Position and Variability of 2A 1704+241

Morgan, W. A.; Garcia, M. R.

doi:10.1086/323626

Cited by 6 publications

(13 citation statements)

References 15 publications

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“…The erratic source variability is clearly visible in the Power Spectral Density (PSD); however, no coherent pulsations or periodicities are detected at any significant level in the f ∼ 10 −4 -10 Hz frequency range. No indication of the ∼900 s X-ray periodicity found by Morgan & Garcia (2001) from Einstein data is found in our data set. Only a 1/f -type PSD distribution, typical of the shot-noise behaviour evident from the light curves in Fig.…”

Section: Light Curves and Timing Analysiscontrasting

confidence: 63%

X–ray and optical monitoring of the peculiar source 4U 1700+24/V934 Her

Masetti¹,

Fiume²,

Cusumano

et al. 2002

A&A

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Abstract. We report on ASCA and BeppoSAX X-ray broad band observations of the galactic low-luminosity X-ray source 4U 1700+24 performed on 1995 and 1998, respectively, and on (quasi-)simultaneous ground observations of its optical counterpart, V934 Her, from the Loiano 1.5-meter telescope. In order to better understand the nature of the source we also analyze public archival ROSAT and RXTE data as well as the RXTE ASM light curve of 4U 1700+24; we also re-analyze a 1985 EXOSAT pointing. The optical spectra are typical of a M2 III star; this allows us to determine a revised distance to the object of ∼400 pc. While these spectra do not show either any spectral change between the two epochs or any peculiar feature apart from those observed in normal red giants, the spectroscopic measurements carried out in X-rays reveal a complex and long-term variable spectrum, with a clear soft excess. The X-ray spectral properties of the source are best described by a thermal Comptonization spectrum plus a soft energy (<1 keV) excess, which can be modeled in the form of a blackbody emission with kTBB ∼ 1 keV; the latter component is not detected at the lowest source flux levels. The ratio between the two components varies substantially with the source flux. The X-ray emission from the object appears to become harder as its luminosity increases: indeed, the RXTE data acquired during an outburst occurred in October-November 1997 display a hard tail, detected up to 100 keV and modeled with a comptonizing cloud which is hotter and less opaque than that seen in the low intensity state. Apart from erratic shot-noise variability on timescales of tens to thousands of seconds, no significant properties (such as pulsations or QPOs) are found from the timing analysis of the X-ray light curves extracted from the observations presented here. With the new distance determination, the 2-10 keV X-ray luminosity range spanned in the considered observations lies between ∼2×10 32 and ∼1×10 34 erg s −1 . All this information, combined with the findings by other authors, allows us to suggest that the scenario which best describes the object consists of a wide binary system in which a neutron star accretes matter from the wind of a M-type giant star. Implications of such a model are discussed.

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Section: Light Curves and Timing Analysiscontrasting

confidence: 63%

X–ray and optical monitoring of the peculiar source 4U 1700+24/V934 Her

Masetti¹,

Fiume²,

Cusumano

et al. 2002

A&A

View full text Add to dashboard Cite

show abstract

“…Rescaling the interloper chance probabilities computed in Morgan & Garcia (2001) using the more precise Chandra error box, we find that the numbers computed by these authors become smaller by a factor of ∼40.…”

Section: U 1700+24mentioning

confidence: 76%

“…As one can see from Fig. 1, the HRC error box is perfectly consistent with the position of optical star, and inconsistent at a 3.5-σ level with the ROSAT/HRI localization of Morgan & Garcia (2001). Moreover, HD 154791 lies within one HRC detector pixel from the PSF peak of the Chandra X-ray image.…”

Section: U 1700+24mentioning

confidence: 77%

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M-typegiants as optical counterparts of X-ray sources 4U 1700+24 and 4U 1954+319

Masetti¹,

Orlandini²,

Palazzi³

et al. 2006

A&A

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We observed with Chandra two peculiar galactic X-ray sources, 4U 1700+24 and 4U 1954+319, which are suspected to have a M-type giant star as optical counterpart, in order to get a high-precision astrometric position for both of them. The peculiarity of these sources lies in the fact that these are the only two cases among low-mass X-ray binaries (LMXBs), besides the confirmed case of GX 1+4, for which the companion can possibly be a M-type giant. We found that in both cases the field M-type giant star is indeed the counterpart of these X-ray sources. We also determined the distance to 4U 1954+319 to be ∼1.7 kpc. This result suggests that a number of faint (L X ∼ 10 32 −10 34 erg s −1 ) Galactic X-ray sources are "symbiotic X-ray binaries", that is, wide-orbit LMXBs composed of a compact object, most likely a neutron star, accreting from the wind of a M-type giant.

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“…The lack of signatures of binarity and the initially marginal positional coincidence (Morgan & Garcia 2001) originally made this identification uncertain. More recently, the detection of radial velocity variations from the proposed optical counterpart with the same period as X-ray brightness variations (Galloway et al 2002) has added support to the identification.…”

Section: Introductionmentioning

confidence: 99%

Discovery of a redshifted X-ray emission line in the symbiotic neutron star binary 4U 1700+24

Tiengo

Salvo

Méndez

et al. 2005

A&A

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Abstract. We present the spectral analysis of an XMM-Newton observation of the X-ray binary 4U 1700+24, performed during an outburst in August 2002. The EPIC-PN spectrum above 1 keV can be modeled by a blackbody plus Comptonization model, as in previous observations. At lower energies, however, we detect a prominent soft excess, which we model with a broad Gaussian centered at ∼0.5 keV. In the high resolution RGS spectrum we detect a single emission line, centered at 19.19

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Position and Variability of 2A 1704+241

Cited by 6 publications

References 15 publications

X–ray and optical monitoring of the peculiar source 4U 1700+24/V934 Her

X–ray and optical monitoring of the peculiar source 4U 1700+24/V934 Her

M-typegiants as optical counterparts of X-ray sources 4U 1700+24 and 4U 1954+319

Discovery of a redshifted X-ray emission line in the symbiotic neutron star binary 4U 1700+24

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