Luminous X-ray flares from low-mass X-ray binary candidates in the early-type galaxy NGC 4697

Gregory R. Sivakoff; Craig L. Sarazin; Andrés Jordán

doi:10.1086/430374

Luminous X-ray flares from low-mass X-ray binary candidates in the early-type galaxy NGC 4697

Gregory R. Sivakoff, Craig L. Sarazin, Andrés Jordán

Research output: Contribution to journal › Article › peer-review

29 Scopus citations

Abstract

We report results of the first search specifically targeting short-timescale X-ray flares from low-mass X-ray binaries in an early-type galaxy. A new method for flare detection is presented. In NGC 4697, the nearest, optically luminous. X-ray-faint elliptical galaxy, three out of 157 sources are found to display flares at>99.95% probability, and all show more than one flare. Two sources are coincident with globular clusters and show flare durations and luminosities similar to (but larger than) type I X-ray superbursts found in Galactic neutron star (NS) X-ray binaries (XRBs). The third source shows more extreme flares. Its flare luminosity (∼6 × 10³⁹ ergs s^-1) is very super-Eddington for an NS and is similar to the peak luminosities of the brightest Galactic black hole (BH) XRBs. However, the flare duration (∼70 s) is much shorter than are typically seen for outbursts reaching those luminosities in Galactic BH sources. Alternative models for the flares are considered.

Original language	English
Pages (from-to)	L17-L20
Journal	Astrophysical Journal
Volume	624
Issue number	1 II
DOIs	https://doi.org/10.1086/430374
State	Published - 1 May 2005
Externally published	Yes

Keywords

Binaries: close
Galaxies: elliptical and lenticular, cD
Galaxies: individual (NGC 4697)
X-rays: Binaries
X-rays: bursts
X-rays: galaxies

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@article{f28449a9707b4c6c841f92ee779cbd70,

title = "Luminous X-ray flares from low-mass X-ray binary candidates in the early-type galaxy NGC 4697",

abstract = "We report results of the first search specifically targeting short-timescale X-ray flares from low-mass X-ray binaries in an early-type galaxy. A new method for flare detection is presented. In NGC 4697, the nearest, optically luminous. X-ray-faint elliptical galaxy, three out of 157 sources are found to display flares at>99.95% probability, and all show more than one flare. Two sources are coincident with globular clusters and show flare durations and luminosities similar to (but larger than) type I X-ray superbursts found in Galactic neutron star (NS) X-ray binaries (XRBs). The third source shows more extreme flares. Its flare luminosity (∼6 × 1039 ergs s-1) is very super-Eddington for an NS and is similar to the peak luminosities of the brightest Galactic black hole (BH) XRBs. However, the flare duration (∼70 s) is much shorter than are typically seen for outbursts reaching those luminosities in Galactic BH sources. Alternative models for the flares are considered.",

keywords = "Binaries: close, Galaxies: elliptical and lenticular, cD, Galaxies: individual (NGC 4697), X-rays: Binaries, X-rays: bursts, X-rays: galaxies",

author = "Sivakoff, {Gregory R.} and Sarazin, {Craig L.} and Andr{\'e}s Jord{\'a}n",

note = "Funding Information: We thank Adrienne Juett and Eric Pfahl for their very helpful comments. Support for this work was provided by NASA through HST Award GO-10003.01-A and Chandra Awards GO4-5093X, AR3-4005X, GO3-4099X, and AR4-5008X. G. R. S. acknowledges the receipt of an ARCS fellowship and support provided by the F. H. Levinson Fund.",

year = "2005",

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doi = "10.1086/430374",

language = "English",

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AU - Sivakoff, Gregory R.

AU - Sarazin, Craig L.

AU - Jordán, Andrés

N1 - Funding Information: We thank Adrienne Juett and Eric Pfahl for their very helpful comments. Support for this work was provided by NASA through HST Award GO-10003.01-A and Chandra Awards GO4-5093X, AR3-4005X, GO3-4099X, and AR4-5008X. G. R. S. acknowledges the receipt of an ARCS fellowship and support provided by the F. H. Levinson Fund.

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N2 - We report results of the first search specifically targeting short-timescale X-ray flares from low-mass X-ray binaries in an early-type galaxy. A new method for flare detection is presented. In NGC 4697, the nearest, optically luminous. X-ray-faint elliptical galaxy, three out of 157 sources are found to display flares at>99.95% probability, and all show more than one flare. Two sources are coincident with globular clusters and show flare durations and luminosities similar to (but larger than) type I X-ray superbursts found in Galactic neutron star (NS) X-ray binaries (XRBs). The third source shows more extreme flares. Its flare luminosity (∼6 × 1039 ergs s-1) is very super-Eddington for an NS and is similar to the peak luminosities of the brightest Galactic black hole (BH) XRBs. However, the flare duration (∼70 s) is much shorter than are typically seen for outbursts reaching those luminosities in Galactic BH sources. Alternative models for the flares are considered.

AB - We report results of the first search specifically targeting short-timescale X-ray flares from low-mass X-ray binaries in an early-type galaxy. A new method for flare detection is presented. In NGC 4697, the nearest, optically luminous. X-ray-faint elliptical galaxy, three out of 157 sources are found to display flares at>99.95% probability, and all show more than one flare. Two sources are coincident with globular clusters and show flare durations and luminosities similar to (but larger than) type I X-ray superbursts found in Galactic neutron star (NS) X-ray binaries (XRBs). The third source shows more extreme flares. Its flare luminosity (∼6 × 1039 ergs s-1) is very super-Eddington for an NS and is similar to the peak luminosities of the brightest Galactic black hole (BH) XRBs. However, the flare duration (∼70 s) is much shorter than are typically seen for outbursts reaching those luminosities in Galactic BH sources. Alternative models for the flares are considered.

KW - Binaries: close

KW - Galaxies: elliptical and lenticular, cD

KW - Galaxies: individual (NGC 4697)

KW - X-rays: Binaries

KW - X-rays: bursts

KW - X-rays: galaxies

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ER -

Luminous X-ray flares from low-mass X-ray binary candidates in the early-type galaxy NGC 4697

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Keywords

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