MAXI News

IceCube project is awarded by the Nobel Prize 2026. MAXI is checking the X-ray flux for every Very High Energy (VHE) neutrino detected by IceCube since 2016. The total number is 200 to date.
The list is MAXI neutrino list , left column in the top page.
All of them are upper limits. 10 out of them occurred exactly in the MAXI field of view. Specific 5 events were reported to GCN. There is no X-ray candidate, not only X-ray but other wavelengths, either. It results in that the origin remains unknown.

MAXI detected an X-ray brightening of 30 mCrab from 1ES 1959+650 in the constellation Draco on 2026 September 25. SVOM/ECLAIRs detected 4-20 keV X-ray of 20 mCrab on Sep. 18 ( ATel 18077 ). It is a BL Lac object, a kind of Blazar, a giant black hole at the center of an active galaxy, whose jet is heading toward us. The distance is 650 million lt-yr. The very high energy (VHE) gamma-ray emission above 2 TeV was detected on Sep. 18 with SST-1M ( ATel 18065 ), and also with LHAASO-WCDA ( ATel 18072 ). The TeV flux was 0.5 times the Crab Nebula flux. It is surprising that the Crab emission is used as a standard unit both in X-ray (keV) and VHE gamma-ray (TeV), which are 9 orders of magnitude apart.

MAXI detected a bright X-ray burst at 2026 September 12 12:43 UT in the constellation Sagittarius ( ATel 18039 ). There are two known bursters in the region. One is the X-ray burster XTE J1810-189 and the other is the anomalous X-ray pulsar (AXP) XTE J1810-197. From the burst light curve, this burst is likely from XTE J1810-189.

click here for the whole sky in the latest sky page. Watch carefully at the center.

MAXI detected GRB 260916A at 2026 September 16, 8:51 UT with 160 mCrab intensity in the constellation Sculptor (GCN 45592). The galactic latitude was -85.6 deg. which is almost at the south edge in the galactic coordinates. The optical MASTER-OAFA robotic telescope in Argentina observed it at 9:38 UT, but no transient star brighter than 20 mag. was detected (GCN 45591).

click here for the whole sky in the latest sky page. The GRB is at the bottom.

MAXI detected an outburst from the Be/X-ray binary pulsar GS 0834-430 on 2026 August 29 in the constellation Vela ( ATel 18031 ). The flux reached 50 mCrab on September 4. This is the third detection of this source by MAXI following in 2012 ( ATel 4218 , 4235 ) and 2015 ( ATel 8175 ). It was discovered with Granat and Ginga satellites in 1990. It stopped activity in 1993 and was reactivated in 2012.

MAXI detected a sudden X-ray outburst from the Be/X-ray binary pulsar 1A 0538-66 in LMC on 2026 August 28 ( ATel 18020 ). The outburst began near the periastron in the eccentric binary orbit. The flux increased rapidly, as from 0 to 0.3 Crab in 11h to 17h UT on August 28. The 0.3 Crab, which increased to 0.4 Crab later, was the highest flux ever recorded from this source by MAXI. Since 1A 0558-66 locates in LMC whose distance is 50 kpc, the flux corresponds to an X-ray luminosity of 1.1e39 erg/s. It exceeds 5 times over the Eddington Luminosity, which strongly suggests the emission would be highly dependent on the direction.

MAXI detected a bright X-ray nova MAXI J1750-327 at 02:41 UT on August 13, 2026 ( ATel 17963 ). The X-ray flux was 120 mCrab. 6 hours later than MAXI's ATel, EP/WXT reported the detection actually 6 hours earlier than MAXI's detection ( ATel 17964 ). EP/FXT confirmed the source was new on August 14 ( ATel 17969 ). Chandra archive shows no source in 2000, either ( ATel 17978 ). Optical observation was reported by some telescopes ( ATel 17971 , 17977 , 17990 ). Radio telescope ( ATel 17979 ), HXMT ( ATel 17983 ) and SVOM ( ATel 17993 ) observations all suggest that MAXI J1750-327 is a black hole binary.
If so, MAXI J1750-327 becomes the 38th MAXI nova, and the 16th MAXI black hole.

MAXI detected the start of an outburst from GK Persei on 2026 August 9 ( ATel 17958 ). The intensity was 40 mCrab in 4-10 keV. GK Per is the nova in 1901 and has an outburst once in about three years. The system is a binary of a white dwarf and a normal star at a 1500 lt-yr distance. This time, the flux of optical light started to increase on July 7. It reached 2.5 magnitude brighter state on August 11, when it is still on the 3/4 way to the peak.

