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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"

26150 results found.

  1. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  2. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  3. EP251124b: NOT r- and z-band optical upper limits
  4. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  5. Fermi GRB 251125B: Global MASTER-Net observations report
  6. EP251124b: Global MASTER-Net observations report
  7. EP251124b: EP-WXT detection of a fast X-ray transient
  8. EP251124a: Xinglong GWAC-F60A optical observation
  9. Fermi GRB 251125A: Global MASTER-Net observations report
  10. EP251124a: NOT r- and z-band optical upper limits
  11. EP251124a: Global MASTER-Net observations report
  12. EP251124a: Swift-XRT observations
  13. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  14. EP251124a: Optical upper limit with Kinder observations
  15. Fermi GRB 251124a: Global MASTER-Net observations report
  16. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  17. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  18. EP251124a: GROWTH-India Telescope optical upper limits
  19. EP251124a: Einstein Probe detection of an X-ray transient
  20. GRB 251116C: Swift-XRT confirmation of fading
  21. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  22. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  23. EP251118A: 3.6m DOT optical afterglow detection
  24. GRB 251122A / EP251122a: EP-FXT counterpart detection
  25. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  26. GRB 251122A / EP251122a: WFST optical observations
  27. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  28. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  29. GRB 251122A / EP251122a: LCO optical upper limits
  30. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  31. EP251122a: Global MASTER-Net observations report
  32. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  33. GRB 251122A / EP251122a: SVOM detection of a long burst
  34. EP251122a: Einstein Probe detection of an X-ray transient
  35. EP251118a: Continued Optical Detection with Kinder observations
  36. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  37. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  38. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  39. EP251118a: Xinglong-2.16m optical observation
  40. GRB 251115A: Fermi GBM Observation
  41. Fermi trigger No 785388351: Global MASTER-Net observations report
  42. EP251118A: 1.3m DFOT optical afterglow detection
  43. GRB 251118A: Swift/UVOT Detection
  44. EP251118a / GRB 251118C: SAO RAS optical observations
  45. GRB 251118A: Glowbug gamma-ray detection
  46. GRB 251118A: Fermi GBM Observation
  47. GRB 251118A: Swift-XRT afterglow detection
  48. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  49. EP251118a: Optical detection with Kinder observations
  50. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  51. GRB 251118A: NuSTAR detection of bright prompt emission
  52. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  53. GRB 251116C: NOT optical observations
  54. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  55. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  56. GRB 251117A: Swift-XRT observations
  57. EP251118A / GRB 251118C : MASTER optical counterpart observations
  58. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  59. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  60. EP251118a: VLT near-infrared observation
  61. GRB 251116D: SVOM/GRM observation of a long GRB
  62. GRB 251119A: SVOM detection of a possible burst
  63. EP251118a: Global MASTER-Net observations report
  64. LAT GRB251118.86: Global MASTER-Net observations report
  65. EP251118a: NOT candidate optical counterpart
  66. EP251118a: Einstein Probe detected of a fast X-ray transient
  67. Fermi GRB 251118B: Global MASTER-Net observations report
  68. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  69. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  70. GRB 251117A: AstroSat CZTI detection
  71. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  72. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  73. GRB 251115A: Swift-XRT observations
  74. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  75. GRB 251117A: SVOM/GRM observation of a short burst
  76. LAT GRB251117.51: Global MASTER-Net observations report
  77. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  78. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  79. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  80. GRB 251116C: Swift-XRT observations
  81. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  82. GRB 251116D: Glowbug gamma-ray detection
  83. EP251023a: Assy AZT-20 optical observations
  84. EP251023a: UAFO and AbAO optical observations
  85. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  86. GRB 251116C: SVOM/VT optical upper limit
  87. GRB 251025B: further Mondy optical observations
  88. GRB 251111A: Mondy optical upper limit
  89. GRB 251116B: EP-FXT follow-up observation
  90. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  91. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  92. GRB 251116B: LCO optical upper limits
  93. GRB 251116C: LCO optical upper limits
  94. SVOM GRB251116C: Global MASTER-Net observations report
  95. GRB 251116B: SVOM detection of a burst
  96. IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
  97. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  98. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  99. Fermi GRB 251115A: Global MASTER-Net observations report
  100. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume

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