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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"
  1. GRB 250129A: AKO Optical Afterglow Detection
  2. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  3. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  4. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  5. GRB 250128B: VLA radio upper limit
  6. Ep250125A: 1.3m DFOT optical upper limit
  7. GRB 250129A: Skynet optical observations
  8. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  9. GRB 250129A: Swift-XRT refined Analysis
  10. GRB 250128B: Gemini-North optical extended source detection
  11. The EP-WXT trigger 01709131085: KAIT confirmation of the stellar flare
  12. GRB 250128B: TNG optical upper limit
  13. GRB 250129A: Swift/UVOT Detection
  14. GRB 250128B: VLT/HAWKI near-infrared observations
  15. GRB 250127A: CrAO and Terskol optical upper limits
  16. GRB 250129A: Enhanced Swift-XRT position
  17. GRB 250128B: NOT optical upper limit
  18. GRB 250128B: VLT/FORS2 optical observations
  19. GRB 250129A: REM optical/NIR afterglow detection
  20. GRB 250129A: OHP/T193 optical and spectroscopy observations
  21. GRB 250129A: Early afterglow detection by LCO.
  22. GRB 250128B: OHP/T193 optical upper limit
  23. Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
  24. GRB 250129A: LCO optical observations
  25. GRB 250129A: NOT optical observations and redshift confirmation
  26. GRB 250129A: GOTO optical observations show brightening afterglow
  27. GRB 250129A: VLT/X-shooter redshift of z = 2.151
  28. Swift GRB 250129A: Global MASTER-Net observations report
  29. GRB 250128B: Enhanced Swift-XRT position
  30. The EP-WXT trigger 01709131085 is likely a flaring star
  31. Fermi GRB 250128B: Global MASTER-Net observations report
  32. GRB 250129A: Swift detection of a burst with an optical counterpart
  33. Swift GRB 250129A: Global MASTER-Net OT detection
  34. GRB 250128B: Swift-XRT refined Analysis
  35. GRB 250128B: Fermi GBM Observation
  36. GRB 250128B: GOTO optical upper limit
  37. Swift GRB 250128B: Global MASTER-Net observations report
  38. EP250125a: Upper limits from Swift/BAT-GUANO
  39. GRB 250128B: LCO optical observations
  40. GRB 250128B: Swift detection of a short burst
  41. GRB 250128B: Fermi GBM Final Real-time Localization
  42. GRB 250127A: Swift-XRT observations
  43. GRB 250127B: DDOTI Upper Limit on the Afterglow
  44. Fermi-LAT Gamma-ray Observations of IceCube-250102A
  45. GRB 250127A: EP-FXT afterglow detection
  46. Fermi GRB 250128A: Global MASTER-Net observations report
  47. GRB 250128A: Fermi GBM Final Real-time Localization
  48. GRB 250117A: Fermi GBM Observation
  49. Fermi GRB 250127B: Global MASTER-Net observations report
  50. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  51. GRB 250127A: SVOM/VT upper limit
  52. GRB 250127B: Fermi GBM Final Real-time Localization
  53. IPN triangulation of GRB 250119C
  54. GRB 250127A: Swift ToO observations
  55. GRB 250127A: LCO optical upper limit
  56. GRB 241223A: cubesat Avion detection
  57. GRB 250127A: SVOM detection of a long burst
  58. GRB 250126A: CALET Gamma-Ray Burst Monitor detection
  59. EP250125A: Non-detection from Fermi-GBM Observations
  60. GRB 250126A: MAXI/GSC detection
  61. EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection
  62. GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208)
  63. GRB 250126A: Fermi GBM Final Real-time Localization
  64. GECAM-A detection of a bright burst from SGR 1E1841-045
  65. GRB 250118A: Fermi GBM Observation
  66. EP250125a: Optical upper limit with Kinder observations
  67. EP250125a: REM optical counterpart detection
  68. GRB 250119C: Fermi GBM Observation
  69. EP250125a: Swift/XRT detection of a fading counterpart
  70. EP250125a: a new X-ray transient detected by Einstein Probe
  71. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  72. The EP-WXT trigger 01709130758 is a false trigger
  73. The EP-WXT trigger 01709130758 is a false trigger
  74. Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
  75. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  76. IPN triangulation of a bright burst from SGR 1E1841-045
  77. GRB 250121A: CALET Gamma-Ray Burst Monitor detection
  78. EP250108a: AbAO, CMO and Terskol optical upper limits
  79. Konus-Wind detection of GRB 250118B
  80. GRB 250121A: Fermi GBM Observation
  81. IPN triangulation of GRB 250118B
  82. Konus-Wind detection of GRB 250119B
  83. IPN triangulation of GRB 250119B
  84. GRB 250122A: Fermi GBM Final Real-time Localization
  85. Improved IPN triangulation of GRB 250107C
  86. GRB 250114A: Swift-BAT refined analysis
  87. GRB 250121A: INTEGRAL/SPI-ACS detection
  88. GRB 250121A: Fermi-LAT detection
  89. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  90. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  91. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  92. GRB 250121A: Fermi GBM Final Real-time Localization
  93. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  94. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  95. GRB 250119B: Fermi GBM Observation
  96. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  97. Konus-Wind detection of GRB 250117A
  98. IPN triangulation of GRB 250117A (short)
  99. ATCA detection of possible radio counterpart to GRB 250114A
  100. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations

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