detected NIR candidate counterparts to six of them. Two of these have an absolute magnitude consistent with a single red supergiant (RSG). Three counterparts are too bright for a RSG and spatially extended, and thus we classify them as stellar clusters. The other candidate is too faint for a RSG. Additionally, we present the results of our NIR spectroscopic follow-up of five sources: four originally classified as RSG and one as a stellar cluster on the basis of previous photometry. The stellar cluster candidate is actually a nebula. Of the four RSGs candidates, one source has a broad Hα emission line redshifted by ∼z = 1, making it a background AGN. Two other sources show stellar spectra consistent with them being RSGs. The final RSG candidate is too faint to classify, but does not show strong (nebular) emission lines in its spectrum. After our search for NIR counterparts to 113 ULXs, where we detected a candidate counterpart for 38 ULXs, we have spectroscopically confirmed the nature of 12: five sources are nebulae, one source is not classified, one source is an AGN and five are RSGs. These possible five ULX-RSG binary systems would constitute ≃ $(4 \pm 2)\%$ of the observed ULXs, a fraction almost four times larger than what was predicted by binary evolution simulations.

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“…RSG donors exist outside our Galaxy as well. Lau et al (2019) searched for Spitzer/IRAC mid-IR counterparts of ultraluminious X-ray sources (ULXs), which are thought to be X-ray binaries with luminosities equal to or above the Eddington luminosity of a stellar-mass black hole. This luminosity is powered by accretion onto a compact object.…”

Section: Does Xid 6592 Really Contain An Rsg Donor?mentioning

confidence: 99%

“…This luminosity is powered by accretion onto a compact object. Lau et al (2019) found 12 counterparts with SG-like fluxes, where 4 sources were "red" ([3.6]-[4.5]∼0.7) and 5 were "blue" ([3.6]-[4.5]∼0) based on the IRAC colors. These correspond to sgB[e] and RSG companions, respectively.…”

Section: Does Xid 6592 Really Contain An Rsg Donor?mentioning

confidence: 99%

A Rapidly Varying Red Supergiant X-Ray Binary in the Galactic Center

Gottlieb

Eikenberry

Ackley

et al. 2020

ApJ

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We analyzed multiwavelength observations of the previously identified Galactic center X-ray binary CXO 174528.79-290942.8 (XID 6592) and determine that the near-infrared counterpart is a red supergiant based on its spectrum and luminosity. Scutum X-1 is the only previously known X-ray binary with a red supergiant donor star and closely resembles XID 6592 in terms of X-ray luminosity (L X), absolute magnitude, and IR variability (L IR,var), supporting the conclusion that XID 6592 contains a red supergiant donor star. The XID 6592 infrared counterpart shows variability of ∼0.5 mag in the Wide-field Infrared Survey Explorer-1 band (3.4 μm) on timescales of a few hours. Other infrared data sets also show large-amplitude variability from this source at earlier epochs but do not show significant variability in recent data. We do not expect red supergiants to vary by ∼50% in luminosity over these short timescales, indicating that the variability should be powered by the compact object. However, the X-ray luminosity of this system is typically ∼1000× less than the variable luminosity in the infrared and falls below the Chandra detection limit. While X-ray reprocessing can produce large-amplitude fast infrared variability, it typically requires >> L X L IR,var to do so, indicating that another process must be at work. We suggest that this system may be a supergiant fast X-ray transient (SFXT), and that a large (∼10 38 ergs s −1), fast (10 2-4 s) X-ray flare could explain the rapid IR variability and lack of a long-lasting X-ray outburst detection. SFXTs are normally associated with blue supergiant companions, so if confirmed, XID 6592 would be the first red supergiant SFXT, as well as the second X-ray red supergiant binary.

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Uncovering Red and Dusty Ultraluminous X-Ray Sources with Spitzer

Cited by 31 publications

References 160 publications

Discovery of a Red Supergiant Donor Star in SN2010da/NGC 300 ULX-1

Discovery of a Red Supergiant Donor Star in SN2010da/NGC 300 ULX-1

NIR counterparts to ULXs (III): completing the photometric survey and selected spectroscopic results★

A Rapidly Varying Red Supergiant X-Ray Binary in the Galactic Center

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