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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"

2744 results found.

  1. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect.
  2. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  3. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  4. GRB 250207A: FRAM-Auger optical detection
  5. IceCube-250207A - IceCube observation of a high-energy neutrino candidate track-like event
  6. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  7. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  8. IceCube-250203A - IceCube observation of a high-energy neutrino candidate track-like event
  9. GRB 250128B: VLA possible radio detection
  10. GRB 250128B: VLT/HAWKI near-infrared observations
  11. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  12. ATCA detection of possible radio counterpart to GRB 250114A
  13. EP250108a: optical follow-up observations with the Liverpool Telescope
  14. EP250108a: further NOT optical observations
  15. GRB 250108A: Swift/XRT afterglow fading
  16. GRB 250109A: Fermi GBM Observation
  17. GRB 250108B: Gemini-North likely redshift z = 2.197
  18. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  19. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  20. GRB 241229B: CrAO ZTSh possible optical counterpart of SVOM/VT confirmation
  21. GRB 241228B: GOTO possible optical counterpart candidate
  22. IceCube-241224A - IceCube observation of a high-energy neutrino candidate track-like event
  23. GRB 241223A: GOTO optical observations summary
  24. GRB 241105A: JWST photometric observations of the host galaxy
  25. GRB 241209B: host galaxy detection and GTC/OSIRIS+ spectroscopy
  26. GRB 241218A: Swift-BAT refined analysis
  27. EP 241217a: NIR detection with P200/WIRC
  28. EP 241217a: Possible J-band detection with WINTER
  29. EP241217a: Kinder optical follow-up observations
  30. EP241107a: VLA Radio Observation
  31. GRB 241212A: Fermi GBM detection
  32. GRB 241206C: GRBAlpha detection
  33. LIGO/Virgo/KAGRA S241102br: continued GRAWITA observations and detection of an optical transient (AT2024adip)
  34. EP241113a: Keck/LRIS spectroscopic observation and tentative redshift
  35. EP241201a: 1.6m Mephisto Optical Upper Limits
  36. GRB 241201A: GRBAlpha detection
  37. EP241202b: Kinder optical counterpart candidate
  38. EP241201a: Kinder optical counterpart candidate
  39. Swift-XRT observations of IceCube -241127A
  40. IceCube-241127A: IceCube observation of a high-energy neutrino candidate track-like event
  41. EP241125a: EP detection of an X-ray transient
  42. Konus-Wind detection of GRB 241117A
  43. IPN triangulation of GRB 241117A
  44. EP241021a and EP241026b: Keck/LRIS spectroscopic observations
  45. EP trigger ID 01709065118: Keck/LRIS spectroscopic observations
  46. GRB 241120A: Mondy and AbAO optical observations
  47. GRB 241113A: Possible ATCA Radio detection
  48. EP241115a/GRB 241115D: Swift/XRT follow-up observation
  49. EP 241113a: LBT possible optical counterpart
  50. IceCube-241113A - IceCube observation of a high-energy neutrino candidate track-like event
  51. LIGO/Virgo/KAGRA S241109bn: ATLAS observations and discovery of the potential counterpart AT2024aawt
  52. GRB 241030A: Mondy optical observations
  53. LIGO/Virgo/KAGRA S241102br: OHP/T193 optical observations
  54. EP241101a: Possible detection of an optical counterpart with FTW
  55. GRB 241030A / EP241030a: GMG possible spectroscopic redshift at z ~ 1.4
  56. GRB 241030A: detection of the bright optical counterpart in ATLAS forced photometry
  57. GRB 241030A: Keck/LRIS spectroscopic redshift z = 1.411
  58. EP 241026b: LBT possible optical counterpart (brightening source)
  59. GRB 240821A: Keck/LRIS spectroscopic observations
  60. GRB 241026A: SAO RAS observations of possible optical afterglow
  61. IceCube-241006A - IceCube observation of a high-energy neutrino candidate track-like event
  62. EP trigger ID 01709064214: GOTO confirms detection as a flare star
  63. IceCube-240929A - IceCube observation of a high-energy neutrino candidate track-like event
  64. EP240918a: Swift-XRT observation
  65. EP240918a: YAHPT Optical Upper Limit
  66. GRB 240912A: Swift-BAT refined analysis
  67. Fast X-ray Transient EP240801a: GMRT radio observations
  68. GRB 240905E: CrAO Optical Afterglow observations, possible OT candidate
  69. GRB 240819A as a likely X-Ray Flash
  70. GRB 240828B : Detection of a possible very soft X-ray transient by SVOM/ECLAIRs
  71. EP240801a: Keck/LRIS spectroscopic redshift confirmation
  72. IceCube-240808A - IceCube observation of a high-energy neutrino candidate track-like event
  73. The EP-WXT trigger 01709018832 on August 7th is likely a flaring star
  74. EP240801a: NOT optical observations
  75. IceCube-240725A - IceCube observation of a high-energy neutrino candidate track-like event
  76. IceCube-240721A - IceCube observation of a high-energy neutrino candidate track-like event
  77. EP240708a: X-ray follow-up observations with Swift/XRT
  78. The EP-WXT source triggered on July 14th is likely a flaring star
  79. GRB 240713A: J-band upper limit from WINTER
  80. GRB240713A: X-ray follow-up observation with EP-FXT
  81. EP240708a: X-ray follow-up observations with EP/FXT and Swift/XRT
  82. EP240703a and EP240703b: Swift/XRT upper limits
  83. EP240702a: Swift/XRT upper limit
  84. EP240626a: Montarrenti Observatory optical upper limit
  85. EP240618a: NOT further optical observations
  86. X-ray transient EP240618a: Fermi/GBM non-detection
  87. EP240618a: Swift/XRT upper limit
  88. EP240617a: tentative Swift/XRT detection of the afterglow
  89. GRB 240615A: possible transient detection from Wendelstein observations
  90. EP240618a: OHP/T193 MISTRAL i' and Y band upper limits
  91. Swift Trigger 1235109: a possible GRB 240606A
  92. GRB 240603B: Swift detection of a possible burst
  93. GRB 240529A: MASTER prompt OT detection
  94. The EP-WXT source triggered on June 1st is likely a flaring star
  95. EP240518a: GSP optical upper limit
  96. EP240518a: possibly identified with a flare star by EP-FXT
  97. GRB 240514E: A possible candidate BD-21 1074
  98. GRB 240502C: Zeiss-1000 at Koshka observations of GOTO24bao optical counterpart candidate
  99. GRB 240514B: GOTO candidate optical counterpart
  100. LIGO/Virgo/KAGRA S240422ed: P200 observations of AT2024hit

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