Investigating the Optical Counterpart Candidates of Four INTEGRAL Sources localized with Chandra

Abstract

We report on the optical spectroscopic follow up observations of the candidate counterparts to four INTEGRAL sources: IGR J04069+5042, IGR J06552-1146, IGR J21188+4901 and IGR J22014+6034. The candidate counterparts were determined with Chandra, and the optical observations were performed with 1.5-m RTT-150 telescope (TÜBİTAK National Observatory, Antalya, Turkey) and 2.4-m Hiltner Telescope (MDM Observatory, Kitt Peak, Arizona). Our spectroscopic results show that one of the two candidates of IGR J04069+5042 and the one observed for IGR J06552-1146 could be active late-type stars in RS CVn systems. However, according to the likelihood analysis based on Chandra and INTEGRAL, two optically weaker sources in the INTEGRAL error circle of IGR J06552-1146 have higher probabilities to be the actual counterpart. The candidate counterparts of IGR J21188+4901 are classified as an active M-type star and a late-type star. Among the optical spectra of four candidates of IGR J22014+6034, two show Hαemission lines, one is a late-type star and the other is a M type. The likelihood analysis favors a candidate with no distinguishing features in the optical spectrum. Two of the candidates classified as M type dwarfs are similar to some IGR candidates claimed to be symbiotic stars. However, some of the prominent features of symbiotic systems are missing in our spectra, and their NIR colors are not consistent with those expected for giants. We consider the IR colors of all IGR candidates claimed to be symbiotic systems and find that low resolution optical spectrum may not be enough for conclusive identification.

24 pages, 12 figures; accepted for publication in ApJ

References in corpus (12)

• Multi-wavelength observations of Galactic hard X-ray sources discovered by INTEGRAL. I. The nature of the companion star
• Unveiling the nature of INTEGRAL objects through optical spectroscopy. VI. A multi-observatory identification campaign
• Nonthermal Hard X-ray Emission and Iron Kalpha Emission from a Superflare on II Pegasi
• IPHAS and the symbiotic stars. I. Selection method and first discoveries
• Unveiling the nature of INTEGRAL objects through optical spectroscopy. VII. Identification of 20 Galactic and extragalactic hard X-ray sources
• Chandra Localizations and Spectra of INTEGRAL Sources in the Galactic Plane: The Cycle 9 Sample
• The Nature of the Hard-X-Ray Emitting Symbiotic Star RT Cru
• Swift Follow-up Observations of INTEGRAL Sources of Unknown Nature
• Swift follow-up observations of 17 INTEGRAL sources of uncertain or unknown nature
• Localizing INTEGRAL Sources with Chandra: X-Ray and Multi-Wavelength Identifications and Energy Spectra
• Chandra observations of five INTEGRAL sources: new X-ray positions for IGR J16393-4643 and IGR J17091-3624
• Hunting the nature of IGR J17497-2821 with X-ray and NIR observations

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