MAXI is monitoring the X-ray flux of EP 260531a (figure). EP 260531a was discovered by EinsteinProbe on 2026 May 31 ( ATel 17828 , 17833 ). The flux was 1 mCrab and the spectrum was soft. It was too faint for MAXI to detect with 4-day exposure. SVOM reported a brightened flux of 10 mCrab on June 7 ( ATel 17842 ). MAXI can detect the flux of this level. The flux kept increasing, and had a peak at around 61210 MJD (June 19) in the MAXI light curve. It is decreasing since then, but still has some flux (5 mCrab).

MAXI detected the gamma-ray burst GRB 260708B at 16:43 UT on 2026 July 8 in the constellation Aquarius near "water jar" (GCN 45118). The intensity was 170 mCrab.

MAXI detected the outburst from the Be/Xray binary pulsar 4U 0115+63 on 2026 June 29 in the constellation Cassiopeia ( ATel 17858 ). The intensity was 47 mCrab. It is a binary system with a 15-magnitude Be star and a neutron star. The orbit is long-ellipse and the orbital period is 24.3 day. The pulse period of the pulsar is 3.6 s. The surface magnetic field at the magnetic pole is 10^8 T. The binary locates at 26,000 lt-yr away. The previous X-ray outburst was observed in April 2024 ( ATel 16573 ). It shows a giant outburst with the peak intensity of about 0.3 Crab once in roughly 3 years.

MAXI detected beginnings of the outbursts from the two Be/Xray binary pulsars.
One is XTE J1946+274 on 2026 June 16 in the constellation Vulpecula ( ATel 17847 ). It is a 16 s pulsar at 31 thousand lt-yr away. The last X-ray outburst was observed in 2024 by MAXI/GSC ( ATel 16717 ).
see MAXI News 1407
The other is 1A 1118-616 on 2026 June 17 in the constellation Centaurus ( ATel 17853 ). It is a 406 s pulsar at 16 thousand lt-yr away. 1A 1118-61 exhibited a giant X-ray outburst in 2026 January ( ATel 17608 ).
see MAXI News 1449

Gamma-ray burst GRB 260616C

news-1464 June 18, 2026 by Mihara MAXI detected the gamma-ray burst GRB 260616C at 14:47 UT on 2026 June 16 in the constellation Taurus (GCN 44961). The intensity was 150 mCrab. We are lucky that it was just before turning off the high voltage. Three GSC cameras detected it out of nine working ones. GECAM-B satellite also detected the gamma-ray (GCN 44974). Since it was close to the sun (21 deg.), no follow-up observation was made.

MAXI detected the gamma-ray burst GRB 260531A at 5:30 UT on 2026 May 31 in the constellation Eridanus (GCN 44746). The intensity was 230 mCrab. Since it was so close to the sun (32 deg.), no follow-up observation was made.

This week MAXI detected new outbursts from two Be/X-ray Binary Pulsars.
One is 1A 0535-66 detected on 2026 May 21 ( ATel 17815 ) in Large Magellanic Cloud. After it woke up in 2025 September after 45 years of sleep ( ATel 17455 ), it had one outburst in 2026 February ( ATel 17705 ) and this time. It is a 0.068 s pulsar, which is the fastest among the accreting binary pulsars. The intensity was 100 mCrab. Since it is very far as 160,000 lt-yr, the real luminosity is very high, almost at the Eddington luminosity (2 x 10^31 W).
The other is LS V+44 17 on 2026 May 22 in the constellation Perseus ( ATel 17816 ). MAXI detection is after three years, since the last major outburst in 2023 ( ATel 15835 ). The flux reached the peak of 50 mCrab. Since the distance is 8,600 lt-yr, the luminosity was 10^29 W, a typical value for a BeXRB.
Note that the optical solar luminosity is 4 x 10^26 W.

At 17:13:42 UT on 2026 May 10, the MAXI triggered GRB 260510C in the constellation Sextans. X-ray flux was 340 mCrab. There was no flux in the previous or next transits before / after 93 minutes. The trigger time and position are consistent with reports by the Fermi (GCN 44520) and the SVOM (GCN 44521). EP/FXT performed a follow-up observation at 50 minutes later and found an X-ray afterglow of 2 mCrab intensity (GCN 44541). The ground telescope COLIBRI performed a follow-up observation in 12 hour later and found a 20 mag optical transient. At the location, there was a faint galaxy of 23 mag, which is thought to be the host galaxy of the GRB. The redshift is 0.89, which means the distance is 7.3 billion light-year (GCN 44530).

