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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"

20490 results found.

  1. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  2. Swift GRB250807.45: Global MASTER-Net observations report
  3. GRB 250807B: NTT optical observations
  4. EP250807a: EP-WXT detection of a fast X-ray transient
  5. EP 250807.979: GOTO optical upper limit
  6. GRB 250807A: SVOM/VT optical observation
  7. EP250806a: Upper limit from Fermi-GBM Observations
  8. Swift GRB250807.65: Global MASTER-Net observations report
  9. GRB 250805A: Kilonova-Catcher optical upper limits
  10. GRB 250805A: Swift/UVOT Upper Limits
  11. GRB 250806A: Swift/UVOT U-band detection
  12. IceCube Alert 250804.84: Global MASTER-Net observations report
  13. EP#01709198415/EP250806a: Swift-XRT observations
  14. EP250806a: Global MASTER-Net observations report
  15. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  16. EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
  17. GRB 250806A: J-band upper limit from WINTER
  18. GRB 250806A: KAIT optical upper limit
  19. GRB 250806A: Kilonova-Catcher optical upper limits
  20. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  21. GRB 250805A: ESO/VLT observations
  22. GRB 250804B: Swift-XRT observations
  23. GRB 250805A: TRT optical upper limits
  24. GRB 250805A: Swift-XRT observations
  25. Swift GRB250805.26: Global MASTER-Net observations report
  26. GRB 250804B: Tiled Swift observations
  27. Fermi trigger No 776041355: Global MASTER-Net observations report
  28. EP250802a: Global MASTER-Net observations report
  29. EP250802a: Einstein Probe detection of an X-ray transient
  30. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  31. GRB 250702B: SMA observations
  32. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  33. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  34. EP250711a: CrAO and Assy optical observations
  35. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  36. EP250730a: Global MASTER-Net observations report
  37. EP250730a: Einstein Probe detection of an X-ray transient
  38. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  39. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  40. GRB 250725A: PRIME near-infrared observations
  41. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  42. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  43. GRB 250728A: Swift-XRT observations
  44. GRB 250727A: SVOM/ECLAIRs refined analysis
  45. EP-WXT trigger 01709195487: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  46. GRB 250728A: COLIBRÍ optical upper limit
  47. Fermi trigger No 775387550: Global MASTER-Net observations report
  48. GRB 250728A: Swift ToO observations
  49. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  50. GRB 250727A: AST3-2 Upper limit
  51. GRB250727A: SVOM/VT optical upper limit
  52. GRB 250727A: Swift-XRT observations
  53. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  54. LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
  55. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  56. GRB 250725A: Swift/UVOT Upper Limits
  57. Fermi GRB 250725A: Global MASTER-Net observations report
  58. Swift GRB 250725A: Global MASTER-Net observations report
  59. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  60. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  61. SVOM J195836+32283/sb25072103: Second VT observation
  62. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  63. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  64. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  65. GRB 250721A: Swift-XRT observations
  66. GRB 250713A : SVOM/ECLAIRs refined analysis
  67. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  68. GRB 250721A: Tiled Swift observations
  69. Fermi trigger No 774730635: Global MASTER-Net observations report
  70. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  71. GRB 250717B: Swift-XRT observations
  72. Swift GRB250718.01: Global MASTER-Net observations report
  73. GRB 250717B: Swift ToO observations
  74. GRB 270713A: Kitab and AbAO Optical Observations
  75. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  76. GRB 250716A: Swift-XRT afterglow detection
  77. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  78. GRB 250716A: Swift ToO observations
  79. GRB 250716A: GOTO tentative optical counterpart candidate
  80. Fermi GRB 250716A: Global MASTER-Net observations report
  81. Fermi GRB 250715A: Global MASTER-Net observations report
  82. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  83. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  84. GRB 250713A: Mephisto optical upper limits
  85. Fermi GRB 250714A: Global MASTER-Net observations report
  86. GRB 250713A: NOT optical upper limits
  87. GRB 250713A: OHP/T193 upper limit
  88. GRB 250713A: SVOM/C-GFT upper limit
  89. GRB 250706B/C: 7DT Follow-up Observations
  90. GRB 250713A: Swift-XRT observations
  91. EP250711a: COLIBRÍ continuous optical observations
  92. GRB 250713A: JinShan optical upper limits
  93. EP250711a: Global MASTER-Net observations report
  94. GRB 250711A: DDOTI Optical Upper Limit
  95. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  96. Fermi GRB 250711A: Global MASTER-Net observations report
  97. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  98. GRB 250704A: GRANDMA observations
  99. GRB 250704A: SVOM/ECLAIRs refined analysis
  100. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz

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