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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"

26333 results found.

  1. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  2. EP251118A: 3.6m DOT optical afterglow detection
  3. GRB 251122A / EP251122a: EP-FXT counterpart detection
  4. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  5. GRB 251122A / EP251122a: WFST optical observations
  6. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  7. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  8. GRB 251122A / EP251122a: LCO optical upper limits
  9. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  10. EP251122a: Global MASTER-Net observations report
  11. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  12. GRB 251122A / EP251122a: SVOM detection of a long burst
  13. EP251122a: Einstein Probe detection of an X-ray transient
  14. EP251118a: Continued Optical Detection with Kinder observations
  15. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  16. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  17. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  18. EP251118a: Xinglong-2.16m optical observation
  19. GRB 251115A: Fermi GBM Observation
  20. Fermi trigger No 785388351: Global MASTER-Net observations report
  21. EP251118A: 1.3m DFOT optical afterglow detection
  22. GRB 251118A: Swift/UVOT Detection
  23. EP251118a / GRB 251118C: SAO RAS optical observations
  24. GRB 251118A: Glowbug gamma-ray detection
  25. GRB 251118A: Fermi GBM Observation
  26. GRB 251118A: Swift-XRT afterglow detection
  27. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  28. EP251118a: Optical detection with Kinder observations
  29. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  30. GRB 251118A: NuSTAR detection of bright prompt emission
  31. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  32. GRB 251116C: NOT optical observations
  33. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  34. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  35. GRB 251117A: Swift-XRT observations
  36. EP251118A / GRB 251118C : MASTER optical counterpart observations
  37. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  38. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  39. EP251118a: VLT near-infrared observation
  40. GRB 251116D: SVOM/GRM observation of a long GRB
  41. GRB 251119A: SVOM detection of a possible burst
  42. EP251118a: Global MASTER-Net observations report
  43. LAT GRB251118.86: Global MASTER-Net observations report
  44. EP251118a: NOT candidate optical counterpart
  45. EP251118a: Einstein Probe detected of a fast X-ray transient
  46. Fermi GRB 251118B: Global MASTER-Net observations report
  47. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  48. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  49. GRB 251117A: AstroSat CZTI detection
  50. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  51. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  52. GRB 251115A: Swift-XRT observations
  53. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  54. GRB 251117A: SVOM/GRM observation of a short burst
  55. LAT GRB251117.51: Global MASTER-Net observations report
  56. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  57. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  58. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  59. GRB 251116C: Swift-XRT observations
  60. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  61. GRB 251116D: Glowbug gamma-ray detection
  62. EP251023a: Assy AZT-20 optical observations
  63. EP251023a: UAFO and AbAO optical observations
  64. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  65. GRB 251116C: SVOM/VT optical upper limit
  66. GRB 251025B: further Mondy optical observations
  67. GRB 251111A: Mondy optical upper limit
  68. GRB 251116B: EP-FXT follow-up observation
  69. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  70. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  71. GRB 251116B: LCO optical upper limits
  72. GRB 251116C: LCO optical upper limits
  73. SVOM GRB251116C: Global MASTER-Net observations report
  74. GRB 251116B: SVOM detection of a burst
  75. IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
  76. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  77. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  78. Fermi GRB 251115A: Global MASTER-Net observations report
  79. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  80. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  81. LIGO/Virgo/KAGRA S251112cm: Updated Sky localization and false alarm rate estimate
  82. GRB 251113A: Glowbug gamma-ray detection
  83. GRB 251112A: Swift-BAT refined analysis
  84. Fermi trigger No 784717756: Global MASTER-Net observations report
  85. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  86. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  87. Fermi GRB 251114A: Global MASTER-Net observations report
  88. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  89. Fermi GRB 251113A: Global MASTER-Net observations report
  90. GRB 251113A: BALROG localization (Fermi Trigger 784748255 / GRB 251113734)
  91. GRB 251112A: Swift/UVOT Upper Limits
  92. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  93. GRB 251112A: Swift-XRT refined Analysis
  94. GRB 251112B: MAXI/GSC detection
  95. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  96. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  97. GRB 251108B: Glowbug gamma-ray detection
  98. Swift Trigger 1413695: a possible GRB 251112A
  99. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
  100. Fermi trigger No 784621743: Global MASTER-Net observations report

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