PoS(MQW7)105 Cygni γ radio flaring http://pos.sissa.it/ ce. Cygni remnant γ 17 is also located in the ell established yet. The e-EVN SO funded Communication Network De- st the work) observations of the counter- n of gamma-ray flaring activity in t to the IGR source has a compact nc, Hungary hort timescale. is a technique which makes it possible to image the structure ∗ ive Commons Attribution-NonCommercial-ShareAlike Licen 10 mas scales that could be related to a compact object, but no ∼ [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] e-VLBI developments in Europe are supported by the EC DG-INF (SNR). The brightest unidentified EGRET source 3EG J2020+40 the region. Our observationsstructure show that on the the radio counterpar region, though its relation toobservations IGR were J20187+4041 carried has out not been following w the AGILE detectio of radio sources at the highest angular resolution on a very s We present radio results from short e-EVN (EuropeanVLBI net part to IGR J20187+4041, a hard X-ray source projected again activity has been observed. e-VLBI ∗ Copyright owned by the author(s) under the terms of the Creat c

VII Microquasar Workshop: Microquasars and Beyond September 1-5 2008 Foca, Izmir, Turkey Zsolt Paragi JIVE, Dwingeloo, Netherlands MTA Research Group for Physical Geodesy and Geodynamics, Pe The compact radio counterpart ofnear IGR the J20187+4041 flaring source AGL 2021+40293EG and J2020+4017 E-mail: Alfonso Trejo Cruz CRyA-UNAM, Morelia, Mexico E-mail: Elsa Giacani IAFE, , E-mail: Gloria Dubner IAFE, Buenos Aires, Argentina E-mail: Andrei M. Bykov Ioffe Institute, St. Petersburg, Russia E-mail: Huib J. van Langevelde JIVE, Dwingeloo, Netherlands Sterrewacht Leiden, Leiden University, Netherlands E-mail: PoS(MQW7)105 Jy. µ 100 ∼ 2.4 mJy. With a ∼ the hard X-ray source .6 GHz. The participating ion with AGILE of a variable ennea et al. 2006, ATel #788). lved source, which was 2 mJy 1.4 and 5 GHz revealed a point- 347, Dec (J2000) 40 40 59.984, pects to detect this radio source Such discovery provided further le gamma-ray emission detected r data from this single frequency llow-up observations with SWIFT re streamed to the EVN Data Pro- sitionally coincident with 2MASX urce 3EG J2020+4017. This enig- in the Galactic plane, this 1 Jy cal- ngest baselines. Because this was a lved structure on 10 mas scales. At hnique, providing immediate results apparent extension in the optical and Cygni SNR (G78.2+2.1), and turned LE announcement we carried out e- e the target was very weak, we used ing. Although parts of the region are (MkII), Medicina, Onsala, Torun and e suggestion that there is a NIR coun- that IGR J20187+4041 is an obscured γ own to flux density levels of kind of studies because it permits a fast ss is 0.8 mJy/beam (Figure 2). It is hard he CGRO EGRET catalog (Figure 1). tegrated flux density is 1. . 0 n time was less than 2 hours. However, at a ww.expres-eu.org/). The European VLBI Network < z 2 hinese, South African and other radio astronomy institutes The target is detected at the position of RA (J2000) 20 18 38.7 On 2008 April 28 Longo et al. (ATel #1492) reported the detect Recent VLA observations carried out in the C configuration at We observed the radio source with the e-EVN on 2008 June 25 at 1 In the same region Bykov et al. (2004) detected with INTEGRAL the position error is estimated to 2 milliarcseconds. The in resolution of around 30 milliarcseconds, theto peak estimate brightne how much scatterrun. broadening But may the have source affected1.4 appears ou to GHz have the a VLA compact, in partially the reso C-array showed a 8.7 mJy, partially reso funded by their national research councils. (http://www.evlbi.org/) is a joint facility of European, C velopments project ’EXPReS’, Contract No. 02662 (http://w The compact radio counterpart of IGR J20187+4041 1. A variable gamma-ray source, and possible counterparts gamma-ray source positionally consistent withmatic the object was EGRET discovered so back in 1981 in the field of the like radio source within theJ20183871+4041003 error (Dubner box et of al., IGR 2008 J20187+4041,support May po 13, to ATel #1518). the obscuredby AGN AGILE hypothesis. on 2008 Assuming April theon 28 variab the was milliarcsecond due to scales. radio-jetEVN activity, Therefore, observations one to following ex investigate the this AGI after source. the The observations, e-VLBI is tec anorganization excellent of tool follow to up conduct monitoring this of the target. 