We present the first unbiased source catalog of the Monitor of All-sky X-ray Image (MAXI) mission at high Galactic latitudes ($|b| > 10^{\circ}$), produced from the first 7-month data (2009 September 1 to 2010 March 31) of the Gas Slit Camera in the 4--10 keV band. We develop an analysis procedure to detect faint sources from the MAXI data, utilizing a maximum likelihood image fitting method, where the image response, background, and detailed observational conditions are taken into account. The catalog consists of 143 X-ray sources above 7 sigma significance level with a limiting sensitivity of $\sim1.5\times10^{-11}$ ergs cm$^{-2}$ s$^{-1}$ (1.2 mCrab) in the 4--10 keV band. Among them, we identify 38 Galactic/LMC/SMC objects, 48 galaxy clusters, 39 Seyfert galaxies, 12 blazars, and 1 galaxy. Other 4 sources are confused with multiple objects, and one remains unidentified. The log $N$ - log $S$ relation of extragalactic objects is in a good agreement with the HEAO-1 A-2 result, although the list of the brightest AGNs in the entire sky has significantly changed since that in 30 years ago.

Limiting magnitude

10.1093/pasj/63.sp3.s677

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Citations (23)

Rotation and X‐Ray Emission from Protostars

The Astrophysical Journal (2000)

T. Montmerle N. Grosso Y. Tsuboi Katsuji Koyama

The ASCA satellite has recently detected variable hard X-ray emission from two class I protostars in the ρ Oph cloud, YLW 15 (IRS 43) and WL 6, with a characteristic timescale of ~20 hr. In YLW 15, the X-ray emission is in the form of quasi-periodic energetic flares, which we explain in terms of strong magnetic shearing and reconnection between the central star and the accretion disk. The flare modeling, based on the solar analogy, gives us access to the size of the magnetic structures, which in turn allows us to calculate the rotation parameters of the star and the disk. In WL 6, X-ray flaring is rotationally modulated and appears to be more like the solar-type magnetic activity ubiquitous on T Tauri stars. On the basis of these observations, we find that YLW 15 is a fast rotator (near break-up), while WL 6 rotates with a significantly longer period. We thus use X-ray flaring as a "clock" to measure the rotation of protostars. With the help of the mass-radius relation on the stellar "birthline," we derive masses of M* ~ 2 M☉ and ≲ 0.4 M☉ for the central stars of YLW 15 and WL 6, respectively. YLW 15 thus appears to be a future A star. In the long term, the magnetic interactions between the star and the disk result in magnetic braking and angular momentum loss of the star. A comparison of the rotation behavior of YLW 15 and WL 6 confirms that for solar-mass stars magnetic braking takes place on timescales tbr ~ a few × 105 yr, i.e., of the same order as the estimated duration of the class I protostar stage. The main parameter determining tbr turns out to be the stellar mass, so that close to the birthline there must be a mass-rotation relation, tbr ~∝ M*, such that stars with M* ≳ 1-2 M☉ are fast rotators, while their lower mass counterparts have had the time to spin down and reach synchronous rotation with the inner surrounding accretion disk. The rapid rotation and strong star-disk magnetic interactions of YLW 15 also naturally explain the observation of "superflares" of X-ray luminosities as high as LX ≳ 1033-1034 ergs s-1 during a few hours, while at the WL 6 stage the lower X-ray luminosities are likely to be of purely stellar origin. The mass-rotation relation through magnetic braking may also explain why so few class I protostars have been detected in X-rays to date, and why they all lie in clusters. In the case of YLW 15, and perhaps also in other protostars, a hot coronal wind (T ~ 106 K) may be responsible for the VLA thermal radio emission. This paper thus proposes the first clues to the magnetic properties of protostars, which govern their rotation status and evolution.

Protostar

Stellar rotation

Rotation period

Flare

10.1086/308611

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Citations (92)

XMM-Newton observations of the Mouse, SLX 1744–299 and SLX 1744–300

Advances in Space Research (2005)

Hideyuki Mori Yoshitomo Maeda George G. Pavlov Masaaki Sakano Y. Tsuboi

Pulsar wind nebula

ROSAT

10.1016/j.asr.2005.05.048

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Citations (9)

Quasi-Periodic X-Ray Flares from the Class I Protostar YLW15

Kazutoshi Imanishi Y. Tsuboi K. Koyama N. Grosso T. Montmerle

Protostar

Source

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MAXI/GSC detection of a soft X-ray transient MAXI J0637-430

ATel (2019)

H. Negoro K. Miike M. Nakajima W. Maruyama M. Aoki

Transient (computer programming)

Source

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Citations (3)

MAXI/GSC detection of an unexpected brightening from Be/X-ray binary pulsar, GRO J1008-57

The astronomer's telegram (2012)

M. Nakajima T. Mihara M. Sugizaki K. Yoshidome M. Yamauchi

Source

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Iron Fluorescent Line Emission from Young Stellar Objects in the Orion Nebula

The Astrophysical Journal Supplement Series (2005)

Masahiro Tsujimoto Eric D. Feigelson N. Grosso G. Micela Y. Tsuboi

We present the result of a systematic search for the iron Kalpha fluorescent line at 6.4 keV among 1616 X-ray sources detected by ultra-deep Chandra observations of the Orion Nebula Cluster and the obscured Orion Molecular Cloud 1 population as part of the Chandra Orion Ultra-deep Project (COUP). Seven sources are identified to have an excess emission at 6.4 keV among 127 control sample sources with significant counts in the 6.0-9.0 keV band. These seven sources are young stellar objects (YSOs) characterized by intense flare-like flux variations, thermal spectra, and near-infrared (NIR) counterparts. The observed equivalent widths of the line cannot be attributed to the fluorescence by interstellar or circumstellar matter along the line of sight. The X-ray spectral fits and NIR colors of the 6.4 keV sources show that these sources have X-ray absorption of > 1x10^22 cm^(-2) and NIR excess emission, which is not expected when the fluorescence occurs at the stellar photosphere. We therefore conclude that the iron fluorescent line of YSOs arises from reflection off of circumstellar disks, which are irradiated by the hard X-ray continuum emission of magnetic reconnection flares.

Young stellar object

Orion Nebula

Line (geometry)

Photosphere

Stellar population

10.1086/432093

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Citations (82)

XRF 120626B: MAXI/GSC detection.

GRB Coordinates Network (2012)

Y. Nakano H. Negoro M. Serino T. Mihara M. Sugizaki

Source

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