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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. 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. GRB 251122A / EP251122a: SVOM detection of a long burst
  5. EP251122a: Einstein Probe detection of an X-ray transient
  6. EP251118a: Continued Optical Detection with Kinder observations
  7. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  8. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  9. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  10. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  11. EP251118a: Xinglong-2.16m optical observation
  12. GRB 251115A: Fermi GBM Observation
  13. The EP-WXT trigger 01709248635 is likely a flaring star
  14. GRB 251121A: Fermi GBM Final Real-time Localization
  15. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  16. Fermi trigger No 785388351: Global MASTER-Net observations report
  17. EP251118A: 1.3m DFOT optical afterglow detection
  18. GRB 251118A: Swift/UVOT Detection
  19. EP251118a / GRB 251118C: SAO RAS optical observations
  20. GRB 251118A: Glowbug gamma-ray detection
  21. GRB 251118A: Fermi GBM Observation
  22. GRB 251118A: Swift-XRT afterglow detection
  23. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  24. EP251118a: Optical detection with Kinder observations
  25. GRB 251118A: GECAM-B detection
  26. EP-WXT trigger 01709248403: confirmation of a stellar flare by SVOM/VT
  27. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  28. EP251118a / GRB 251118C: SVOM/VT optical observation
  29. The EP-WXT trigger 01709248403 is likely a flaring star
  30. GRB 251118A: NuSTAR detection of bright prompt emission
  31. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  32. GRB 251116C: NOT optical observations
  33. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  34. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  35. GRB 251018A: FRAM-Auger optical detection
  36. GRB 251117A: Swift-XRT observations
  37. EP251118A / GRB 251118C : MASTER optical counterpart observations
  38. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  39. Konus-Wind detection of GRB 251118C (EP251118a)
  40. The EP-WXT trigger 01709248388 is likely a flaring star
  41. EP251118a: FTW optical and NIR observations
  42. GRB 251117A: Insight-HXMT/HE detection
  43. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  44. EP251118a: VLT near-infrared observation
  45. GRB 251116D: SVOM/GRM observation of a long GRB
  46. EP251118a: GOTO optical afterglow detection
  47. GRB 251119A: SVOM detection of a possible burst
  48. EP251118a: NOT spectroscopic redshift of z = 1.216
  49. EP251118a: Global MASTER-Net observations report
  50. EP251118a: preliminary result of EP-FXT follow-up observation
  51. LAT GRB251118.86: Global MASTER-Net observations report
  52. GRB 251118A: Fermi-LAT detection
  53. EP251118a: NOT candidate optical counterpart
  54. GRB 251118A: Swift ToO observations
  55. EP251118a: Einstein Probe detected of a fast X-ray transient
  56. Fermi GRB 251118B: Global MASTER-Net observations report
  57. GRB 251118B: Fermi GBM Final Real-time Localization
  58. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  59. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  60. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  61. GRB 251118A: Fermi GBM Final Real-time Localization
  62. GRB 251116C: SVOM/ECLAIRs refined analysis
  63. GRB 251116B: SVOM/ECLAIRs refined analysis
  64. GRB 251117A: AstroSat CZTI detection
  65. GRB 251114B: Insight-HXMT/HE detection
  66. GRB 251114B: GECAM-B detection of a short burst
  67. GRB 251117A: Fermi GBM observation
  68. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  69. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  70. GRB 251116D: Insight-HXMT/HE detection
  71. GRB 251115A: Swift-XRT observations
  72. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  73. GRB 251117A: SVOM/GRM observation of a short burst
  74. GRB 251117A: Tiled Swift observations
  75. GRB 251117A: Fermi-LAT detection
  76. LAT GRB251117.51: Global MASTER-Net observations report
  77. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  78. GRB 251116C: Swift/BAT arcminute localization of a burst
  79. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  80. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  81. GRB 251116B: SVOM/VT optical upper limit
  82. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  83. GRB 251116C: Swift-XRT observations
  84. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  85. GRB 251117A: Fermi GBM Final Localization Correction
  86. GRB 251116D: Glowbug gamma-ray detection
  87. EP251023a: Assy AZT-20 optical observations
  88. EP251023a: UAFO and AbAO optical observations
  89. GRB 251116D: AstroSat CZTI detection
  90. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  91. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  92. GRB 251116C: SVOM/VT optical upper limit
  93. GRB 251025B: further Mondy optical observations
  94. GRB 251111A: Mondy optical upper limit
  95. GRB 251116B: EP-FXT follow-up observation
  96. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  97. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  98. GRB 251116B: LCO optical upper limits
  99. GRB 251116C: LCO optical upper limits
  100. SVOM GRB251116C: Global MASTER-Net observations report

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