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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
  1. GRB 250316A: Fermi GBM Final Real-time Localization
  2. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  3. GRB 250314A: EP-FXT afterglow detection
  4. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  5. GRB 250314A: Swift/UVOT Upper Limits
  6. GRB 250312B: GRBAlpha detection
  7. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  8. GRB 250314A: Swift XRT Detection
  9. EP250315a: optical counterpart candidate detected by Gemini North
  10. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  11. EP250315a: Einstein Probe detection of an X-ray transient
  12. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  13. SVOM/MXT upper limit on GRB 250314A
  14. GRB 250314A: SVOM/VT upper limit
  15. GRB 250314A: NOT near-infrared candidate counterpart
  16. GRB 250313A: Fermi GBM Detection
  17. GRB 250313A: CALET Gamma-Ray Burst Monitor detection
  18. GRB 250312B: Fermi GBM Observation
  19. GRB 250313A: Swift-XRT observations
  20. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  21. Konus-Wind detection of GRB 250313A
  22. Konus-Wind detection of GRB 250308A
  23. GRB 250314A: SVOM detection of a burst
  24. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  25. GRB 250313B: SVOM/GRM observation of a soft bright short burst
  26. GRB 250313A: SVOM/GRM observation of a bright long burst
  27. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  28. GRB 250313A: AstroSat CZTI detection of a bright long burst
  29. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  30. Fermi trigger No 763581136: Global MASTER-Net observations report
  31. GRB 250313A: Fermi-LAT detection
  32. GRB 250313A: Swift ToO observations
  33. EP250304a: Pan-STARRS r and i-band imaging and photometry
  34. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  35. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  36. Fermi GRB 250313A: Global MASTER-Net observations report
  37. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  38. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  39. GRB 250313A: Fermi GBM Final Real-time Localization
  40. The EP-WXT trigger 01709132551 is not a real source
  41. EP250304a: SVOM/VT optical observation
  42. EP250311a/GRB 250311A: EP-FXT follow-up observation
  43. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  44. EP250302a: Chandra X-ray Detection
  45. GRB 250312A: Swift-XRT refined Analysis
  46. Fermi Gamma-ray Burst Monitor trigger 763509110/250312911 is not a GRB
  47. Fermi trigger No 763509110: Global MASTER-Net observations report
  48. Fermi GRB 250312B: Global MASTER-Net observations report
  49. GRB 250312A: Enhanced Swift-XRT position
  50. GRB 250312B: Fermi GBM Final Localization
  51. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  52. GRB 250226B: Fermi GBM Observation
  53. Swift GRB 250312A: Global MASTER-Net observations report
  54. GRB 250302A: Fermi GBM Observation
  55. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  56. GRB 250312A: Swift detection of a burst
  57. GRB 241213A: VIRT Optical Upper Limit
  58. GRB 241228A: VIRT Optical Upper Limit
  59. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  60. GRB 250223B: Fermi GBM Observation
  61. GRB 250311A: Swift-XRT observations
  62. GRB 250228A: Fermi GBM Observation
  63. GRB 230509B: 1.3m DFOT Optical observations
  64. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  65. EP250311a: Global MASTER-Net observations report
  66. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  67. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  68. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  69. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  70. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  71. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  72. GRB 250309B: PRIME near-infrared detection
  73. EP250304a: Chandra detection
  74. GRB 250225B: Swift-BAT refined analysis
  75. GRB 250311A/EP250311a: TRT optical upper limit
  76. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  77. GRB 250311A: Tiled Swift observations
  78. EP250311a/GRB 250311A: EP-WXT detection
  79. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  80. GRB 250311B: SVOM detection of a burst
  81. GRB 250309B: SVOM/VT optical observation
  82. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  83. The EP-WXT trigger 01709132425 is not a real source
  84. GRB 250309B / AT2025dws: further SAO RAS optical observations
  85. IceCube-250309A: Upper limits from Fermi-GBM Observations
  86. EP250308a: 1.6m Mephisto optical upper limits
  87. Konus-Wind detection of GRB 250309B
  88. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  89. IPN triangulation of GRB 250308A (short)
  90. IPN triangulation of GRB 250309B
  91. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  92. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  93. GRB 250309B: Swift-XRT refined Analysis
  94. GRB 250309B / IceCube-250309A: GECAM-B observations
  95. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  96. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  97. GRB 250309B / AT2025dws: SAO RAS optical observations
  98. GRB 250309B / AT2025dws: Swift-UVOT detection
  99. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  100. GRB 250309B: Fermi GBM Observation

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