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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"

2850 results found.

  1. GRB 250826A: Fermi GBM Final Real-time Localization
  2. Fermi GRB 250824B: Global MASTER-Net observations report
  3. GRB 250821B: AstroSat CZTI detection
  4. GRB 250819A: AstroSat CZTI detection
  5. LIGO/Virgo/KAGRA S250818k: GRAWITA TNG NIR observations of AT2025ulz
  6. GRB 250821C: Fermi GBM Final Real-time Localization
  7. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  8. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  9. GRB 250818A: AstroSat CZTI detection
  10. LIGO/Virgo/KAGRA S250818k: Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  11. GRB 250818C: Fermi GBM Final Real-time Localization
  12. Fermi trigger No 776849714: Global MASTER-Net observations report
  13. LIGO/Virgo/KAGRA S250818t: Identification of a GW compact binary merger candidate
  14. GRB 250813B: Liverpool Telescope optical upper limits
  15. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  16. Fermi trigger No 776818276: Global MASTER-Net observations report
  17. GRB 250813A: AstroSat CZTI detection
  18. IceCube Alert 250813.14: Global MASTER-Net observations report
  19. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  20. GRB 250809A: LCOGT Optical Upper Limits
  21. Fermi GRB 250808A: Global MASTER-Net observations report
  22. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  23. GRB 250807A: AstroSat CZTI detection of bright long burst
  24. EP250802a: EP-FXT follow-up observation
  25. GRB 250805A: SVOM/VT optical counterpart
  26. GRB 250804B: Swift-XRT observations
  27. GRB 250804C: AstroSat CZTI detection of a long burst
  28. EP250802a: Liverpool Telescope optical upper limits
  29. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  30. EP250730a: Global MASTER-Net observations report
  31. GRB 250725A: AstroSat CZTI detection
  32. Fermi trigger No 775387550: Global MASTER-Net observations report
  33. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  34. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  35. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  36. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  37. GRB 250713A : SVOM/ECLAIRs refined analysis
  38. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  39. EP250711a: Global MASTER-Net observations report
  40. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  41. EP250711a: NOT optical counterpart candidate
  42. Fermi GRB 250711A: Global MASTER-Net observations report
  43. GRB 250704A: SVOM/ECLAIRs refined analysis
  44. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  45. IceCube-250708A: No Candidates from WINTER
  46. IceCube-250706A: No Candidates from WINTER
  47. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  48. IceCube-250706A: COLIBRÍ optical upper limits
  49. GRB 250706B: SVOM detection of a long burst
  50. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  51. IPN triangulation of GRB 250703A
  52. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  53. GRB 250704A: SVOM detection of a burst
  54. GRB 250702F: AKO Optical Afterglow Detection
  55. EP250702a: Global MASTER-Net observations report
  56. Fermi GRB 250702F: Global MASTER-Net observations report
  57. Fermi GRB 250702C: Global MASTER-Net observations report
  58. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  59. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  60. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  61. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  62. Fermi GRB 250626A: Global MASTER-Net observations report
  63. GRB 250625A: ABObservatory afterglow detection
  64. GRB 250625A: COLIBRÍ optical observations
  65. GRB 250620A: AstroSat CZTI detection
  66. GRB 250620C: AstroSat CZTI detection
  67. Fermi GRB 250623A: Global MASTER-Net observations report
  68. Fermi GRB 250621A: Global MASTER-Net observations report
  69. Fermi trigger No 772058337: Global MASTER-Net observations report
  70. GRB 250617B: SAO RAS optical observations
  71. GRB 250615A / EP250615a: AstroSat CZTI detection
  72. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  73. Fermi trigger No 771752663: Global MASTER-Net observations report
  74. Swift GRB 250615A: Global MASTER-Net observations report
  75. Fermi trigger No 771424081: Global MASTER-Net observations report
  76. EP250612a: Global MASTER-Net observations report
  77. Swift GRB250612.04: Global MASTER-Net observations report
  78. GRB 250610C: Fermi GBM Final Real-time Localization
  79. EP250610a: Global MASTER-Net observations report
  80. Fermi trigger No 771072240: Global MASTER-Net observations report
  81. GRB 250607A: Fermi GBM Final Localization
  82. Fermi GRB 250606A: Global MASTER-Net observations report
  83. Fermi trigger No 770867684: Global MASTER-Net observations report
  84. GRB 250605A: Swift detection of a burst
  85. Fermi GRB 250601A: Global MASTER-Net observations report
  86. GRB 250601A: Fermi GBM Final Real-time Localization
  87. GRB 250530C: BOOTES-7 optical upper limit
  88. GRB 250530C: Swift detection of a burst
  89. GRB 250529A: Fermi GBM Final Real-time Localization
  90. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  91. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  92. Fermi trigger No 769611916: Global MASTER-Net observations report
  93. GRB 250520A: GRBAlpha detection
  94. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  95. Konus-Wind detection of GRB 250520A (short/hard)
  96. GRB 250520B: Fermi GBM Final Real-time Localization
  97. GRB 250520A: COLIBRÍ optical upper limit
  98. GRB 250520A: AstroSat CZTI detection of a short burst
  99. GRB 250520A: SVOM/GRM observation
  100. GRB 250520A: Swift detection of a burst

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