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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"

23572 results found.

  1. GRB 250702F: COLIBRÍ Observations of the Afterglow
  2. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  3. GRB 250702F: GOTO optical counterpart detection
  4. GRB 250702F: Ondrejov D50 optical afterglow detection
  5. GRB 250702F: Swift detection of a burst with an optical counterpart
  6. Konus-Wind detection of GRB 250627A
  7. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  8. GRB 250628B: Swift-XRT observations
  9. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  10. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  11. GRB 250628A: REM optical/NIR upper limits
  12. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  13. GRB 250628A: Swift/UVOT Upper Limits
  14. GRB 250628A: Swift-XRT refined Analysis
  15. Swift GRB 250628A: Global MASTER-Net observations report
  16. GRB 250628A: Swift detection of a burst
  17. GRB 250625A: Swift-BAT refined analysis
  18. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  19. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  20. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  21. GRB 250625A: Swift/UVOT Upper Limits
  22. GRB 250625A: ABObservatory afterglow detection
  23. GRB 250625A: OHP/T193 optical detection
  24. GRB 250625A: COLIBRÍ optical observations
  25. GRB 250625A: Swift-XRT refined Analysis
  26. Swift GRB 250625A: Global MASTER-Net observations report
  27. GRB 250625A: NOT z-band upper limit
  28. GRB 250625A: SAO RAS possible optical afterglow
  29. GRB 250625A: Swift detection of a burst
  30. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  31. GRB 250620A: AstroSat CZTI detection
  32. GRB 250620C: AstroSat CZTI detection
  33. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  34. GRB 250521A: VZLUSAT-2 detection
  35. GRB 250617B: Swift-BAT refined analysis
  36. Konus-Wind detection of GRB 250620C
  37. IPN triangulation of GRB 250620C (long/bright)
  38. GRB 250506A - SVOM/ECLAIRs Refined analysis
  39. GRB 250617B: Nickel telescope optical observations
  40. GRB 250615A: Kilonova-Catcher optical upper limits
  41. GRB 250617B: Assy AZT-20 Optical Observations
  42. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  43. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  44. GRB 250617B: Swift/UVOT Detection
  45. GRB 250617B: Kilonova-Catcher optical afterglow detection
  46. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  47. GRB 250617B: COLIBRÍ optical observations
  48. GRB 250617B: Swift-XRT refined Analysis
  49. GRB 250617B: NUTTelA-TAO early time optical observations
  50. GRB 250617B: GOTO optical upper limit
  51. GRB 250615A: Swift-BAT refined analysis
  52. The EP-WXT trigger 01709178990 is likely a flaring star
  53. GRB 250617B: Ondrejov D50 optical afterglow detection
  54. GRB 250617B: SAO RAS optical observations
  55. GRB 250617B: Swift detection of a burst with an optical counterpart
  56. IPN triangulation of GRB 250612C (short/hard)
  57. EP#01709178975: Swift-XRT counterpart detection
  58. EP-WXT trigger 01709178975: GOTO optical upper limit
  59. Konus-Wind detection of GRB 250615A / EP250615a
  60. GRB 250615A / EP250615a: AstroSat CZTI detection
  61. GRB 250615A: COLIBRÍ optical upper limit
  62. GRB 250615A: DDOTI Optical Upper Limit
  63. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  64. GRB 250615A: Swift-XRT refined Analysis
  65. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  66. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  67. sb25061207: Mephisto optical upper limits
  68. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  69. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  70. sb25061218: Swift-XRT observations
  71. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  72. sb25061207: EP-FXT follow-up observation and afterglow candidate
  73. sb25061207: Swift-XRT observations
  74. EP250610a: Upper limit from Fermi-GBM Observations
  75. GRB 250610B - SVOM/ECLAIRs refined analysis
  76. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  77. EP250610A: Swift/UVOT Upper limits
  78. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  79. EP250610a: TNG NIR upper limit
  80. GRB 250610B: REM optical/NIR observations
  81. GRB 250610B: Swift-XRT counterpart detection
  82. GRB 250610B: GOTO optical upper limit
  83. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  84. GRB 250605A: Swift-BAT refined analysis
  85. EP250610a: REM optical/NIR observations
  86. GRBAlpha reentry on June 9, 2025
  87. EP250610a: Swift-XRT counterpart detection
  88. EP250610a: COLIBRÍ optical upper limit
  89. GRB 250605A: Swift/UVOT Upper Limits
  90. The EP-WXT trigger 01709178283 is likely a flaring star
  91. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  92. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  93. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  94. GRB 250605A: Swift-XRT refined Analysis
  95. EP/WXT 01709177873: GOTO observations confirm stellar variability
  96. GRB 250606A: Fermi GBM Final Real-time Localization
  97. GRB 250605A: Swift detection of a burst
  98. Konus-Wind detection of GRB 250601A
  99. IPN triangulation of GRB 250529A
  100. GRB 250601A: PRIME H band upper limit.

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