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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"

45443 results found.

  1. EP250903a: Einstein Probe detection of an X-ray transient
  2. EP 250827B: Detection of supernova counterpart by LCO.
  3. EP/WXT01709201159: GOTO optical follow-up
  4. EP250827b / AT 2025wkm: TRT optical observations
  5. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  6. EP250827b: continued Liverpool Telescope observations
  7. GRB 250902B: SVOM/GRM observation
  8. EP250827b: SVOM/VT observation of AT 2025wkm
  9. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  10. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  11. Fermi GRB 250902B: Global MASTER-Net observations report
  12. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  13. GRB 250902A: Fermi GBM Detection
  14. GRB 250901A: Swift/UVOT Upper Limit
  15. GRB 250902B: Fermi GBM Final Real-time Localization
  16. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  17. GRB 250830B: Swift-XRT afterglow detection
  18. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  19. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  20. EP250827b: Liverpool Telescope observations
  21. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  22. GRB 250902A: SVOM/GRM observation
  23. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  24. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  25. GRB 250901A: EP-FXT follow-up observation
  26. GRB 250901A: NOT optical observations
  27. GRB 250902A: Fermi GBM Final Real-time Localization
  28. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  29. GRB 250901A: SVOM/VT optical afterglow with VHF data
  30. GRB 250901A: Swift-XRT afterglow detection
  31. EP250901a: Swift-XRT observations
  32. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  33. GRB 250901A: LCO optical upper limit
  34. EP250827b: Swift observations of AT 2025wkm
  35. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  36. EP250827b: Gemini Spectroscopy of AT 2025wkm
  37. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  38. EP250831a: NOT optical observations and tentative afterglow candidate
  39. EP250827b: FTW Observations of AT 2025wkm
  40. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  41. GRB 250901A: SVOM detection of a burst
  42. GRB 250831B: SVOM/GRM observation
  43. GRB 250830C: Insight-HXMT detection
  44. EP250901a: Mephisto optical upper limits
  45. GRB 250830C: GECAM-B detection
  46. EP250901a: Global MASTER-Net observations report
  47. GRB 250830C: AstroSat CZTI detection of a long burst
  48. EP250901a: Einstein Probe detection of an X-ray transient
  49. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  50. EP250831a: EP-FXT follow-up observation
  51. EP250831a: Swift-XRT observations
  52. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  53. IceCube Alert 250831.75: Global MASTER-Net observations report
  54. EP250831a: Global MASTER-Net observations report
  55. IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event
  56. EP250831a: EP-WXT detection of a fast X-ray transient
  57. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  58. GRB 250831A: Swift-XRT counterpart detection
  59. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  60. GRB 250831A: SVOM/VT upper limit with VHF data
  61. GRB 250831A: SVOM detection of a soft burst
  62. GRB 250830B: Swift-XRT observations
  63. EP250830a: Global MASTER-Net observations report
  64. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  65. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  66. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  67. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  68. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  69. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  70. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  71. GRB 250830B: Swift ToO observations
  72. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  73. GRB 250830B: MAXI/GSC detection
  74. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  75. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  76. The EP-WXT trigger 01709200994 is likely a flaring star
  77. GRB 250828B: Swift-BAT refined analysis
  78. EP250821a: SOAR observations
  79. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  80. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  81. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  82. GRB 250808B: SVOM detection of a burst through offline search
  83. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  84. EP250828a: Optical counterpart detection with Kinder observations
  85. EP250828a: Liverpool Telescope upper limits
  86. Swift GRB 250828B: Global MASTER-Net observations report
  87. EP250828a: Global MASTER-Net observations report
  88. EP-WXT trigger 01709200800 : KAIT optical observations
  89. EP250828a: KAIT optical upper limit
  90. EP250827a: Swift/UVOT Detection
  91. EP250828a: NOT optical counterpart confirmation
  92. EP250828a: SVOM/VT optical candidate
  93. EP250828a: Seimei/TriCCS optical counterpart detection
  94. GRB 250828B: Swift detection of a burst
  95. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  96. EP250828a: Optical upper limit with Kinder observations
  97. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  98. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  99. EP250827a: LCO observations show fading optical counterpart
  100. GRB 250828A: Fermi GBM Final Localization

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