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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"

45440 results found.

  1. GRB 250903A: TRT optical counterpart detection
  2. GRB 250902B: AstroSat CZTI detection
  3. GRB 250903A: SVOM detection of a burst
  4. EP250903a: Global MASTER-Net observations report
  5. EP250903a: TRT optical observations
  6. EP250903a: Einstein Probe detection of an X-ray transient
  7. EP 250827B: Detection of supernova counterpart by LCO.
  8. EP/WXT01709201159: GOTO optical follow-up
  9. EP250827b / AT 2025wkm: TRT optical observations
  10. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  11. EP250827b: continued Liverpool Telescope observations
  12. GRB 250902B: SVOM/GRM observation
  13. EP250827b: SVOM/VT observation of AT 2025wkm
  14. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  15. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  16. Fermi GRB 250902B: Global MASTER-Net observations report
  17. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  18. GRB 250902A: Fermi GBM Detection
  19. GRB 250901A: Swift/UVOT Upper Limit
  20. GRB 250902B: Fermi GBM Final Real-time Localization
  21. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  22. GRB 250830B: Swift-XRT afterglow detection
  23. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  24. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  25. EP250827b: Liverpool Telescope observations
  26. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  27. GRB 250902A: SVOM/GRM observation
  28. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  29. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  30. GRB 250901A: EP-FXT follow-up observation
  31. GRB 250901A: NOT optical observations
  32. GRB 250902A: Fermi GBM Final Real-time Localization
  33. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  34. GRB 250901A: SVOM/VT optical afterglow with VHF data
  35. GRB 250901A: Swift-XRT afterglow detection
  36. EP250901a: Swift-XRT observations
  37. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  38. GRB 250901A: LCO optical upper limit
  39. EP250827b: Swift observations of AT 2025wkm
  40. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  41. EP250827b: Gemini Spectroscopy of AT 2025wkm
  42. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  43. EP250831a: NOT optical observations and tentative afterglow candidate
  44. EP250827b: FTW Observations of AT 2025wkm
  45. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  46. GRB 250901A: SVOM detection of a burst
  47. GRB 250831B: SVOM/GRM observation
  48. GRB 250830C: Insight-HXMT detection
  49. EP250901a: Mephisto optical upper limits
  50. GRB 250830C: GECAM-B detection
  51. EP250901a: Global MASTER-Net observations report
  52. GRB 250830C: AstroSat CZTI detection of a long burst
  53. EP250901a: Einstein Probe detection of an X-ray transient
  54. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  55. EP250831a: EP-FXT follow-up observation
  56. EP250831a: Swift-XRT observations
  57. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  58. IceCube Alert 250831.75: Global MASTER-Net observations report
  59. EP250831a: Global MASTER-Net observations report
  60. IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event
  61. EP250831a: EP-WXT detection of a fast X-ray transient
  62. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  63. GRB 250831A: Swift-XRT counterpart detection
  64. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  65. GRB 250831A: SVOM/VT upper limit with VHF data
  66. GRB 250831A: SVOM detection of a soft burst
  67. GRB 250830B: Swift-XRT observations
  68. EP250830a: Global MASTER-Net observations report
  69. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  70. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  71. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  72. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  73. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  74. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  75. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  76. GRB 250830B: Swift ToO observations
  77. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  78. GRB 250830B: MAXI/GSC detection
  79. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  80. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  81. The EP-WXT trigger 01709200994 is likely a flaring star
  82. GRB 250828B: Swift-BAT refined analysis
  83. EP250821a: SOAR observations
  84. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  85. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  86. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  87. GRB 250808B: SVOM detection of a burst through offline search
  88. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  89. EP250828a: Optical counterpart detection with Kinder observations
  90. EP250828a: Liverpool Telescope upper limits
  91. Swift GRB 250828B: Global MASTER-Net observations report
  92. EP250828a: Global MASTER-Net observations report
  93. EP-WXT trigger 01709200800 : KAIT optical observations
  94. EP250828a: KAIT optical upper limit
  95. EP250827a: Swift/UVOT Detection
  96. EP250828a: NOT optical counterpart confirmation
  97. EP250828a: SVOM/VT optical candidate
  98. EP250828a: Seimei/TriCCS optical counterpart detection
  99. GRB 250828B: Swift detection of a burst
  100. EP250827a: STEP/T80S Confirmation of fading optical counterpart

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