We have analysed an archival XMM-Newton EPIC observation that serendipitouslycovered the sky position of a variable X-ray source AX J1714.1-3912, previouslysuggested to be a Supergiant Fast X-ray Transient (SFXT). During the XMM-Newtonobservation the source is variable on a timescale of hundred seconds and showstwo luminosity states, with a flaring activity followed by unflared emission,with a variability amplitude of a factor of about 50. We have discovered anintense iron emission line with a centroid energy of 6.4 keV in the powerlaw-like spectrum, modified by a large absorption (NH around 1e24 cm-2), neverobserved before from this source. This X-ray spectrum is unusual for an SFXT,but resembles the so-called "highly obscured sources", high mass X-ray binaries(HMXBs) hosting an evolved B[e] supergiant companion (sgB[e]). This mightsuggest that AX J1714.1-3912 is a new member of this rare type of HMXBs, whichincludes IGR J16318-4848 and CI Camelopardalis. Increasing this smallpopulation of sources would be remarkable, as they represent an interestingshort transition evolutionary stage in the evolution of massive binaries.Nevertheless, AX J1714.1-3912 appears to share X-ray properties of both kindsof HMXBs (SFXT vs sgB[e] HMXB). Therefore, further investigations of thecompanion star are needed to disentangle the two hypothesis.
XMM-Newton discovery of very high obscuration in the candidate Supergiant Fast X-ray Transient AX J1714.1-3912
P. Esposito;
2022-01-01
Abstract
We have analysed an archival XMM-Newton EPIC observation that serendipitouslycovered the sky position of a variable X-ray source AX J1714.1-3912, previouslysuggested to be a Supergiant Fast X-ray Transient (SFXT). During the XMM-Newtonobservation the source is variable on a timescale of hundred seconds and showstwo luminosity states, with a flaring activity followed by unflared emission,with a variability amplitude of a factor of about 50. We have discovered anintense iron emission line with a centroid energy of 6.4 keV in the powerlaw-like spectrum, modified by a large absorption (NH around 1e24 cm-2), neverobserved before from this source. This X-ray spectrum is unusual for an SFXT,but resembles the so-called "highly obscured sources", high mass X-ray binaries(HMXBs) hosting an evolved B[e] supergiant companion (sgB[e]). This mightsuggest that AX J1714.1-3912 is a new member of this rare type of HMXBs, whichincludes IGR J16318-4848 and CI Camelopardalis. Increasing this smallpopulation of sources would be remarkable, as they represent an interestingshort transition evolutionary stage in the evolution of massive binaries.Nevertheless, AX J1714.1-3912 appears to share X-ray properties of both kindsof HMXBs (SFXT vs sgB[e] HMXB). Therefore, further investigations of thecompanion star are needed to disentangle the two hypothesis.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
