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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"
  1. EP250901a: Mephisto optical upper limits
  2. GRB 250830C: GECAM-B detection
  3. EP250901a: Global MASTER-Net observations report
  4. GRB 250830C: AstroSat CZTI detection of a long burst
  5. EP250901a: Einstein Probe detection of an X-ray transient
  6. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  7. EP250831a: EP-FXT follow-up observation
  8. EP250831a: Swift-XRT observations
  9. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  10. IceCube Alert 250831.75: Global MASTER-Net observations report
  11. EP250831a: Global MASTER-Net observations report
  12. IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event
  13. EP250831a: EP-WXT detection of a fast X-ray transient
  14. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  15. GRB 250831A: Swift-XRT counterpart detection
  16. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  17. GRB 250831A: SVOM/VT upper limit with VHF data
  18. GRB 250831A: SVOM detection of a soft burst
  19. GRB 250830B: Swift-XRT observations
  20. EP250830a: Global MASTER-Net observations report
  21. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  22. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  23. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  24. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  25. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  26. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  27. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  28. GRB 250830B: Swift ToO observations
  29. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  30. GRB 250830B: MAXI/GSC detection
  31. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  32. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  33. The EP-WXT trigger 01709200994 is likely a flaring star
  34. GRB 250828B: Swift-BAT refined analysis
  35. EP250821a: SOAR observations
  36. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  37. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  38. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  39. GRB 250808B: SVOM detection of a burst through offline search
  40. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  41. EP250828a: Optical counterpart detection with Kinder observations
  42. EP250828a: Liverpool Telescope upper limits
  43. Swift GRB 250828B: Global MASTER-Net observations report
  44. EP250828a: Global MASTER-Net observations report
  45. EP-WXT trigger 01709200800 : KAIT optical observations
  46. EP250828a: KAIT optical upper limit
  47. EP250827a: Swift/UVOT Detection
  48. EP250828a: NOT optical counterpart confirmation
  49. EP250828a: SVOM/VT optical candidate
  50. EP250828a: Seimei/TriCCS optical counterpart detection
  51. GRB 250828B: Swift detection of a burst
  52. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  53. EP250828a: Optical upper limit with Kinder observations
  54. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  55. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  56. EP250827a: LCO observations show fading optical counterpart
  57. GRB 250828A: Fermi GBM Final Localization
  58. EP250828a: Einstein Probe detection of an X-ray transient
  59. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  60. GRID detection of GRB 250824A
  61. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  62. EP250827A: VLT/X-shooter redshift confirmation
  63. Fermi GRB 250827A: Global MASTER-Net observations report
  64. EP250827a: confirmation of optical rebrightening with LCO
  65. EP250827a: GOTO observation of the optical afterglow
  66. GRB 250826A: SVOM/GRM observation
  67. GRB 250827A: Fermi GBM Final Real-time Localization
  68. EP250827A: An optical rebrightening was detected by LCO.
  69. EP250827a: Swift-XRT counterpart detection
  70. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  71. The EP-WXT trigger 01709200800 is likely a flaring star
  72. EP250827a: TRT optical observations
  73. EP250827a: BOOTES-7 early optical dectection
  74. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  75. EP250827a: Gemini-South redshift z = 1.613
  76. EP250827a: Global MASTER-Net observations report
  77. EP250827a: Las Cumbres independent detection of the optical counterpart
  78. EP250827a: Gemini-South optical counterpart detection
  79. EP250827a: Einstein Probe detection of an X-ray transient
  80. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  81. Fermi GRB 250826A: Global MASTER-Net observations report
  82. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  83. EP250821a: Gemini GMOS Redshift Confirmation
  84. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  85. Fermi trigger No 777883624: Global MASTER-Net observations report
  86. Fermi Gamma-ray Burst Monitor trigger 777883624/250826283 is not a GRB
  87. GRB 250826A: Fermi GBM Final Real-time Localization
  88. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  89. Fermi GRB 250824B: Global MASTER-Net observations report
  90. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  91. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  92. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  93. GRB 250823A: Swift-BAT refined analysis
  94. LIGO/Virgo/KAGRA S250818k: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  95. GRB 250821B: AstroSat CZTI detection
  96. GRB 250819A: AstroSat CZTI detection
  97. LIGO/Virgo/KAGRA S250818k: FTW Observations Show Continued Reddening of AT 2025ulz
  98. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  99. GRB 250821B: Insight-HXMT detection
  100. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova

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