XRISM RESOLVE observation 902004010

Title

DDT TOO REQUEST OF 1A 1118-61

Abstract

A 1118−61 is a transient Be X-ray binary pulsar with a circumstellar disk, exhibiting recurring massive eruptions every ~17 years. Swift and MAXI detected a fresh, huge outburst from this source on January 12, 2026. A NuSTAR observation found a strong Fe K-alpha emission line at 6.4 keV whose origin remains elusive. XRISM/Resolve may reveal temporal delays in the variability of the line flux relative to the continuum, helping establish the line-emitting region. The energy difference between the K-alpha and K-beta lines helps determine the ionization state. The plasma density in the line-emitting region can be estimated from these constraints. The exceptionally long pulse period of 407 s in Be X-ray binaries enables distance measurements up to ~10e13 cm, making this approach ideal.

FITS header

TELESCOP= 'XRISM   '           / Mission name
INSTRUME= 'RESOLVE '           / Instrument name
FILTER  = 'OPEN    '           / Filter name used
OBS_ID  = '902004010'          / Observation identification string
OBJECT  = '1A1118-61'          / Object name
OBSERVER= 'XRISM Collaboration' / PI name
OBS_MODE= 'POINTING'           / POINTING or SLEW or ALL
RA_OBJ  =             170.2382 / [deg] Object Right ascension
DEC_OBJ =             -61.9167 / [deg] Object Declination
RA_PNT  =     170.233209922998 / Pointing RA
DEC_PNT =    -61.9140889964897 / Pointing DEC
RA_NOM  =      170.23897275191 / [deg] Nominal aspect point R.A.
DEC_NOM =     -61.917146182734 / [deg] Nominal aspect point Dec.
PA_NOM  =     144.988699371567 / [deg] Nominal aspect point roll.
TELAPSE =     64817.0161070228 / Elapsed time
DATE-OBS= '2026-02-07T01:09:17.015099' / Start date
DATE-END= '2026-02-07T19:09:34.031206' / Stop date
ONTIME  =         41883.976711 / On-source time
EXPOSURE=         41883.976711 / Exposure time
PROCVER = '03.03.015.012'      / Processing script version
MKFFF   = 'ISAS/JAXA'          / Origin of First FITS file
ORIGIN  = 'GSFC/NASA'          / Origin of Processed FITS file
SOFTVER = 'Hea_26Sep2025_V6.36_XRISM_12Sep2025_V003' / Version of HEADAS used
CALDBVER= 'gen20241115_xtd20250915_rsl20250915' / Version of CALDB used
DATE    = '2026-02-12T00:42:39' / Date and time this file was created or updated
SIB2_VER= 'V04.00  '           / SIB2 version JAXA

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