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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').

22278 results found.

  1. EP240426a: GMG optical upper limit
  2. LVK S240422ed: Further Swift-XRT followup of three sources
  3. LIGO/Virgo/KAGRA S240426s: Identification of a GW compact binary merger candidate
  4. IceCube-240424A: Upper limits from a search for additional neutrino events in IceCube
  5. LIGO/Virgo/KAGRA S240422ed: PRIME near-infrared observations
  6. LIGO/Virgo/KAGRA S240422ed: 2.5m PRL Telescope follow-up of the Swift/XRT source S240422ed_X190
  7. LIGO/Virgo/KAGRA S240422ed: Second night Pan-STARRS observations of the skymap
  8. LIGO/Virgo/KAGRA S240422ed: Further near-infrared observations with Subaru/MOIRCS by J-GEM Collaboration
  9. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-FXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  10. LIGO/Virgo/KAGRA S240422ed: Upper limits from GECAM Observations
  11. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA and Kilonova-Catcher galaxy targeting observations
  12. LIGO/Virgo/KAGRA S240422ed: Additional DECam GW-MMADS Candidates from the first two nights of observations
  13. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limits for Swift/XRT candidates
  14. GRB 240419B: Swift-BAT refined analysis
  15. GRB 240421B: Swift-BAT refined analysis
  16. GRB 240422A: Glowbug gamma-ray detection
  17. LIGO/Virgo/KAGRA S240422ed: Archival BlackGEM/MeerLICHT detections of AT 2024hdr & AT 2024hdq
  18. LIGO/Virgo/KAGRA S240422ed: Himalayan Chandra Telescope follow-up of the Swift/XRT source S240422ed_X101
  19. LIGO/Virgo/KAGRA S240422ed: No significant counterpart candidates in HAWC observations
  20. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA/FRAM Observations
  21. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  22. LIGO/Virgo S240422ed: Swift-XRT detection of 3 possible counterparts
  23. LIGO/Virgo/KAGRA S240422ed: Early X-ray Upper Limits from EP-WXT for the LVK Sky Localization Region
  24. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of Mag24a
  25. LIGO/Virgo/KAGRA S240422ed: Continued Imaging of Mag24a
  26. LIGO/Virgo/KAGRA S240422ed: Archival DECaPSs2 observations of the field of Mag24a
  27. LIGO/Virgo/KAGRA S240422ed: NOT J-band upper limit on the Swift/XRT source S240422ed_X61
  28. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Three Potential Electromagnetic Counterparts Reported So Far
  29. LIGO/Virgo/KAGRA S240422ed: Subaru/MOIRCS near-infrared observations by J-GEM Collaboration
  30. LIGO/Virgo/KAGRA S240422ed: WINTER J-band upper limits on the Swift/XRT source S240422ed_X61
  31. IceCube-240419A: Upper limits from a search for additional neutrino events in IceCube
  32. LIGO/Virgo/KAGRA S240421ar: Updated Sky localization
  33. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam upper limits on the Swift/XRT source S240422ed_X61
  34. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from Pan-STARRS observations of the skymap
  35. LIGO/Virgo/KAGRA S240422ed: No Counterparts in DDOTI/OAN Optical Observations
  36. GRB 240419A: Swift-BAT refined analysis
  37. GRB 240418A: Swift-BAT refined analysis
  38. LXT240402A/GRB240402B: Chandra X-ray detection
  39. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from ATLAS observations
  40. LIGO/Virgo/KAGRA S240422ed: WINTER near-infrared J-band observations
  41. LIGO/Virgo S240422ed: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  42. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam observations
  43. LIGO/Virgo/KAGRA S240422ed: Updated NED Galaxies in the Localization Volume
  44. LIGO/Virgo/KAGRA S240422ed: AstroSat CZTI non-detection and upper limits
  45. LIGO/Virgo/KAGRA S240422ed: Upper limits from Fermi-GBM Observations
  46. LIGO/Virgo/KAGRA S240422ed: Updated Sky localization and EM Bright Classification
  47. LIGO/Virgo/KAGRA S240421ar: Upper limits from Swift/BAT-GUANO
  48. LIGO/Virgo/KAGRA S240422ed: Coverage and upper limits from MAXI/GSC observations
  49. LIGO/Virgo/KAGRA S240422ed: Identification of a GW compact binary merger candidate
  50. LIGO/Virgo/Kagra S240422ed: NED Galaxies in the Localization Volume
  51. GRB 240421A: Glowbug gamma-ray detection
  52. GRB 240414A: radio detection with the VLA
  53. Fermi-LAT gamma-ray observations of IceCube-240419A
  54. GRB 240414A: AMI-LA radio observations
  55. GRB 240414A: LBT optical detection
  56. GRB 240419B : MITSuME Akeno optical upper limits
  57. GRB 240415B: Swift-XRT observations
  58. GRB 240415A: Swift-XRT refined Analysis
  59. GRB240421B: Zadko Observations
  60. GRB 240421B: Fermi GBM Observation
  61. GRB 240421B: Swift-XRT refined Analysis
  62. GRB240421B: BOOTES-5/JGT optical upper limit
  63. GRB 240421B: J-band upper limits from WINTER
  64. GRB 240421B: Swift/UVOT Upper Limits
  65. GRB 240421B: Enhanced Swift-XRT position
  66. EP240417a: no counterpart detection by SOAR
  67. EP240420a: Xinglong decaying optical counterpart
  68. GRB 240421B: Swift detection of a burst
  69. EP240420a: Nanshan optical counterpart observations
  70. EP240420a: GWAC-F50A optical upper limit
  71. LIGO/Virgo/KAGRA S240421ar: Identification of a GW unmodeled transient candidate
  72. EP240420a: detection of fading X-ray emission with refined position by EP-FXT
  73. EP240420a: NOT optical counterpart candidate and potential host
  74. GRB240419A: Skynet Optical Afterglow Analysis
  75. GRB240418A - Candidate afterglow from NIRES
  76. GRB 240419B: Swift/UVOT Upper Limits
  77. EP240420a: EP-WXT detection of a fast X-ray transient
  78. GRB 240419A: Swift/UVOT Upper Limits
  79. GRB 240419B: Swift-XRT refined Analysis
  80. GRB 240419B: optical afterglow from the NOT
  81. EP240414a: Near-IR observations with NIRES and WINTER
  82. GRB 240419B: Enhanced Swift-XRT position
  83. GRB 240418A: Swift/UVOT Upper Limits
  84. GRB 240419A: REM NIR afterglow detection
  85. GRB 240419A: Swift-XRT refined Analysis
  86. GRB 240418A: Swift-XRT refined Analysis
  87. GRB 240419B: Swift detection of a burst
  88. GRB 240411B: Swift/UVOT Detection
  89. GRB 240419A: VLT optical afterglow detection
  90. GRB 240419A: Enhanced Swift-XRT position
  91. EP240416a: J-band observations with WINTER
  92. EP240414a: GMG observation
  93. GRB 240419A: Swift detection of a burst
  94. GRB 240418A: TSHAO Zeiss-1000 optical upper limit
  95. GRB 240418A: NOT optical upper limits
  96. GRB 240418A: Enhanced Swift-XRT position
  97. GRB 240418A: AKO Upper Limit
  98. GRB 240418A: Swift detection of a burst
  99. EP240417a: EP-WXT detection of a fast X-ray transient
  100. LIGO/Virgo/KAGRA S240413p: X-ray upper limits from EP-WXT for the candidate AGN counterpart

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