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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"

45423 results found.

  1. GRB 250902A: Fermi GBM Detection
  2. GRB 250901A: Swift/UVOT Upper Limit
  3. GRB 250902B: Fermi GBM Final Real-time Localization
  4. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  5. GRB 250830B: Swift-XRT afterglow detection
  6. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  7. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  8. EP250827b: Liverpool Telescope observations
  9. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  10. GRB 250902A: SVOM/GRM observation
  11. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  12. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  13. GRB 250901A: EP-FXT follow-up observation
  14. GRB 250901A: NOT optical observations
  15. GRB 250902A: Fermi GBM Final Real-time Localization
  16. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  17. GRB 250901A: SVOM/VT optical afterglow with VHF data
  18. GRB 250901A: Swift-XRT afterglow detection
  19. EP250901a: Swift-XRT observations
  20. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  21. GRB 250901A: LCO optical upper limit
  22. EP250827b: Swift observations of AT 2025wkm
  23. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  24. EP250827b: Gemini Spectroscopy of AT 2025wkm
  25. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  26. EP250831a: NOT optical observations and tentative afterglow candidate
  27. EP250827b: FTW Observations of AT 2025wkm
  28. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  29. GRB 250901A: SVOM detection of a burst
  30. GRB 250831B: SVOM/GRM observation
  31. GRB 250830C: Insight-HXMT detection
  32. EP250901a: Mephisto optical upper limits
  33. GRB 250830C: GECAM-B detection
  34. EP250901a: Global MASTER-Net observations report
  35. GRB 250830C: AstroSat CZTI detection of a long burst
  36. EP250901a: Einstein Probe detection of an X-ray transient
  37. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  38. EP250831a: EP-FXT follow-up observation
  39. EP250831a: Swift-XRT observations
  40. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  41. IceCube Alert 250831.75: Global MASTER-Net observations report
  42. EP250831a: Global MASTER-Net observations report
  43. IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event
  44. EP250831a: EP-WXT detection of a fast X-ray transient
  45. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  46. GRB 250831A: Swift-XRT counterpart detection
  47. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  48. GRB 250831A: SVOM/VT upper limit with VHF data
  49. GRB 250831A: SVOM detection of a soft burst
  50. GRB 250830B: Swift-XRT observations
  51. EP250830a: Global MASTER-Net observations report
  52. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  53. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  54. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  55. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  56. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  57. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  58. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  59. GRB 250830B: Swift ToO observations
  60. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  61. GRB 250830B: MAXI/GSC detection
  62. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  63. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  64. The EP-WXT trigger 01709200994 is likely a flaring star
  65. GRB 250828B: Swift-BAT refined analysis
  66. EP250821a: SOAR observations
  67. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  68. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  69. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  70. GRB 250808B: SVOM detection of a burst through offline search
  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. GRB 250828B: Swift detection of a burst
  83. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  84. EP250828a: Optical upper limit with Kinder observations
  85. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  86. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  87. EP250827a: LCO observations show fading optical counterpart
  88. GRB 250828A: Fermi GBM Final Localization
  89. EP250828a: Einstein Probe detection of an X-ray transient
  90. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  91. GRID detection of GRB 250824A
  92. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  93. EP250827A: VLT/X-shooter redshift confirmation
  94. Fermi GRB 250827A: Global MASTER-Net observations report
  95. EP250827a: confirmation of optical rebrightening with LCO
  96. EP250827a: GOTO observation of the optical afterglow
  97. GRB 250826A: SVOM/GRM observation
  98. GRB 250827A: Fermi GBM Final Real-time Localization
  99. EP250827A: An optical rebrightening was detected by LCO.
  100. EP250827a: Swift-XRT counterpart detection

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