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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"

2747 results found.

  1. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  2. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  3. EP250207a: EP-WXT detection and XRT follow-up observation
  4. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect.
  5. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  6. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  7. GRB 250207A: FRAM-Auger optical detection
  8. IceCube-250207A - IceCube observation of a high-energy neutrino candidate track-like event
  9. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  10. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  11. IceCube-250203A - IceCube observation of a high-energy neutrino candidate track-like event
  12. GRB 250128B: VLA possible radio detection
  13. GRB 250128B: VLT/HAWKI near-infrared observations
  14. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  15. ATCA detection of possible radio counterpart to GRB 250114A
  16. EP250108a: optical follow-up observations with the Liverpool Telescope
  17. EP250108a: further NOT optical observations
  18. GRB 250108A: Swift/XRT afterglow fading
  19. GRB 250109A: Fermi GBM Observation
  20. GRB 250108B: Gemini-North likely redshift z = 2.197
  21. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  22. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  23. GRB 241229B: CrAO ZTSh possible optical counterpart of SVOM/VT confirmation
  24. GRB 241228B: GOTO possible optical counterpart candidate
  25. IceCube-241224A - IceCube observation of a high-energy neutrino candidate track-like event
  26. GRB 241223A: GOTO optical observations summary
  27. GRB 241105A: JWST photometric observations of the host galaxy
  28. GRB 241209B: host galaxy detection and GTC/OSIRIS+ spectroscopy
  29. GRB 241218A: Swift-BAT refined analysis
  30. EP 241217a: NIR detection with P200/WIRC
  31. EP 241217a: Possible J-band detection with WINTER
  32. EP241217a: Kinder optical follow-up observations
  33. EP241107a: VLA Radio Observation
  34. GRB 241212A: Fermi GBM detection
  35. GRB 241206C: GRBAlpha detection
  36. LIGO/Virgo/KAGRA S241102br: continued GRAWITA observations and detection of an optical transient (AT2024adip)
  37. EP241113a: Keck/LRIS spectroscopic observation and tentative redshift
  38. EP241201a: 1.6m Mephisto Optical Upper Limits
  39. GRB 241201A: GRBAlpha detection
  40. EP241202b: Kinder optical counterpart candidate
  41. EP241201a: Kinder optical counterpart candidate
  42. Swift-XRT observations of IceCube -241127A
  43. IceCube-241127A: IceCube observation of a high-energy neutrino candidate track-like event
  44. EP241125a: EP detection of an X-ray transient
  45. Konus-Wind detection of GRB 241117A
  46. IPN triangulation of GRB 241117A
  47. EP241021a and EP241026b: Keck/LRIS spectroscopic observations
  48. EP trigger ID 01709065118: Keck/LRIS spectroscopic observations
  49. GRB 241120A: Mondy and AbAO optical observations
  50. GRB 241113A: Possible ATCA Radio detection
  51. EP241115a/GRB 241115D: Swift/XRT follow-up observation
  52. EP 241113a: LBT possible optical counterpart
  53. IceCube-241113A - IceCube observation of a high-energy neutrino candidate track-like event
  54. LIGO/Virgo/KAGRA S241109bn: ATLAS observations and discovery of the potential counterpart AT2024aawt
  55. GRB 241030A: Mondy optical observations
  56. LIGO/Virgo/KAGRA S241102br: OHP/T193 optical observations
  57. EP241101a: Possible detection of an optical counterpart with FTW
  58. GRB 241030A / EP241030a: GMG possible spectroscopic redshift at z ~ 1.4
  59. GRB 241030A: detection of the bright optical counterpart in ATLAS forced photometry
  60. GRB 241030A: Keck/LRIS spectroscopic redshift z = 1.411
  61. EP 241026b: LBT possible optical counterpart (brightening source)
  62. GRB 240821A: Keck/LRIS spectroscopic observations
  63. GRB 241026A: SAO RAS observations of possible optical afterglow
  64. IceCube-241006A - IceCube observation of a high-energy neutrino candidate track-like event
  65. EP trigger ID 01709064214: GOTO confirms detection as a flare star
  66. IceCube-240929A - IceCube observation of a high-energy neutrino candidate track-like event
  67. EP240918a: Swift-XRT observation
  68. EP240918a: YAHPT Optical Upper Limit
  69. GRB 240912A: Swift-BAT refined analysis
  70. Fast X-ray Transient EP240801a: GMRT radio observations
  71. GRB 240905E: CrAO Optical Afterglow observations, possible OT candidate
  72. GRB 240819A as a likely X-Ray Flash
  73. GRB 240828B : Detection of a possible very soft X-ray transient by SVOM/ECLAIRs
  74. EP240801a: Keck/LRIS spectroscopic redshift confirmation
  75. IceCube-240808A - IceCube observation of a high-energy neutrino candidate track-like event
  76. The EP-WXT trigger 01709018832 on August 7th is likely a flaring star
  77. EP240801a: NOT optical observations
  78. IceCube-240725A - IceCube observation of a high-energy neutrino candidate track-like event
  79. IceCube-240721A - IceCube observation of a high-energy neutrino candidate track-like event
  80. EP240708a: X-ray follow-up observations with Swift/XRT
  81. The EP-WXT source triggered on July 14th is likely a flaring star
  82. GRB 240713A: J-band upper limit from WINTER
  83. GRB240713A: X-ray follow-up observation with EP-FXT
  84. EP240708a: X-ray follow-up observations with EP/FXT and Swift/XRT
  85. EP240703a and EP240703b: Swift/XRT upper limits
  86. EP240702a: Swift/XRT upper limit
  87. EP240626a: Montarrenti Observatory optical upper limit
  88. EP240618a: NOT further optical observations
  89. X-ray transient EP240618a: Fermi/GBM non-detection
  90. EP240618a: Swift/XRT upper limit
  91. EP240617a: tentative Swift/XRT detection of the afterglow
  92. GRB 240615A: possible transient detection from Wendelstein observations
  93. EP240618a: OHP/T193 MISTRAL i' and Y band upper limits
  94. Swift Trigger 1235109: a possible GRB 240606A
  95. GRB 240603B: Swift detection of a possible burst
  96. GRB 240529A: MASTER prompt OT detection
  97. The EP-WXT source triggered on June 1st is likely a flaring star
  98. EP240518a: GSP optical upper limit
  99. EP240518a: possibly identified with a flare star by EP-FXT
  100. GRB 240514E: A possible candidate BD-21 1074

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