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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"

26142 results found.

  1. EP251124a: Global MASTER-Net observations report
  2. EP251124a: Swift-XRT observations
  3. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  4. EP251124a: Optical upper limit with Kinder observations
  5. Fermi GRB 251124a: Global MASTER-Net observations report
  6. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  7. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  8. EP251124a: GROWTH-India Telescope optical upper limits
  9. EP251124a: Einstein Probe detection of an X-ray transient
  10. GRB 251116C: Swift-XRT confirmation of fading
  11. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  12. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  13. EP251118A: 3.6m DOT optical afterglow detection
  14. GRB 251122A / EP251122a: EP-FXT counterpart detection
  15. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  16. GRB 251122A / EP251122a: WFST optical observations
  17. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  18. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  19. GRB 251122A / EP251122a: LCO optical upper limits
  20. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  21. EP251122a: Global MASTER-Net observations report
  22. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  23. GRB 251122A / EP251122a: SVOM detection of a long burst
  24. EP251122a: Einstein Probe detection of an X-ray transient
  25. EP251118a: Continued Optical Detection with Kinder observations
  26. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  27. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  28. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  29. EP251118a: Xinglong-2.16m optical observation
  30. GRB 251115A: Fermi GBM Observation
  31. Fermi trigger No 785388351: Global MASTER-Net observations report
  32. EP251118A: 1.3m DFOT optical afterglow detection
  33. GRB 251118A: Swift/UVOT Detection
  34. EP251118a / GRB 251118C: SAO RAS optical observations
  35. GRB 251118A: Glowbug gamma-ray detection
  36. GRB 251118A: Fermi GBM Observation
  37. GRB 251118A: Swift-XRT afterglow detection
  38. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  39. EP251118a: Optical detection with Kinder observations
  40. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  41. GRB 251118A: NuSTAR detection of bright prompt emission
  42. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  43. GRB 251116C: NOT optical observations
  44. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  45. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  46. GRB 251117A: Swift-XRT observations
  47. EP251118A / GRB 251118C : MASTER optical counterpart observations
  48. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  49. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  50. EP251118a: VLT near-infrared observation
  51. GRB 251116D: SVOM/GRM observation of a long GRB
  52. GRB 251119A: SVOM detection of a possible burst
  53. EP251118a: Global MASTER-Net observations report
  54. LAT GRB251118.86: Global MASTER-Net observations report
  55. EP251118a: NOT candidate optical counterpart
  56. EP251118a: Einstein Probe detected of a fast X-ray transient
  57. Fermi GRB 251118B: Global MASTER-Net observations report
  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: AstroSat CZTI detection
  61. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  62. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  63. GRB 251115A: Swift-XRT observations
  64. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  65. GRB 251117A: SVOM/GRM observation of a short burst
  66. LAT GRB251117.51: Global MASTER-Net observations report
  67. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  68. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  69. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  70. GRB 251116C: Swift-XRT observations
  71. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  72. GRB 251116D: Glowbug gamma-ray detection
  73. EP251023a: Assy AZT-20 optical observations
  74. EP251023a: UAFO and AbAO optical observations
  75. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  76. GRB 251116C: SVOM/VT optical upper limit
  77. GRB 251025B: further Mondy optical observations
  78. GRB 251111A: Mondy optical upper limit
  79. GRB 251116B: EP-FXT follow-up observation
  80. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  81. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  82. GRB 251116B: LCO optical upper limits
  83. GRB 251116C: LCO optical upper limits
  84. SVOM GRB251116C: Global MASTER-Net observations report
  85. GRB 251116B: SVOM detection of a burst
  86. IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
  87. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  88. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  89. Fermi GRB 251115A: Global MASTER-Net observations report
  90. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  91. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  92. LIGO/Virgo/KAGRA S251112cm: Updated Sky localization and false alarm rate estimate
  93. GRB 251113A: Glowbug gamma-ray detection
  94. GRB 251112A: Swift-BAT refined analysis
  95. Fermi trigger No 784717756: Global MASTER-Net observations report
  96. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  97. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  98. Fermi GRB 251114A: Global MASTER-Net observations report
  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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