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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

32719 results found.

  1. GRB 250903A: EP-FXT counterpart detection
  2. GRB 250902A: GECAM-B detection
  3. GRB 250903A: LCO optical observation
  4. GRB 250903A: LCO optical afterglow detection
  5. GRB 250903A: SVOM/VT optical confirmation with VHF data
  6. EP250903a: SVOM/VT optical confirmation
  7. EP250901a: Mondy, Assy and SAO RAS optical limits
  8. Subject GRB 250903A: SVOM/MXT afterglow detection
  9. EP250903a: LCO candidate counterpart discovery
  10. GRB 250903A: TRT optical counterpart detection
  11. GRB 250902B: AstroSat CZTI detection
  12. EP250903a: Global MASTER-Net observations report
  13. EP250903a: TRT optical observations
  14. EP250903a: Einstein Probe detection of an X-ray transient
  15. EP 250827B: Detection of supernova counterpart by LCO.
  16. EP250827b / AT 2025wkm: TRT optical observations
  17. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  18. EP250827b: continued Liverpool Telescope observations
  19. GRB 250902B: SVOM/GRM observation
  20. EP250827b: SVOM/VT observation of AT 2025wkm
  21. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  22. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  23. Fermi GRB 250902B: Global MASTER-Net observations report
  24. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  25. GRB 250902A: Fermi GBM Detection
  26. GRB 250901A: Swift/UVOT Upper Limit
  27. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  28. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  29. EP250827b: Liverpool Telescope observations
  30. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  31. GRB 250902A: SVOM/GRM observation
  32. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  33. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  34. GRB 250901A: EP-FXT follow-up observation
  35. GRB 250901A: NOT optical observations
  36. GRB 250901A: SVOM/VT optical afterglow with VHF data
  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 250830C: Insight-HXMT detection
  47. EP250901a: Mephisto optical upper limits
  48. EP250901a: Global MASTER-Net observations report
  49. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  50. EP250831a: EP-FXT follow-up observation
  51. EP250831a: Swift-XRT observations
  52. EP250831a: Global MASTER-Net observations report
  53. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  54. GRB 250831A: Swift-XRT counterpart detection
  55. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  56. GRB 250831A: SVOM/VT upper limit with VHF data
  57. EP250830a: Global MASTER-Net observations report
  58. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  59. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  60. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  61. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  62. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  63. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  64. GRB 250830B: Swift ToO observations
  65. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  66. GRB 250828B: Swift-BAT refined analysis
  67. EP250821a: SOAR observations
  68. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  69. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  70. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  71. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  72. EP250828a: Optical counterpart detection with Kinder observations
  73. EP250828a: Liverpool Telescope upper limits
  74. Swift GRB 250828B: Global MASTER-Net observations report
  75. EP250828a: Global MASTER-Net observations report
  76. EP-WXT trigger 01709200800 : KAIT optical observations
  77. EP250828a: KAIT optical upper limit
  78. EP250827a: Swift/UVOT Detection
  79. EP250828a: NOT optical counterpart confirmation
  80. EP250828a: SVOM/VT optical candidate
  81. EP250828a: Seimei/TriCCS optical counterpart detection
  82. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  83. EP250828a: Optical upper limit with Kinder observations
  84. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  85. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  86. EP250827a: LCO observations show fading optical counterpart
  87. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  88. GRID detection of GRB 250824A
  89. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  90. EP250827A: VLT/X-shooter redshift confirmation
  91. Fermi GRB 250827A: Global MASTER-Net observations report
  92. EP250827a: confirmation of optical rebrightening with LCO
  93. EP250827a: GOTO observation of the optical afterglow
  94. GRB 250826A: SVOM/GRM observation
  95. EP250827A: An optical rebrightening was detected by LCO.
  96. EP250827a: Swift-XRT counterpart detection
  97. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  98. EP250827a: TRT optical observations
  99. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  100. EP250827a: Gemini-South redshift z = 1.613

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