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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"

21320 results found.

  1. GRB 251126A: Swift/UVOT Detection
  2. GRB 251126A: Mondy and SAO RAS optical observations
  3. GRB 251126A: NOT optical observations
  4. GRB 251126A: 1.3m DFOT optical afterglow detection
  5. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  6. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  7. Fermi GRB 251127A: Global MASTER-Net observations report
  8. GRB 251126A: Kilonova-Catcher optical afterglow detection
  9. GRB 251126A: Asiago i-band detection
  10. GRB 251126A: Nanshan/HMT optical afterglow detection
  11. Swift GRB 251126A: Global MASTER-Net observations report
  12. GRB 251126A: GIT discovery of the likely optical afterglow
  13. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  14. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  15. EP251124b: NOT r- and z-band optical upper limits
  16. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  17. Fermi GRB 251125B: Global MASTER-Net observations report
  18. EP251124b: Global MASTER-Net observations report
  19. Fermi GRB 251125A: Global MASTER-Net observations report
  20. EP251124a: NOT r- and z-band optical upper limits
  21. EP251124a: Global MASTER-Net observations report
  22. EP251124a: Swift-XRT observations
  23. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  24. EP251124a: Optical upper limit with Kinder observations
  25. EP251118A: 6 GHz VLA Detection
  26. Fermi GRB 251124a: Global MASTER-Net observations report
  27. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  28. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  29. GRB 251116C: Swift-XRT confirmation of fading
  30. GRB 251122A/EP251122a: FTW optical and NIR observations
  31. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  32. EP251118A: 3.6m DOT optical afterglow detection
  33. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  34. GRB 251122A / EP251122a: WFST optical observations
  35. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  36. GRB 251122A / EP251122a: LCO optical upper limits
  37. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  38. EP251122a: Global MASTER-Net observations report
  39. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  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. EP251118a: Xinglong-2.16m optical observation
  45. Fermi trigger No 785388351: Global MASTER-Net observations report
  46. EP251118A: 1.3m DFOT optical afterglow detection
  47. GRB 251118A: Swift/UVOT Detection
  48. EP251118a / GRB 251118C: SAO RAS optical observations
  49. GRB 251118A: Swift-XRT afterglow detection
  50. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  51. EP251118a: Optical detection with Kinder observations
  52. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  53. EP251118a / GRB 251118C: SVOM/VT optical observation
  54. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  55. GRB 251116C: NOT optical observations
  56. GRB 251117A: Swift-XRT observations
  57. EP251118A / GRB 251118C : MASTER optical counterpart observations
  58. EP251118a: FTW optical and NIR observations
  59. EP251118a: VLT near-infrared observation
  60. EP251118a: GOTO optical afterglow detection
  61. EP251118a: Global MASTER-Net observations report
  62. LAT GRB251118.86: Global MASTER-Net observations report
  63. EP251118a: NOT candidate optical counterpart
  64. GRB 251118A: Swift ToO observations
  65. EP251118a: Einstein Probe detected of a fast X-ray transient
  66. Fermi GRB 251118B: Global MASTER-Net observations report
  67. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  68. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  69. GRB 251116C: SVOM/ECLAIRs refined analysis
  70. GRB 251116B: SVOM/ECLAIRs refined analysis
  71. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  72. GRB 251115A: Swift-XRT observations
  73. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  74. GRB 251117A: Tiled Swift observations
  75. LAT GRB251117.51: Global MASTER-Net observations report
  76. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  77. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  78. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  79. GRB 251116C: Swift-XRT observations
  80. EP251023a: Assy AZT-20 optical observations
  81. EP251023a: UAFO and AbAO optical observations
  82. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  83. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  84. GRB 251025B: further Mondy optical observations
  85. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  86. SVOM GRB251116C: Global MASTER-Net observations report
  87. GRB 251116B: SVOM detection of a burst
  88. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  89. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  90. GRB 251115A: Tiled Swift observations
  91. Fermi GRB 251115A: Global MASTER-Net observations report
  92. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  93. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  94. Fermi trigger No 784717756: Global MASTER-Net observations report
  95. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  96. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  97. Fermi GRB 251114A: Global MASTER-Net observations report
  98. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  99. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  100. Fermi GRB 251113A: Global MASTER-Net observations report

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