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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"

18131 results found.

  1. GRB 250805A: SVOM/VT optical counterpart
  2. GRB 250805A: Enhanced Swift-XRT position
  3. GRB 250804C: AstroSat CZTI detection of a long burst
  4. GRB 250805A: TRT optical upper limits
  5. GRB 250805A: Swift-XRT observations
  6. GRB 250804B: Tiled Swift observations
  7. GRB 250804B: SVOM/GRM observation of a short burst
  8. EP250802a: additional Liverpool Telescope upper limits
  9. EP250730a: SVOM/VT optical upper limit
  10. EP250802a: Liverpool Telescope optical upper limits
  11. EP250802a: GROWTH-India Telescope optical upper limit
  12. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  13. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  14. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  15. EP250711a: CrAO and Assy optical observations
  16. EP250730a: COLIBRÍ optical upper limit
  17. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  18. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  19. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  20. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  21. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  22. GRB 250725A: PRIME near-infrared observations
  23. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  24. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  25. GRB 250728A: COLIBRÍ optical upper limit
  26. GRB 250728A: Swift ToO observations
  27. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  28. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  29. GRB 250727A: SVOM detection of a burst
  30. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  31. GRB 250725A: SVOM/GRM observation
  32. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  33. GRB 250725A: Swift/UVOT Upper Limits
  34. GRB 250725A: SVOM/VT optical candidate
  35. GRB 250725A: Enhanced Swift-XRT position
  36. GRB 250725A: Swift detection of a burst
  37. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  38. SVOM J195836+32283 is not a real source
  39. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  40. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  41. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  42. GRB 250721A: Swift-XRT observations
  43. GRB 250713A : SVOM/ECLAIRs refined analysis
  44. GRB 250717B: SVOM/GRM observation
  45. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  46. GRB 250721A: Tiled Swift observations
  47. GRB 250717B: COLIBRÍ optical upper limit
  48. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  49. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  50. GRB 250717B: Swift ToO observations
  51. GRB 270713A: Kitab and AbAO Optical Observations
  52. GRB 250716A: Swift-XRT afterglow detection
  53. GRB 250716A: Swift ToO observations
  54. GRB 250714A: SVOM/GRM observation
  55. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  56. GRB 250713A: Mephisto optical upper limits
  57. GRB 250713A: SVOM/VT optical upper limit
  58. GRB 250713A: NOT optical upper limits
  59. GRB 250713A: OHP/T193 upper limit
  60. GRB 250713A: SVOM/C-GFT upper limit
  61. GRB 250706B/C: 7DT Follow-up Observations
  62. EP250711a: COLIBRÍ continuous optical observations
  63. GRB 250713A: JinShan optical upper limits
  64. GRB 250713A: SVOM detection of a long burst
  65. GRB 250711A: DDOTI Optical Upper Limit
  66. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  67. GRB 250711A: SVOM/GRM observation
  68. EP250711a: NOT optical counterpart candidate
  69. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  70. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  71. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  72. GRB 250704A: GRANDMA observations
  73. GRB 250704A: SVOM/ECLAIRs refined analysis
  74. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  75. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  76. IceCube-250708A: No Candidates from WINTER
  77. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  78. EP250704a/GRB 250704B: 10 GHz VLA detection
  79. IceCube-250706A: No Candidates from WINTER
  80. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  81. GRB 250704B / EP250704a: VLA radio detection
  82. EP250704a/GRB250704B : HCT optical and NIR upper limits
  83. GRB 250708A: Fermi GBM Final Real-time Localization
  84. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  85. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  86. GRB 250702F: radio detection with the VLA
  87. IceCube-250706A: EP-FXT follow-up observations
  88. GRB 250706B/C: Fermi-LAT detection
  89. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  90. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  91. GRB 250706B: Swift/UVOT Detection
  92. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  93. GRB 250702F: GRANDMA observations
  94. GRB 250706A: Swift/UVOT Upper Limits
  95. GRB 250706B: REM optical observations
  96. GRB 250706A: REM optical/NIR observations
  97. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  98. IceCube-250416A: DDOTI Optical Upper Limit
  99. IceCube-250706A: COLIBRÍ optical upper limits
  100. GRB 250706A: JinShan optical upper limits

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