OAO1657-415
Our primary objective is to establish the first observational signature of the weak s-process, a key nucleosynthetic pathway responsible for producing lighter trans-iron elements such as Cu. We propose to search for the Cu Ka line as a probe of the weak s-process in the high-mass X-ray binary OAO 1657-415 during its eclipse phase. This system hosts a luminous blue variable (LBV) candidate and is the only viable target for this study. In a 75-ks Resolve observation, we expect to detect an enhanced Cu Ka line at a ~6 sigma significance level. With the measured Cu/Fe ratio and Fe spectral features, we will also investigate the internal and wind properties of the LBV, which attract interest in the context of stellar evolution and supernova mechanisms.
obsid = 202084010 / Unique Observation/Sequence Number
object = OAO1657-415 / Object name
pi_name = MATSUNAGA KAI / Proposal Principal Investigator Name
ra = 255.202446169296 / Right Ascension (Pointing Position) (deg)
dec = -41.6556063561477 / Declination (Pointing Position) (deg)
roll_angle = 95.1602189882346 / Roll Angle (deg)
start_time = 2026-03-04T18:54:04 / Start Time of the Observation
stop_time = 2026-03-06T21:35:04 / Stop Time of the Observation
exposure = 85237.954335 / Effective Total Observation Exposure (s)
public_date= 2027-03-13 / Public Date