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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 250403A : SVOM detection of a burst
  2. GRB 250403A: Fermi GBM Final Real-time Localization
  3. GRB 250225B: VLT host galaxy redshift z = 0.950
  4. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  5. GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
  6. GRB 250402A: REM optical/NIR upper limits
  7. GRB 250402A: LCO optical counterpart detection
  8. GRB 250402A: refined SVOM/MXT data analysis
  9. The EP-WXT trigger 01709133862 is a flaring star
  10. EP250402a: Einstein Probe detection of a fast X-ray transient
  11. GRB 250402B: AstroSat CZTI detection of a short burst
  12. GRB 250402A: SVOM/VT optical counterpart
  13. GRB 250402A: SVOM detection of a burst
  14. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  15. GRB 250314A: ALMA detection
  16. GRB 250329B: Swift/UVOT Upper Limit
  17. GRB 250329A: Swift/UVOT Upper Limit
  18. GRB 250327B: Swift/UVOT Detection
  19. GRB 250327A: Swift/UVOT Upper Limits
  20. GRB 250331E: SVOM/GRM observation
  21. GRB 250327B: Kilonova-Catcher Observations
  22. GRB250331D: AbAO optical observations
  23. GRB 250331D: Fermi GBM observation
  24. GRB 250331C: Swift/UVOT Upper Limits
  25. GRB 250331B: Swift/UVOT Upper Limits
  26. GRB 250328A: AbAO AS-32 Optical Observations
  27. GRB 250219A: NOT candidate host galaxy detection
  28. GRB 250322B: GRBAlpha detection
  29. GRB 250331D: Swift-XRT observations
  30. GRB 250331C: Swift-XRT refined Analysis
  31. GRB 250331B: Swift-XRT refined Analysis
  32. GRB 250331B: Swift-XRT refined Analysis
  33. GRB 250322B possible detection by the AstroSat Satellite
  34. GRB 250330B: SVOM/GRM observation of a short burst
  35. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  36. Fermi GRB 250331E: Global MASTER-Net observations report
  37. Fermi GRB 250331D: Global MASTER-Net observations report
  38. GRB 250330B: EIRSAT-1 GMOD Detection
  39. GRB 250331E: Fermi GBM Final Real-time Localization
  40. GRB 250327A Swift-BAT refined analysis
  41. LIGO/Virgo/KAGRA S250331o: Updated Sky localization
  42. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  43. Fermi trigger No 765078057: Global MASTER-Net observations report
  44. GRB 250329B: CAHA 2.2m telescope optical limit
  45. GRB 250331D: Swift ToO observations
  46. Swift GRB 250331C: Global MASTER-Net observations report
  47. Swift GRB 250331B: Global MASTER-Net observations report
  48. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  49. Konus-Wind detection of GRB 250327B
  50. GRB 250331C: Enhanced Swift-XRT position
  51. IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
  52. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  53. GRB 250331B: Enhanced Swift-XRT position
  54. GRB 250320C : SVOM detection of a burst through offline search
  55. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  56. GRB 250329B: Swift-XRT confirmation of fading
  57. GRB 250330A: VLT/FORS2 Afterglow Detection
  58. GRB20250327B: 45th Parallel Observatory upper limit
  59. GRB 250328A: Swift/UVOT Detection
  60. GRB 250328A: Swift-XRT refined Analysis
  61. Fermi-LAT gamma-ray observations of IceCube-250330A
  62. SVOM/sb25033102 is a false trigger
  63. GRB 250330A: Fermi GBM Observation
  64. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  65. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  66. GRB 250331D: Fermi GBM Final Real-time Localization
  67. GRB 250331C: Prompt enhanced Swift-XRT position
  68. GRB 250331C: Swift detection of a burst
  69. GRB 250331B: Swift detection of a burst
  70. GRB 250330A: SVOM/VT optical upper limit
  71. GRB 250331A: MAXI/GSC detection
  72. SVOM/sb25033102: SVOM detection of an X-ray transient
  73. GRB 250314A: VLA detection
  74. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  75. Fermi GRB 250330B: Global MASTER-Net observations report
  76. GRB 250330B: Fermi GBM Final Real-time Localization
  77. Fermi GRB 250330A: Global MASTER-Net observations report
  78. GRB 250330A: BOOTES-7 early optical upper limit
  79. GRB 250330A: Swift/UVOT Upper Limits
  80. GRB 250330A: Swift-XRT afterglow detection
  81. GRB 250328A: 1.6m Mephisto optical observations
  82. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  83. GRB 250330A: Fermi GBM Final Localization
  84. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  85. IceCube Alert 250330.35: Global MASTER-Net observations report
  86. GRB 250330A: VLT/FORS2 Optical Observations
  87. GRB 250330A: Prompt Swift-XRT position
  88. GRB 250329B: Swift-XRT afterglow detection
  89. GRB 250330A: Swift detection of a burst
  90. Swift GRB250330.26: Global MASTER-Net observations report
  91. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  92. GRB 250329B: SVOM/C-GFT optical upper limit
  93. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  94. GRB 250327B: ALMA detection
  95. GRB 250327B: VLA detection
  96. GRB 250329B: SVOM/VT optical upper limit
  97. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  98. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  99. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  100. GRB250329A: REM optical afterglow detection

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