Optical follow-up of 4U2238+60 (alias SAXJ2239.3+6116)
ATel #16803; Roberto Nesci (INAF/IAPS), Mariateresa Fiocchi (INAF/IAPS), Antonio Vagnozzi (MPC589)
on 6 Sep 2024; 07:53 UT
Credential Certification: Roberto Nesci (roberto.nesci@inaf.it)
Subjects: Optical, X-ray, Binary, Neutron Star, Transient, Pulsar
Following the ATels #16800 #16762 and #16750 regarding the detection of an X-ray outburst of the HMXB 4U2238+60, we obtained a spectrum of the source with the 50 cm telescope of the S.Lucia di Stroncone Observatory (MPC589) on 2024-09-05. A strong (11 Angstrom equivalent width) was clearly present, as expected if the X-ray emission is due to the interaction of the neutron star with the circumstellar envelope of the Be companion. We point out that past spectroscopic monitoring of the source by Reig et al. (2016, A&A 590, 122) showed a long monotonic decrease of the line from 2001 (E.W. 12 Angstrom) to 2015 (E.W. 2 Angstrom).
Archival (unpublished) spectra of the Stroncone Observatory taken in July and August 2022 show that the H-alpha line was again strong (11 Angstrom E.W.). Given the orbital period of 262 days (in't Zand 2000, A&A 361, 85) X-ray outbursts should have happened around 2022-06-08, 2023-02-25 and 2023-11-14 .
