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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"
  1. GRB 251018A: FRAM-Auger optical detection
  2. GRB 251117A: Swift-XRT observations
  3. EP251118A / GRB 251118C : MASTER optical counterpart observations
  4. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  5. Konus-Wind detection of GRB 251118C (EP251118a)
  6. The EP-WXT trigger 01709248388 is likely a flaring star
  7. EP251118a: FTW optical and NIR observations
  8. GRB 251117A: Insight-HXMT/HE detection
  9. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  10. EP251118a: VLT near-infrared observation
  11. GRB 251116D: SVOM/GRM observation of a long GRB
  12. EP251118a: GOTO optical afterglow detection
  13. GRB 251119A: SVOM detection of a possible burst
  14. EP251118a: NOT spectroscopic redshift of z = 1.216
  15. EP251118a: Global MASTER-Net observations report
  16. EP251118a: preliminary result of EP-FXT follow-up observation
  17. LAT GRB251118.86: Global MASTER-Net observations report
  18. GRB 251118A: Fermi-LAT detection
  19. EP251118a: NOT candidate optical counterpart
  20. GRB 251118A: Swift ToO observations
  21. EP251118a: Einstein Probe detected of a fast X-ray transient
  22. Fermi GRB 251118B: Global MASTER-Net observations report
  23. GRB 251118B: Fermi GBM Final Real-time Localization
  24. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  25. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  26. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  27. GRB 251118A: Fermi GBM Final Real-time Localization
  28. GRB 251116C: SVOM/ECLAIRs refined analysis
  29. GRB 251116B: SVOM/ECLAIRs refined analysis
  30. GRB 251117A: AstroSat CZTI detection
  31. GRB 251114B: Insight-HXMT/HE detection
  32. GRB 251114B: GECAM-B detection of a short burst
  33. GRB 251117A: Fermi GBM observation
  34. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  35. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  36. GRB 251116D: Insight-HXMT/HE detection
  37. GRB 251115A: Swift-XRT observations
  38. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  39. GRB 251117A: SVOM/GRM observation of a short burst
  40. GRB 251117A: Tiled Swift observations
  41. GRB 251117A: Fermi-LAT detection
  42. LAT GRB251117.51: Global MASTER-Net observations report
  43. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  44. GRB 251116C: Swift/BAT arcminute localization of a burst
  45. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  46. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  47. GRB 251116B: SVOM/VT optical upper limit
  48. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  49. GRB 251116C: Swift-XRT observations
  50. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  51. GRB 251117A: Fermi GBM Final Localization Correction
  52. GRB 251116D: Glowbug gamma-ray detection
  53. EP251023a: Assy AZT-20 optical observations
  54. EP251023a: UAFO and AbAO optical observations
  55. GRB 251116D: AstroSat CZTI detection
  56. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  57. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  58. GRB 251116C: SVOM/VT optical upper limit
  59. GRB 251025B: further Mondy optical observations
  60. GRB 251111A: Mondy optical upper limit
  61. GRB 251116B: EP-FXT follow-up observation
  62. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  63. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  64. GRB 251116B: LCO optical upper limits
  65. GRB 251116C: LCO optical upper limits
  66. SVOM GRB251116C: Global MASTER-Net observations report
  67. GRB 251116C: SVOM detection of a burst
  68. GRB 251116B: SVOM detection of a burst
  69. IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
  70. GRB 251116A: Fermi GBM Final Real-time Localization
  71. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  72. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  73. GRB 251115A: Tiled Swift observations
  74. GRB 251115A: Fermi-LAT detection
  75. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  76. Fermi GRB 251115A: Global MASTER-Net observations report
  77. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  78. GRB 251115A: Fermi GBM Final Real-time Localization
  79. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  80. LIGO/Virgo/KAGRA S251112cm: Updated Sky localization and false alarm rate estimate
  81. GRB 251113A: Glowbug gamma-ray detection
  82. GRB 251113A: AstroSat CZTI detection
  83. GRB 251114B: Fermi GBM Final Real-time Localization
  84. GRB 251112A: Swift-BAT refined analysis
  85. Konus-Wind detection of GRB 251108C
  86. Fermi trigger No 784717756: Global MASTER-Net observations report
  87. Konus-Wind detection of GRB 251103A
  88. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  89. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  90. IPN triangulation of GRB 251108C
  91. The EP-WXT trigger 01709248221 is likely a flaring star
  92. Fermi GRB 251114A: Global MASTER-Net observations report
  93. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  94. GRB 251114A: Fermi GBM Final Real-time Localization
  95. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  96. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  97. Fermi GRB 251113A: Global MASTER-Net observations report
  98. GRB 251113A: BALROG localization (Fermi Trigger 784748255 / GRB 251113734)
  99. GRB 251113A: Fermi GBM Final Real-time Localization
  100. GRB 251111A: SVOM/ECLAIRs refined analysis

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