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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"

5845 results found.

  1. EP250903a: SVOM/VT optical confirmation
  2. Subject GRB 250903A: SVOM/MXT afterglow detection
  3. EP250903a: LCO candidate counterpart discovery
  4. GRB 250903A: TRT optical counterpart detection
  5. GRB 250902B: AstroSat CZTI detection
  6. GRB 250903A: SVOM detection of a burst
  7. EP250903a: Global MASTER-Net observations report
  8. EP250903a: TRT optical observations
  9. EP250903a: Einstein Probe detection of an X-ray transient
  10. EP 250827B: Detection of supernova counterpart by LCO.
  11. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  12. EP250827b: continued Liverpool Telescope observations
  13. GRB 250902B: SVOM/GRM observation
  14. EP250827b: SVOM/VT observation of AT 2025wkm
  15. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  16. Fermi GRB 250902B: Global MASTER-Net observations report
  17. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  18. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  19. EP250827b: Liverpool Telescope observations
  20. GRB 250902A: SVOM/GRM observation
  21. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  22. GRB 250901A: EP-FXT follow-up observation
  23. GRB 250901A: SVOM/VT optical afterglow with VHF data
  24. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  25. GRB 250901A: LCO optical upper limit
  26. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  27. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  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. EP250901a: Mephisto optical upper limits
  32. EP250901a: Global MASTER-Net observations report
  33. EP250901a: Einstein Probe detection of an X-ray transient
  34. IceCube Alert 250831.75: Global MASTER-Net observations report
  35. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  36. Swift GRB 250828B: Global MASTER-Net observations report
  37. EP250828a: Global MASTER-Net observations report
  38. EP250828a: KAIT optical upper limit
  39. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  40. Fermi GRB 250827A: Global MASTER-Net observations report
  41. EP250827a: Global MASTER-Net observations report
  42. Fermi trigger No 777883624: Global MASTER-Net observations report
  43. Fermi GRB 250824B: Global MASTER-Net observations report
  44. Fermi GRB 250821B: Global MASTER-Net observations report
  45. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  46. LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
  47. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  48. LIGO/Virgo/KAGRA S250818k: FTW Fast reddening of AT 2025ulz
  49. GRB 250818B: GOTO optical counterpart candidate
  50. GRB 250818B: SVOM detection of a short burst
  51. sb25081602: Swift-XRT observations
  52. SVOM/sb25081602: detection of a likely X-ray transient
  53. GRB 250814A: Possible afterglow candidate from P200/WIRC
  54. Fermi trigger No 776818276: Global MASTER-Net observations report
  55. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  56. GRB 250814A: DDOTI Optical Upper Limit
  57. GRB 250814A: Fermi GBM Final Real-time Localization
  58. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  59. GRB 250812A: Swift/UVOT Detection
  60. EP250812a: SVOM/VT optical counterpart
  61. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  62. IceCube Alert 250813.14: Global MASTER-Net observations report
  63. EP250812a: Einstein Probe detection of an X-ray transient
  64. GRB 250812A: Swift-XRT afterglow detection
  65. GRB 250812A: TRT likely optical counterpart detection
  66. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  67. GRB 250702B: Chandra X-ray Detection
  68. Fermi GRB 250808A: Global MASTER-Net observations report
  69. Fermi Gamma-ray Burst Monitor trigger 776449964/250809689 is not a GRB
  70. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  71. Swift GRB250807.45: Global MASTER-Net observations report
  72. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  73. EP250806a: SVOM /VT optical candidate
  74. GRB 250805A: ESO/VLT observations
  75. GRB 250805A: Swift detection of a burst
  76. Swift GRB250805.26: Global MASTER-Net observations report
  77. EP250730a: SVOM/VT optical upper limit
  78. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  79. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  80. EP250730a: Global MASTER-Net observations report
  81. EP250730a: Einstein Probe detection of an X-ray transient
  82. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  83. GRB 250728A: Fermi GBM Observation
  84. GRB 250727A: AST3-2 Upper limit
  85. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  86. GRB 250721A: Fermi GBM Observation
  87. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  88. GRB 250722A: Fermi GBM Final Real-time Localization
  89. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  90. GRB 250721A: MAXI/GSC detection
  91. GRB 250721A: Fermi GBM Final Localization
  92. Fermi trigger No 774730635: Global MASTER-Net observations report
  93. GRB 250717B: COLIBRÍ optical upper limit
  94. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  95. GRB 250713A: SVOM/VT optical upper limit
  96. GRB 250713A: SVOM/C-GFT upper limit
  97. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  98. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  99. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  100. GRB 250702B,D,E / EP250702a: ALMA detection

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