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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"

23093 results found.

  1. Konus-Wind detection of GRB 250702F
  2. EP250704a / GRB 250704B - REM observations
  3. GRB 250702F: GROWTH-India Telescope optical observations
  4. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  5. EP250704a: COLIBRÍ optical counterpart candidate
  6. GRB 250704A: REM detection of the optical afterglow
  7. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  8. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  9. GRB 250702F: Swift/UVOT Detection
  10. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  11. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  12. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  13. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  14. GRB 250702F: TRT Optical Observation
  15. GRB 250703A: DDOTI Optical Upper Limit
  16. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  17. GRB 250702F: REM optical afterglow detection
  18. EP250702a: Global MASTER-Net observations report
  19. GRB 250702F: DDOTI Optical Observation
  20. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  21. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  22. GRB 250702F: COLIBRÍ Observations of the Afterglow
  23. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  24. GRB 250702F: GOTO optical counterpart detection
  25. GRB 250702F: Ondrejov D50 optical afterglow detection
  26. GRB 250702F: Swift detection of a burst with an optical counterpart
  27. Konus-Wind detection of GRB 250627A
  28. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  29. GRB 250628B: Swift-XRT observations
  30. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  31. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  32. GRB 250628A: REM optical/NIR upper limits
  33. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  34. GRB 250628A: Swift/UVOT Upper Limits
  35. GRB 250628A: Swift-XRT refined Analysis
  36. Swift GRB 250628A: Global MASTER-Net observations report
  37. GRB 250628A: Swift detection of a burst
  38. GRB 250625A: Swift-BAT refined analysis
  39. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  40. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  41. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  42. GRB 250625A: Swift/UVOT Upper Limits
  43. GRB 250625A: ABObservatory afterglow detection
  44. GRB 250625A: OHP/T193 optical detection
  45. GRB 250625A: COLIBRÍ optical observations
  46. GRB 250625A: Swift-XRT refined Analysis
  47. Swift GRB 250625A: Global MASTER-Net observations report
  48. GRB 250625A: NOT z-band upper limit
  49. GRB 250625A: SAO RAS possible optical afterglow
  50. GRB 250625A: Swift detection of a burst
  51. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  52. GRB 250620A: AstroSat CZTI detection
  53. GRB 250620C: AstroSat CZTI detection
  54. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  55. GRB 250521A: VZLUSAT-2 detection
  56. GRB 250617B: Swift-BAT refined analysis
  57. Konus-Wind detection of GRB 250620C
  58. IPN triangulation of GRB 250620C (long/bright)
  59. GRB 250506A - SVOM/ECLAIRs Refined analysis
  60. GRB 250617B: Nickel telescope optical observations
  61. GRB 250615A: Kilonova-Catcher optical upper limits
  62. GRB 250617B: Assy AZT-20 Optical Observations
  63. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  64. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  65. GRB 250617B: Swift/UVOT Detection
  66. GRB 250617B: Kilonova-Catcher optical afterglow detection
  67. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  68. GRB 250617B: COLIBRÍ optical observations
  69. GRB 250617B: Swift-XRT refined Analysis
  70. GRB 250617B: NUTTelA-TAO early time optical observations
  71. GRB 250617B: GOTO optical upper limit
  72. GRB 250615A: Swift-BAT refined analysis
  73. The EP-WXT trigger 01709178990 is likely a flaring star
  74. GRB 250617B: Ondrejov D50 optical afterglow detection
  75. GRB 250617B: SAO RAS optical observations
  76. GRB 250617B: Swift detection of a burst with an optical counterpart
  77. IPN triangulation of GRB 250612C (short/hard)
  78. EP#01709178975: Swift-XRT counterpart detection
  79. EP-WXT trigger 01709178975: GOTO optical upper limit
  80. Konus-Wind detection of GRB 250615A / EP250615a
  81. GRB 250615A / EP250615a: AstroSat CZTI detection
  82. GRB 250615A: COLIBRÍ optical upper limit
  83. GRB 250615A: DDOTI Optical Upper Limit
  84. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  85. GRB 250615A: Swift-XRT refined Analysis
  86. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  87. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  88. sb25061207: Mephisto optical upper limits
  89. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  90. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  91. sb25061218: Swift-XRT observations
  92. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  93. sb25061207: EP-FXT follow-up observation and afterglow candidate
  94. sb25061207: Swift-XRT observations
  95. EP250610a: Upper limit from Fermi-GBM Observations
  96. GRB 250610B - SVOM/ECLAIRs refined analysis
  97. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  98. EP250610A: Swift/UVOT Upper limits
  99. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  100. EP250610a: TNG NIR upper limit

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