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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"

4254 results found.

  1. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  2. GRB 250919A: SVOM/GRM observation of a very bright GRB
  3. EP250919a: Global MASTER-Net observations report
  4. GRB 250916A: Fermi GBM Observation
  5. GRB 250916A: further SAO RAS optical observations
  6. GRB 250916A: Glowbug gamma-ray detection
  7. GRB 250917B: Swift detection of a short burst
  8. GRB 250916A: AstroSat CZTI detection of a bright long burst
  9. GRB 250916A: Fermi GBM Final Real-time Localization
  10. GRB 250911A: Insight-HXMT detection
  11. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  12. GRB 250911A: GECAM-B detection
  13. GRB 250911A: Swift-BAT refined analysis
  14. GRB 250910B: SVOM/GRM observation
  15. EP250911a: Swift-XRT observations
  16. EP250911a: COLIBRÍ optical observations
  17. Fermi GRB 250910B: Global MASTER-Net observations report
  18. EP250911a: LCO optical counterpart discovery
  19. EP250910a: Global MASTER-Net observations report
  20. EP#01709240653: Swift-XRT observations
  21. EP250908c: SVOM/VT optical observation
  22. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  23. EP250908b: SVOM/VT optical candidate
  24. EP250908c: Global MASTER-Net observations report
  25. EP250905b: Global MASTER-Net observations report
  26. IceCube Alert 250905.84: Global MASTER-Net observations report
  27. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  28. GRB 250902A: VZLUSAT-2 detection
  29. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  30. Fermi GRB 250902B: Global MASTER-Net observations report
  31. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  32. EP250827b: Swift observations of AT 2025wkm
  33. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  34. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  35. GRB 250831A: SVOM detection of a soft burst
  36. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  37. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  38. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  39. The EP-WXT trigger 01709200994 is likely a flaring star
  40. EP250821a: SOAR observations
  41. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  42. EP250828a: Liverpool Telescope upper limits
  43. Swift GRB 250828B: Global MASTER-Net observations report
  44. EP250828a: Global MASTER-Net observations report
  45. EP250827a: Swift/UVOT Detection
  46. Fermi GRB 250827A: Global MASTER-Net observations report
  47. EP250827a: Swift-XRT counterpart detection
  48. EP250827a: Global MASTER-Net observations report
  49. EP250827a: Gemini-South optical counterpart detection
  50. Fermi GRB 250824B: Global MASTER-Net observations report
  51. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  52. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  53. EP250821a: Einstein Probe detection of an X-ray transient
  54. LIGO/Virgo/KAGRA S250818k: Multi-band Gemini GMOS Detections
  55. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  56. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  57. Fermi trigger No 776849714: Global MASTER-Net observations report
  58. GRB 250818B: SVOM detection of a short burst
  59. GRB 250815A: Fermi GBM Final Localization
  60. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  61. GRB 250814A: Possible afterglow candidate from P200/WIRC
  62. Fermi trigger No 776818276: Global MASTER-Net observations report
  63. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  64. IceCube Alert 250813.14: Global MASTER-Net observations report
  65. Fermi GRB 250808A: Global MASTER-Net observations report
  66. Swift GRB250807.65: Global MASTER-Net observations report
  67. The EP-WXT trigger 01709198251 is likely a flaring star
  68. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  69. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  70. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  71. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  72. GRB 250728A: COLIBRÍ optical upper limit
  73. Fermi trigger No 775387550: Global MASTER-Net observations report
  74. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
  75. GRB 250727A: EP-FXT counterpart detection
  76. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  77. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  78. Swift GRB 250725A: Global MASTER-Net OT detection
  79. Fermi GRB 250725A: Global MASTER-Net observations report
  80. Swift GRB 250725A: Global MASTER-Net observations report
  81. GRB 250721A: MAXI/GSC detection
  82. Fermi trigger No 774730635: Global MASTER-Net observations report
  83. GRB 270713A: Kitab and AbAO Optical Observations
  84. Konus-Wind detection of GRB 250716A
  85. GRB 250716A: GOTO tentative optical counterpart candidate
  86. GRB 250716A: Fermi GBM Observation
  87. GRB 250716A: Fermi GBM Final Real-time Localization
  88. GRB 250706B/C: 7DT Follow-up Observations
  89. Fermi GRB 250711A: Global MASTER-Net observations report
  90. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  91. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  92. IceCube-250706A: Global MASTER-Net observations report
  93. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  94. GRB 250702F: Fermi GBM Observation
  95. GRB 250702F: Leavitt Observatory optical observations
  96. EP250702a: Global MASTER-Net observations report
  97. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  98. Fermi GRB 250702F: Global MASTER-Net observations report
  99. Fermi GRB 250702C: Global MASTER-Net observations report
  100. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB

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