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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').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

5154 results found.

  1. GRB 250424A: EIRSAT-1 GMOD Detection
  2. GRB 250424A: SVOM/VT optical observation
  3. GRB 250424A: Swift-XRT refined Analysis
  4. GRB 250424A: AstroSat CZTI detection of a bright long burst
  5. GRB 250424A: BlackGEM optical afterglow detection
  6. GRB 250424A: DDOTI Afterglow Detection
  7. GRB 250424A: REM optical/NIR afterglow detection
  8. Swift GRB 250424A: Global MASTER-Net observations report
  9. Swift GRB 250424A: Global MASTER-Net OT detection
  10. SVOM/sb25042207: BOOTES-2 early optical upper limit
  11. EP250421a: Swift/XRT counterpart detection
  12. Fermi GRB 250421A: Global MASTER-Net observations report
  13. IceCube Alert 250421.71: Global MASTER-Net observations report
  14. EP250421a: JinShan likely optical counterpart
  15. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  16. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  17. IceCube-250416A: DDOTI Optical Observations
  18. EP250404a: Nanshan 0.43m Telescope optical observatios
  19. Fermi trigger No 766148493: Global MASTER-Net observations report
  20. Fermi trigger No 766173972: Global MASTER-Net observations report
  21. Fermi GRB 250411A: Global MASTER-Net observations report
  22. IPN triangulation of GRB 250407A
  23. Fermi GRB 250407A: Global MASTER-Net observations report
  24. IceCube 250406.951: DDOTI Optical Observations
  25. IceCube Alert 250406.95: Global MASTER-Net observations report
  26. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  27. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  28. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  29. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  30. Fermi GRB 250404A: Global MASTER-Net observations report
  31. EP250404a: Xinglong decaying optical counterpart
  32. GRB 250403A: Montarrenti Observatory optical detection
  33. EP250404a: Global MASTER-Net observations report
  34. EP250404a: Nanshan/HMT optical counterpart detection
  35. GRB 250403A: Swift/UVOT Detection
  36. EP250402a: Optical upper limit with Kinder observations
  37. GRB 250403A: Swift-XRT observations
  38. GRB 250403A: GOTO optical counterpart follow-up observations
  39. GRB 250403A: GMG Optical Observation
  40. GRB 250331C: Swift-XRT refined Analysis
  41. GRB 250331B: Swift-XRT refined Analysis
  42. GRB 250331B: Swift-XRT refined Analysis
  43. Fermi GRB 250331E: Global MASTER-Net observations report
  44. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  45. GRB 250331B: Swift detection of a burst
  46. GRB 250331A: MAXI/GSC detection
  47. GRB 250330A: Swift-XRT afterglow detection
  48. IceCube Alert 250330.35: Global MASTER-Net observations report
  49. GRB 250327B: CrAO and SAO RAS Optical Observations
  50. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  51. GRB 250327A: Swift-XRT refined Analysis
  52. GRB 250327B: GOTO optical counterpart detection
  53. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  54. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  55. GRB 250322A: Swift-XRT refined Analysis
  56. GRB 250322A: AstroSat CZTI detection of a short burst
  57. FRB 250316A: DDOTI Continued Optical Observations
  58. EP250321a: Liverpool Telescope optical follow-up
  59. GRB 250312A: GECAM-A detection
  60. GRB 250321A: Swift-BAT refined analysis
  61. GRB 250321A: Swift-XRT refined Analysis
  62. GRB 250317B: NOT optical observations suggest an optical plateau phase
  63. Fermi GRB 250316A: Global MASTER-Net observations report
  64. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  65. Fermi GRB 250313A: Global MASTER-Net observations report
  66. GRB 250312A: Swift-XRT refined Analysis
  67. GRB 250312A: Swift detection of a burst
  68. GRB 250309B: 1.3m DFOT Optical observations
  69. IPN triangulation of GRB 250308A (short)
  70. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  71. GRB 250309B: Swift-XRT refined Analysis
  72. IceCube Alert 250309.32: Global MASTER-Net observations report
  73. Fermi GRB 250307A: Global MASTER-Net observations report
  74. Fermi trigger No 762963055: Global MASTER-Net observations report
  75. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  76. Konus-Wind detection of GRB 250222A
  77. IPN triangulation of GRB 250222A
  78. EP250302a: Global MASTER-Net observations report
  79. Fermi GRB 250302A: Global MASTER-Net observations report
  80. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  81. EP250228a: Optical observations with Kinder and Swift/UVOT
  82. GRB 250225B: VLT/HAWKI near-infrared observations
  83. EP250223a: J band upper limit by SYSU 80cm telescope
  84. GRB 250205A / EP250205A: further radio observations with the VLA
  85. Fermi GRB 250226B: Global MASTER-Net observations report
  86. GRB 250221A: ATCA Detections and Upper Limits
  87. GRB 250225B: VLT/FORS2 candidate optical afterglow
  88. Fermi GRB 250226A: Global MASTER-Net observations report
  89. Fermi trigger No 762205158: Global MASTER-Net observations report
  90. Fermi GRB 250225A: Global MASTER-Net observations report
  91. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  92. EP250223a: Kinder optical follow-up observations
  93. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  94. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  95. EP250223a: GOTO optical afterglow detections
  96. GRB 250222A: SVOM/GRM observation of a burst
  97. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  98. EP250223a: REM NIR upper limit
  99. EP250223a: TRT optical afterglow observation
  100. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart

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