2. e-EVN results radio telescopes were Cambridge, Effelsberg,the Jodrell phased Bank array Westerbork. Thecessor data at from JIVE the real-time, telescopes forJ2015+3710 we immediate at processing. a distance Becaus ofvery 3.55 badly degrees affected for by phase-referenc scatteribrator broadening still by had the a ionized correlated ISM short flux exploratory density project, of the 400 total mJy on-sourcedata on integratio rate of the 512 lo Mbit/s this was sufficient to detect sources d IGR J20187+4041, a likely counterpart toallowed 3EG a J2020+4017. more Fo precise position determinationterpart and from lead the to 2MASS th catalogBased (2MASX on J20183871+4041003, the K multi-wavelength spectrum of thenear-IR source bands and as its well as strongaccreting absorption, object, it probably was an suggested AGN at a redshift of out to be the brightest steady-state unidentified source in t PoS(MQW7)105 0144 . 0 = z ovided by S. Pineault) with Keck, Goncalves et aring these with our result it was hort baselines of the VLA picked as never detected in these objects um radio cores (e.g. Middelberg et fect of scatter broadening and better J20187+4041, and immediate further rt of the source a redshift et. This will be target of future multi- 4041 with coincident radio, IR and optical consistent with a low-luminosity Seyfert n of the radio structure is that we see a April 28 flare or it was an independent event. T source3EG J2020+4017,the April 28 gamma- was reported in June 2008, although there was no 3 Cygni SNR region (image at 1.4 GHz from a VGPS mosaic kindly pr γ The Based on an IR spectrum of 2MASX J20183871+4041003 obtained flat spectrum core region with the e-EVN, while at 1.4 GHz the s counterparts. Rebrightening of the variable gamma-source confirmation whether this indeed agreed in position with the and more point-like at 5 GHzobvious (Dubner that there et was al., no ATel #1518). strongobservations radio Comp flaring were activity not in necessary. IGR A possible interpretatio up additional flux from extended emission,frequency possibly observations, a which radio j will allowconstrain us the to brightness temperature. reduce the ef 3. The nature of the source/s al. (ATel #1623) accurately determined for the IR counterpa flare detected by AGILE, and the hard X-ray source IGR J20187+ with the positions and error circles of the unidentified EGRE and concluded that both, redshift and X-ray properties, are al. 2004). However, strongly variable gamma-ray emission w nucleus. Seyfert galaxies are known to have weak, flat spectr The compact radio counterpart of IGR J20187+4041 Figure 1: PoS(MQW7)105 041. Note that because of the r low-luminosity AGN, or it is ition improvements provided by , 925 (2004). nature of the observed high-energy e lead to the conclusion that either . Norris, A. S. Wilson, H. Falcke, 417 ot be overinterpreted. The source looks resolved, tially responsible for this. 4 Astron. Astrophys. , L21 (2004). 427 Astron. Astrophys. e-EVN detection map of the radio counterpart to IGRJ20187+4 E. J. M. Colbert, A. Witzel, K. J. Fricke, The compact radio counterpart of IGR J20187+4041 Figure 2: [2] E. Middelberg, A. L. Roy, N. M. Nagar, T. P. Krichbaum, R. P 2MASX J20183871+4041003/IGR J20187+4041 is anot very related peculia to the gammaFermi/GLAST flares observations will detected greatly by help AGILE. toemission Further and know pos the the associated true source/s. References [1] A.M.Bykov, before. Based on the observations available at present we ar short-track observations, fine details of thebut image the should there n is a possibility that scatter broadening is par