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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"

3136 results found.

  1. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  2. Fermi trigger No 776818276: Global MASTER-Net observations report
  3. GRB 250813A: AstroSat CZTI detection
  4. IceCube Alert 250813.14: Global MASTER-Net observations report
  5. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  6. GRB 250809A: LCOGT Optical Upper Limits
  7. Fermi GRB 250808A: Global MASTER-Net observations report
  8. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  9. GRB 250807A: AstroSat CZTI detection of bright long burst
  10. EP250802a: EP-FXT follow-up observation
  11. GRB 250805A: SVOM/VT optical counterpart
  12. GRB 250804B: Swift-XRT observations
  13. GRB 250804C: AstroSat CZTI detection of a long burst
  14. EP250802a: Liverpool Telescope optical upper limits
  15. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  16. EP250730a: Global MASTER-Net observations report
  17. GRB 250725A: AstroSat CZTI detection
  18. Fermi trigger No 775387550: Global MASTER-Net observations report
  19. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  20. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  21. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  22. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  23. GRB 250713A : SVOM/ECLAIRs refined analysis
  24. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  25. EP250711a: Global MASTER-Net observations report
  26. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  27. EP250711a: NOT optical counterpart candidate
  28. Fermi GRB 250711A: Global MASTER-Net observations report
  29. GRB 250704A: SVOM/ECLAIRs refined analysis
  30. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  31. IceCube-250708A: No Candidates from WINTER
  32. IceCube-250706A: No Candidates from WINTER
  33. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  34. IceCube-250706A: COLIBRÍ optical upper limits
  35. GRB 250706B: SVOM detection of a long burst
  36. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  37. IPN triangulation of GRB 250703A
  38. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  39. GRB 250704A: SVOM detection of a burst
  40. GRB 250702F: AKO Optical Afterglow Detection
  41. EP250702a: Global MASTER-Net observations report
  42. Fermi GRB 250702F: Global MASTER-Net observations report
  43. Fermi GRB 250702C: Global MASTER-Net observations report
  44. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  45. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  46. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  47. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  48. Fermi GRB 250626A: Global MASTER-Net observations report
  49. GRB 250625A: ABObservatory afterglow detection
  50. GRB 250625A: COLIBRÍ optical observations
  51. GRB 250620A: AstroSat CZTI detection
  52. GRB 250620C: AstroSat CZTI detection
  53. Fermi GRB 250623A: Global MASTER-Net observations report
  54. Fermi GRB 250621A: Global MASTER-Net observations report
  55. Fermi trigger No 772058337: Global MASTER-Net observations report
  56. GRB 250617B: SAO RAS optical observations
  57. GRB 250615A / EP250615a: AstroSat CZTI detection
  58. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  59. Fermi trigger No 771752663: Global MASTER-Net observations report
  60. Swift GRB 250615A: Global MASTER-Net observations report
  61. Fermi trigger No 771424081: Global MASTER-Net observations report
  62. EP250612a: Global MASTER-Net observations report
  63. Swift GRB250612.04: Global MASTER-Net observations report
  64. GRB 250610C: Fermi GBM Final Real-time Localization
  65. EP250610a: Global MASTER-Net observations report
  66. Fermi trigger No 771072240: Global MASTER-Net observations report
  67. GRB 250607A: Fermi GBM Final Localization
  68. Fermi GRB 250606A: Global MASTER-Net observations report
  69. Fermi trigger No 770867684: Global MASTER-Net observations report
  70. GRB 250605A: Swift detection of a burst
  71. Fermi GRB 250601A: Global MASTER-Net observations report
  72. GRB 250601A: Fermi GBM Final Real-time Localization
  73. GRB 250530C: BOOTES-7 optical upper limit
  74. GRB 250530C: Swift detection of a burst
  75. GRB 250529A: Fermi GBM Final Real-time Localization
  76. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  77. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  78. Fermi trigger No 769611916: Global MASTER-Net observations report
  79. GRB 250520A: GRBAlpha detection
  80. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  81. Konus-Wind detection of GRB 250520A (short/hard)
  82. GRB 250520B: Fermi GBM Final Real-time Localization
  83. GRB 250520A: COLIBRÍ optical upper limit
  84. GRB 250520A: AstroSat CZTI detection of a short burst
  85. GRB 250520A: SVOM/GRM observation
  86. GRB 250520A: Swift detection of a burst
  87. Fermi GRB 250516A: Global MASTER-Net observations report
  88. GRB 250516A: AstroSat CZTI detection
  89. MAXI GRB250515.65: Global MASTER-Net observations report
  90. GRB 250424A: COLIBRÍ detection of the associated supernova
  91. GRB 250507B: AstroSat CZTI detection
  92. GRB 250512A: Fermi GBM Final Real-time Localization
  93. EP250511a: COLIBRÍ optical counterpart candidate
  94. Fermi GRB 250510C: Global MASTER-Net observations report
  95. Fermi GRB 250509A: Global MASTER-Net observations report
  96. GRB 250509A: Swift detection of a burst
  97. GRB 250430A / EP250430a: AstroSat CZTI detection
  98. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  99. GRB 250504A: MeerLICHT optical afterglow detection
  100. Fermi GRB 250504A: Global MASTER-Net observations report

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