Abstract
The MAXI/GSC nova alert system detected X-ray brightening from the Be/X-ray binary pulsar LS V +44 17 (also known as BSD 24-491 and RX J0440.9+4431) on 2022 December 29 (ATel #15835). The X-ray flux from the source was seen to increase from December 24 (MJD 59937) and it is still increasing as detected in hard X-rays by Swift/BAT (15−50 keV), reaching a record high value of 572±43 mCrab on MJD 59948. MAXI/GSC (2−20 keV) flux has also been increasing since the trigger on December 29 and reached a maximum of nearly 230 mCrab on MJD 59948. LS V +44 17 was last seen in an outburst in April 2011.
NICER observed the source on December 29 beginning at 19:01:00 UTC (MJD 59942.79) with 26.6 ks exposure and recorded an average (0.5−10 keV) count rate of ∼325 cnts/s. A strong pulsation with a pulse period of ∼204.185 s is evident in the NICER data, with a multi-peak shape including an absorption structure in the pulse profile. The fractional amplitude of the pulse profile is ~25 percent (0.5−10 keV).
The NICER spectrum can be fitted with an absorbed cutoff power-law model together with a blackbody component. The best-fit results provide a photon index of −0.32±0.03 and a column density of (0.53±0.01) × 1022 cm-2 (chi-squared/d.o.f. = 1198/937). The blackbody temperature is found to be 0.33±0.04 keV. A strong iron emission line is also detected at 6.4 keV. There are some spectral residuals in the 1−2 keV range, which is accounted for by adding a Gaussian component near 1.5 keV. The absorbed source flux is 3.25 × 10-9 ergs/cm2/s in 0.5−10 keV. All reported uncertainties are 90% confidence limits.
Further NICER observations of the source are underway. We encourage multi-wavelength observations of the source.
NICER is a 0.2−12 keV X-ray telescope operating on the International Space Station. The NICER mission and portions of the NICER science team activities are funded by NASA.
The latest X-ray light curves can be found on the following pages
Swift/BAT: https://swift.gsfc.nasa.gov/results/transients/weak/LSVp4417/
MAXI: http://maxi.riken.jp/pubdata/v7.7l/J0440+445/index.html
Fermi/GBM: https://gammaray.nsstc.nasa.gov/gbm/science/pulsars/lightcurves/rxj0440.html
BeXRB monitor page: http://integral.esac.esa.int/bexrbmonitor/Plots/sim_plot_LSV+4417.html
NICER observed the source on December 29 beginning at 19:01:00 UTC (MJD 59942.79) with 26.6 ks exposure and recorded an average (0.5−10 keV) count rate of ∼325 cnts/s. A strong pulsation with a pulse period of ∼204.185 s is evident in the NICER data, with a multi-peak shape including an absorption structure in the pulse profile. The fractional amplitude of the pulse profile is ~25 percent (0.5−10 keV).
The NICER spectrum can be fitted with an absorbed cutoff power-law model together with a blackbody component. The best-fit results provide a photon index of −0.32±0.03 and a column density of (0.53±0.01) × 1022 cm-2 (chi-squared/d.o.f. = 1198/937). The blackbody temperature is found to be 0.33±0.04 keV. A strong iron emission line is also detected at 6.4 keV. There are some spectral residuals in the 1−2 keV range, which is accounted for by adding a Gaussian component near 1.5 keV. The absorbed source flux is 3.25 × 10-9 ergs/cm2/s in 0.5−10 keV. All reported uncertainties are 90% confidence limits.
Further NICER observations of the source are underway. We encourage multi-wavelength observations of the source.
NICER is a 0.2−12 keV X-ray telescope operating on the International Space Station. The NICER mission and portions of the NICER science team activities are funded by NASA.
The latest X-ray light curves can be found on the following pages
Swift/BAT: https://swift.gsfc.nasa.gov/results/transients/weak/LSVp4417/
MAXI: http://maxi.riken.jp/pubdata/v7.7l/J0440+445/index.html
Fermi/GBM: https://gammaray.nsstc.nasa.gov/gbm/science/pulsars/lightcurves/rxj0440.html
BeXRB monitor page: http://integral.esac.esa.int/bexrbmonitor/Plots/sim_plot_LSV+4417.html
| Original language | English |
|---|---|
| Publication date | 5 Jan 2023 |
| Publication status | Published - 5 Jan 2023 |
| Series | The Astronomer's telegram |
|---|---|
| Number | ATel #15848 |
Keywords
- X-ray
- Neutron Star
- Transient
- Pulsar