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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. EP251118a: Optical detection with Kinder observations
  2. GRB 251118A: GECAM-B detection
  3. EP-WXT trigger 01709248403: confirmation of a stellar flare by SVOM/VT
  4. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  5. EP251118a / GRB 251118C: SVOM/VT optical observation
  6. The EP-WXT trigger 01709248403 is likely a flaring star
  7. GRB 251118A: NuSTAR detection of bright prompt emission
  8. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  9. GRB 251116C: NOT optical observations
  10. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  11. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  12. GRB 251018A: FRAM-Auger optical detection
  13. GRB 251117A: Swift-XRT observations
  14. EP251118A / GRB 251118C : MASTER optical counterpart observations
  15. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  16. Konus-Wind detection of GRB 251118C (EP251118a)
  17. The EP-WXT trigger 01709248388 is likely a flaring star
  18. EP251118a: FTW optical and NIR observations
  19. GRB 251117A: Insight-HXMT/HE detection
  20. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  21. EP251118a: VLT near-infrared observation
  22. GRB 251116D: SVOM/GRM observation of a long GRB
  23. EP251118a: GOTO optical afterglow detection
  24. GRB 251119A: SVOM detection of a possible burst
  25. EP251118a: NOT spectroscopic redshift of z = 1.216
  26. EP251118a: Global MASTER-Net observations report
  27. EP251118a: preliminary result of EP-FXT follow-up observation
  28. LAT GRB251118.86: Global MASTER-Net observations report
  29. GRB 251118A: Fermi-LAT detection
  30. EP251118a: NOT candidate optical counterpart
  31. GRB 251118A: Swift ToO observations
  32. EP251118a: Einstein Probe detected of a fast X-ray transient
  33. Fermi GRB 251118B: Global MASTER-Net observations report
  34. GRB 251118B: Fermi GBM Final Real-time Localization
  35. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  36. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  37. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  38. GRB 251118A: Fermi GBM Final Real-time Localization
  39. GRB 251116C: SVOM/ECLAIRs refined analysis
  40. GRB 251116B: SVOM/ECLAIRs refined analysis
  41. GRB 251117A: AstroSat CZTI detection
  42. GRB 251114B: Insight-HXMT/HE detection
  43. GRB 251114B: GECAM-B detection of a short burst
  44. GRB 251117A: Fermi GBM observation
  45. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  46. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  47. GRB 251116D: Insight-HXMT/HE detection
  48. GRB 251115A: Swift-XRT observations
  49. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  50. GRB 251117A: SVOM/GRM observation of a short burst
  51. GRB 251117A: Tiled Swift observations
  52. GRB 251117A: Fermi-LAT detection
  53. LAT GRB251117.51: Global MASTER-Net observations report
  54. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  55. GRB 251116C: Swift/BAT arcminute localization of a burst
  56. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  57. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  58. GRB 251116B: SVOM/VT optical upper limit
  59. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  60. GRB 251116C: Swift-XRT observations
  61. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  62. GRB 251117A: Fermi GBM Final Localization Correction
  63. GRB 251116D: Glowbug gamma-ray detection
  64. EP251023a: Assy AZT-20 optical observations
  65. EP251023a: UAFO and AbAO optical observations
  66. GRB 251116D: AstroSat CZTI detection
  67. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  68. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  69. GRB 251116C: SVOM/VT optical upper limit
  70. GRB 251025B: further Mondy optical observations
  71. GRB 251111A: Mondy optical upper limit
  72. GRB 251116B: EP-FXT follow-up observation
  73. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  74. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  75. GRB 251116B: LCO optical upper limits
  76. GRB 251116C: LCO optical upper limits
  77. SVOM GRB251116C: Global MASTER-Net observations report
  78. GRB 251116C: SVOM detection of a burst
  79. GRB 251116B: SVOM detection of a burst
  80. IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
  81. GRB 251116A: Fermi GBM Final Real-time Localization
  82. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  83. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  84. GRB 251115A: Tiled Swift observations
  85. GRB 251115A: Fermi-LAT detection
  86. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  87. Fermi GRB 251115A: Global MASTER-Net observations report
  88. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  89. GRB 251115A: Fermi GBM Final Real-time Localization
  90. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  91. LIGO/Virgo/KAGRA S251112cm: Updated Sky localization and false alarm rate estimate
  92. GRB 251113A: Glowbug gamma-ray detection
  93. GRB 251113A: AstroSat CZTI detection
  94. GRB 251114B: Fermi GBM Final Real-time Localization
  95. GRB 251112A: Swift-BAT refined analysis
  96. Konus-Wind detection of GRB 251108C
  97. Fermi trigger No 784717756: Global MASTER-Net observations report
  98. Konus-Wind detection of GRB 251103A
  99. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  100. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources

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