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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"

27074 results found.

  1. GRB 250903A: TRT optical counterpart detection
  2. GRB 250903A: SVOM detection of a burst
  3. EP250903a: Global MASTER-Net observations report
  4. EP250903a: TRT optical observations
  5. EP250903a: Einstein Probe detection of an X-ray transient
  6. EP 250827B: Detection of supernova counterpart by LCO.
  7. EP/WXT01709201159: GOTO optical follow-up
  8. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  9. GRB 250902B: SVOM/GRM observation
  10. EP250827b: SVOM/VT observation of AT 2025wkm
  11. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  12. Fermi GRB 250902B: Global MASTER-Net observations report
  13. GRB 250902A: Fermi GBM Detection
  14. GRB 250901A: Swift/UVOT Upper Limit
  15. GRB 250902B: Fermi GBM Final Real-time Localization
  16. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  17. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  18. GRB 250902A: SVOM/GRM observation
  19. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  20. GRB 250901A: EP-FXT follow-up observation
  21. GRB 250901A: NOT optical observations
  22. GRB 250902A: Fermi GBM Final Real-time Localization
  23. GRB 250901A: SVOM/VT optical afterglow with VHF data
  24. EP250901a: Swift-XRT observations
  25. GRB 250901A: LCO optical upper limit
  26. EP250831a: NOT optical observations and tentative afterglow candidate
  27. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  28. GRB 250901A: SVOM detection of a burst
  29. GRB 250831B: SVOM/GRM observation
  30. EP250901a: Mephisto optical upper limits
  31. GRB 250830C: GECAM-B detection
  32. EP250901a: Global MASTER-Net observations report
  33. EP250901a: Einstein Probe detection of an X-ray transient
  34. EP250831a: EP-FXT follow-up observation
  35. EP250831a: Swift-XRT observations
  36. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  37. IceCube Alert 250831.75: Global MASTER-Net observations report
  38. EP250831a: Global MASTER-Net observations report
  39. EP250831a: EP-WXT detection of a fast X-ray transient
  40. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  41. GRB 250831A: Swift-XRT counterpart detection
  42. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  43. GRB 250831A: SVOM/VT upper limit with VHF data
  44. GRB 250831A: SVOM detection of a soft burst
  45. EP250830a: Global MASTER-Net observations report
  46. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  47. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  48. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  49. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  50. The EP-WXT trigger 01709200994 is likely a flaring star
  51. GRB 250828B: Swift-BAT refined analysis
  52. EP250821a: SOAR observations
  53. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  54. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  55. GRB 250808B: SVOM detection of a burst through offline search
  56. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  57. EP250828a: Optical counterpart detection with Kinder observations
  58. EP250828a: Liverpool Telescope upper limits
  59. Swift GRB 250828B: Global MASTER-Net observations report
  60. EP250828a: Global MASTER-Net observations report
  61. EP-WXT trigger 01709200800 : KAIT optical observations
  62. EP250827a: Swift/UVOT Detection
  63. EP250828a: NOT optical counterpart confirmation
  64. EP250828a: SVOM/VT optical candidate
  65. GRB 250828B: Swift detection of a burst
  66. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  67. EP250828a: Optical upper limit with Kinder observations
  68. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  69. EP250827a: LCO observations show fading optical counterpart
  70. GRB 250828A: Fermi GBM Final Localization
  71. EP250828a: Einstein Probe detection of an X-ray transient
  72. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  73. GRID detection of GRB 250824A
  74. Fermi GRB 250827A: Global MASTER-Net observations report
  75. EP250827a: confirmation of optical rebrightening with LCO
  76. EP250827a: GOTO observation of the optical afterglow
  77. GRB 250826A: SVOM/GRM observation
  78. GRB 250827A: Fermi GBM Final Real-time Localization
  79. EP250827A: An optical rebrightening was detected by LCO.
  80. EP250827a: Swift-XRT counterpart detection
  81. The EP-WXT trigger 01709200800 is likely a flaring star
  82. EP250827a: TRT optical observations
  83. EP250827a: BOOTES-7 early optical dectection
  84. EP250827a: Gemini-South redshift z = 1.613
  85. EP250827a: Global MASTER-Net observations report
  86. EP250827a: Gemini-South optical counterpart detection
  87. EP250827a: Einstein Probe detection of an X-ray transient
  88. Fermi GRB 250826A: Global MASTER-Net observations report
  89. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  90. Fermi trigger No 777883624: Global MASTER-Net observations report
  91. Fermi Gamma-ray Burst Monitor trigger 777883624/250826283 is not a GRB
  92. GRB 250826A: Fermi GBM Final Real-time Localization
  93. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  94. Fermi GRB 250824B: Global MASTER-Net observations report
  95. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  96. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  97. GRB 250823A: Swift-BAT refined analysis
  98. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  99. GRB 250823A: Swift-XRT refined Analysis
  100. EP triggers 01709200706 and 01709200707: GOTO confirmation of flaring stars

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