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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"

23576 results found.

  1. EP250702a: Global MASTER-Net observations report
  2. GRB 250702F: DDOTI Optical Observation
  3. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  4. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  5. GRB 250702F: COLIBRÍ Observations of the Afterglow
  6. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  7. GRB 250702F: GOTO optical counterpart detection
  8. GRB 250702F: Ondrejov D50 optical afterglow detection
  9. GRB 250702F: Swift detection of a burst with an optical counterpart
  10. Konus-Wind detection of GRB 250627A
  11. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  12. GRB 250628B: Swift-XRT observations
  13. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  14. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  15. GRB 250628A: REM optical/NIR upper limits
  16. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  17. GRB 250628A: Swift/UVOT Upper Limits
  18. GRB 250628A: Swift-XRT refined Analysis
  19. Swift GRB 250628A: Global MASTER-Net observations report
  20. GRB 250628A: Swift detection of a burst
  21. GRB 250625A: Swift-BAT refined analysis
  22. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  23. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  24. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  25. GRB 250625A: Swift/UVOT Upper Limits
  26. GRB 250625A: ABObservatory afterglow detection
  27. GRB 250625A: OHP/T193 optical detection
  28. GRB 250625A: COLIBRÍ optical observations
  29. GRB 250625A: Swift-XRT refined Analysis
  30. Swift GRB 250625A: Global MASTER-Net observations report
  31. GRB 250625A: NOT z-band upper limit
  32. GRB 250625A: SAO RAS possible optical afterglow
  33. GRB 250625A: Swift detection of a burst
  34. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  35. GRB 250620A: AstroSat CZTI detection
  36. GRB 250620C: AstroSat CZTI detection
  37. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  38. GRB 250521A: VZLUSAT-2 detection
  39. GRB 250617B: Swift-BAT refined analysis
  40. Konus-Wind detection of GRB 250620C
  41. IPN triangulation of GRB 250620C (long/bright)
  42. GRB 250506A - SVOM/ECLAIRs Refined analysis
  43. GRB 250617B: Nickel telescope optical observations
  44. GRB 250615A: Kilonova-Catcher optical upper limits
  45. GRB 250617B: Assy AZT-20 Optical Observations
  46. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  47. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  48. GRB 250617B: Swift/UVOT Detection
  49. GRB 250617B: Kilonova-Catcher optical afterglow detection
  50. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  51. GRB 250617B: COLIBRÍ optical observations
  52. GRB 250617B: Swift-XRT refined Analysis
  53. GRB 250617B: NUTTelA-TAO early time optical observations
  54. GRB 250617B: GOTO optical upper limit
  55. GRB 250615A: Swift-BAT refined analysis
  56. The EP-WXT trigger 01709178990 is likely a flaring star
  57. GRB 250617B: Ondrejov D50 optical afterglow detection
  58. GRB 250617B: SAO RAS optical observations
  59. GRB 250617B: Swift detection of a burst with an optical counterpart
  60. IPN triangulation of GRB 250612C (short/hard)
  61. EP#01709178975: Swift-XRT counterpart detection
  62. EP-WXT trigger 01709178975: GOTO optical upper limit
  63. Konus-Wind detection of GRB 250615A / EP250615a
  64. GRB 250615A / EP250615a: AstroSat CZTI detection
  65. GRB 250615A: COLIBRÍ optical upper limit
  66. GRB 250615A: DDOTI Optical Upper Limit
  67. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  68. GRB 250615A: Swift-XRT refined Analysis
  69. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  70. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  71. sb25061207: Mephisto optical upper limits
  72. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  73. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  74. sb25061218: Swift-XRT observations
  75. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  76. sb25061207: EP-FXT follow-up observation and afterglow candidate
  77. sb25061207: Swift-XRT observations
  78. EP250610a: Upper limit from Fermi-GBM Observations
  79. GRB 250610B - SVOM/ECLAIRs refined analysis
  80. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  81. EP250610A: Swift/UVOT Upper limits
  82. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  83. EP250610a: TNG NIR upper limit
  84. GRB 250610B: REM optical/NIR observations
  85. GRB 250610B: Swift-XRT counterpart detection
  86. GRB 250610B: GOTO optical upper limit
  87. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  88. GRB 250605A: Swift-BAT refined analysis
  89. EP250610a: REM optical/NIR observations
  90. GRBAlpha reentry on June 9, 2025
  91. EP250610a: Swift-XRT counterpart detection
  92. EP250610a: COLIBRÍ optical upper limit
  93. GRB 250605A: Swift/UVOT Upper Limits
  94. The EP-WXT trigger 01709178283 is likely a flaring star
  95. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  96. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  97. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  98. GRB 250605A: Swift-XRT refined Analysis
  99. EP/WXT 01709177873: GOTO observations confirm stellar variability
  100. GRB 250606A: Fermi GBM Final Real-time Localization

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