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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"

45640 results found.

  1. GRB 250907A: CALET Gamma-Ray Burst Monitor detection
  2. EP250908c: SVOM/VT optical observation
  3. EP250908c: VLT/FORS2 optical counterpart identification
  4. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  5. EP250908b: SVOM/VT optical candidate
  6. The EP-WXT trigger EP250908a/01709240652 is not a real source
  7. EP250908c: Global MASTER-Net observations report
  8. Fermi GRB 250909A: Global MASTER-Net observations report
  9. EP250908c: Einstein Probe detection of an X-ray transient
  10. GRB 250909A: Fermi GBM Final Real-time Localization
  11. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  12. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  13. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  14. GRB 250907A: GECAM-B detection
  15. GRB 250905A: Swift-BAT refined analysis
  16. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  17. GRB 250903A: Swift-XRT afterglow detection
  18. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  19. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  20. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  21. EP250905a: Liverpool Telescope i-band upper limits
  22. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  23. EP250905b: EP-FXT follow-up observation
  24. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  25. EP250905a: Liverpool Telescope observations
  26. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  27. EP250905b: Global MASTER-Net observations report
  28. EP250905b: EP-WXT detection of a fast X-ray transient
  29. EP250905a: FTW one optical and multiple NIR counterpart candidates
  30. GRB 250905A: Swift-XRT refined Analysis
  31. EP250905a: JinShan likely optical counterpart detection
  32. IceCube-250905A - IceCube observation of a high-energy neutrino candidate track-like event
  33. GRB 250904A: Swift-BAT refined analysis
  34. IceCube Alert 250905.84: Global MASTER-Net observations report
  35. GRB 250905A: Swift/UVOT Upper Limits
  36. EP250905a: Global MASTER-Net observations report
  37. GRB 250901A - SVOM/ECLAIRs refined analysis
  38. EP250905a: Einstein Probe detection of an X-ray transient
  39. GRB 250905B: Fermi GBM Final Localization
  40. GRB250904A: Liverpool Telescope upper limits
  41. GRB 250905A: Enhanced Swift-XRT position
  42. GRB 250904A: Swift/UVOT Detection
  43. GRB 250903A: Swift/UVOT detection
  44. GRB 250904A: Swift-XRT refined Analysis
  45. LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
  46. LIGO/Virgo/KAGRA S250904br: Updated Sky localization
  47. EP detected a brightening of LMXB 1ES 1735-26.9
  48. GRB 250905A: KAIT optical upper limit
  49. GRB 250905A: Swift detection of a burst
  50. Swift GRB250905.09: Global MASTER-Net observations report
  51. Swift GRB 250904A: Global MASTER-Net observations report
  52. GRB 250904A: Enhanced Swift-XRT position
  53. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  54. GRB 250904A: TRT optical counterpart detection
  55. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  56. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  57. GRB 250904A: Prompt enhanced Swift-XRT position
  58. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  59. GRB 250904A: Swift detection of a burst
  60. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  61. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  62. GRB 250902A: VZLUSAT-2 detection
  63. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  64. GRB 250903A: Swift-XRT observations
  65. EP250903a: Swift-XRT observations
  66. EP#01709201209: Swift-XRT observations
  67. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  68. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  69. GRB 250830C: VZLUSAT-2 detection
  70. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  71. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  72. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  73. The EP-WXT trigger 01709201209 is likely a flaring star
  74. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  75. GRB 250903A: EP-FXT counterpart detection
  76. GRB 250902A: GECAM-B detection
  77. GRB 250903A: LCO optical observation
  78. GRB 250903A: LCO optical afterglow detection
  79. GRB 250903A: SVOM/VT optical confirmation with VHF data
  80. EP250903a: SVOM/VT optical confirmation
  81. EP250901a: Mondy, Assy and SAO RAS optical limits
  82. Subject GRB 250903A: SVOM/MXT afterglow detection
  83. EP250903a: LCO candidate counterpart discovery
  84. GRB 250903A: TRT optical counterpart detection
  85. GRB 250902B: AstroSat CZTI detection
  86. GRB 250903A: SVOM detection of a burst
  87. EP250903a: Global MASTER-Net observations report
  88. EP250903a: TRT optical observations
  89. EP250903a: Einstein Probe detection of an X-ray transient
  90. EP 250827B: Detection of supernova counterpart by LCO.
  91. EP/WXT01709201159: GOTO optical follow-up
  92. EP250827b / AT 2025wkm: TRT optical observations
  93. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  94. EP250827b: continued Liverpool Telescope observations
  95. GRB 250902B: SVOM/GRM observation
  96. EP250827b: SVOM/VT observation of AT 2025wkm
  97. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  98. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  99. Fermi GRB 250902B: Global MASTER-Net observations report
  100. Fermi-LAT Gamma-ray Observations of IceCube-250831A

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