MAXI detected an X-ray burst at 08:47 UT on 2026 April 30 in the constellation Vela. The region contains the known X-ray burster GS 0836-429 (MX 0836-42) ( ATel 17772 ). First, it was discovered in 1971 with OSO-7 and named as MX 0836-42. In 1990, Ginga re-discovered it and named as GS 0836-429. It was active again in 2003-2004, as 61 X-ray bursts were detected by the INTEGRAL/JEM-X ( Aranzana et al. 2016 ). However, it has been quiet since 2012. This is the first burst detection from GS 0836-429 by MAXI over 17 years. This burst may be a sign to a new active state of GS 0836-429 for the coming years.

MAXI detected faint transients in the Scutum region. GS 1843+00 was detected on 2026 Feb 28 ( ATel 17706 ), XTE J1859+083 on 2026 March 24 ( ATel 17730 ). In this week, XTE J1855-026 appeared on Apr 13. Aql X-1 and 1E 1841-045 on Apr 14. Swift J1834.9-0846 and 4U 1709+09 on Apr 15 The Scutum region contains many pulsars, magnetars, and neutron stars. They are all known, but they appear in their way.
see also news-1363.

MAXI detected a bright gamma-ray burst GRB 260401A at 2026 April 1 10:53:19 UT in the constellation Libra (GCN 44176). The intensity was 6 Crab, which is the third brightest among the 183 GRBs detected by MAXI in the 16 years. It was detected, in time order of the GCN reports, by Fermi/GBM (44174), MAXI/GSC (44176), CALET/GBM (44177), NuSTAR anti-coincidence shield (44178), GECAM-B (44187), SVOM/GRM (44188), and GRID-11B (44228). Although it was so bright, there was no optical counterpart in the observation at 18 h later (44180). Therefore, the redshift is unknown.

MAXI detected a faint outburst from the 9.8s Be/X-ray binary pulsar XTE J1859+083 on March 24 in the constellation Aquila ( ATel 17730 ). The intensity was 34 mCrab. The detection was since 2015 February 8 ( ATel 7034 ). It was covered with the degraded cameras. Since the intensity was below the detection limit, it failed to be detected. However, ISS turned around on March 24, which made good cameras to cover Aquila region. It led to the detection.

The sky coverage on 2026 March 23.
Aquila region is in the big black hole in the left.

The sky coverage on 2026 March 24 while the ISS turned its back.
XTE J1859+083 is circled.

MAXI detected the spectral transition of the black hole (BH) binary GS 1354-64 on March 9, 2026 ( ATel 17724 ). GS 1354-64 started an outburst on December 25, 2025 ( ATel 17563 ). We reported an indication of the hard-to-soft state transition from around January 19 (ATel 17618). ( ATel 17618 ). The soft X-ray increased once, but got back to the previous level. The soft transition was incomplete. This time the soft X-ray is decreasing, but the hard X-ray has decreased more rapidly. Consequently the spectrum became soft. The soft state is very important because we can know the Schwarzschild radius and therefore the mass of the BH.

MAXI detected a faint outburst from IGR J06074+2205 on 2026 March 7 in the constellation Gemini ( ATel 17714 ). The intensity was 24 mCrab. It is a Be X-ray binary pulsar. They make an outburst at the periastron passage, but not always. MAXI have detected seven outbursts (2022 March, 2022 June, 2023 October, 2023 December, 2024 March, 2024 May, 2024 August) and this time. From the spans of these outbursts, the orbital period was derived to be 80.1 ± 0.6 days.

MAXI detected an outburst from the Large Magellanic Cloud region on 2026 February 27 ( ATel 17705 ). There is a Be/X-ray binary pulsar 1A 0538-66. This is the second firm detection of this source by the MAXI/GSC. The previous one was recorded on 2025 September 30 ( ATel 17455, 17467 , MAXI news #1443 2025 Nov 6

On the same day, February 27, MAXI detected a weak X-ray appearance in the constellation Serpens Cauda ( ATel 17706 ). The position consistent with the Be/X-ray binary pulsar GS 1843+00. This source was discovered by Ginga in 1988. After a minor outburst in 2010 March, no X-ray activity has been reported for the past 16 years. This time NuStar satellite will make a follow-up observation.

