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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. EP251124a: GROWTH-India Telescope optical upper limits
  2. EP251124a: Einstein Probe detection of an X-ray transient
  3. GRB 251116C: Swift-XRT confirmation of fading
  4. GRB 251122A/EP251122a: FTW optical and NIR observations
  5. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  6. The EP-WXT trigger 01709248783 is likely a flaring star
  7. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  8. EP251118A: 3.6m DOT optical afterglow detection
  9. GRB 251122A / EP251122a: EP-FXT counterpart detection
  10. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  11. GRB 251122A / EP251122a: WFST optical observations
  12. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  13. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  14. GRB 251122A / EP251122a: LCO optical upper limits
  15. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  16. EP251122a: Global MASTER-Net observations report
  17. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  18. GRB 251122A / EP251122a: SVOM detection of a long burst
  19. EP251122a: Einstein Probe detection of an X-ray transient
  20. EP251118a: Continued Optical Detection with Kinder observations
  21. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  22. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  23. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  24. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  25. EP251118a: Xinglong-2.16m optical observation
  26. GRB 251115A: Fermi GBM Observation
  27. The EP-WXT trigger 01709248635 is likely a flaring star
  28. GRB 251121A: Fermi GBM Final Real-time Localization
  29. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  30. Fermi trigger No 785388351: Global MASTER-Net observations report
  31. EP251118A: 1.3m DFOT optical afterglow detection
  32. GRB 251118A: Swift/UVOT Detection
  33. EP251118a / GRB 251118C: SAO RAS optical observations
  34. GRB 251118A: Glowbug gamma-ray detection
  35. GRB 251118A: Fermi GBM Observation
  36. GRB 251118A: Swift-XRT afterglow detection
  37. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  38. EP251118a: Optical detection with Kinder observations
  39. GRB 251118A: GECAM-B detection
  40. EP-WXT trigger 01709248403: confirmation of a stellar flare by SVOM/VT
  41. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  42. EP251118a / GRB 251118C: SVOM/VT optical observation
  43. The EP-WXT trigger 01709248403 is likely a flaring star
  44. GRB 251118A: NuSTAR detection of bright prompt emission
  45. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  46. GRB 251116C: NOT optical observations
  47. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  48. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  49. GRB 251018A: FRAM-Auger optical detection
  50. GRB 251117A: Swift-XRT observations
  51. EP251118A / GRB 251118C : MASTER optical counterpart observations
  52. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  53. Konus-Wind detection of GRB 251118C (EP251118a)
  54. The EP-WXT trigger 01709248388 is likely a flaring star
  55. EP251118a: FTW optical and NIR observations
  56. GRB 251117A: Insight-HXMT/HE detection
  57. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  58. EP251118a: VLT near-infrared observation
  59. GRB 251116D: SVOM/GRM observation of a long GRB
  60. EP251118a: GOTO optical afterglow detection
  61. GRB 251119A: SVOM detection of a possible burst
  62. EP251118a: NOT spectroscopic redshift of z = 1.216
  63. EP251118a: Global MASTER-Net observations report
  64. EP251118a: preliminary result of EP-FXT follow-up observation
  65. LAT GRB251118.86: Global MASTER-Net observations report
  66. GRB 251118A: Fermi-LAT detection
  67. EP251118a: NOT candidate optical counterpart
  68. GRB 251118A: Swift ToO observations
  69. EP251118a: Einstein Probe detected of a fast X-ray transient
  70. Fermi GRB 251118B: Global MASTER-Net observations report
  71. GRB 251118B: Fermi GBM Final Real-time Localization
  72. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  73. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  74. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  75. GRB 251118A: Fermi GBM Final Real-time Localization
  76. GRB 251116C: SVOM/ECLAIRs refined analysis
  77. GRB 251116B: SVOM/ECLAIRs refined analysis
  78. GRB 251117A: AstroSat CZTI detection
  79. GRB 251114B: Insight-HXMT/HE detection
  80. GRB 251114B: GECAM-B detection of a short burst
  81. GRB 251117A: Fermi GBM observation
  82. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  83. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  84. GRB 251116D: Insight-HXMT/HE detection
  85. GRB 251115A: Swift-XRT observations
  86. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  87. GRB 251117A: SVOM/GRM observation of a short burst
  88. GRB 251117A: Tiled Swift observations
  89. GRB 251117A: Fermi-LAT detection
  90. LAT GRB251117.51: Global MASTER-Net observations report
  91. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  92. GRB 251116C: Swift/BAT arcminute localization of a burst
  93. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  94. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  95. GRB 251116B: SVOM/VT optical upper limit
  96. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  97. GRB 251116C: Swift-XRT observations
  98. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  99. GRB 251117A: Fermi GBM Final Localization Correction
  100. GRB 251116D: Glowbug gamma-ray detection

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