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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"

3051 results found.

  1. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  2. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  3. Fermi GRB 251103A: Global MASTER-Net observations report
  4. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  5. GRB 251102A: AstroSat CZTI detection
  6. GRB 251103A: Fermi GBM Final Localization
  7. GRB 251102B: Fermi GBM Final Real-time Localization
  8. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  9. GRB 251025C: AstroSat CZTI detection
  10. Fermi GRB 251026B: Global MASTER-Net observations report
  11. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  12. GRB 251025A (sb25102501): Likely a stellar flare by SVOM/VT
  13. GRB 251023C: AstroSat CZTI detection
  14. EP251023b: Global MASTER-Net observations report
  15. IPN triangulation of GRB 251016B
  16. GRB 251023B / MAXI J0451+122: MAXI/GSC detection
  17. Fermi GRB 251023A: Global MASTER-Net observations report
  18. LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate
  19. GRB 251016A: Fermi GBM Observation
  20. GRB 251018A: Fermi GBM Observation
  21. IceCube-251018A: Global MASTER-Net observations report
  22. LIGO/Virgo/KAGRA S251018bi: Identification of a GW compact binary merger candidate
  23. GRB 251016A: AstroSat CZTI detection of a short burst
  24. GRB 251016B: AstroSat CZTI detection
  25. GRB 251017A: Swift detection of a burst with an optical counterpart
  26. Fermi GRB 251016A: Global MASTER-Net observations report
  27. GRB 251013C: SVOM/ECLAIRs refined analysis
  28. GRB 251013D: Fermi GBM Observation
  29. GRB 251013C: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an bright optical counterpart
  30. LIGO/Virgo/KAGRA S251014cn: Identification of a GW compact binary merger candidate
  31. GRB 251013C: J band observations by SYSU 80cm infrared telescope
  32. GRB 251013C: AstroSat CZTI detection
  33. Fermi trigger No 782044789: Global MASTER-Net observations report
  34. Fermi GRB 251013C: Global MASTER-Net observations report
  35. GRB 251013C: BOOTES-6 early optical detection
  36. GRB 251013C: SVOM/VT optical observation
  37. GRB 251013C: SVOM detection of a burst
  38. LIGO/Virgo/KAGRA S251013x: Identification of a GW compact binary merger candidate
  39. GRB 251010A: AstroSat CZTI detection
  40. GRB 251011A: AstroSat CZTI detection
  41. EP251006a: Global MASTER-Net observations report
  42. IceCube Alert 251008A: Global MASTER-Net observations report
  43. GRB 251007A: AstroSat CZTI detection
  44. GRB 251007B: SVOM detection of a faint burst
  45. GRB 251006B/EP251006a: SVOM/VT optical candidate
  46. LIGO/Virgo/KAGRA S251006dd: Identification of a GW compact binary merger candidate
  47. Fermi GRB 251006A: Global MASTER-Net observations report
  48. GRB 251005C: AstroSat CZTI detection
  49. GRB 251001A: AstroSat CZTI detection
  50. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  51. GRB 251002A: SVOM detection of a burst
  52. Fermi GRB 251002A: Global MASTER-Net observations report
  53. Fermi GRB 250929A: Global MASTER-Net observations report
  54. LIGO/Virgo/KAGRA S250929c: Identification of a GW compact binary merger candidate
  55. LIGO/Virgo/KAGRA S250927cy: Identification of a GW compact binary merger candidate
  56. GRB 250926A: AstroSat CZTI detection
  57. GRB 250925A: Leavitt Observatory optical upper limit
  58. GRB 250924A: SAO RAS optical observations
  59. GRB 250924A: AstroSat CZTI detection
  60. GRB 250914A: AstroSat CZTI detection
  61. GRB 250920B: AstroSat CZTI detection
  62. GRB 250922C: AstroSat CZTI detection of a short burst
  63. Fermi trigger No 780156732: Global MASTER-Net observations report
  64. Swift GRB 250920C: Global MASTER-Net observations report
  65. Konus-Wind detection of GRB 250919A
  66. GRB 250920A: AstroSat CZTI detection
  67. EP250919a: Global MASTER-Net observations report
  68. Fermi GRB 250919A: Global MASTER-Net observations report
  69. GRB 250916A: SAO RAS optical observations
  70. GRB250917B: WFST optical observations
  71. GRB 250916A: AstroSat CZTI detection of a bright long burst
  72. Fermi GRB 250916A: Global MASTER-Net observations report
  73. Fermi GRB 250912A: Global MASTER-Net observations report
  74. EP250911a: Global MASTER-Net observations report
  75. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  76. Fermi GRB 250910B: Global MASTER-Net observations report
  77. EP250910a: Global MASTER-Net observations report
  78. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  79. GRB 250909B: AstroSat CZTI detection of a long burst
  80. GRB 250909A: AstroSat CZTI detection
  81. The EP-WXT trigger EP250908a/01709240652 is not a real source
  82. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  83. IceCube Alert 250905.84: Global MASTER-Net observations report
  84. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  85. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  86. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  87. EP250901a: Mondy, Assy and SAO RAS optical limits
  88. GRB 250902B: AstroSat CZTI detection
  89. Fermi GRB 250902B: Global MASTER-Net observations report
  90. EP250901a: Swift-XRT observations
  91. GRB 250901A: LCO optical upper limit
  92. EP250827b: Swift observations of AT 2025wkm
  93. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  94. EP250901a: Global MASTER-Net observations report
  95. GRB 250830C: AstroSat CZTI detection of a long burst
  96. EP250831a: Global MASTER-Net observations report
  97. EP250830a: Global MASTER-Net observations report
  98. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  99. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  100. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate

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