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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"

15985 results found.

  1. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  2. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  3. EP251118A: 3.6m DOT optical afterglow detection
  4. GRB 251122A / EP251122a: EP-FXT counterpart detection
  5. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  6. GRB 251122A / EP251122a: WFST optical observations
  7. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  8. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  9. GRB 251122A / EP251122a: LCO optical upper limits
  10. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  11. EP251118a: Continued Optical Detection with Kinder observations
  12. EP251118a: Xinglong-2.16m optical observation
  13. EP251118A: 1.3m DFOT optical afterglow detection
  14. EP251118a / GRB 251118C: SAO RAS optical observations
  15. EP251118a: Optical detection with Kinder observations
  16. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  17. EP251118a / GRB 251118C: SVOM/VT optical observation
  18. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  19. GRB 251116C: NOT optical observations
  20. GRB 251018A: FRAM-Auger optical detection
  21. EP251118A / GRB 251118C : MASTER optical counterpart observations
  22. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  23. EP251118a: FTW optical and NIR observations
  24. EP251118a: VLT near-infrared observation
  25. GRB 251116D: SVOM/GRM observation of a long GRB
  26. EP251118a: GOTO optical afterglow detection
  27. EP251118a: NOT spectroscopic redshift of z = 1.216
  28. EP251118a: preliminary result of EP-FXT follow-up observation
  29. EP251118a: NOT candidate optical counterpart
  30. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  31. GRB 251117A: SVOM/GRM observation of a short burst
  32. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  33. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  34. GRB 251116B: SVOM/VT optical upper limit
  35. EP251023a: Assy AZT-20 optical observations
  36. EP251023a: UAFO and AbAO optical observations
  37. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  38. GRB 251116C: SVOM/VT optical upper limit
  39. GRB 251025B: further Mondy optical observations
  40. GRB 251111A: Mondy optical upper limit
  41. GRB 251116B: LCO optical upper limits
  42. GRB 251116C: LCO optical upper limits
  43. GRB 251116C: SVOM detection of a burst
  44. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  45. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  46. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  47. GRB 251112A: Swift/UVOT Upper Limits
  48. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  49. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  50. GRB251111A: 1.3m DFOT optical upper limit
  51. GRB 251111A: SVOM/VT optical observations with X-band data
  52. GRB 251111A: Swift-XRT observations
  53. GRB 251111A: EP-FXT counterpart detection
  54. GRB 251111A: SVOM/VT optical observations with VHF data
  55. GRB 251111A: KAIT optical upper limit
  56. GRB 251111A: LCO optical observation
  57. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  58. GRB 251106A: Swift/UVOT Upper Limits
  59. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  60. GRB 251102B: SVOM/GRM observation
  61. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  62. GRB 251106A: Swift-XRT afterglow detection
  63. GRB 251106A: Kilonova-Catcher optical upper limit
  64. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  65. GRB 251106A: MASTER optical observations
  66. GRB 251106A: SVOM detection of a burst
  67. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  68. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  69. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  70. GRB 251103B: Swift/UVOT Upper Limits
  71. GRB 251104A: SVOM detection of a burst
  72. GRB 251103A: Optical afterglow detection by ZTF’s public survey
  73. EP251102a: FTW optical and NIR observations
  74. GRB 251103A: WFST optical observations
  75. EP251102a: OHP/T193 optical observations
  76. GRB 251103A: OHP/T193 optical observations
  77. GRB 251103A: Xinglong 2.16m optical detection
  78. GRB 251103A: KAIT optical observations
  79. GRB 251103B: Nanshan/HMT optical upper limit
  80. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  81. GRB 251103B: MITSuME Akeno optical upper limits
  82. EP251102a: NIR observations with WINTER
  83. GRB 251103A: J-band detection with WINTER
  84. GRB 251103B: GROWTH-India Telescope optical upper limits
  85. GRB 251103A: Kilonova-Catcher optical afterglow detection
  86. GRB 251103A: Swift/UVOT Detection
  87. GRB 251103A: SVOM/GRM observation
  88. GRB 251103A: Swift-XRT afterglow detection
  89. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  90. EP251102a: Einstein Probe detection of a fast X-ray transient
  91. GRB 251025B: OHP/T193 optical upper limit
  92. GRB 251103A: LCO optical observation
  93. EP251102.890: COLIBRÍ optical counterpart candidate
  94. GRB 251103A: GOTO optical afterglow detection
  95. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  96. GRB 251103A: NOT spectroscopic redshift z = 0.76
  97. GRB 251103A: BOOTES-2/TELMA optical afterglow
  98. GRB 251103A: LCO optical afterglow detection
  99. GRB 251103A: NOT optical afterglow candidate (duplicate submission)
  100. GRB 251103A: NOT optical afterglow candidate

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