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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"

28060 results found.

  1. GRB 251126A: Kilonova-Catcher optical afterglow detection
  2. GRB 251126A: Nanshan/HMT optical afterglow detection
  3. Swift GRB 251126A: Global MASTER-Net observations report
  4. GRB 251121A: Fermi GBM Observation
  5. GRB 251126A: GIT discovery of the likely optical afterglow
  6. GRB 251126A: Swift detection of a burst
  7. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  8. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  9. EP251124b: NOT r- and z-band optical upper limits
  10. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  11. Fermi GRB 251125B: Global MASTER-Net observations report
  12. EP251124b: Global MASTER-Net observations report
  13. EP251124b: EP-WXT detection of a fast X-ray transient
  14. EP251124a: Xinglong GWAC-F60A optical observation
  15. Fermi GRB 251125A: Global MASTER-Net observations report
  16. EP251124a: NOT r- and z-band optical upper limits
  17. EP251124a: Global MASTER-Net observations report
  18. EP251124a: Swift-XRT observations
  19. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  20. EP251124a: Optical upper limit with Kinder observations
  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. EP251124a: Einstein Probe detection of an X-ray transient
  26. GRB 251116C: Swift-XRT confirmation of fading
  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. EP251122a: Einstein Probe detection of an X-ray transient
  41. EP251118a: Continued Optical Detection with Kinder observations
  42. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  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. Fermi trigger No 785388351: Global MASTER-Net observations report
  48. EP251118A: 1.3m DFOT optical afterglow detection
  49. GRB 251118A: Swift/UVOT Detection
  50. EP251118a / GRB 251118C: SAO RAS optical observations
  51. GRB 251118A: Glowbug gamma-ray detection
  52. GRB 251118A: Fermi GBM Observation
  53. GRB 251118A: Swift-XRT afterglow detection
  54. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  55. EP251118a: Optical detection with Kinder observations
  56. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  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. GRB 251117A: Swift-XRT observations
  63. EP251118A / GRB 251118C : MASTER optical counterpart observations
  64. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  65. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  66. EP251118a: VLT near-infrared observation
  67. GRB 251116D: SVOM/GRM observation of a long GRB
  68. GRB 251119A: SVOM detection of a possible burst
  69. EP251118a: Global MASTER-Net observations report
  70. LAT GRB251118.86: Global MASTER-Net observations report
  71. EP251118a: NOT candidate optical counterpart
  72. EP251118a: Einstein Probe detected of a fast X-ray transient
  73. Fermi GRB 251118B: Global MASTER-Net observations report
  74. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  75. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  76. GRB 251117A: AstroSat CZTI detection
  77. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  78. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  79. GRB 251115A: Swift-XRT observations
  80. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  81. GRB 251117A: SVOM/GRM observation of a short burst
  82. LAT GRB251117.51: Global MASTER-Net observations report
  83. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  84. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  85. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  86. GRB 251116C: Swift-XRT observations
  87. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  88. GRB 251116D: Glowbug gamma-ray detection
  89. EP251023a: Assy AZT-20 optical observations
  90. EP251023a: UAFO and AbAO optical 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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