Kenji Hamaguchi

Developments of engineering model of the X-ray CCD camera of the MAXI experiment onboard the International Space Station

Abstract MAXI, Monitor of All-sky X-ray Image, is an X-ray observatory on the Japanese Experimental Module (JEM) Exposed Facility (EF) on the International Space Station (ISS). MAXI is a slit scanning camera which consists of two kinds of X-ray detectors: one is a one-dimensional position-sensitive proportional counter with a total area of ∼5000 cm 2 , the Gas Slit Camera (GSC), and the other is an X-ray CCD array with a total area ∼200 cm 2 , the Solid-state Slit Camera (SSC). The GSC subtends a field of view with an angular dimension of 1°×180° while the SSC subtends a field of view with an angular dimension of 1° times a little less than 180°. In the course of one station orbit, MAXI can scan almost the entire sky with a precision of 1° and with an X-ray energy range 0.5– 30 keV . We have developed an engineering model (EM) for all components of the SSC. Their performance test is underway. We have also developed several kinds of CCDs fabricated from different wafers. Since the thermal condition of the ISS is not suitable for the CCD operation, the operating temperature of the CCD is estimated to be −85° to −50°C at the end of mission life. We therefore carefully need to choose CCD considering not only detection efficiency and readout noise but also the dark current. Here we report the current status of the EM of the SSC and the X-ray responsivity of CCDs.

Developments of CCDs and relevant electronics for the x-ray CCD camera of the MAXI experiment onboard the International Space Station

MAXI, Monitor of All-sky X-ray Image, is an X-ray observatory on the Japanese Experimental Module (JEM) Exposed Facility (EF) on the International Space Station (ISS). MAXI is a slit scanning camera which consists of two kinds of X-ray detectors: one is a one-dimensional position-sensitive proportional counter with a total area of approximately 5000 cm2, the Gas Slit Camera (GSC), and the other is an X-ray CCD array with a total area approximately 200 cm2, the Solid-state Slit Camera (SSC). The GSC subtends a field of view with an angular dimension of 1 degree(s) times 180 degree(s) while the SSC subtends a field of view with an angular dimension of 1 degree(s) times a little less than 180 degree(s). In the course of one station orbit,MAXI can scan almost the entire sky with a precision of 1 degree(s) and with an X-ray energy range of 0.5- 30keV. We have developed an engineering model (EM) for all components of the SSC. Their performance test is ongoing. We have also developed several kinds of CCDs fabricated from different wafers. Since the thermal condition of the ISS is not suitable for the CCD operation, the operating temperature of the CCD estimated to be -85 approximately -50 degree(s) at the end of mission life. We therefore carefully need to choose CCD considering not only detection efficiency and readout noise but also the dark current. We report here the current status of the EM of the SSC and the X-ray responsibity of CCDs.

4-D Imaging and Modeling of Eta Carinae’s Inner Fossil Wind Structures

Eta Carinae is the most massive active binary within 10,000 light-years and is famous for the largest non-terminal stellar explosion ever recorded. Observations reveal that the supermassive (∼120 M ) binary, consisting of an LBV and either a WR or extreme O star, undergoes dramatic changes every 5.54 years due to the stars’ very eccentric orbits (e ≈ 0.9). Many of these changes are caused by a dynamic wind-wind collision region (WWCR) between the stars, plus expanding fossil WWCRs formed one, two, and three 5.54-year cycles ago. The fossil WWCRs can be spatially and spectrally resolved by the Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS ). Starting in June 2009, we used the HST/STIS to spatially map Eta Carinae’s fossil WWCRs across one full orbit, following temporal changes in several forbidden emission lines (e.g. [Fe iii] 4659 Å, [Fe ii] 4815 Å), creating detailed data cubes at multiple epochs. Multiple wind structures were imaged, revealing details about the binary’s orbital motion, photoionization properties, and recent (∼ 5 − 15 year) mass-loss history. These observations allow us to test 3-D hydrodynamical and radiative-transfer models of the interacting winds. Our observations and models strongly suggest that the wind and photoionization properties of Eta Carinae’s binary have not changed substantially over the past several orbital cycles. They also provide a baseline for following future changes in Eta Carinae, essential for understanding the late-stage evolution of this nearby supernova progenitor. For more details, see Gull et al. (2016) and references therein.

Eclipse and collapse of the colliding wind X-ray emission from Eta Carinae

X-ray emission from the massive stellar binary system, η Carinae, drops strongly around periastron passage; the event is called the X-ray minimum. We launched a focused observing campaign in early 2009 to understand the mechanism of causing the X-ray minimum. During the campaign, hard X-ray emission (<10 keV) from η Carinae declined as in the previous minimum, though it recovered a month earlier. Extremely hard X-ray emission between 15-25 keV, closely monitored for the first time with the Suzaku HXD/PIN, decreased similarly to the hard X-rays, but it reached minimum only after hard X-ray emission from the star had already began to recover. This indicates that the X-ray minimum is produced by two composite mechanisms: the thick primary wind first obscured the hard, 2-10 keV thermal X-ray emission from the wind-wind collision (WWC) plasma; the WWC activity then decays as the two stars reach periastron.