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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

27211 results found.

  1. GRB 250320B: Fermi-LAT detection
  2. GRB 250321B: SVOM detection of a sub-threshold transient event
  3. EP250321a: SVOM/VT optical observation
  4. EP 250321A: Optical counterpart detection by LCO.
  5. EP250321a: Kinder optical follow-up observations
  6. GRB 250321A: Swift/UVOT Upper Limits
  7. GRB 250320B: SVOM/GRM observation of a long burst
  8. EP250321a: LCO optical counterpart detection
  9. EP250321a: Swift-XRT detection of an X-ray source
  10. EP250321A: COLIBRÍ Optical Observations
  11. EP250321a: VLT/X-shooter redshift z = 4.368
  12. EP250321a: REM optical/NIR afterglow detection
  13. Fermi GRB 250320B: Global MASTER-Net observations report
  14. EP250321a: TRT optical counterpart detection
  15. EP250321a: Global MASTER-Net observations report
  16. Swift GRB 250321A: Global MASTER-Net observations report
  17. Fermi GRB 250321A: Global MASTER-Net observations report
  18. EP250321a: Einstein Probe detection of an X-ray transient
  19. GRB 250321A: GOTO optical upper limits
  20. GRB 250321A: Swift-XRT localisation
  21. EP250226a/GRB 250226A: KAIT optical observations
  22. GRB 250321A: Fermi GBM Observation
  23. GRB 250321A: Swift detection of a burst
  24. GRB 250321A: Fermi GBM Final Real-time Localization
  25. GRB 250320B: Fermi GBM Final Real-time Localization
  26. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  27. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  28. GRB 250320A: Fermi GBM Final Real-time Localization
  29. Fermi GRB 250319B: Global MASTER-Net observations report
  30. GRB 250319B: Fermi GBM Final Localization
  31. GRB 250319A: Fermi GBM Final Localization
  32. GRB 250317D: EIRSAT-1 GMOD Detection
  33. EP250302a: VLA observations
  34. GRB 250317B: OHP/T193 continued follow-up
  35. GRB 250317C: SVOM/GRM observation of a long burst
  36. GRB 250317B: Leavitt Observatory optical upper limit
  37. GRB 250317B: Mondy AZT-33IK Optical Observations
  38. GRB 250317B: NOT optical observations suggest an optical plateau phase
  39. GRB 250317C: GECAM-B detection
  40. GRB 250317B: OHP/T193 optical observations
  41. Fermi trigger No 763933627: Global MASTER-Net observations report
  42. GRB250312A: Swift/UVOT Upper Limits
  43. GRB 250317B: REM optical/NIR observations
  44. GRB 250316A: Swift/UVOT Upper Limits
  45. GRB 250314A: REM optical/NIR upper limits
  46. GRB 250316A: AbAO AS-32 Optical Upper Limit
  47. EP 250317B: Fading optical counterpart detection by LCO
  48. GRB 250317B: LCO detection of the fading optical afterglow
  49. GRB 250317B: refined SVOM/MXT analysis
  50. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  51. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  52. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  53. GRB 250317B: SVOM detection of a burst
  54. GRB 250316A: Fermi GBM Observation
  55. Fermi trigger No 763862734: Global MASTER-Net observations report
  56. GRB 250317A: Fermi GBM Final Real-time Localization
  57. Fermi GRB 250316A: Global MASTER-Net observations report
  58. GRB 250314A: SVOM/GRM analysis
  59. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  60. The EP-WXT trigger 01709132801 is likely a flaring star
  61. GRB 250316A: Fermi GBM Final Real-time Localization
  62. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  63. GRB 250314A: EP-FXT afterglow detection
  64. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  65. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  66. EP250315a: optical counterpart candidate detected by Gemini North
  67. EP250315a: Einstein Probe detection of an X-ray transient
  68. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  69. SVOM/MXT upper limit on GRB 250314A
  70. GRB 250314A: SVOM/VT upper limit
  71. GRB 250314A: NOT near-infrared candidate counterpart
  72. GRB 250313A: Fermi GBM Detection
  73. GRB 250313A: CALET Gamma-Ray Burst Monitor detection
  74. GRB 250312B: Fermi GBM Observation
  75. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  76. GRB 250314A: SVOM detection of a burst
  77. GRB 250313B: SVOM/GRM observation of a soft bright short burst
  78. GRB 250313A: SVOM/GRM observation of a bright long burst
  79. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  80. Fermi trigger No 763581136: Global MASTER-Net observations report
  81. GRB 250313A: Fermi-LAT detection
  82. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  83. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  84. Fermi GRB 250313A: Global MASTER-Net observations report
  85. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  86. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  87. GRB 250313A: Fermi GBM Final Real-time Localization
  88. The EP-WXT trigger 01709132551 is not a real source
  89. EP250304a: SVOM/VT optical observation
  90. EP250311a/GRB 250311A: EP-FXT follow-up observation
  91. EP250302a: Chandra X-ray Detection
  92. GRB 250312A: Swift-XRT refined Analysis
  93. Fermi Gamma-ray Burst Monitor trigger 763509110/250312911 is not a GRB
  94. Fermi trigger No 763509110: Global MASTER-Net observations report
  95. Fermi GRB 250312B: Global MASTER-Net observations report
  96. GRB 250312B: Fermi GBM Final Localization
  97. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  98. GRB 250226B: Fermi GBM Observation
  99. Swift GRB 250312A: Global MASTER-Net observations report
  100. GRB 250302A: Fermi GBM Observation

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