MAXI detected a burst in the constellation Columba at 08:47 UT on February 6, 2026 (GCN 43624). We reported it either a gamma-ray burst GRB 260206A or an X-ray burst from 4U 0513-40 because the 4U 0513 was just outside of the MAXI error circle. Swift performed a follow-up observation 10 hour later and found a bright source in the globular cluster NGC 1851 ( ATel 17682 ). Although the MAXI burst was harder in the spectrum than the typical X-ray burst, the luminosity and temperature was consistent with an X-ray burst. So, the X-ray burst from the neutron star binary 4U 0513-40 is more likely.

MAXI detected an outburst from the neutron-star low-mass X-ray binary Aql X-1 on 2026 February 8 ( ATel 17657 ). The intensity was 34 mCrab. The previous outburst was reported in 2024 September by EP ( ATel 16821 ), optical observatory ( ATel 16822 ), radio observatory ( ATel 16823 ), Swift ( ATel 16826 ) and NuSTAR ( ATel 16829 ) before MAXI. But this time MAXI reported it first. It is mostly because the sun is close to Aql X-1 (36 degrees) and EP and optical observatories cannot observe it.

MAXI detected a gamma-ray bust at 06:43:02 UT on January 31, 2026. in the constellation Triangulum (GCN 43580). The flux was 800 mCrab. We reported as GRB 260131B. Another GRB 260131A was detected by Fermi/GBM, Konus-Wind, Insight-HXMT, and GRID 4 minutes before GRB 260131B. The location agreed with the large Fermi/GBM error box, and they reported A and B are from the same source (GCN 43585). Some optical telescopes detected the optical afterglow (GCN 43586, 43587, 43610). Nordic Optical Telescope measured the redshift as z = 1.434 (GCN 43595), which is 9.2 billion light years away. X-ray afterglow was detected by EP/FXT at the flux of 0.2 mCrab at 34 hour later (GCN 43600). Afterall, GRB 260131A/B was a twice peaked GRB at the moderate distance with a bright X-ray and optical afterglow.

Konus/Wind light curve. Center is GRB 260131A and right is B.
From https://www.ioffe.ru/LEA/GRBs/GRB260131_T23972/

MAXI detected an outburst from the black hole X-ray binary GS 1354-64 in the constellation Circinus on 2025 December 25 ( ATel 17563 ). On 2026 January 18 the hard X-ray started to decrease and the soft X-ray started to increase according to the observation with MAXI, which indicates the hard-to-soft transition of the spectrum ( ATel 17618 ). This means that the accretion disk started to go inward close to the black hole.
GS 1354-64 was discovered in February 25, 1987 with Ginga ( IAUC 4342 ) when Ginga/ASM just started the observation. It would be identical to MX 1353-64 appeared in 1971-73 with OSO-7 ( Markert et al. 1977). GS 1354-64 showed more outbursts in November 1997 with RXTE ( IAUC 6772 ), and June 2015 with Swift/BAT and MAXI ( ATel 7612 ). These suggest that the source exhibits outbursts at intervals of 8-10 years since 1971, although those around 1979 and 2006 were not reported. GS 1354-64 is also known as one of the most distant black hole X-ray binaries in our galaxy.

Swift/BAT triggered the outburst from 1A 1118-61 on 2026 January 17 (GCN 43435). After receiving the news, we looked up the MAXI data, and noticed that MAXI alert system already noticed the beginning of the outburst on January 12 ( ATel 17613 ). Because it locates just next to the bright X-ray pulsar Cen X-3, we could not recognize the event to come from the long-time-absent X-ray pulsar. It was the Be/X-ray binary pulsar discovered in 1974 December. The second and third outbursts were in 1992 January, and 2009 January. It is not only "always January" but also "17-year interval" for all ! Coe instantly noticed it and reported that it could be the orbital period ( ATel 17615 ).

When Payload Data Handler 3 (PDH3) was switched over to PDH on 2026 January 4, GSC B-camera 1 watched the sun at 20:28 UT, since no ISS attitude data was ditributed to MAXI. The camera 1 was turned off by itself by the safety function using the count rate. The sun had entered the camera FOV for about 7 seconds upto 0.3 of the transmission maximum. At the off time, the count rate was about 36000 c/s. The intensity of the sun was calculated to be about 10000 Crab mostly in 2-4 keV. There was no damage in the B-camera 1. Next time, it will be a safe way to avoid it by starting the PDH switch over in the polar or SAA radiation zone.