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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"

21784 results found.

  1. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  2. EP251122a: Global MASTER-Net observations report
  3. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  4. EP251118a: Continued Optical Detection with Kinder observations
  5. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  6. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  7. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  8. EP251118a: Xinglong-2.16m optical observation
  9. Fermi trigger No 785388351: Global MASTER-Net observations report
  10. EP251118A: 1.3m DFOT optical afterglow detection
  11. GRB 251118A: Swift/UVOT Detection
  12. EP251118a / GRB 251118C: SAO RAS optical observations
  13. GRB 251118A: Swift-XRT afterglow detection
  14. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  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 251117A: Swift-XRT observations
  21. EP251118A / GRB 251118C : MASTER optical counterpart observations
  22. EP251118a: FTW optical and NIR observations
  23. EP251118a: VLT near-infrared observation
  24. EP251118a: GOTO optical afterglow detection
  25. EP251118a: Global MASTER-Net observations report
  26. LAT GRB251118.86: Global MASTER-Net observations report
  27. EP251118a: NOT candidate optical counterpart
  28. GRB 251118A: Swift ToO observations
  29. EP251118a: Einstein Probe detected of a fast X-ray transient
  30. Fermi GRB 251118B: Global MASTER-Net observations report
  31. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  32. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  33. GRB 251116C: SVOM/ECLAIRs refined analysis
  34. GRB 251116B: SVOM/ECLAIRs refined analysis
  35. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  36. GRB 251115A: Swift-XRT observations
  37. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  38. GRB 251117A: Tiled Swift observations
  39. LAT GRB251117.51: Global MASTER-Net observations report
  40. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  41. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  42. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  43. GRB 251116C: Swift-XRT observations
  44. EP251023a: Assy AZT-20 optical observations
  45. EP251023a: UAFO and AbAO optical observations
  46. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  47. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  48. GRB 251025B: further Mondy optical observations
  49. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  50. SVOM GRB251116C: Global MASTER-Net observations report
  51. GRB 251116B: SVOM detection of a burst
  52. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  53. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  54. GRB 251115A: Tiled Swift observations
  55. Fermi GRB 251115A: Global MASTER-Net observations report
  56. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  57. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  58. Fermi trigger No 784717756: Global MASTER-Net observations report
  59. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  60. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  61. Fermi GRB 251114A: Global MASTER-Net observations report
  62. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  63. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  64. Fermi GRB 251113A: Global MASTER-Net observations report
  65. GRB 251111A: SVOM/ECLAIRs refined analysis
  66. GRB 251025B: SVOM/ECLAIRs refined analysis
  67. GRB 251112A: Swift/UVOT Upper Limits
  68. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  69. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  70. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  71. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  72. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
  73. Fermi trigger No 784621743: Global MASTER-Net observations report
  74. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 3-Initial Localization Volume
  75. GRB251111A: 1.3m DFOT optical upper limit
  76. GRB 251111A: Swift-XRT afterglow detection
  77. GRB 251111A: SVOM/VT optical observations with X-band data
  78. SVOM GRB251111.42: Global MASTER-Net observations report
  79. GRB 251111A: Swift-XRT observations
  80. SVOM GRB251111.22: Global MASTER-Net observations report
  81. GRB 251013C: Chandra X-ray observations and jet break detection
  82. GRB 251111A: SVOM/VT optical observations with VHF data
  83. GRB 251111A: KAIT optical upper limit
  84. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  85. GRB 251106A: Swift/UVOT Upper Limits
  86. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  87. Fermi trigger No 784329591: Global MASTER-Net observations report
  88. Fermi trigger No 784279167: Global MASTER-Net observations report
  89. SVOM GRB251108.54: Global MASTER-Net observations report
  90. SVOM GRB251106.83: Global MASTER-Net observations report
  91. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  92. GRB 251106A: Swift-XRT afterglow detection
  93. GRB 251106A: Kilonova-Catcher optical upper limit
  94. Fermi GBM Sub-Threshold Detection of GRB 251106A
  95. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  96. GRB 251106A: MASTER optical observations
  97. Fermi trigger No 784034269: Global MASTER-Net observations report
  98. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  99. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  100. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst

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