XRISM RESOLVE observation 201018010

Title

DETERMINING THE MAGNETIC FIELD STRENGTH OF THE LOW MASS X-RAY BINARY PULSAR GX 1+4: A UNIQUE MAGNETAR BINARY?

Abstract

One of the big questions in neutron stars is how the strong magnetic field is formed and evolved. We propose a 40 ks observation of a low-mass X-ray binary pulsar GX 1+4, which has long been suspected to have a very high magnetic field strength, perhaps ~ 1e14 G. Thanks to the excellent energy resolution of the Resolve, the proposed observation enables us for the first time to resolve the profile of the Fe K alpha lines and to measure the magnetic field strength above 1e13 G, which is impossible to probe using the cyclotron resonance scattering feature (CRSF). From this observation we can determine whether or not the source is the first magnetar binary ever detected. Moreover, Resolve may provide a unique opportunity to search for the proton CRSF.

FITS header

TELESCOP= 'XRISM   '           / Mission name
INSTRUME= 'RESOLVE '           / Instrument name
FILTER  = 'OPEN    '           / Filter name used
OBS_ID  = '201018010'          / Observation identification string
OBJECT  = 'GX1+4   '           / Object name
OBSERVER= 'TOSHIHIRO TAKAGI'   / PI name
OBS_MODE= 'POINTING'           / POINTING or SLEW or ALL
RA_OBJ  =              263.009 / [deg] Object Right ascension
DEC_OBJ =             -24.7456 / [deg] Object Declination
RA_PNT  =     263.003033326268 / Pointing RA
DEC_PNT =    -24.7454868347367 / Pointing DEC
RA_NOM  =     263.007525585089 / [deg] Nominal aspect point R.A.
DEC_NOM =    -24.7452375802524 / [deg] Nominal aspect point Dec.
PA_NOM  =     93.0802889869987 / [deg] Nominal aspect point roll.
TELAPSE =     111725.785957009 / Elapsed time
DATE-OBS= '2025-03-25T06:15:22' / Start date
DATE-END= '2025-03-26T13:17:27.785957' / Stop date
ONTIME  =          47378.86731 / On-source time
EXPOSURE=          47378.86731 / Exposure time
PROCVER = '03.00.013.010'      / Processing script version
MKFFF   = 'ISAS/JAXA'          / Origin of First FITS file
ORIGIN  = 'GSFC/NASA'          / Origin of Processed FITS file
SOFTVER = 'Hea_21Aug2024_V6.34_XRISM_21Aug2024_V001' / Version of HEADAS used
CALDBVER= 'gen20241115_xtd20241115_rsl20241115' / Version of CALDB used
DATE    = '2025-04-11T06:15:51' / Date and time this file was created or updated
SIB2_VER= 'V03.01  '           / SIB2 version JAXA

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