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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"

16158 results found.

  1. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  2. GRB 251122A / EP251122a: LCO optical upper limits
  3. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  4. EP251118a: Continued Optical Detection with Kinder observations
  5. EP251118a: Xinglong-2.16m optical observation
  6. EP251118A: 1.3m DFOT optical afterglow detection
  7. EP251118a / GRB 251118C: SAO RAS optical observations
  8. EP251118a: Optical detection with Kinder observations
  9. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  10. EP251118a / GRB 251118C: SVOM/VT optical observation
  11. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  12. GRB 251116C: NOT optical observations
  13. GRB 251018A: FRAM-Auger optical detection
  14. EP251118A / GRB 251118C : MASTER optical counterpart observations
  15. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  16. EP251118a: FTW optical and NIR observations
  17. EP251118a: VLT near-infrared observation
  18. GRB 251116D: SVOM/GRM observation of a long GRB
  19. EP251118a: GOTO optical afterglow detection
  20. EP251118a: NOT spectroscopic redshift of z = 1.216
  21. EP251118a: preliminary result of EP-FXT follow-up observation
  22. EP251118a: NOT candidate optical counterpart
  23. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  24. GRB 251117A: SVOM/GRM observation of a short burst
  25. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  26. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  27. GRB 251116B: SVOM/VT optical upper limit
  28. EP251023a: Assy AZT-20 optical observations
  29. EP251023a: UAFO and AbAO optical observations
  30. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  31. GRB 251116C: SVOM/VT optical upper limit
  32. GRB 251025B: further Mondy optical observations
  33. GRB 251111A: Mondy optical upper limit
  34. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  35. GRB 251116B: LCO optical upper limits
  36. GRB 251116C: LCO optical upper limits
  37. GRB 251116C: SVOM detection of a burst
  38. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  39. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  40. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  41. GRB 251112A: Swift/UVOT Upper Limits
  42. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  43. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  44. GRB251111A: 1.3m DFOT optical upper limit
  45. GRB 251111A: SVOM/VT optical observations with X-band data
  46. GRB 251111A: Swift-XRT observations
  47. GRB 251111A: EP-FXT counterpart detection
  48. GRB 251111A: SVOM/VT optical observations with VHF data
  49. GRB 251111A: KAIT optical upper limit
  50. GRB 251111A: LCO optical observation
  51. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  52. GRB 251106A: Swift/UVOT Upper Limits
  53. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  54. GRB 251102B: SVOM/GRM observation
  55. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  56. GRB 251106A: Swift-XRT afterglow detection
  57. GRB 251106A: Kilonova-Catcher optical upper limit
  58. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  59. GRB 251106A: MASTER optical observations
  60. GRB 251106A: SVOM detection of a burst
  61. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  62. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  63. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  64. GRB 251103B: Swift/UVOT Upper Limits
  65. GRB 251104A: SVOM detection of a burst
  66. GRB 251103A: Optical afterglow detection by ZTF’s public survey
  67. EP251102a: FTW optical and NIR observations
  68. GRB 251103A: WFST optical observations
  69. EP251102a: OHP/T193 optical observations
  70. GRB 251103A: OHP/T193 optical observations
  71. GRB 251103A: Xinglong 2.16m optical detection
  72. GRB 251103A: KAIT optical observations
  73. GRB 251103B: Nanshan/HMT optical upper limit
  74. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  75. GRB 251103B: MITSuME Akeno optical upper limits
  76. EP251102a: NIR observations with WINTER
  77. GRB 251103A: J-band detection with WINTER
  78. GRB 251103B: GROWTH-India Telescope optical upper limits
  79. GRB 251103A: Kilonova-Catcher optical afterglow detection
  80. GRB 251103A: Swift/UVOT Detection
  81. GRB 251103A: SVOM/GRM observation
  82. GRB 251103A: Swift-XRT afterglow detection
  83. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  84. EP251102a: Einstein Probe detection of a fast X-ray transient
  85. GRB 251025B: OHP/T193 optical upper limit
  86. GRB 251103A: LCO optical observation
  87. EP251102.890: COLIBRÍ optical counterpart candidate
  88. GRB 251103A: GOTO optical afterglow detection
  89. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  90. GRB 251103A: NOT spectroscopic redshift z = 0.76
  91. GRB 251103A: BOOTES-2/TELMA optical afterglow
  92. GRB 251103A: LCO optical afterglow detection
  93. GRB 251103A: NOT optical afterglow candidate (duplicate submission)
  94. GRB 251103A: NOT optical afterglow candidate
  95. GRB 251103A: SVOM detection of a bright burst
  96. GRB 251025C: SVOM/GRM observation
  97. GRB 251028A: SVOM/GRM observation
  98. GRB 251026B: SOAR Classification of GOTO25jgl/SN2025absf as a Type Ia supernova
  99. GRB 251026B: LBT near-infrared observations
  100. GRB 251026A/EP251026a: SVOM/VT optical counterpart

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