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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"

30483 results found.

  1. GRB 251126A: Nanshan/HMT optical afterglow detection
  2. Swift GRB 251126A: Global MASTER-Net observations report
  3. GRB 251121A: Fermi GBM Observation
  4. GRB 251126A: GIT discovery of the likely optical afterglow
  5. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  6. EP251124b follow-up observation by EP-FXT
  7. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  8. EP251124b: NOT r- and z-band optical upper limits
  9. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  10. Fermi GRB 251125B: Global MASTER-Net observations report
  11. EP251124b: Global MASTER-Net observations report
  12. EP251124a: Xinglong GWAC-F60A optical observation
  13. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  14. Fermi GRB 251125A: Global MASTER-Net observations report
  15. EP251124a: NOT r- and z-band optical upper limits
  16. EP251124a: Global MASTER-Net observations report
  17. GRB 251124A: Fermi GBM Localization by automated pipeline
  18. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  19. EP251124a: Optical upper limit with Kinder observations
  20. EP251118A: 6 GHz VLA Detection
  21. Fermi GRB 251124a: Global MASTER-Net observations report
  22. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  23. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  24. EP251124a: GROWTH-India Telescope optical upper limits
  25. GRB 251116C: Swift-XRT confirmation of fading
  26. GRB 251122A/EP251122a: FTW optical and NIR observations
  27. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  28. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  29. EP251118A: 3.6m DOT optical afterglow detection
  30. GRB 251122A / EP251122a: EP-FXT counterpart detection
  31. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  32. GRB 251122A / EP251122a: WFST optical observations
  33. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  34. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  35. GRB 251122A / EP251122a: LCO optical upper limits
  36. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  37. EP251122a: Global MASTER-Net observations report
  38. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  39. GRB 251122A / EP251122a: SVOM detection of a long burst
  40. EP251118a: Continued Optical Detection with Kinder observations
  41. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  42. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  43. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  44. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  45. EP251118a: Xinglong-2.16m optical observation
  46. GRB 251115A: Fermi GBM Observation
  47. EP251118A: 1.3m DFOT optical afterglow detection
  48. GRB 251118A: Swift/UVOT Detection
  49. EP251118a / GRB 251118C: SAO RAS optical observations
  50. GRB 251118A: Glowbug gamma-ray detection
  51. GRB 251118A: Fermi GBM Observation
  52. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  53. EP251118a: Optical detection with Kinder observations
  54. GRB 251118A: GECAM-B detection
  55. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  56. EP251118a / GRB 251118C: SVOM/VT optical observation
  57. GRB 251118A: NuSTAR detection of bright prompt emission
  58. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  59. GRB 251116C: NOT optical observations
  60. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  61. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  62. EP251118A / GRB 251118C : MASTER optical counterpart observations
  63. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  64. Konus-Wind detection of GRB 251118C (EP251118a)
  65. EP251118a: FTW optical and NIR observations
  66. GRB 251117A: Insight-HXMT/HE detection
  67. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  68. EP251118a: VLT near-infrared observation
  69. GRB 251116D: SVOM/GRM observation of a long GRB
  70. EP251118a: GOTO optical afterglow detection
  71. EP251118a: NOT spectroscopic redshift of z = 1.216
  72. EP251118a: Global MASTER-Net observations report
  73. EP251118a: preliminary result of EP-FXT follow-up observation
  74. GRB 251118A: Fermi-LAT detection
  75. EP251118a: NOT candidate optical counterpart
  76. GRB 251118A: Swift ToO observations
  77. EP251118a: Einstein Probe detected of a fast X-ray transient
  78. Fermi GRB 251118B: Global MASTER-Net observations report
  79. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  80. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  81. GRB 251116C: SVOM/ECLAIRs refined analysis
  82. GRB 251116B: SVOM/ECLAIRs refined analysis
  83. GRB 251117A: AstroSat CZTI detection
  84. GRB 251114B: Insight-HXMT/HE detection
  85. GRB 251114B: GECAM-B detection of a short burst
  86. GRB 251117A: Fermi GBM observation
  87. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  88. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  89. GRB 251116D: Insight-HXMT/HE detection
  90. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  91. GRB 251117A: SVOM/GRM observation of a short burst
  92. GRB 251117A: Tiled Swift observations
  93. GRB 251117A: Fermi-LAT detection
  94. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  95. GRB 251116C: Swift/BAT arcminute localization of a burst
  96. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  97. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  98. GRB 251116B: SVOM/VT optical upper limit
  99. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  100. LIGO/Virgo/KAGRA S251116en: Updated Sky localization

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