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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 250128B: VLA radio upper limit
  2. Ep250125A: 1.3m DFOT optical upper limit
  3. GRB 250129A: Skynet optical observations
  4. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  5. GRB 250129A: Swift-XRT refined Analysis
  6. GRB 250128B: Gemini-North optical extended source detection
  7. The EP-WXT trigger 01709131085: KAIT confirmation of the stellar flare
  8. GRB 250128B: TNG optical upper limit
  9. GRB 250129A: Swift/UVOT Detection
  10. GRB 250128B: VLT/HAWKI near-infrared observations
  11. GRB 250127A: CrAO and Terskol optical upper limits
  12. GRB 250129A: Enhanced Swift-XRT position
  13. GRB 250128B: NOT optical upper limit
  14. GRB 250128B: VLT/FORS2 optical observations
  15. GRB 250129A: REM optical/NIR afterglow detection
  16. GRB 250129A: OHP/T193 optical and spectroscopy observations
  17. GRB 250129A: Early afterglow detection by LCO.
  18. GRB 250128B: OHP/T193 optical upper limit
  19. Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
  20. GRB 250129A: LCO optical observations
  21. GRB 250129A: NOT optical observations and redshift confirmation
  22. GRB 250129A: GOTO optical observations show brightening afterglow
  23. GRB 250129A: VLT/X-shooter redshift of z = 2.151
  24. Swift GRB 250129A: Global MASTER-Net observations report
  25. GRB 250128B: Enhanced Swift-XRT position
  26. The EP-WXT trigger 01709131085 is likely a flaring star
  27. Fermi GRB 250128B: Global MASTER-Net observations report
  28. GRB 250129A: Swift detection of a burst with an optical counterpart
  29. Swift GRB 250129A: Global MASTER-Net OT detection
  30. GRB 250128B: Swift-XRT refined Analysis
  31. GRB 250128B: Fermi GBM Observation
  32. GRB 250128B: GOTO optical upper limit
  33. Swift GRB 250128B: Global MASTER-Net observations report
  34. EP250125a: Upper limits from Swift/BAT-GUANO
  35. GRB 250128B: LCO optical observations
  36. GRB 250128B: Swift detection of a short burst
  37. GRB 250128B: Fermi GBM Final Real-time Localization
  38. GRB 250127A: Swift-XRT observations
  39. GRB 250127B: DDOTI Upper Limit on the Afterglow
  40. Fermi-LAT Gamma-ray Observations of IceCube-250102A
  41. GRB 250127A: EP-FXT afterglow detection
  42. Fermi GRB 250128A: Global MASTER-Net observations report
  43. GRB 250128A: Fermi GBM Final Real-time Localization
  44. GRB 250117A: Fermi GBM Observation
  45. Fermi GRB 250127B: Global MASTER-Net observations report
  46. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  47. GRB 250127A: SVOM/VT upper limit
  48. GRB 250127B: Fermi GBM Final Real-time Localization
  49. IPN triangulation of GRB 250119C
  50. GRB 250127A: Swift ToO observations
  51. GRB 250127A: LCO optical upper limit
  52. GRB 241223A: cubesat Avion detection
  53. GRB 250127A: SVOM detection of a long burst
  54. GRB 250126A: CALET Gamma-Ray Burst Monitor detection
  55. EP250125A: Non-detection from Fermi-GBM Observations
  56. GRB 250126A: MAXI/GSC detection
  57. EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection
  58. GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208)
  59. GRB 250126A: Fermi GBM Final Real-time Localization
  60. GECAM-A detection of a bright burst from SGR 1E1841-045
  61. GRB 250118A: Fermi GBM Observation
  62. EP250125a: Optical upper limit with Kinder observations
  63. EP250125a: REM optical counterpart detection
  64. GRB 250119C: Fermi GBM Observation
  65. EP250125a: Swift/XRT detection of a fading counterpart
  66. EP250125a: a new X-ray transient detected by Einstein Probe
  67. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  68. The EP-WXT trigger 01709130758 is a false trigger
  69. The EP-WXT trigger 01709130758 is a false trigger
  70. Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
  71. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  72. IPN triangulation of a bright burst from SGR 1E1841-045
  73. GRB 250121A: CALET Gamma-Ray Burst Monitor detection
  74. EP250108a: AbAO, CMO and Terskol optical upper limits
  75. Konus-Wind detection of GRB 250118B
  76. GRB 250121A: Fermi GBM Observation
  77. IPN triangulation of GRB 250118B
  78. Konus-Wind detection of GRB 250119B
  79. IPN triangulation of GRB 250119B
  80. GRB 250122A: Fermi GBM Final Real-time Localization
  81. Improved IPN triangulation of GRB 250107C
  82. GRB 250114A: Swift-BAT refined analysis
  83. GRB 250121A: INTEGRAL/SPI-ACS detection
  84. GRB 250121A: Fermi-LAT detection
  85. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  86. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  87. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  88. GRB 250121A: Fermi GBM Final Real-time Localization
  89. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  90. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  91. GRB 250119B: Fermi GBM Observation
  92. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  93. Konus-Wind detection of GRB 250117A
  94. IPN triangulation of GRB 250117A (short)
  95. ATCA detection of possible radio counterpart to GRB 250114A
  96. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  97. GRB 250119B: INTEGRAL/SPI-ACS detection
  98. LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  99. EP 250108A: Late-time optical observation by LCO
  100. GRB 250117A: SVOM/GRM observation of a short burst

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