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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"

4252 results found.

  1. EP250919a: Global MASTER-Net observations report
  2. GRB 250916A: Fermi GBM Observation
  3. GRB 250916A: further SAO RAS optical observations
  4. GRB 250916A: Glowbug gamma-ray detection
  5. GRB 250917B: Swift detection of a short burst
  6. GRB 250916A: AstroSat CZTI detection of a bright long burst
  7. GRB 250916A: Fermi GBM Final Real-time Localization
  8. GRB 250911A: Insight-HXMT detection
  9. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  10. GRB 250911A: GECAM-B detection
  11. GRB 250911A: Swift-BAT refined analysis
  12. GRB 250910B: SVOM/GRM observation
  13. EP250911a: Swift-XRT observations
  14. EP250911a: COLIBRÍ optical observations
  15. Fermi GRB 250910B: Global MASTER-Net observations report
  16. EP250911a: LCO optical counterpart discovery
  17. EP250910a: Global MASTER-Net observations report
  18. EP#01709240653: Swift-XRT observations
  19. EP250908c: SVOM/VT optical observation
  20. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  21. EP250908b: SVOM/VT optical candidate
  22. EP250908c: Global MASTER-Net observations report
  23. EP250905b: Global MASTER-Net observations report
  24. IceCube Alert 250905.84: Global MASTER-Net observations report
  25. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  26. GRB 250902A: VZLUSAT-2 detection
  27. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  28. Fermi GRB 250902B: Global MASTER-Net observations report
  29. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  30. EP250827b: Swift observations of AT 2025wkm
  31. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  32. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  33. GRB 250831A: SVOM detection of a soft burst
  34. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  35. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  36. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  37. The EP-WXT trigger 01709200994 is likely a flaring star
  38. EP250821a: SOAR observations
  39. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  40. EP250828a: Liverpool Telescope upper limits
  41. Swift GRB 250828B: Global MASTER-Net observations report
  42. EP250828a: Global MASTER-Net observations report
  43. EP250827a: Swift/UVOT Detection
  44. Fermi GRB 250827A: Global MASTER-Net observations report
  45. EP250827a: Swift-XRT counterpart detection
  46. EP250827a: Global MASTER-Net observations report
  47. EP250827a: Gemini-South optical counterpart detection
  48. Fermi GRB 250824B: Global MASTER-Net observations report
  49. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  50. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  51. EP250821a: Einstein Probe detection of an X-ray transient
  52. LIGO/Virgo/KAGRA S250818k: Multi-band Gemini GMOS Detections
  53. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  54. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  55. Fermi trigger No 776849714: Global MASTER-Net observations report
  56. GRB 250818B: SVOM detection of a short burst
  57. GRB 250815A: Fermi GBM Final Localization
  58. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  59. GRB 250814A: Possible afterglow candidate from P200/WIRC
  60. Fermi trigger No 776818276: Global MASTER-Net observations report
  61. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  62. IceCube Alert 250813.14: Global MASTER-Net observations report
  63. Fermi GRB 250808A: Global MASTER-Net observations report
  64. Swift GRB250807.65: Global MASTER-Net observations report
  65. The EP-WXT trigger 01709198251 is likely a flaring star
  66. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  67. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  68. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  69. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  70. GRB 250728A: COLIBRÍ optical upper limit
  71. Fermi trigger No 775387550: Global MASTER-Net observations report
  72. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
  73. GRB 250727A: EP-FXT counterpart detection
  74. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  75. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  76. Swift GRB 250725A: Global MASTER-Net OT detection
  77. Fermi GRB 250725A: Global MASTER-Net observations report
  78. Swift GRB 250725A: Global MASTER-Net observations report
  79. GRB 250721A: MAXI/GSC detection
  80. Fermi trigger No 774730635: Global MASTER-Net observations report
  81. GRB 270713A: Kitab and AbAO Optical Observations
  82. Konus-Wind detection of GRB 250716A
  83. GRB 250716A: GOTO tentative optical counterpart candidate
  84. GRB 250716A: Fermi GBM Observation
  85. GRB 250716A: Fermi GBM Final Real-time Localization
  86. GRB 250706B/C: 7DT Follow-up Observations
  87. Fermi GRB 250711A: Global MASTER-Net observations report
  88. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  89. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  90. IceCube-250706A: Global MASTER-Net observations report
  91. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  92. GRB 250702F: Fermi GBM Observation
  93. GRB 250702F: Leavitt Observatory optical observations
  94. EP250702a: Global MASTER-Net observations report
  95. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  96. Fermi GRB 250702F: Global MASTER-Net observations report
  97. Fermi GRB 250702C: Global MASTER-Net observations report
  98. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  99. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  100. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate

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