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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').

23953 results found.

  1. GRB 250108A: Swift-XRT afterglow detection
  2. GRB 250108A:SVOM/VT optical candidate
  3. LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
  4. GRB 250108B: Swift/UVOT Upper Limits
  5. GRB 250103A: Swift-XRT afterglow detection
  6. GRB 250108B: Enhanced Swift-XRT position
  7. GRB 250108B: Swift detection of a burst
  8. GRB 250107A: Fermi GBM Observation
  9. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  10. GRB 250106A: SVOM/VT 2nd optical deep observation
  11. GRB 250101A: J band upper limit by SYSU 80cm telescope
  12. EPWXT01709129925: Xinglong optical observations
  13. GRB 250106A: NOT optical observations
  14. LIGO/Virgo/KAGRA S250104v: Updated Sky localization
  15. GRB 250103B: REM optical/NIR upper limits
  16. GRB 250101A: REM optical/NIR counterpart detection
  17. GRB 250106A: Swift-XRT observations
  18. GRB 250106A: SVOM/VT optical candidate
  19. The EP-WXT trigger 01709129925 is likely a flaring star
  20. GRB 250103B: Swift-XRT refined Analysis
  21. GRB 250103B: LCO/1m optical afterglow candidate detection
  22. GRB 250103A: Bassano Bresciano Observatory upper limit
  23. GRB 250103A: Swift-XRT observations
  24. GRB 250101A: 1.3m DFOT optical afterglow detection
  25. GRB 241229A: 1.3m DFOT upper limit
  26. GRB 241228B: 1.3m DFOT Optical observations
  27. GRB 241228A: 1.3m DFOT upper limit
  28. LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
  29. GRB 250103A: Montarrenti Observatory optical detection
  30. GRB 250101A: further LCOGT optical afterglow observations
  31. GRB 250103A: TSHAO optical upper limit
  32. GRB 250103A: Fermi GBM Observation
  33. GRB 250103B: LCOGT Optical Upper Limit
  34. IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
  35. EP250101a: Liverpool Telescope optical upper limit
  36. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  37. GRB 250101a: Liverpool Telescope optical follow-up
  38. GRB 250103B: Swift detection of a burst
  39. GRB 250103A: Xinglong 2.16m Optical Candidate
  40. GRB 250101B: SVOM/GRM observation
  41. GRB 250103A: GOTO optical upper limit
  42. GRB 250103A: SVOM/C-GFT optical upper limit
  43. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  44. EP241231b: optical upper limit with the Liverpool Telescope
  45. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  46. GRB 250103A: SVOM detection of a long burst
  47. EP250101a: Xinglong optical upper limit
  48. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  49. GRB 250101A: Swift-BAT refined analysis
  50. GRB 250101A: further SAO RAS optical observations
  51. GRB 250101A: LCO optical counterpart detection
  52. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  53. GRB 250101A: Swift/UVOT Detection
  54. GRB 250101A: 1.6m Mephisto multi-band optical followup
  55. GRB 250101A: Swift-XRT refined Analysis
  56. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  57. GRB 250101A: LCOGT optical afterglow detection
  58. GRB 250101A: OASDG optical observations
  59. GRB 250101B: Fermi GBM Final Real-time Localization
  60. GRB 250101A: SAO RAS observations of optical brightening
  61. GRB 250101A: BOOTES-4/MET optical afterglow detection
  62. GRB 250101A: AKO Optical Afterglow Detection
  63. GRB 250101A: SAO RAS optical observations
  64. GRB 250101A: Enhanced Swift-XRT position
  65. LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
  66. GRB 250101A: SVOM/C-GFT early optical observations
  67. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  68. GRB 250101A: Nanshan/HMT optical observations
  69. GRB 250101A : GIT optical detection
  70. GRB 250101A: GMG Optical Observation
  71. GRB 250101A: Swift detection of a burst with an optical counterpart
  72. LIGO/Virgo/KAGRA S241231du: Coverage and upper limit from MAXI/GSC observations
  73. LIGO/Virgo/KAGRA S250101k: Identification of a GW compact binary merger candidate
  74. GRB 241229B: Continued CrAO ZTSh observations
  75. LIGO/Virgo/KAGRA S241231bg: Updated NED Galaxies in the Localization Volume
  76. LIGO/Virgo/KAGRA S241231bg: Updated Sky localization and EM Bright Classification
  77. LIGO/Virgo/KAGRA S241230ev: Updated Sky localization
  78. LIGO/Virgo/KAGRA S241231bg: NED Galaxies in the Localization Volume
  79. LIGO/Virgo/KAGRA S241230bd: Updated Sky localization
  80. GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
  81. GRB 241229B: SVOM/GRM observation
  82. LIGO/Virgo/KAGRA S241231bg: Identification of a GW compact binary merger candidate
  83. EP241217A: J band upper limit by SYSU 80cm telescope
  84. LIGO/Virgo/KAGRA S241230ev: Identification of a GW compact binary merger candidate
  85. GRB 241229B: SAO RAS optical upper limit
  86. GRB 241228B: SAO RAS optical observations
  87. GRB 241229A: SAO RAS optical observations
  88. IceCube-Cascade 241228A: Upper limits from a search for additional neutrino events in IceCube
  89. GRB 241229A: Swift-XRT observations
  90. EP240702a: 7DT Optical upper limits
  91. GRB 240606B: 7DT Optical upper limits
  92. LIGO/Virgo/KAGRA S241230bd: Identification of a GW compact binary merger candidate
  93. GRB 241229B: Swift-BAT refined analysis
  94. LIGO/Virgo/KAGRA S241225v: Updated Sky localization
  95. LIGO/Virgo/KAGRA S241225c: Updated Sky localization and EM Bright Classification
  96. GRB241229B: UVOT upper limits
  97. GRB 241228B: Fermi GBM Observation
  98. GRB 241228B: Swift-XRT afterglow detection
  99. GRB 241229B: Fermi GBM Observation
  100. GRB 241229B: NUTTelA-TAO / BSTI Optical Limits

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