A fresh look at the low-mass X-ray binaries

Gallas, Annette; Kundt, Wolfgang; Mohr, J. J.

doi:10.1007/bf00642704

Cited by 2 publications

(1 citation statement)

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“…If we place X-2 at a distance < 3 kpc (roughly the maximum height at which low-mass XRBs are found from the disk of the MW, see e.g. Gallas et al 1991) from the plane of the Galaxy ( < 4.2 kpc from the Sun), it would have an X-ray luminosity < 10 34 erg s 1 . In addition, the large ( > 10 21 cm 2 , Table 2) absorbing column must be accounted for.…”

Section: The Mysterious Source X-2mentioning

confidence: 99%

Soft X-Ray Emission from the Spiral Galaxy NGC 1313

Colbert¹,

Petre²,

Schlegel³

et al. 1995

ApJ

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The nearby barred spiral galaxy NGC 1313 has been observed with the PSPC instrument on board the ROSAT X-ray satellite. Ten individual sources are found. Three sources (X-1, X-2 and X-3 SN 1978K]) are very bright ( 10 40 erg s 1 ) and are unusual in that analogous objects do not exist in our Galaxy. We present an X-ray image of NGC 1313 and X-ray spectra for the three bright sources. The emission from the nuclear region (R < 2 kpc) is dominated by source X-1, which is located 1 kpc north of the photometric (and dynamical) center of NGC 1313. Optical, far-infrared and radio images do not indicate the presence of an active galactic nucleus at that position; however, the compact nature of the X-ray source (X-1) suggests that it is an accretion-powered object with central mass M > 10 3 M . Additional emission (L X 10 39 erg s 1 ) in the nuclear region extends out to 2.6 kpc and roughly follows the spiral arms. This emission is from 4 sources with luminosity of several 10 38 erg s 1 , two of which are consistent with emission from population I sources (e.g., supernova remnants, and hot interstellar gas which has been heated by supernova remnants). The other two sources could be emission from population II sources (e.g., low-mass X-ray binaries). The bright sources X-2 and SN 1978K are positioned in the southern disk of NGC 1313. X-2 is variable and has no optical counterpart brighter than 20. m 8 (V-band). It is likely that it is an accretion-powered object in NGC 1313. The type-II supernova SN 1978K (Ryder et al. 1993) has become extraordinarily luminous in X-rays 13 years after optical maximum. { 2 {Subject headings: galaxies: by name (NGC 1313) | galaxies: nuclei | galaxies: spiral | X-rays: galaxies Einstein observations also revealed X-ray sources with L X > 10 39 erg s 1 in the nuclear region of many spiral galaxies (cf. Fabbiano 1989). Such a high luminosity implies that if { 3 { the emission is from a single object powered by (sub-Eddington) accretion, then the central compact object is a black hole. However, most of these galactic nuclei do not show signs of activity at other wavelengths. In a sample of 13 nearby normal spirals, Fabbiano & Trinchieri (1987, hereafter FT87) found unresolved ( < 2 kpc), very-luminous ( 10 39 10 40 erg s 1 ) X-ray sources apparently coincident with the nuclei of three galaxies (IC 342, NGC 6946 and NGC 1313). FT87 suggested that the central sources in these galaxies are powered by luminous starbursts, or, in the case of NGC 1313, possibly by a low-luminosity active nucleus. The spatial and spectral resolution of the Einstein Imaging Proportional Counter (IPC; with which most of the Einstein observations were made) is fairly crude, so a de nitive conclusion of what powers these X-ray sources is not forthcoming from the IPC data.The question of whether low-luminosity active galactic nuclei (AGN) are prevalent in normal galaxies remains unanswered. One would like to know if such AGN have properties similar to those of Seyfert galaxies and quasars. LINERs (Low Ionization Nuclear Em...

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Section: The Mysterious Source X-2mentioning

confidence: 99%