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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"

21793 results found.

  1. EP250908b/EP#01709240653: Swift/UVOT Detection
  2. EP#01709240653: Swift-XRT observations
  3. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  4. EP250908c: Global MASTER-Net observations report
  5. Fermi GRB 250909A: Global MASTER-Net observations report
  6. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  7. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  8. GRB 250903A: Swift-XRT afterglow detection
  9. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  10. EP250905b: EP-FXT follow-up observation
  11. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  12. EP250905a: Liverpool Telescope observations
  13. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  14. EP250905b: Global MASTER-Net observations report
  15. EP250905b: EP-WXT detection of a fast X-ray transient
  16. EP250905a: FTW one optical and multiple NIR counterpart candidates
  17. EP250905a: JinShan likely optical counterpart detection
  18. IceCube Alert 250905.84: Global MASTER-Net observations report
  19. GRB 250905A: Swift/UVOT Upper Limits
  20. EP250905a: Global MASTER-Net observations report
  21. GRB 250901A - SVOM/ECLAIRs refined analysis
  22. GRB 250904A: Swift/UVOT Detection
  23. GRB 250903A: Swift/UVOT detection
  24. Swift GRB250905.09: Global MASTER-Net observations report
  25. Swift GRB 250904A: Global MASTER-Net observations report
  26. GRB 250904A: TRT optical counterpart detection
  27. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  28. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  29. GRB 250903A: Swift-XRT observations
  30. EP250903a: Swift-XRT observations
  31. EP#01709201209: Swift-XRT observations
  32. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  33. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  34. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  35. GRB 250903A: LCO optical afterglow detection
  36. EP250903a: SVOM/VT optical confirmation
  37. EP250903a: LCO candidate counterpart discovery
  38. GRB 250903A: TRT optical counterpart detection
  39. EP250903a: Global MASTER-Net observations report
  40. EP250903a: TRT optical observations
  41. EP 250827B: Detection of supernova counterpart by LCO.
  42. EP/WXT01709201159: GOTO optical follow-up
  43. EP250827b / AT 2025wkm: TRT optical observations
  44. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  45. EP250827b: continued Liverpool Telescope observations
  46. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  47. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  48. Fermi GRB 250902B: Global MASTER-Net observations report
  49. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  50. GRB 250901A: Swift/UVOT Upper Limit
  51. GRB 250830B: Swift-XRT afterglow detection
  52. EP250827b: Liverpool Telescope observations
  53. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  54. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  55. GRB 250901A: NOT optical observations
  56. GRB 250901A: Swift-XRT afterglow detection
  57. EP250901a: Swift-XRT observations
  58. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  59. EP250827b: Swift observations of AT 2025wkm
  60. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  61. EP250827b: Gemini Spectroscopy of AT 2025wkm
  62. EP250831a: NOT optical observations and tentative afterglow candidate
  63. EP250827b: FTW Observations of AT 2025wkm
  64. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  65. EP250901a: Mephisto optical upper limits
  66. EP250901a: Global MASTER-Net observations report
  67. EP250831a: Swift-XRT observations
  68. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  69. IceCube Alert 250831.75: Global MASTER-Net observations report
  70. EP250831a: Global MASTER-Net observations report
  71. EP250831a: EP-WXT detection of a fast X-ray transient
  72. GRB 250831A: Swift-XRT counterpart detection
  73. GRB 250830B: Swift-XRT observations
  74. EP250830a: Global MASTER-Net observations report
  75. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  76. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  77. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  78. GRB 250830B: Swift ToO observations
  79. EP250821a: SOAR observations
  80. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  81. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  82. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  83. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  84. EP250828a: Optical counterpart detection with Kinder observations
  85. Swift GRB 250828B: Global MASTER-Net observations report
  86. EP250828a: Global MASTER-Net observations report
  87. EP-WXT trigger 01709200800 : KAIT optical observations
  88. EP250827a: Swift/UVOT Detection
  89. EP250828a: NOT optical counterpart confirmation
  90. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  91. EP250828a: Optical upper limit with Kinder observations
  92. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  93. EP250827a: LCO observations show fading optical counterpart
  94. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  95. EP250827A: VLT/X-shooter redshift confirmation
  96. Fermi GRB 250827A: Global MASTER-Net observations report
  97. EP250827a: confirmation of optical rebrightening with LCO
  98. EP250827a: GOTO observation of the optical afterglow
  99. EP250827A: An optical rebrightening was detected by LCO.
  100. EP250827a: Swift-XRT counterpart detection

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