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36 Chapter 2. Multiwavelength approach to LS 5039 DECLINATION (J2000) -14 49 00 30 50 00 30 51 00 30 52 00 30 LS 5039 V band LS 5039 ROSAT 53 00 18 26 20 15 10 RIGHT ASCENSION (J2000) 05 Figure 2.1: CCD image of LS 5039 obtained on 1998 June 7 with the 1.52 m OAN tele- scope in the V Johnson filter. The circle with 35 ′′ radius represents the 90% confidence position from the ROSAT PSPC pointed observations quoted in M97. 2.4 The radio counterpart: NVSS J182614−145054 2.4.1 A radio counterpart in the NVSS The NRAO VLA Sky Survey (NVSS) (Condon et al. 1998) provides a valuable tool to search for new REXBs. This catalog covers the sky north of δ = −40 ◦ (82% of the celestial sphere) at a frequency of 1.4 GHz (20 cm wavelength) using the Very Large Array (VLA) configurations D and DnC. It contains over 1.8 × 10 6 sources stronger than its 2.5 mJy completeness limit. The rms positional uncertainties are less than 1 ′′ for sources stronger than 15 mJy and 7 ′′ for the faintest detectable sources. For all the sources listed in M97 we examined the corresponding NVSS maps at the 20 cm wavelength in a search for possible radio counterparts. We found one interesting object in the M97 list that deserved special attention, namely LS 5039 (l = 16.88 ◦ , b = −1.29 ◦ ).
2.4. The radio counterpart: NVSS J182614−145054 37 The existence of a radio counterpart to LS 5039 was first suspected after inspec- tion of the corresponding NVSS image. The 24 mJy source NVSS J182614−145054 lied outside, but very close to, the 90% confidence error circle of RX J1826.2−1450, with 22 ′′ radius. This was the RASS source identified with LS 5039 by M97. These authors also quoted another pointed ROSAT observation that yielded a 90% confidence radius of 35 ′′ , again consistent with NVSS J182614−145054. In addition, the NVSS coordinates were found to agree within 2 ′′ with the optical position of LS 5039, as derived from the USNO-A1.0 catalog (Monet 1996, Monet et al. 1999). All these coincidences together stimulated our interest about this source and lead us to carry out higher resolution radio observations. This was considered to be the next logical step in order to better measure both its position and spectral properties. Therefore, we conducted a multiepoch and multifrequency radio study of LS 5039 with the VLA. 2.4.2 VLA observations, discovery of a REXB Observations and results We observed 8 LS 5039 on several epochs at the wavelengths of 20, 6, 3.6 and 2.0 cm with the Very Large Array (VLA) interferometer of the NRAO 9 . The VLA data were processed following standard procedures within the aips package of NRAO. 3C 286 was used as the amplitude calibrator, while the phase calibrators observed were 1834−126 at 20 cm, 1820−254 at 6 and 3.6 cm, and 1911−201 at 2 cm, respectively. The results of the interferometric runs on LS 5039 are summarized in Table 2.1, where the flux density at several wavelengths is listed for the different observing dates. Some 20 cm values collected from the literature have been also included. The VLA data obtained in A configuration were further concatenated at 3.6 and 2.0 cm in order to obtain very sensitive sub-arcsec resolution maps. These are displayed in Fig. 2.2, where LS 5039 appears always as an unresolved point source (≤ 0.1 ′′ ). For the epochs when nearly simultaneous multifrequency observations are available, we have plotted in Fig. 2.3 the observed radio spectrum of LS 5039. 8 Published in Martí, J., Paredes, J. M. & Ribó, M. 1998, A&A, 338, L71. 9 The National Radio Astronomy Observatory is a facility of the USA National Science Foun- dation operated under cooperative agreement by Associated Universities, Inc.
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UNIVERSITAT DE BARCELONA Departamen
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Per a la meva neboda Blanca, que va
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feina no presentada en aquesta tesi
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desfogar-nos conjuntament, per la s
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From the scientifical point of view
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Gràcies a la meva germana Nàdia,
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ii CONTENTS I Discovery and study o
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iv CONTENTS II A search for new mic
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vi CONTENTS
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viii Resum de la tesi d’Eddington
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x Resum de la tesi imprescindible p
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xii Resum de la tesi dels sistemes
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xiv Resum de la tesi un comportamen
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xvi Resum de la tesi MilliARC SEC 4
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2.9. Conclusions 87 8. We have carr
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Bibliography Blandford, R. D., & K
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BIBLIOGRAPHY 91 Merck, M., Bertsch,
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Chapter 3 LS 5039 as a runaway micr
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3.1. Positions and proper motions 9
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3.1. Positions and proper motions 9
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3.3. The past trajectory of LS 5039
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3.4. SNR G016.8−01.1 101 DECLINAT
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3.4. SNR G016.8−01.1 103 Normaliz
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3.4. SNR G016.8−01.1 105 Galactic
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3.6. Discussion 109 experienced a h
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3.6. Discussion 111 At this point w
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3.7. Conclusions 113 6. Finally, th
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Bibliography Ankay, A., Kaper, L.,
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BIBLIOGRAPHY 117 Schaerer, D., de K
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Part II A search for new microquasa
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122 Chapter 4. The cross-identifica
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130 BIBLIOGRAPHY
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132 Chapter 5. Radio and optical ob
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DECLINATION (J2000) DECLINATION (J2
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148 BIBLIOGRAPHY
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150 Chapter 6. EVN and MERLIN obser
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166 BIBLIOGRAPHY
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General conclusions 171 Since each
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