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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"

27941 results found.

  1. GRB 250821B: Fermi GBM Final Localization of a Bright Burst
  2. GRB 250821A: Enhanced Swift-XRT position
  3. GRB 250821A: Swift/UVOT Upper Limits
  4. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  5. EP250821a: Swift XRT and UVOT counterpart detection
  6. GRB 250821A: LCOGT Optical Upper Limits
  7. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  8. LIGO/Virgo/KAGRA S250818k: 10 GHz VLA observations of AT2025ulz
  9. GRB 250821A: Prompt enhanced Swift-XRT position
  10. GRB 250821A: Swift detection of a burst
  11. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  12. EP250821a: Einstein Probe detection of an X-ray transient
  13. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  14. GRB 250819A: Insight-HXMT detection
  15. GRB 250818B: 10 GHz VLA detection
  16. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  17. LIGO/Virgo/KAGRA S250818k: Multi-band Gemini GMOS Detections
  18. GRB 250814A: Swift/UVOT Upper Limits
  19. GRB 250813B: Swift/UVOT Upper Limit
  20. IPN triangulation of GRB 250816A (short)
  21. IPN triangulation of GRB 250814C (short)
  22. IPN triangulation of GRB 250804B (short)
  23. GRB 250818B: Kilonova-Catcher optical afterglow detection
  24. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  25. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  26. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  27. GRB 250818A: AstroSat CZTI detection
  28. GRB 250818B: Swift/UVOT Detection
  29. GRB 250820A: Fermi GBM Final Real-time Localization
  30. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  31. GRB 250818B: SAO RAS optical observations
  32. Swift GRB 250818A: Global MASTER-Net observations report
  33. GRB 250818A: Swift-XRT refined Analysis
  34. GRB 250818B: EP-FXT counterpart detection
  35. GRB 250818A: Swift-BAT refined analysis
  36. GRB 250818C: Fermi GBM Final Real-time Localization
  37. GRB 250818B: Keck redshift of the optical afterglow
  38. GRB 250818A: Swift/UVOT Upper Limits
  39. GRB 250818A: Enhanced Swift-XRT position
  40. GRB 250818A: Fermi GBM Observation
  41. GRB 250818B: SVOM/VT optical observation
  42. GRB 250814A: Further GRAWITA TNG NIR observations
  43. GRB 250818B: Swift-XRT afterglow detection
  44. GRB 250818B: SVOM detection of a short burst
  45. GRB 250818A: Swift detection of a burst
  46. GRB 250818A: Fermi GBM Final Real-time Localization
  47. sb25081602: Swift-XRT observations
  48. SVOM/sb25081602: detection of a likely X-ray transient
  49. GRB 250816A: Fermi GBM Final Real-time Localization
  50. GRB 250814A: Swift-BAT refined analysis
  51. GRB 250815A: Fermi GBM Final Localization
  52. GRB 250814A: Further COLIBRÍ optical upper limit
  53. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  54. GRB 250814A: GRAWITA TNG NIR observations
  55. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  56. GRB250814A: TRT optical upper limits
  57. GRB 250814C: SVOM/GRM observation of a short burst
  58. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  59. GRB 250813B: SVOM/GRM observation
  60. GRB 250814A: P200/WIRC observations of the afterglow candidate
  61. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  62. GRB 250814A: KAIT optical upper limit
  63. GRB 250814A: Swift-XRT refined Analysis
  64. GRB 240814A: Fermi GBM Observation
  65. GRB 250814A: Possible afterglow candidate from P200/WIRC
  66. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  67. Swift GRB250814.32: Global MASTER-Net observations report
  68. GRB 250814A: J-band upper limit from WINTER
  69. GRB 250813B: SVOM/VT optical observations
  70. GRB 250814A: COLIBRÍ optical upper limit
  71. GRB 250814B: Fermi GBM Final Real-time Localization
  72. GRB 250813A: AstroSat CZTI detection
  73. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  74. GRB 250813B: VLT X-shooter spectroscopic redshift z = 1.752
  75. GRB 250814A: DDOTI Optical Upper Limit
  76. GRB 250813B: EP-FXT counterpart detection
  77. GRB 250813B: Swift-XRT afterglow detection
  78. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  79. GRB 250814A: Fermi GBM Final Real-time Localization
  80. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  81. GRB 250813B: Ondrejov D50 optical afterglow detection
  82. GRB 250813B: SVOM detection of a bright long burst
  83. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  84. GRB250812a: STEP/T80S Indication of slow decay of afterglow
  85. EP250812a: NOT, NTT, and GS observations
  86. GRB 250812A: Swift/UVOT Detection
  87. GRB 250813A: Fermi GBM Final Localization
  88. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  89. EP250812a: Liverpool Telescope upper limits
  90. EP250812a: SVOM/VT optical counterpart
  91. IceCube-250813A - IceCube observation of a high-energy neutrino candidate track-like event
  92. GRB 250812A: EP-FXT counterpart detection
  93. GRB 250812A: Swift ToO observations
  94. GRB 250807B: Swift-BAT refined analysis
  95. EP 250812a: GOTO optical upper limit
  96. GRB 250812A: Kilonova-Catcher optical afterglow detection
  97. EP250812a: Swift-XRT counterpart detection
  98. EP250812a: Einstein Probe detection of an X-ray transient
  99. GRB 250812A: SVOM/VT optical afterglow confirmation
  100. GRB 250812A: Swift-XRT afterglow detection

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