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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"

23442 results found.

  1. GRB 250807A: SVOM/GRM observation
  2. GRB 250807A: AstroSat CZTI detection of bright long burst
  3. GRB 250807B: Swift-XRT refined Analysis
  4. EP250807a: EP-WXT detection of a fast X-ray transient
  5. EP 250807.979: GOTO optical upper limit
  6. EP250807a: COLIBRÍ optical upper limit
  7. GRB 250807A: SVOM/VT optical observation
  8. GRB 250807B: Enhanced Swift-XRT position
  9. GRB 250807A: Enhanced Swift-XRT position
  10. GRB 250807B: Swift detection of a burst with an optical counterpart.
  11. GRB 250805A: Kilonova-Catcher optical upper limits
  12. EP250806a:SVOM/VT refined analysis
  13. GRB 250805A: Swift/UVOT Upper Limits
  14. GRB 250806A: Swift/UVOT U-band detection
  15. EP250806a: Liverpool telescope optical upper limit
  16. GRB 250807A: Swift detection of a burst with an optical counterpart
  17. EP250802a: EP-FXT follow-up observation
  18. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  19. EP250806a: SVOM /VT optical candidate
  20. GRB 250806A: J-band upper limit from WINTER
  21. GRB 250806A: KAIT optical upper limit
  22. GRB 250806A: SVOM/VT refined analysis
  23. EP250806a: COLIBRÍ optical upper limit
  24. GRB 250806A: Kilonova-Catcher optical upper limits
  25. EP250806a: Einstein Probe detection of an X-ray transient
  26. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  27. GRB 250806A: SVOM/VT optical upper limit
  28. GRB 250806A: SVOM detection of a soft burst
  29. GRB 250805A: SVOM/VT optical counterpart
  30. GRB 250804B: Swift-XRT observations
  31. GRB 250805A: Enhanced Swift-XRT position
  32. GRB 250805A: TRT optical upper limits
  33. GRB 250805A: Swift-XRT observations
  34. GRB 250805A: Swift detection of a burst
  35. GRB 250804B: SVOM/GRM observation of a short burst
  36. EP250802a: additional Liverpool Telescope upper limits
  37. EP250730a: SVOM/VT optical upper limit
  38. EP250802a: Liverpool Telescope optical upper limits
  39. EP250802a: GROWTH-India Telescope optical upper limit
  40. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  41. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  42. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  43. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  44. EP250711a: CrAO and Assy optical observations
  45. EP250730a: COLIBRÍ optical upper limit
  46. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  47. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  48. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT follow up of AT 2025smm
  49. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  50. GRB 250727A: EP-FXT follow-up observation
  51. GRB 250725A: PRIME near-infrared observations
  52. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  53. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  54. GRB 250728A: Swift-XRT observations
  55. GRB 250728A: COLIBRÍ optical upper limit
  56. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  57. GRB 250727A: EP-FXT counterpart detection
  58. GRB250727A: SVOM/VT optical upper limit
  59. GRB 250727A: Swift-XRT observations
  60. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  61. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  62. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  63. GRB 250727A: SVOM detection of a burst
  64. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  65. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  66. GRB 250725A: Swift-XRT refined Analysis
  67. LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
  68. GRB 250725A: SVOM/GRM observation
  69. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  70. GRB 250725A: Swift/UVOT Upper Limits
  71. GRB 250725A: SVOM/VT optical candidate
  72. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  73. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  74. GRB 250725A: Enhanced Swift-XRT position
  75. GRB 250725A: Swift detection of a burst
  76. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  77. SVOM J195836+32283 is not a real source
  78. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  79. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  80. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  81. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  82. GRB 250721A: Swift-XRT observations
  83. GRB 250717B: SVOM/GRM observation
  84. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  85. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  86. GRB 250717B: COLIBRÍ optical upper limit
  87. GRB 250717B: Swift-XRT observations
  88. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  89. Swift Trigger 1334535: a possible GRB 250718A
  90. GRB 270713A: Kitab and AbAO Optical Observations
  91. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  92. GRB 250716A: Swift-XRT afterglow detection
  93. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  94. GRB 250714A: SVOM/GRM observation
  95. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  96. GRB 250713A: Mephisto optical upper limits
  97. GRB 250713A: SVOM/VT optical upper limit
  98. GRB 250713A: NOT optical upper limits
  99. GRB 250713A: OHP/T193 upper limit
  100. GRB 250713A: SVOM/C-GFT upper limit

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