No radio counterpart for IGR J18179-1621 detected during a serendipitous VLBA observation
ATel #13737; Hao Ding (Swinburne University of Technology "SUT"), Adam T. Deller (SUT), Marcus E. Lower (SUT), Ryan M. Shannon (SUT)
on 15 May 2020; 13:57 UT
Credential Certification: Hao Ding (haoding@swin.edu.au)
Subjects: Radio, Binary, Neutron Star, Star, Transient, Pulsar
Referred to by ATel #: 14005
IGR J18179-1621 (hereafter J1817) is an X-ray pulsar (Halpern 2012, ATel #3949; Li et al. 2012, ATel #3950) accreting from a donor star, which is believed to be a high-mass star (Bozzo et al. 2012, A&A, 545, A83; Li et al. 2012, MNRAS, 426, L16; Nowak et al. 2012, ApJ, 757, 143).
On 10 April, J1817 was found to have re-brightened in X-rays (Esposito et al., ATel #13625). At that time, we had an approved Very Long Baseline Array (VLBA) program to observe the newly discovered magnetar Swift J1818.0-1607 (Enoto et al., ATel #13551) at 1.6 GHz. As J1817 could be observed in the same primary beam to Swift J1818.0-1607 with the VLBA, we shifted the pointing center by 3.6 arcmin towards J1817. The VLBA observation was carried out from UT 09:56 to 13:26 on 20 April. The J1817 data was correlated at the J2000 position 18:17:52.19, -16:21:31.7, of which the 90% uncertainty is 0.6 arcsecond (Paizis et al. 2012, ATel #3988).
We performed a standard data reduction procedure including primary-beam correction, and searched a 1-arcsecond-radius region around the correlation position of J1817. No radio counterpart to J1817 was identified. We place an upper limit on the radio flux density in the searched region of 0.18 mJy/beam, 4 times the image sensitivity.
We thank the VLBA team for arranging the observation and allowing an extra correlation pass on J1817.
