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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"

16761 results found.

  1. GRB 250805A: Swift-XRT observations
  2. GRB 250804B: SVOM/GRM observation of a short burst
  3. EP250802a: additional Liverpool Telescope upper limits
  4. EP250730a: SVOM/VT optical upper limit
  5. EP250802a: Liverpool Telescope optical upper limits
  6. EP250802a: GROWTH-India Telescope optical upper limit
  7. EP250802a: Einstein Probe detection of an X-ray transient
  8. The EP-WXT trigger 01709198251 is likely a flaring star
  9. The EP-WXT trigger 01709198202 is likely a flaring star
  10. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  11. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  12. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  13. EP250711a: CrAO and Assy optical observations
  14. EP250730a: COLIBRÍ optical upper limit
  15. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  16. EP250730a: Einstein Probe detection of an X-ray transient
  17. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  18. GRB 250725A: AstroSat CZTI detection
  19. GRB 250727A: EP-FXT follow-up observation
  20. GRB 250725A: PRIME near-infrared observations
  21. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  22. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  23. GRB 250728A: COLIBRÍ optical upper limit
  24. GRB 250727A: AST3-2 Upper limit
  25. GRB 250727A: EP-FXT counterpart detection
  26. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  27. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  28. The EP-WXT trigger 01709195487 is likely a flaring star
  29. Konus-Wind detection of GRB 250725A
  30. GRB 250725A: SVOM/GRM observation
  31. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  32. GRB 250725A: Swift/UVOT Upper Limits
  33. GRB 250725A: SVOM/VT optical candidate
  34. GRB 250725A: Enhanced Swift-XRT position
  35. GRB 250725A: Swift detection of a burst
  36. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  37. SVOM J195836+32283 is not a real source
  38. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  39. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  40. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  41. GRB 250721A: Swift-XRT observations
  42. GRB 250717B: SVOM/GRM observation
  43. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  44. GRB 250717B: COLIBRÍ optical upper limit
  45. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  46. GRB 270713A: Kitab and AbAO Optical Observations
  47. GRB 250716A: Swift-XRT afterglow detection
  48. GRB 250714A: SVOM/GRM observation
  49. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  50. GRB 250713A: Mephisto optical upper limits
  51. GRB 250713A: SVOM/VT optical upper limit
  52. GRB 250713A: NOT optical upper limits
  53. GRB 250713A: OHP/T193 upper limit
  54. GRB 250713A: SVOM/C-GFT upper limit
  55. GRB 250706B/C: 7DT Follow-up Observations
  56. GRB 250713A: EP-FXT counterpart detection
  57. EP250711a: COLIBRÍ continuous optical observations
  58. GRB 250628A: Swift-BAT refined analysis
  59. GRB 250713A: JinShan optical upper limits
  60. GRB 250713A: SVOM detection of a long burst
  61. GRB 250711A: DDOTI Optical Upper Limit
  62. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  63. GRB 250711A: SVOM/GRM observation
  64. EP250711a: NOT optical counterpart candidate
  65. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  66. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  67. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  68. GRB 250704A: GRANDMA observations
  69. GRB 250702B,D,E / EP250702a: ALMA detection
  70. IceCube-250708A: No Candidates from WINTER
  71. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  72. EP250704a/GRB 250704B: 10 GHz VLA detection
  73. The EP-WXT trigger 01709181970 is likely a flaring star
  74. IceCube-250706A: No Candidates from WINTER
  75. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  76. EP250704a/GRB250704B : HCT optical and NIR upper limits
  77. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  78. GRB 250702F: radio detection with the VLA
  79. IceCube-250706A: EP-FXT follow-up observations
  80. GRB 250706B/C: Fermi-LAT detection
  81. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  82. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  83. GRB 250706B: Swift/UVOT Detection
  84. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  85. GRB 250702F: GRANDMA observations
  86. GRB 250706A: Swift/UVOT Upper Limits
  87. GRB 250706B: REM optical observations
  88. GRB 250706A: REM optical/NIR observations
  89. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  90. IceCube-250416A: DDOTI Optical Upper Limit
  91. IceCube-250706A: COLIBRÍ optical upper limits
  92. GRB 250706A: JinShan optical upper limits
  93. GRB 250706A: SAO RAS optical observations
  94. EP250704A: NOWT Detection
  95. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  96. The EP-WXT trigger 01709181580 is likely a flaring star
  97. GRB 250706B: iTelescope optical observations
  98. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  99. GRB 250706B: SVOM/VT optical observation
  100. GRB 250706B: TRT bright optical counterpart detection

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