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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"

45642 results found.

  1. Fermi GRB 250902B: Global MASTER-Net observations report
  2. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  3. GRB 250902A: Fermi GBM Detection
  4. GRB 250901A: Swift/UVOT Upper Limit
  5. GRB 250902B: Fermi GBM Final Real-time Localization
  6. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  7. GRB 250830B: Swift-XRT afterglow detection
  8. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  9. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  10. EP250827b: Liverpool Telescope observations
  11. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  12. GRB 250902A: SVOM/GRM observation
  13. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  14. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  15. GRB 250901A: EP-FXT follow-up observation
  16. GRB 250901A: NOT optical observations
  17. GRB 250902A: Fermi GBM Final Real-time Localization
  18. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  19. GRB 250901A: SVOM/VT optical afterglow with VHF data
  20. GRB 250901A: Swift-XRT afterglow detection
  21. EP250901a: Swift-XRT observations
  22. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  23. GRB 250901A: LCO optical upper limit
  24. EP250827b: Swift observations of AT 2025wkm
  25. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  26. EP250827b: Gemini Spectroscopy of AT 2025wkm
  27. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  28. EP250831a: NOT optical observations and tentative afterglow candidate
  29. EP250827b: FTW Observations of AT 2025wkm
  30. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  31. GRB 250901A: SVOM detection of a burst
  32. GRB 250831B: SVOM/GRM observation
  33. GRB 250830C: Insight-HXMT detection
  34. EP250901a: Mephisto optical upper limits
  35. GRB 250830C: GECAM-B detection
  36. EP250901a: Global MASTER-Net observations report
  37. GRB 250830C: AstroSat CZTI detection of a long burst
  38. EP250901a: Einstein Probe detection of an X-ray transient
  39. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  40. EP250831a: EP-FXT follow-up observation
  41. EP250831a: Swift-XRT observations
  42. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  43. IceCube Alert 250831.75: Global MASTER-Net observations report
  44. EP250831a: Global MASTER-Net observations report
  45. IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event
  46. EP250831a: EP-WXT detection of a fast X-ray transient
  47. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  48. GRB 250831A: Swift-XRT counterpart detection
  49. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  50. GRB 250831A: SVOM/VT upper limit with VHF data
  51. GRB 250831A: SVOM detection of a soft burst
  52. GRB 250830B: Swift-XRT observations
  53. EP250830a: Global MASTER-Net observations report
  54. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  55. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  56. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  57. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  58. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  59. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  60. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  61. GRB 250830B: Swift ToO observations
  62. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  63. GRB 250830B: MAXI/GSC detection
  64. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  65. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  66. The EP-WXT trigger 01709200994 is likely a flaring star
  67. GRB 250828B: Swift-BAT refined analysis
  68. EP250821a: SOAR observations
  69. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  70. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  71. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  72. GRB 250808B: SVOM detection of a burst through offline search
  73. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  74. EP250828a: Optical counterpart detection with Kinder observations
  75. EP250828a: Liverpool Telescope upper limits
  76. Swift GRB 250828B: Global MASTER-Net observations report
  77. EP250828a: Global MASTER-Net observations report
  78. EP-WXT trigger 01709200800 : KAIT optical observations
  79. EP250828a: KAIT optical upper limit
  80. EP250827a: Swift/UVOT Detection
  81. EP250828a: NOT optical counterpart confirmation
  82. EP250828a: SVOM/VT optical candidate
  83. EP250828a: Seimei/TriCCS optical counterpart detection
  84. GRB 250828B: Swift detection of a burst
  85. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  86. EP250828a: Optical upper limit with Kinder observations
  87. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  88. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  89. EP250827a: LCO observations show fading optical counterpart
  90. GRB 250828A: Fermi GBM Final Localization
  91. EP250828a: Einstein Probe detection of an X-ray transient
  92. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  93. GRID detection of GRB 250824A
  94. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  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. GRB 250826A: SVOM/GRM observation
  100. GRB 250827A: Fermi GBM Final Real-time Localization

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