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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"

5050 results found.

  1. GRB 250424A: BlackGEM optical afterglow detection
  2. GRB 250424A: DDOTI Afterglow Detection
  3. GRB 250424A: REM optical/NIR afterglow detection
  4. Swift GRB 250424A: Global MASTER-Net observations report
  5. Swift GRB 250424A: Global MASTER-Net OT detection
  6. SVOM/sb25042207: BOOTES-2 early optical upper limit
  7. EP250421a: Swift/XRT counterpart detection
  8. Fermi GRB 250421A: Global MASTER-Net observations report
  9. IceCube Alert 250421.71: Global MASTER-Net observations report
  10. EP250421a: JinShan likely optical counterpart
  11. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  12. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  13. IceCube-250416A: DDOTI Optical Observations
  14. EP250404a: Nanshan 0.43m Telescope optical observatios
  15. Fermi trigger No 766148493: Global MASTER-Net observations report
  16. Fermi trigger No 766173972: Global MASTER-Net observations report
  17. Fermi GRB 250411A: Global MASTER-Net observations report
  18. IPN triangulation of GRB 250407A
  19. Fermi GRB 250407A: Global MASTER-Net observations report
  20. IceCube 250406.951: DDOTI Optical Observations
  21. IceCube Alert 250406.95: Global MASTER-Net observations report
  22. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  23. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  24. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  25. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  26. Fermi GRB 250404A: Global MASTER-Net observations report
  27. EP250404a: Xinglong decaying optical counterpart
  28. GRB 250403A: Montarrenti Observatory optical detection
  29. EP250404a: Global MASTER-Net observations report
  30. EP250404a: Nanshan/HMT optical counterpart detection
  31. GRB 250403A: Swift/UVOT Detection
  32. EP250402a: Optical upper limit with Kinder observations
  33. GRB 250403A: Swift-XRT observations
  34. GRB 250403A: GOTO optical counterpart follow-up observations
  35. GRB 250403A: GMG Optical Observation
  36. GRB 250331C: Swift-XRT refined Analysis
  37. GRB 250331B: Swift-XRT refined Analysis
  38. GRB 250331B: Swift-XRT refined Analysis
  39. Fermi GRB 250331E: Global MASTER-Net observations report
  40. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  41. GRB 250331B: Swift detection of a burst
  42. GRB 250331A: MAXI/GSC detection
  43. GRB 250330A: Swift-XRT afterglow detection
  44. IceCube Alert 250330.35: Global MASTER-Net observations report
  45. GRB 250327B: CrAO and SAO RAS Optical Observations
  46. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  47. GRB 250327A: Swift-XRT refined Analysis
  48. GRB 250327B: GOTO optical counterpart detection
  49. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  50. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  51. GRB 250322A: Swift-XRT refined Analysis
  52. GRB 250322A: AstroSat CZTI detection of a short burst
  53. FRB 250316A: DDOTI Continued Optical Observations
  54. EP250321a: Liverpool Telescope optical follow-up
  55. GRB 250312A: GECAM-A detection
  56. GRB 250321A: Swift-BAT refined analysis
  57. GRB 250321A: Swift-XRT refined Analysis
  58. GRB 250317B: NOT optical observations suggest an optical plateau phase
  59. Fermi GRB 250316A: Global MASTER-Net observations report
  60. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  61. Fermi GRB 250313A: Global MASTER-Net observations report
  62. GRB 250312A: Swift-XRT refined Analysis
  63. GRB 250312A: Swift detection of a burst
  64. GRB 250309B: 1.3m DFOT Optical observations
  65. IPN triangulation of GRB 250308A (short)
  66. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  67. GRB 250309B: Swift-XRT refined Analysis
  68. IceCube Alert 250309.32: Global MASTER-Net observations report
  69. Fermi GRB 250307A: Global MASTER-Net observations report
  70. Fermi trigger No 762963055: Global MASTER-Net observations report
  71. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  72. Konus-Wind detection of GRB 250222A
  73. IPN triangulation of GRB 250222A
  74. EP250302a: Global MASTER-Net observations report
  75. Fermi GRB 250302A: Global MASTER-Net observations report
  76. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  77. EP250228a: Optical observations with Kinder and Swift/UVOT
  78. GRB 250225B: VLT/HAWKI near-infrared observations
  79. EP250223a: J band upper limit by SYSU 80cm telescope
  80. GRB 250205A / EP250205A: further radio observations with the VLA
  81. Fermi GRB 250226B: Global MASTER-Net observations report
  82. GRB 250221A: ATCA Detections and Upper Limits
  83. GRB 250225B: VLT/FORS2 candidate optical afterglow
  84. Fermi GRB 250226A: Global MASTER-Net observations report
  85. Fermi trigger No 762205158: Global MASTER-Net observations report
  86. Fermi GRB 250225A: Global MASTER-Net observations report
  87. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  88. EP250223a: Kinder optical follow-up observations
  89. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  90. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  91. EP250223a: GOTO optical afterglow detections
  92. GRB 250222A: SVOM/GRM observation of a burst
  93. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  94. EP250223a: REM NIR upper limit
  95. EP250223a: TRT optical afterglow observation
  96. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  97. Fermi trigger No 761805304: Global MASTER-Net observations report
  98. GRB 250221A: Swift-XRT refined Analysis
  99. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  100. GRB 250220B: Fermi GBM Final Real-time Localization

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