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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"

4900 results found.

  1. IceCube-251025A: DDOTI Optical Upper Limit
  2. GRB 251025B: MASTER OT detection
  3. GRB 251025B: SVOM detection of a burst
  4. GRB 251023C: Glowbug gamma-ray detection
  5. GRB 251024A: LCOGT Optical Afterglow Detection
  6. Swift GRB 251024A: Global MASTER-Net observations report
  7. GRB 251023B / EP251023b: COLIBRÍ Confirmation of the Fading Nature of the Optical Candidate
  8. GRB 251022A: COLIBRÍ Further Multi-frequency Optical Observations
  9. GRB 251023B: OHP/T193 optical observations
  10. EP251023a: OHP/T193 optical observations
  11. GRB 251023C: AstroSat CZTI detection
  12. EP251023b: Global MASTER-Net observations report
  13. GRB 251023C: CALET Gamma-Ray Burst Monitor detection
  14. GRB 251023C: Swift/BAT-GUANO localization skymap of a burst
  15. EP251023a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at Teide Observatory
  16. Fermi GRB 251023A: Global MASTER-Net observations report
  17. GRB 251018A: Swift-XRT refined Analysis
  18. IceCube-251018A: Global MASTER-Net observations report
  19. GRB 251016A: VLT/FORS2 Optical Observation
  20. GRB 251017A: Swift-XRT refined Analysis
  21. GRB 251018A: MASTER OT detection
  22. Swift GRB 251018A: Global MASTER-Net observations report
  23. Fermi GRB 251016B: Global MASTER-Net observations report
  24. sb25101602: Swift-XRT counterpart detection
  25. Fermi GRB 251016A: Global MASTER-Net observations report
  26. GRB 251014A: Swift-XRT observations
  27. Upper limits from a search for additional neutrino events in IceCube
  28. GRB 251014B: VLT/FORS2 Optical Observation
  29. LIGO/Virgo/KAGRA S251014cn: Identification of a GW compact binary merger candidate
  30. GRB 251014A: Swift detection of a possibly-short burst
  31. GRB 251014A: Fermi GBM Final Real-time Localization
  32. GRB 251013C: NOT spectroscopic redshift z = 0.572
  33. GRB 251013B: SVOM/GRM observation
  34. GRB 251013B: Fermi GBM Final Real-time Localization
  35. GRB 251011B: Swift-XRT refined Analysis
  36. Fermi Gamma-ray Burst Monitor trigger 781824269/251010892 is not a GRB
  37. EP251006a: Global MASTER-Net observations report
  38. GRB 251007A: Swift-XRT refined Analysis
  39. GRB 251007B: Swift-XRT refined Analysis
  40. Swift GRB 251007B: Global MASTER-Net observations report
  41. GRB 251007A: Swift detection of a burst with an optical counterpart
  42. GRB 251006B: SVOM/GRM observation
  43. Fermi GRB 251006B: Global MASTER-Net observations report
  44. GRB 251005C: VLT/X-shooter Imaging
  45. GRB 251005C: Swift-XRT refined Analysis
  46. GRB 251003A: Swift-XRT refined Analysis
  47. GRB 251002A: Swift-XRT afterglow detection
  48. GRB 251002A: FRAM-ORM afterglow detection
  49. GRB 251001B: Swift-XRT refined Analysis
  50. GRB 250930A: SVOM/GRM observation
  51. LIGO/Virgo/KAGRA S250927ck: Identification of a GW compact binary merger candidate
  52. GRB 250925A: Mondy and AbAO optical observations
  53. Fermi GRB 250926A: Global MASTER-Net observations report
  54. GRB 250924A: 1.6m Mephisto optical upper limits
  55. GRB 250924A: SAO RAS optical observations
  56. GRB 250924A: AstroSat CZTI detection
  57. GRB 250924A: Swift-XRT refined Analysis
  58. GRB 250924A: GROWTH-India Telescope Upper Limits
  59. GRB 250924A: Mondy optical observations, afterglow fading
  60. GRB 250924B: Fermi GBM Final Localization
  61. GRB 250924A: COLIBRÍ optical observations
  62. Swift GRB 250924A: Global MASTER-Net observations report
  63. GRB 250924A: DDOTI Detection of the Optical Counterpart
  64. Fermi trigger No 780156732: Global MASTER-Net observations report
  65. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  66. GRB 250920B: Swift-XRT refined Analysis
  67. GRB 250919A/EP250919a: SVOM/VT optical observation
  68. EP250916a: EP-FXT follow-up observation
  69. GRB 250917B: Fermi GBM Observation
  70. Fermi GRB 250917B: Global MASTER-Net observations report
  71. GRB 250916A: GOTO optical counterpart candidate
  72. GRB 250916A: AstroSat CZTI detection of a bright long burst
  73. GRB 250912A: SVOM detection of a burst
  74. GRB 250911A: Swift-XRT refined Analysis
  75. EP250911a: Optical detection with Kinder observations
  76. Fermi GRB 250910B: Global MASTER-Net observations report
  77. EP250910a: Global MASTER-Net observations report
  78. GRB 250903A: SVOM/ECLAIRs refined analysis
  79. EP250908C: GROND observation of the fading optical counterpart
  80. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  81. GRB 250905A: Swift-XRT refined Analysis
  82. IceCube Alert 250905.84: Global MASTER-Net observations report
  83. GRB 250904A: Swift-XRT refined Analysis
  84. GRB 250903A: Swift-XRT observations
  85. The EP-WXT trigger 01709201209 is likely a flaring star
  86. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  87. GRB 250903A: SVOM detection of a burst
  88. Fermi GRB 250902B: Global MASTER-Net observations report
  89. GRB 250901A: Swift-XRT afterglow detection
  90. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  91. EP250827b: FTW Observations of AT 2025wkm
  92. EP250831a: Swift-XRT observations
  93. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  94. GRB 250831A: Swift-XRT counterpart detection
  95. EP250830a: Global MASTER-Net observations report
  96. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  97. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  98. EP250828a: Optical counterpart detection with Kinder observations
  99. GRB 250828B: Swift detection of a burst
  100. GRID detection of GRB 250824A

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